Physics
- [1] arXiv:2405.13029 [pdf, ps, html, other]
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Title: Equations of motion for general nonholonomic systems from the d'Alembert principle via an algebraic methodSubjects: Classical Physics (physics.class-ph); Mathematical Physics (math-ph)
The aim of this study is to present an alternative way to deduce the equations of motion of general (i.e., also nonlinear) nonholonomic constrained systems starting from the d'Alembert principle and proceeding by an algebraic procedure. The two classical approaches in nonholonomic mechanics -- Cetaev method and vakonomic method -- are treated on equal terms, avoiding integrations or other steps outside algebraic operations. In the second part of the work we compare our results with the standard forms of the equations of motion associated to the two method and we discuss the role of the transpositional relation and of the commutation rule within the question of equivalence and compatibility of the Cetaev and vakonomic methods for general nonholonomic systems.
- [2] arXiv:2405.13040 [pdf, ps, html, other]
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Title: The role of the Silberstein/Thomas/Wigner-rotation in the rod and slit paradoxSubjects: Classical Physics (physics.class-ph)
The rod and slit paradox, as first proposed by R. Shaw, is revisited. In this paradox, a rod of rest length $l_0$ moves parallel to the horizontal x-axis. Simultaneously, a thin sheet parallel to the horizontal xz-plane with a rod-shaped slit of rest length $d < l_0$ moves along the vertical y-axis. The rod passes through the slit due to relativistic effects. Earlier papers do not link the thought experiment to the Silberstein/Thomas/Wigner-rotation (STW-rotation), which is essential to its outcome. In this paper the role of the STW-rotation is discussed, and additional clarifying figures are provided. Some misleading aspects of earlier treatments are pointed out and corrected.
- [3] arXiv:2405.13043 [pdf, ps, other]
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Title: Towards Specialized Supercomputers for Climate Sciences: Computational Requirements of the Icosahedral Nonhydrostatic Weather and Climate ModelTorsten Hoefler, Alexandru Calotoiu, Anurag Dipankar, Thomas Schulthess, Xavier Lapillonne, Oliver FuhrerSubjects: Atmospheric and Oceanic Physics (physics.ao-ph); Hardware Architecture (cs.AR); Distributed, Parallel, and Cluster Computing (cs.DC); Computational Physics (physics.comp-ph)
We discuss the computational challenges and requirements for high-resolution climate simulations using the Icosahedral Nonhydrostatic Weather and Climate Model (ICON). We define a detailed requirements model for ICON which emphasizes the need for specialized supercomputers to accurately predict climate change impacts and extreme weather events. Based on the requirements model, we outline computational demands for km-scale simulations, and suggests machine learning techniques to enhance model accuracy and efficiency. Our findings aim to guide the design of future supercomputers for advanced climate science.
- [4] arXiv:2405.13063 [pdf, ps, html, other]
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Title: Aurora: A Foundation Model of the AtmosphereCristian Bodnar, Wessel P. Bruinsma, Ana Lucic, Megan Stanley, Johannes Brandstetter, Patrick Garvan, Maik Riechert, Jonathan Weyn, Haiyu Dong, Anna Vaughan, Jayesh K. Gupta, Kit Tambiratnam, Alex Archibald, Elizabeth Heider, Max Welling, Richard E. Turner, Paris PerdikarisSubjects: Atmospheric and Oceanic Physics (physics.ao-ph); Machine Learning (cs.LG)
Deep learning foundation models are revolutionizing many facets of science by leveraging vast amounts of data to learn general-purpose representations that can be adapted to tackle diverse downstream tasks. Foundation models hold the promise to also transform our ability to model our planet and its subsystems by exploiting the vast expanse of Earth system data. Here we introduce Aurora, a large-scale foundation model of the atmosphere trained on over a million hours of diverse weather and climate data. Aurora leverages the strengths of the foundation modelling approach to produce operational forecasts for a wide variety of atmospheric prediction problems, including those with limited training data, heterogeneous variables, and extreme events. In under a minute, Aurora produces 5-day global air pollution predictions and 10-day high-resolution weather forecasts that outperform state-of-the-art classical simulation tools and the best specialized deep learning models. Taken together, these results indicate that foundation models can transform environmental forecasting.
- [5] arXiv:2405.13098 [pdf, ps, html, other]
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Title: How glassy are neural networks?Subjects: Computational Physics (physics.comp-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
Deep Neural Networks (DNNs) share important similarities with structural glasses. Both have many degrees of freedom, and their dynamics are governed by a high-dimensional, non-convex landscape representing either the loss or energy, respectively. Furthermore, both experience gradient descent dynamics subject to noise. In this work we investigate, by performing quantitative measurements on realistic networks trained on the MNIST and CIFAR-10 datasets, the extent to which this qualitative similarity gives rise to glass-like dynamics in neural networks. We demonstrate the existence of a Topology Trivialisation Transition as well as the previously studied under-to-overparameterised transition analogous to jamming. By training DNNs with overdamped Langevin dynamics in the resulting disordered phases, we do not observe diverging relaxation times at non-zero temperature, nor do we observe any caging effects, in contrast to glass phenomenology. However, the weight overlap function follows a power law in time, with an exponent of approximately -0.5, in agreement with the Mode-Coupling Theory of structural glasses. In addition, the DNN dynamics obey a form of time-temperature superposition. Finally, dynamic heterogeneity and ageing are observed at low temperatures. These results highlight important and surprising points of both difference and agreement between the behaviour of DNNs and structural glasses.
- [6] arXiv:2405.13165 [pdf, ps, html, other]
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Title: Adaptive coupling of 3D and 2D fluid flow modelsSubjects: Fluid Dynamics (physics.flu-dyn); Numerical Analysis (math.NA)
Similar to the notion of h-adaptivity, where the discretization resolution is adaptively changed, I propose the notion of model adaptivity, where the underlying model (the governing equations) is adaptively changed in space and time. Specifically, this work introduces a hybrid and adaptive coupling of a 3D bulk fluid flow model with a 2D thin film flow model. As a result, this work extends the applicability of existing thin film flow models to complex scenarios where, for example, bulk flow develops into thin films after striking a surface. At each location in space and time, the proposed framework automatically decides whether a 3D model or a 2D model must be applied. Using a meshless approach for both 3D and 2D models, at each particle, the decision to apply a 2D or 3D model is based on the user-prescribed resolution and a local principal component analysis. When a particle needs to be changed from a 3D model to 2D, or vice versa, the discretization is changed, and all relevant data mapping is done on-the-fly. Appropriate two-way coupling conditions and mass conservation considerations between the 3D and 2D models are also developed. Numerical results show that this model adaptive framework shows higher flexibility and compares well against finely resolved 3D simulations. In an actual application scenario, a 3 factor speed up is obtained, while maintaining the accuracy of the solution.
- [7] arXiv:2405.13168 [pdf, ps, html, other]
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Title: Modeling and Simulation of Charge-Induced Signals in Photon-Counting CZT Detectors for Medical Imaging ApplicationsManuel Ballester, Jaromir Kaspar, Francesc Massanes, Srutarshi Banerjee, Alexander Hans Vija, Aggelos K. KatsaggelosSubjects: Instrumentation and Detectors (physics.ins-det); Image and Video Processing (eess.IV)
Photon-counting detectors based on CZT are essential in nuclear medical imaging, particularly for SPECT applications. Although CZT detectors are known for their precise energy resolution, defects within the CZT crystals significantly impact their performance. These defects result in inhomogeneous material properties throughout the bulk of the detector. The present work introduces an efficient computational model that simulates the operation of semiconductor detectors, accounting for the spatial variability of the crystal properties. Our simulator reproduces the charge-induced pulse signals generated after the X/gamma-rays interact with the detector. The performance evaluation of the model shows an RMSE in the signal below 0.70%. Our simulator can function as a digital twin to accurately replicate the operation of actual detectors. Thus, it can be used to mitigate and compensate for adverse effects arising from crystal impurities.
- [8] arXiv:2405.13207 [pdf, ps, other]
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Title: Dielectric and energy-storage properties of Ba0.85Ca0.15Zr0.10Ti0.90O3 ceramics with BaO-Na2O-Nb2O5-WO3-P2O5 glass additionA. Ihyadn, S. Merselmiz, D. Mezzane, L. Bih, A. Lahmar, A. Alimoussa, M. Amjoud, Igor A. Luk'yanchuk, M. El MarssiSubjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)
Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramics with different BaO-Na2O-Nb2O5-WO3-P2O5 (BNNWP) glass content, forming (1-x)BCZT-xBNNWP lead-free ceramics (abbreviated as BCZTx; x=0, 2, 4, 6, and 8wt%) were synthesized using the conventional solid-state processing route. The XRD investigation shows the coexistence of tetragonal and orthorhombic phases in BCZT pure. Likewise, only the tetragonal phase was detected in BCZTx (x = 2-8 wt%) ceramics. The SEM findings indicate that the average grain size decreases as the amount of BNNWP glass additives increases. In addition, BCZT ceramics Amodified with glass additions showed narrower hysteresis loops and a large electric field. The BCZT4 showed the highest recovered energy density of 0.52 J/cm3 at 135kV/cm with an energy storage efficiency of 62.4%, which is increased by 6.6 compared to BCZT0 (0.075 J/cm3). The energy density was also calculated using the Landau-Ginzburg-Devonshire (LGD) theory
- [9] arXiv:2405.13210 [pdf, ps, html, other]
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Title: Magnetic black hole thermodynamics in an extended phase space with nonlinear electrodynamicsComments: 17 pages, 6 figuresJournal-ref: Entropy, 2024, Vol.26(3)Subjects: General Physics (physics.gen-ph)
We study Einstein's gravity coupled to nonlinear electrodynamics with two parameters in Anti-de Sitter spacetime. Magnetically charged black holes in an extended phase space is investigated. We obtain the mass and metric functions, their asymptotic and corrections to the Reissner--Nordström metric function when the cosmological constant vanishes. The first law of black hole thermodynamics in extended phase space is formulated and the magnetic potential and the thermodynamic conjugate to the coupling are obtained. We proved the generalized Smarr relation. The heat capacity and the Gibbs free energy are computed and phase transitions are studied. It was shown that the electric field of charged objects at the origin and electrostatic self-energy are finite within the nonlinear electrodynamics proposed.
- [10] arXiv:2405.13214 [pdf, ps, html, other]
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Title: Multi-Frequency Progressive Refinement for Learned Inverse ScatteringComments: 25 pages, 8 figuresSubjects: Computational Physics (physics.comp-ph)
Interpreting scattered acoustic and electromagnetic wave patterns is a computational task that enables remote imaging in a number of important applications, including medical imaging, geophysical exploration, sonar and radar detection, and nondestructive testing of materials. However, accurately and stably recovering an inhomogeneous medium from far-field scattered wave measurements is a computationally difficult problem, due to the nonlinear and non-local nature of the forward scattering process. We design a neural network, called Multi-Frequency Inverse Scattering Network (MFISNet), and a training method to approximate the inverse map from far-field scattered wave measurements at multiple frequencies. We consider three variants of MFISNet, with the strongest performing variant inspired by the recursive linearization method -- a commonly used technique for stably inverting scattered wavefield data -- that progressively refines the estimate with higher frequency content.
- [11] arXiv:2405.13224 [pdf, ps, html, other]
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Title: Integrating behavioral experimental findings into dynamical models to inform social change interventionsComments: Main text pp. 1-13; Supplementary Material pp. 14-36Subjects: Physics and Society (physics.soc-ph); Social and Information Networks (cs.SI); Econometrics (econ.EM)
Addressing global challenges -- from public health to climate change -- often involves stimulating the large-scale adoption of new products or behaviors. Research traditions that focus on individual decision making suggest that achieving this objective requires better identifying the drivers of individual adoption choices. On the other hand, computational approaches rooted in complexity science focus on maximizing the propagation of a given product or behavior throughout social networks of interconnected adopters. The integration of these two perspectives -- although advocated by several research communities -- has remained elusive so far. Here we show how achieving this integration could inform seeding policies to facilitate the large-scale adoption of a given behavior or product. Drawing on complex contagion and discrete choice theories, we propose a method to estimate individual-level thresholds to adoption, and validate its predictive power in two choice experiments. By integrating the estimated thresholds into computational simulations, we show that state-of-the-art seeding methods for social influence maximization might be suboptimal if they neglect individual-level behavioral drivers, which can be corrected through the proposed experimental method.
- [12] arXiv:2405.13232 [pdf, ps, html, other]
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Title: A generative machine learning surrogate model of plasma turbulenceSubjects: Plasma Physics (physics.plasm-ph); Computational Physics (physics.comp-ph)
State-of-the-art techniques in generative artificial intelligence are employed for the first time to construct a surrogate model for plasma turbulence that enables long time transport simulations. The proposed GAIT (Generative Artificial Intelligence Turbulence) model is based on the coupling of a convolutional variational auto-encoder, that encodes precomputed turbulence data into a reduce latent space, and a deep neural network and decoder that generate new turbulence states 400 times faster than the direct numerical integration. The model is applied to the Hasegawa-Wakatani (HW) plasma turbulence model, that is closely related to the quasigeostrophic model used in geophysical fluid dynamics. Very good agreement is found between the GAIT and the HW models in the spatio-temporal Fourier and Proper Orthogonal Decomposition spectra as well as in the flow topology characterized by the Okubo-Weiss decomposition. Agreement is also found in the probability distribution function of particle displacements and the effective turbulent diffusivity.
- [13] arXiv:2405.13234 [pdf, ps, html, other]
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Title: Deep operator learning-based surrogate models for aerothermodynamic analysis of AEDC hypersonic waveriderKhemraj Shukla, Jasmine Ratchford, Luis Bravo, Vivek Oommen, Nicholas Plewacki, Anindya Ghoshal, George KarniadakisComments: 71st JANNAF Propulsion Meeting, Oklahoma City, OK, 6-10 May 2024, 10 pages, 6 figuresSubjects: Fluid Dynamics (physics.flu-dyn)
Neural networks are universal approximators that traditionally have been used to learn a map between function inputs and outputs. However, recent research has demonstrated that deep neural networks can be used to approximate operators, learning function-to-function mappings. Creating surrogate models to supplement computationally expensive hypersonic aerothermodynamic models in characterizing the response of flow fields at different angles of attack (AoA) is an ideal application of neural operators. We investigate the use of neural operators to infer flow fields (volume and surface quantities) around a geometry based on a 3D waverider model based on experimental data measured at the Arnold Engineering Development Center (AEDC) Hypervelocity Wind Tunnel Number 9. We use a DeepONet neural operator which consists of two neural networks, commonly called a branch and a trunk network. The final output is the inner product of the output of the branch network and the output of the trunk net. Because the flow field contains shocks across the entire volume, we conduct a two-step training approach of the DeepONet that facilitates accurate approximation of solutions even in the presence of discontinuities. We train various DeepONet models to understand and predict pressure $(p)$, density $(\rho)$, velocity $(u)$, heat flux $(Q_w)$, and total shear stress $(\tau_{w})$ for the AEDC waverider geometry at Ma=7.36 across AoA that range from $-10^{\circ}$ to $10^{\circ}$ for surface quantities and from $-14^{\circ}$ to $14^{\circ}$ for volume quantities.
- [14] arXiv:2405.13260 [pdf, ps, html, other]
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Title: Assessing Proton-Boron Fusion Feasibility under non-Thermal Equilibrium Conditions: Rider's Inhibition RevisitedSubjects: Plasma Physics (physics.plasm-ph)
Compared to the D-T reaction, the neutron-free proton-boron (p-$^{11}$B) fusion has garnered increasing attention in recent years. However, significant Bremsstrahlung losses pose a formidable challenge in p-$^{11}$B plasmas in achieving $Q>1$ in thermal equilibrium. The primary aim of this study is to corroborate Todd H. Rider's seminal work in the 1997 Physics of Plasmas, who investigated the feasibility of sustaining p-$^{11}$B fusion under non-thermal equilibrium conditions. Employing a series of simulations with new fusion cross-section, we assessed the minimum recirculating power that must be recycled to maintain the system's non-thermal equilibrium and found that it is substantially greater than the fusion power output, aligning with Rider's conclusions, whether under the conditions of non-Maxwellian electron distribution or Maxwellian electron distribution, reactors reliant on non-equilibrium plasmas for p-$^{11}$B fusion are unlikely to achieve net power production without the aid of highly efficient external heat engines. However, maintaining the ion temperature at 300 keV and the Coulomb logarithm at 15, while increasing the electron temperature beyond 23.33 keV set by Rider, leads to diminished electron-ion energy transfer and heightened Bremsstrahlung radiation. When the electron temperature approaches approximately 140 keV, this progression ultimately leads to a scenario where the power of Bremsstrahlung loss equals the power of electron-ion interactions, yet remains inferior to the fusion power. Consequently, this results in a net gain in energy production.
- [15] arXiv:2405.13294 [pdf, ps, html, other]
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Title: Deformation and breakup of the liquid ligament with various disturbances on the interface in shear flowComments: 27 pages, 26 figures, 1 tableSubjects: Fluid Dynamics (physics.flu-dyn)
This study performed a numerical analysis of the deformation and breakup of a liquid ligament with various disturbances on the interface in shear flow. The shear flow generates a three-dimensional flow and vortices around the liquid ligament. These vortices promote the movement of the liquid inside the liquid ligament. When the velocity difference of shear flow increases, a nonlinear effect becomes strong, and turbulence with higher wavenumber components than the initial disturbance occurs at the interface. This turbulence accelerates the ligament splitting and increases the number of breakup droplets. Then, the droplet diameters become uniform, and the atomization quality improves. As the wavenumber of the disturbance applied to the interface increases, the liquid moving velocity along the central axis of the liquid ligament increases. As the wavenumber increases, the breakup time of the liquid ligament becomes short. In addition to the initial reference disturbance with a low wavenumber, when turbulence with twice the wavenumber of the reference disturbance is applied to the interface, the interface deformation and the splitting of the liquid ligament are similar to those with the single reference disturbance. When turbulence with four times the wavenumber is added to the initial disturbance with the low wavenumber at the interface, the deformation of the liquid ligament is accelerated, and the liquid ligament splits faster. In addition, the total surface area of the liquid increases because the number of breakup droplets increases. The droplet diameter becomes uniform, and therefore, the atomization quality of the liquid ligament is improved.
- [16] arXiv:2405.13303 [pdf, ps, other]
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Title: Giant Real-time Strain-Induced Anisotropy Field Tuning in Suspended Yttrium Iron Garnet Thin FilmsSubjects: Applied Physics (physics.app-ph)
Yttrium Iron Garnet based tunable magnetostatic wave and spin wave devices are poised to revolutionize the fields of Magnonics, Spintronics, Microwave devices, and quantum information science. The magnetic bias required for operating and tuning these devices is traditionally achieved through large power-hungry electromagnets, which significantly restraints the integration scalability, energy efficiency and individual resonator addressability. While controlling the magnetism of YIG mediated through its magnetostrictive/magnetoelastic interaction would address this constraint and enable novel strain/stress coupled magnetostatic wave (MSW) and spin wave (SW) devices, effective real-time strain-induced magnetism change in YIG remains elusive due to its weak magnetoelastic coupling efficiency and substrate clamping effect. We demonstrate a heterogeneous YIG-on-Si MSW resonator with a suspended thin-film device structure, which allows significant straining of YIG to generate giant magnetism change in YIG. By straining the YIG thin-film in real-time up to 1.06%, we show, for the first time, a 1.837 GHz frequency-strain tuning in MSW/SW resonators, which is equivalent to an effective strain-induced magnetocrystalline anisotropy field of 642 Oe. This is significantly higher than the previous state-of-the-art of 0.27 GHz of strain tuning in YIG. The unprecedented strain tunability of these YIG resonators paves the way for novel energy-efficient integrated on-chip solutions for tunable microwave, photonic, magnonic, and spintronic devices.
- [17] arXiv:2405.13306 [pdf, ps, html, other]
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Title: Measures to mitigate the coherent beam-beam instability at CEPCComments: 4 pages, 5 figures, IPAC24 WECD2Subjects: Accelerator Physics (physics.acc-ph)
Both horizontal and vertical coherent beam-beam instability are important issues at CEPC. The horizontal instability (X-Z instability) could be induced by beam-beam itself. In this paper we try to study the effect of chromaticity and resistive feedback by analysis and simulation. The vertical instability may be induced due to the combined effect of beam-beam interaction and vacuum impedance. Finite chromaticity and asymmetrical tunes have been proposed to suppress the vertical instability. Due to the further increase of impedance budget, we need to find more measures to mitigate the instability. The effect of resistive feedback and hourglass effect are evaluated by simulation.
- [18] arXiv:2405.13334 [pdf, ps, other]
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Title: Enhanced continuous aerosol optical depth (AOD) estimation using geostationary satellite data: focusing on nighttime AOD over East AsiaComments: 38 pages (including references and supplementary); 3 tables, 9 figures; 2 supplementary tables, 4 supplementary figuresSubjects: Atmospheric and Oceanic Physics (physics.ao-ph)
Continuous aerosol monitoring in East Asia is essential due to the massive aerosol emissions from natural and anthropogenic sources. Geostationary satellites enable continuous aerosol monitoring; however, the observation is limited to the daytime. This study proposed machine learning-based models to estimate daytime and nighttime aerosol optical depth (AOD) in East Asia using a geostationary satellite, Geo-KOMPSAT-2A (GK-2A). The input variables for the machine learning models include the brightness temperature (BT) and top-of-atmosphere (TOA) reflectance from GK-2A, meteorological and geographical data, and auxiliary variables. The two models that used different combinations of GK-2A variables were proposed and compared: the all-day BT model, which estimates AOD during both day and night using BT variables, and the daytime TOA model, which estimates AOD during the day using TOA reflectance variables as well. The estimated AODs by the models were validated with ground-based AOD data from the Aerosol Robotic Network (AERONET) by 10-fold cross-validation and hold-out validation methods. The performance of the daytime TOA model was slightly higher than the all-day BT model during the day (R2 = 0.80-0.82, root mean square error (RMSE) = 0.107-0.116 for the all-day BT model, R2 = 0.83, RMSE = 0.098 for the daytime TOA model). The SHapley Additive exPlanations (SHAP) analysis showed that total precipitable water content and seasonality contributed the most for both proposed models. BT differences and TOA reflectance variables were identified as the next most contributing variables for the all-day BT and daytime TOA models. The spatiotemporal distributions of estimated AODs from the proposed models show similar patterns compared with other AOD products. A time series comparison at a test station demonstrated that the estimated AOD of the proposed models was consistent with the AERONET AOD.
- [19] arXiv:2405.13361 [pdf, ps, other]
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Title: Mechanistic Insights into Non-Adiabatic Interband Transitions on a Semiconductor Surface Induced by Hydrogen Atom CollisionsLingjun Zhu, Qijing Zheng, Yingqi Wang, Kerstin Krüger, Alec M. Wodtke, Oliver Bünermann, Jin Zhao, Hua Guo, Bin JiangSubjects: Chemical Physics (physics.chem-ph)
To understand the recently observed mysterious non-adiabatic energy transfer for hyperthermal H atom scattering from a semiconductor surface, Ge(111)c(2*8), we present a mixed quantum-classical non-adiabatic molecular dynamics model based on time-dependent evolution of Kohn-Sham orbitals and a classical path approximation. Our results suggest that facile non-adiabatic transitions occur selectively at the rest atom site, featuring excitation of valance band electrons to the conduction band, but not at the adatom site. This drastic site specificity can be attributed to the changes of the local band structure upon energetic H collisions at different surface sites, leading to transient near-degeneracies and significant couplings between occupied and unoccupied orbitals at the rest atom, but not at the adatom. These insights shed valuable light on the collisional induced non-adiabatic dynamics at semiconductor surfaces.
- [20] arXiv:2405.13421 [pdf, ps, other]
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Title: Positivism in Newtonian Mechanics: The Ousia or a Historical Liability?Subjects: History and Philosophy of Physics (physics.hist-ph)
The positivistic assumptions of determinism and objectivism in the realm of Newtonian mechanics are questioned in this paper. While objectivism is only challenged through proposing the mildest form of subjectivism, determinism is structurally disputed by proposing that the physical reality, at least in the examples discussed, is, in essence, probabilistic and unpredictable. It is discussed that the physical reality and experimenter's identification of it could basically have inconsistent characteristics, and the study of the physical reality can therefore be conducted in ontic and epistemic levels, leading to two distinct identifications. Four scientific topics, showing two different types of indeterminacy, are introduced and briefly reviewed: chaotic systems, turbulence, fluid transport in porous media, and hydromechanics of fractures. It is proposed that determinism is only meaningful in epistemic level, the first two examples are ontically indeterministic, the last two examples are epistemically indeterministic, and more examples of indeterministic phenomena could, most likely, be found in the nature. Indeterminacy of the physical reality, it is discussed, has always been considered in engineering design processes and such effects have normally been covered through safety factors and feedback loops. By reviewing Hadamard's well-posedness criteria, Poincae's complete deterministic approach, and Leibniz's principles of sufficient reason and identity of indiscernibles, it is claimed that positivism stands on Leibniz's metaphysical assumptions, which are not necessarily in full agreement with the physical reality. A few suggestions for a path beyond positivism in Newtonian mechanics are finally provided.
- [21] arXiv:2405.13443 [pdf, ps, html, other]
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Title: High-precision, reference-free measurements of 2p $\rightarrow$ 1s transitions in boron-like sulfur and argonLouis Duval (LKB (Jussieu), INSP), Emily Lamour (INSP), Stéphane Macé (INSP), Jorge Machado (LIBPhys-UNL), Marleen Maxton (INSP), Nancy Paul (LKB (Jussieu)), Christophe Prigent (INSP), Martino Trassinelli (INSP), Paul Indelicato (LKB (Jussieu))Subjects: Atomic Physics (physics.atom-ph)
We have measured several 2p $\rightarrow$ 1s transition energies in core-excited boron-like ions of sulfur and argon. The measurements are reference-free, with an accuracy of a few parts per million. The x-rays were produced by the plasma of a an electron-cyclotron resonance ion source and were measured by a double-crystal x-ray spectrometer. The precision obtained for the measured 1s2s22p2 J -- 1s2 2s2 2p J ' lines is $\approx$4 ppm for sulfur and $\approx$2 ppm for argon. The line energies are compared to relativistic atomic structure calculations performed with the mdfgme multi-configuration Dirac-Fock code. This comparison is used for line identification and test the theoretical methods, which reach an agreement with experimental data up to 15 meV. The theoretical calculations have been extended to C+, Si9+, Cr19+ and Fe21+, which were the only B-like ions where such transitions were measured up to now.
- [22] arXiv:2405.13475 [pdf, ps, html, other]
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Title: Sensitivity and control of a 6-axis fused-silica seismometerJiri Smetana, Amit Singh Ubhi, Emilia Chick, Leonid Prokhorov, John Bryant, Artemiy Dmitriev, Alex Gill, Lari Koponen, Haixing Miao, Alan V. Cumming, Giles Hammond, Valery Frolov, Richard Mittleman, Peter Fritchel, Denis MartynovComments: 11 pages, 3 figuresSubjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)
We present a pair of seismometers capable of measurement in all six axes of rigid motion. The vacuum-compatible devices implement compact interferometric displacement sensors to surpass the sensitivity of typical electrical readout schemes. Together with the capability to subtract the sensitivity-limiting coupling of ground tilt into horizontal motion, our seismometers can widen the sensing band towards mHz frequencies. This has notable applications across a range of fields requiring access to low-frequency signals, such as seismology and climate research. We particularly highlight their potential application in gravitational-wave observatories (LIGO) for observation of intermediate-mass black holes ($\sim 1000\,M_\odot$). The sensors are based on a near-monolithic fused-silica design consisting of a fused-silica mass and fibre, showing improved stability and robustness to tilt drifts, alignment, and control compared to all-metal or mixed metal-silica designs. We demonstrate tilt sensitivity that surpasses the best commercial alternatives in a significantly reduced footprint compared to our previous iterations of these sensors.
- [23] arXiv:2405.13480 [pdf, ps, html, other]
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Title: What is a typical signalized intersection in a city? A pipeline for intersection data imputation from OpenStreetMapSubjects: Physics and Society (physics.soc-ph); Computers and Society (cs.CY)
Signalized intersections, arguably the most complicated type of traffic scenario, are essential to urban mobility systems. With recent advancements in intelligent transportation technologies, signalized intersections have great prospects for making transportation greener, safer, and faster. Several studies have been conducted focusing on intersection-level control and optimization. However, arbitrarily structured signalized intersections that are often used do not represent the ground-truth distribution, and there is no standardized way that exists to extract information about real-world signalized intersections. As the largest open-source map in the world, OpenStreetMap (OSM) has been used by many transportation researchers for a variety of studies, including intersection-level research such as adaptive traffic signal control and eco-driving. However, the quality of OSM data has been a serious concern.
In this paper, we propose a pipeline for effectively extracting information about signalized intersections from OSM and constructing a comprehensive dataset. We thoroughly discuss challenges related to this task and we propose our solution for each challenge. We also use Salt Lake City as an example to demonstrate the performance of our methods. The pipeline has been published as an open-source Python library so everyone can freely download and use it to facilitate their research. Hopefully, this paper can serve as a starting point that inspires more efforts to build a standardized and systematic data pipeline for various types of transportation problems. - [24] arXiv:2405.13519 [pdf, ps, other]
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Title: Multi-fidelity topology optimization of flow boiling heat transfer in microchannelsSubjects: Fluid Dynamics (physics.flu-dyn)
Topology optimization (TO) is a powerful method to design innovative structures with improved heat transfer performance. In the present study, a multi-fidelity TO method with a delicately defined objective function is developed for flow boiling heat transfer in microchannels. Low-fidelity TO is conducted for the reduced-order process of single-phase laminar convective heat transfer, which generates a set of structure candidates for subsequent high-fidelity evaluation of flow boiling heat transfer. To avoid the possible iteration between the low-fidelity TO and high-fidelity evaluation which leads to inefficient solution of the multi-fidelity TO, distributions of velocity, temperature and two-phase in microchannels with single-phase and/or flow boiling heat transfer are investigated and compared in detail, based on which a new objective function is delicately defined, which can be employed in the low-fidelity TO yet can stand for the performance of the high-fidelity problem. With the help of the new objective function, the efficiency of the multi-fidelity TO is significantly improved and TO structures are designed with hot spots eliminated, thermal resistance reduced and temperature uniformity improved. The present work provides a new method for TO of complicated heat and mass transfer problems. Keywords: topology optimization, flow boiling, multi-fidelity optimization, microchannels, convective heat transfer
- [25] arXiv:2405.13530 [pdf, ps, html, other]
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Title: Through energy droughts: hydropower's ability to sustain a high outputSubjects: Physics and Society (physics.soc-ph)
Previous research has raised concerns about energy droughts in renewables-based energy systems. This study explores the ability of reservoir hydropower to sustain a high output and, thereby, mitigate such energy droughts. Using detailed modelling, we estimate that Swedish hydropower can sustain 67-92% of its installed capacity for 3 weeks, with higher values possible in springtime. The variation of the sustained output, equivalent to the capacity of 3-4 Swedish nuclear reactors, under-scores the importance of understanding the potential output levels when devising strategies to counteract energy droughts. Moreover, we find that regulations imposed on the flows in river bottlenecks hinder higher sustained output levels. With the upcoming renewal of environmental permits for hydropower plants in Sweden, these findings provide valuable insights for policymakers. Furthermore, the sustained output capabilities demonstrated in this study challenge the prevalent simplified representations of hydropower in energy models, suggesting a need for more-sophisticated modelling approaches.
- [26] arXiv:2405.13539 [pdf, ps, html, other]
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Title: Turbulent Thermal Equilibration of Collisionless Magnetospheric PlasmasComments: 4 pages, 2 figures, submitted to Phys. Rev. LettSubjects: Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)
How thermal equilibrium is determined in a weakly collisional plasma is a fundamental question in plasma physics. This letter shows that the turbulence driven by the magnetic curvature and density gradient tends to equilibrate the temperature between species without collisions in a magnetospheric plasma. The classical stability analysis in terms of energetic consideration reveals the interchangeable roles of electrons and ions for destabilization depending on their temperatures. Nonlinear gyrokinetic simulations confirm that the higher-temperature destabilizing species gives free energy to heat the other species to achieve the equal temperature state.
- [27] arXiv:2405.13545 [pdf, ps, html, other]
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Title: Optimal transient growth and transition to turbulence in the MHD pipe flow subject to a transverse magnetic fieldSubjects: Fluid Dynamics (physics.flu-dyn)
We consider the influence of a transverse magnetic field on the transient growth of perturbations in a liquid-metal circular pipe flow with an electrically insulating or conducting wall. In this configuration, the mean flow profile and the amplification of perturbations are strongly affected by the applied magnetic field, leading to a rich dynamical landscape depending on its intensity. The analysis is performed for Reynolds numbers 5000 and 10 000, close to the transitional regime for moderate values of the Hartmann number, a non-dimensional parameter proportional to the applied magnetic field's intensity. Aside from a slight modification of hydrodynamic optimal perturbations at very small Hartmann numbers, we observe three other characteristic topologies of optimal perturbations depending on the intensity of the magnetic field. Their growth mechanisms differ, with the lift-up effect dominating at low Hartmann numbers and the Orr-mechanism becoming increasingly important as the magnetic field intensity is increased. In particular, we show in the intermediate regime of Hartmann numbers how transient growth occurs in two stages, with initial growth through the lift-up effect followed by a further increase of energy through the Orr-mechanism. We also conduct three-dimensional nonlinear simulations to track the time evolution of optimal perturbations, illustrating their nonlinear growth and eventual breakdown to a sustained turbulent state or the return of the system to a laminar state.
- [28] arXiv:2405.13608 [pdf, ps, html, other]
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Title: Tracking Chirality in Photoelectron Circular DichroismSubjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
Photoelectron circular dichroism (PECD) originates from the interplay between a molecule's chiral nuclear scaffold and a circularly polarized ionizing laser field. It is one of the most sensitive characterization techniques for the chirality of molecules in the gas phase. However, due to the complexity of the observable, it is generally difficult to predict and track how and when the chirality of the molecule is imprinted onto the photoelectron. Here, we present simulations of PECD for single-photon ionization in a hydrogenic single-electron model with an artificial chiral potential. This framework allows us to systematically tune the system's chirality and characterize the emergence of PECD. To this end, we propose chirality measures for potentials and wave functions to establish a quantitative connection with the resulting anisotropy in the photelectron distribution. We show that these chirality measures are suitable indicators for chirality in our model, paving the way for tracking the evolution of chirality from the nuclear scaffold to the final observable.
- [29] arXiv:2405.13626 [pdf, ps, html, other]
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Title: Harnessing Complexity: Nonlinear Optical Phenomena in L-Shapes, Nanocrescents, and Split-Ring ResonatorsSubjects: Optics (physics.optics); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We conduct systematic studies of the optical characteristics of plasmonic nanoparticles that exhibit C2v symmetry. We analyze three distinct geometric configurations: an L-type shape, a crescent, and a split-ring resonator. Optical properties are examined using the FDTD method. It is demonstrated that all three shapes exhibit two prominent plasmon bands associated with the two axes of symmetry. This is in addition to a wide range of resonances observed at high frequencies corresponding to quadrupole modes and peaks due to sharp corners. Next, to facilitate nonlinear analysis, we employ a semiclassical hydrodynamic model where the electron pressure term is explicitly accounted for. Employing this model enables us to rigorously examine the second-order angular resolved nonlinear optical response of these nanoparticles in each of the three configurations. For CW pumping, we explore properties of the SHG. Polarization and angle-resolved SHG spectra are obtained, revealing strong dependence on the nanoparticle geometry and incident wave polarization. For pulsed excitations, we discuss the phenomenon of broadband THz generation induced by the DFG. It is shown that the THz emission spectra exhibit unique features attributed to the plasmonic resonances and symmetry of the nanoparticles. The polarization of the generated THz waves is also examined, revealing interesting patterns tied to the nanoparticle geometry. To gain deeper insight, we propose a simple analytical theory that agrees very well with the numerical experiments. An expression for the far-field THz intensity is derived in terms of the incident pulse parameters and the nonlinear response tensor of the nanoparticle. The results presented in this work offer new insights into the linear and nonlinear optical properties of nanoparticles with C2v symmetry.
- [30] arXiv:2405.13627 [pdf, ps, html, other]
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Title: Fabrication and characterization of optical nanofiber tipsComments: 13 pages, five figuresSubjects: Optics (physics.optics); Applied Physics (physics.app-ph)
We demonstrate the fabrication of an optical nanofiber tip (ONFT) using a two-step chemical etching technique. This technique employs 30% and 24% hydrofluoric (HF) acid for the first and second steps, respectively. In the first step, a silica single-mode fiber with clad diameter of 125 um and core diameter of 10 um is immersed in the HF acid for 90 minutes. The resultant fiber diameter is reduced to 45 um. In the second step, such a fiber is again immersed in the HF acid for 60-80 minutes. The etching time is controlled to achieve the desired tip diameter of the ONFT. We characterize fabricated ONFTs by measuring optical transmission and surface morphology. The observed optical transmissions are more than 30% and tip diameters are less than 500 nm. The measured results readily reveal the merit of the employed technique as it is easy and cost-effective. Due to the strong confinement of the electromagnetic field at the tip of ONFTs, these structures lay versatile platforms with potential applications in sensing, photonics, and quantum optics.
- [31] arXiv:2405.13633 [pdf, ps, html, other]
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Title: 1D Photonic Band Gap Atlas, Formula Extension and Design ApplicationsComments: 17 pages, 18 figures, regular articleSubjects: Optics (physics.optics)
The design and development of new photonic devices for technological applications requires a deep understanding of the effect of structural properties on the resulting band gap size and its position. Here, we perform a theoretical study of behavior of the photonic band gap sizes, positions and percentages under variations of the parameters characterizing binary (two materials), ternary (three materials) and linear dielectric grating multilayer structures. The resulting band gap atlas show that binary systems may suffice for most applications but ternary systems may add additional flexibility in design if needed. Linear gratings show a regular pattern for all gaps studied, this regularity was able to be reproduced with only few materials involved. The position of the gaps showed a very monotonous behavior for all calculations performed. Finally, additional extensions of formulas commonly used in the design of Bragg mirrors/reflectors using binary materials were proposed with their corresponding limitations discussed. These results can be seen as a technological horizon for photonic device development.
- [32] arXiv:2405.13660 [pdf, ps, html, other]
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Title: A fixed phase tunable directional coupler based on coupling tuningSubjects: Optics (physics.optics); Quantum Physics (quant-ph)
The field of photonic integrated circuits has witnessed significant progress in recent years, with a growing demand for devices that offer high-performance reconfigurability. Due to the inability of conventional tunable directional couplers (TDCs) to maintain a fixed phase while tuning the reflectivity, Mach-Zehnder interferometers (MZIs) are employed as the primary building blocks for reflectivity tuning in constructing large-scale circuits. However, MZIs are prone to fabrication errors due to the need for perfect balanced directional couplers to achieve 0-1 reflectivity, which hinders their scalability. In this study, we introduce a design of a TDC based on coupling constant tuning in the thin film Lithium Niobate platform and present an optimized design. Our optimized TDC design enables arbitrary reflectivity tuning while ensuring a consistent phase across a wide range of operating wavelengths. Furthermore, it exhibits fewer bending sections than MZIs and is inherently resilient to fabrication errors in waveguide geometry and coupling length compared to both MZIs and conventional TDCs. Our work contributes to developing high-performance photonic integrated circuits with implications for various fields, including optical communication systems and quantum information processing.
- [33] arXiv:2405.13681 [pdf, ps, other]
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Title: Unsupervised data driven approaches to Raman imaging through a multimode optical fiberSubjects: Optics (physics.optics); Chemical Physics (physics.chem-ph)
Raman spectroscopy is a label-free, chemically specific optical technique which provides detailed information about the chemical composition and structure of the excited analyte. Because of this, there is growing research interest in miniaturizing Raman probes to reach deep regions of the body. Typically, such probes utilize multiple optical fibers to act as separate excitation/collection channels with optical filters attached to the distal facet to separate the collected signal from the background optical signal from the probe itself. Although these probes have achieved impressive diagnostic performance, their use is limited by the overall size of the probe, which is typically several hundred micrometers to millimeters. Here, we show how a wavefront shaping technique can be used to measure Raman images through a single, hair thin multimode fiber. The wavefront shaping technique transforms the tip of the fiber to a sub-cellular spatial resolution Raman microscope. The resultant Raman images were analyzed with a variety of state-of-the-art statistical techniques including PCA, t-SNE, UMAP and k-means clustering. Our data-driven approach enables us to create high quality Raman images of microclusters of pharmaceuticals through a standard silica multimode optical fiber.
- [34] arXiv:2405.13691 [pdf, ps, html, other]
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Title: Neural Networks-based Random Vortex Methods for Modelling Incompressible FlowsComments: 16 pages, 5 figuresSubjects: Fluid Dynamics (physics.flu-dyn); Numerical Analysis (math.NA); Probability (math.PR); Machine Learning (stat.ML)
In this paper we introduce a novel Neural Networks-based approach for approximating solutions to the (2D) incompressible Navier--Stokes equations. Our algorithm uses a Physics-informed Neural Network, that approximates the vorticity based on a loss function that uses a computationally efficient formulation of the Random Vortex dynamics. The neural vorticity estimator is then combined with traditional numerical PDE-solvers for the Poisson equation to compute the velocity field. The main advantage of our method compared to standard Physics-informed Neural Networks is that it strictly enforces physical properties, such as incompressibility or boundary conditions, which might otherwise be hard to guarantee with purely Neural Networks-based approaches.
- [35] arXiv:2405.13702 [pdf, ps, other]
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Title: Impurity-level induced broadband photoelectric response in wide-band semiconductor SrSnO3Comments: 5 FiguresSubjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)
Broadband spectrum detectors exhibit great promise in fields such as multispectral imaging and optical communications. Despite significant progress, challenges like materials instability, complex manufacturing process and high costs still hinder further application. Here we present a method that achieves broadband spectral detect by impurity-level in SrSnO3. We report over 200 mA/W photo-responsivity at 275 nm (ultraviolet C solar-bind) and 367 nm (ultraviolet A) and ~ 1 mA/W photo-responsivity at 532 nm and 700 nm (visible) with a voltage bias of 5V. Further transport and photoluminescence results indicate that the broadband response comes from the impurity levels and mutual interactions. Additionally, the photodetector demonstrates excellent robustness and stability under repeated tests and prolonged exposure in air. These findings show the potential of SSO photodetectors and propose a method to achieve broadband spectrum detection, creating new possibility for the development of single-phase, low-cost, simple structure and high-efficiency photodetectors.
- [36] arXiv:2405.13716 [pdf, ps, html, other]
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Title: Bose-Einstein condensation of an optical thermodynamic system into a solitonic stateComments: 23 pages, 12 figuresSubjects: Optics (physics.optics); Pattern Formation and Solitons (nlin.PS)
Recent years have seen a resurgence of interest in multimode fibers due to their intriguing physics and applications, with spatial beam self-cleaning (BSC) having received special attention. In BSC light condenses into the fundamental fiber mode at elevated intensities. Despite extensive efforts utilizing optical thermodynamics to explain such counterintuitive beam reshaping process, several challenges still remain in fully understanding underlying physics. Here we provide compelling experimental evidence that BSC in a dissipative dual-core fiber can be understood in full analogy to Bose-Einstein condensation (BEC) in dilute gases. Being ruled by the identical Gross-Pitaevskii Equation, both systems feature a Townes soliton solution, for which we find further evidence by modal decomposition of our experimental data. Specifically, we observe that efficient BSC only sets in after an initial thermalization phase, causing converge towards a Townes beam profile once a threshold intensity has been surpassed. This process is akin to a transition from classical to quantum-mechanical thermodynamics in BEC. Furthermore, our analysis also identifies dissipative processes as a crucial, yet previously unidentified component for efficient BSC in multimode fiber. This discovery paves the way for unprecedented applications of multimode-fiber based systems in ultrafast lasers, communications, and fiber-based delivery of high-power laser beams.
- [37] arXiv:2405.13723 [pdf, ps, other]
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Title: Sub-cycle modulation of light's Orbital Angular MomentumComments: 18 pages, 3 figures, and supplementary materialsSubjects: Optics (physics.optics)
The exploration of light has traditionally focused on its spatial properties, particularly its orbital angular momentum (OAM), while its temporal dynamics have remained an underexplored frontier due to the slow response times of existing modulation techniques. In this context, we introduce a method to modulate the OAM of light on a femtosecond scale by engineering a controllable space-time coupling in ultrashort pulses. By intricately linking azimuthal position with time, we implement a static, azimuthally varying wavefront transformation to dynamically alter the spatial distribution of light in a fixed transverse plane. Our experiments demonstrate self-torqued wave packets that exhibit spiraling motions and rapid temporal OAM changes down to a few femtoseconds. We further extend this concept to generate wave packets that angularly self-accelerate. We reveal that these wave packets dynamically adjust their OAM by redistributing their energy density across their spectral bandwidth, all without the influence of external forces. Owing to the unique properties of self-torque and angular acceleration, these time-varying OAM beams offer an accessible avenue for exploring light at fundamental time scales, with far-reaching implications for ultrafast spectroscopy, nano- and micro-structure manipulation, condensed matter physics, and other related areas.
- [38] arXiv:2405.13742 [pdf, ps, html, other]
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Title: Generalized Einstein Relations between Absorption and Emission Spectra at Thermodynamic EquilibriumComments: 15 pages, 4 figuresSubjects: Chemical Physics (physics.chem-ph); Atomic Physics (physics.atom-ph)
We present Einstein coefficient spectra and a detailed-balance derivation of generalized Einstein relations between them that is based on the connection between spontaneous and stimulated emission. If two broadened levels or bands overlap in energy, transitions between them need not be purely absorptive or emissive. Consequently, spontaneous emission can occur in both transition directions, and four Einstein coefficient spectra replace the three Einstein coefficients for a line. At equilibrium, the four different spectra obey five pairwise relationships and one lineshape generates all four. These relationships are independent of molecular quantum statistics and predict the Stokes' shift between forward and reverse transitions required by equilibrium with blackbody radiation. For Boltzmann statistics, the relative strengths of forward and reverse transitions depend on the formal chemical potential difference between the initial and final bands, which becomes the standard chemical potential difference for ideal solutes. The formal chemical potential of a band replaces both the energy and degeneracy of a quantum level. Like the energies of quantum levels, the formal chemical potentials of bands obey the Rydberg-Ritz combination principle. Each stimulated Einstein coefficient spectrum gives a frequency-dependent transition cross section. Transition cross sections obey causality and a detailed-balance condition with spontaneous emission, but do not directly obey generalized Einstein relations. Even with an energetic width much less than the photon energy, an absorptive forward transition with an energetic width much greater than the thermal energy can have such an extreme Stokes' shift that its reverse transition cross section becomes predominantly absorptive rather than emissive.
- [39] arXiv:2405.13776 [pdf, ps, other]
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Title: Ballistic Energy Transport via Long Alkyl Chains: A New Initiation MechanismSithara U. Nawagamuwage, Elliot S. Williams, Md Muhaiminul Islam, Igor V. Parshin, Alexander L. Burin, Nathalie Busschaert, Igor V. RubtsovComments: Submitted to JPCSubjects: Chemical Physics (physics.chem-ph); Optics (physics.optics)
In an effort to increase the speed and efficiency of ballistic energy transport via oligomeric chains, we performed measurements of the transport in compounds featuring long alkyl chains of up to 37 methylene units. Compounds of the N3-(CH2)n-COOMe type (denoted as aznME) were synthesized with n = 5, 10, 15, 19, 28, 37 and studied using relaxation-assisted two-dimensional infrared spectroscopy. The speed of the ballistic transport, initiated by the N3 tag excitation, increased ca. 3-fold for the longer chains (n = 19-37) compared to the shorter chains, from 14.7 Å/ps to 48 Å/ps, in line with an earlier prediction (Nawagamuwage et al. 2021, J. Phys. Chem. B, 125, 7546). Modeling, based on solving numerically the Liouville equation, was capable of reproducing the experimental data only if three wavepackets are included, involving CH2 twisting (Tw), wagging (W), and rocking (Ro) chain bands. The approaches for designing molecular systems featuring higher speed and efficiency of energy transport are discussed.
- [40] arXiv:2405.13790 [pdf, ps, other]
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Title: Bent Crystal Design and Characterization for High-Energy Physics ExperimentsMarco Romagnoni, Vincenzo Guidi, Laura Bandiera, Davide De Salvador, Andrea Mazzolari, Francesco Sgarbossa, Mattia Soldani, Alexei Sytov, Melissa TamisariJournal-ref: Crystals, 12(9), 1263 (2022)Subjects: Accelerator Physics (physics.acc-ph); High Energy Physics - Experiment (hep-ex)
Bent crystal are widely used as optics for X-rays, but via the phenomenon of planar channeling they may act as waveguide for relativistic charged particles beam as well, outperforming some of the traditional technologies currently employed. A physical description of the phenomenon and the resulting potential for applications in a particle accelerator is reported. The elastic properties of the anisotropic crystal lattice medium are discussed, introducing different types of curvature which can enable a wide array of bending schemes optimized for each different case features. The technological development of machining strategy and bending solutions useful for the fabrication of crystals suitable in high energy particle manipulations are described. As well as the high precision characterization processes developed in order to satisfy the strict requirements for installation in an accelerator. Finally, the characterization of channeling phenomenon in bent crystal is described, pointing out several experimental setups suitable to comply each specific case constrains.
- [41] arXiv:2405.13814 [pdf, ps, html, other]
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Title: Extension of the SpK Atomic Physics Code to Generate Global Equation of State DataAdam R. Fraser (1 and 2), A. J. Crilly (2), N. P. L. Niasse (1 and 2), D. A. Chapman (1), J. D. Pecover (1 and 2), S. J. O'Neill (2), J. P. Chittenden (2) ((1) First Light Fusion Ltd., (2) Imperial College London)Comments: 23 pages (14 of content), 13 figures, 2 tables, submitted for inclusion in the IFSA 2023 conference proceedingsSubjects: Plasma Physics (physics.plasm-ph); Materials Science (cond-mat.mtrl-sci); Statistical Mechanics (cond-mat.stat-mech); Atomic Physics (physics.atom-ph); Computational Physics (physics.comp-ph)
Global microphysics models are required for the modelling of high-energy-density physics (HEDP) experiments, the improvement of which are critical to the path to inertial fusion energy. This work presents further developments to the atomic and microphysics code, SpK, part of the numerical modelling suite of Imperial College London and First Light Fusion. We extend the capabilities of SpK to allow the calculation of the equation of state (EoS). The detailed configuration accounting calculations are interpolated into finite-temperature Thomas-Fermi calculations at high coupling to form the electronic component of the model. The Cowan model provides the ionic contribution, modified to approximate the physics of diatomic molecular dissociation. By utilising bonding corrections and performing a Maxwell construction, SpK captures the EoS from states ranging from the zero-pressure solid, through the liquid-vapour coexistence region and into plasma states. This global approach offers the benefit of capturing electronic shell structure over large regions of parameter space, building highly-resolved tables in minutes on a simple desktop. We present shock Hugoniot and off-Hugoniot calculations for a number of materials, comparing SpK to other models and experimental data. We also apply EoS and opacity data generated by SpK in integrated simulations of indirectly-driven capsule implosions, highlighting physical sensitivities to the choice of EoS models.
- [42] arXiv:2405.13850 [pdf, ps, html, other]
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Title: Enhancing lattice kinetic schemes for fluid dynamics with Lattice-Equivariant Neural NetworksSubjects: Computational Physics (physics.comp-ph); Machine Learning (cs.LG); Fluid Dynamics (physics.flu-dyn)
We present a new class of equivariant neural networks, hereby dubbed Lattice-Equivariant Neural Networks (LENNs), designed to satisfy local symmetries of a lattice structure. Our approach develops within a recently introduced framework aimed at learning neural network-based surrogate models Lattice Boltzmann collision operators. Whenever neural networks are employed to model physical systems, respecting symmetries and equivariance properties has been shown to be key for accuracy, numerical stability, and performance.
Here, hinging on ideas from group representation theory, we define trainable layers whose algebraic structure is equivariant with respect to the symmetries of the lattice cell. Our method naturally allows for efficient implementations, both in terms of memory usage and computational costs, supporting scalable training/testing for lattices in two spatial dimensions and higher, as the size of symmetry group grows. We validate and test our approach considering 2D and 3D flowing dynamics, both in laminar and turbulent regimes. We compare with group averaged-based symmetric networks and with plain, non-symmetric, networks, showing how our approach unlocks the (a-posteriori) accuracy and training stability of the former models, and the train/inference speed of the latter networks (LENNs are about one order of magnitude faster than group-averaged networks in 3D). Our work opens towards practical utilization of machine learning-augmented Lattice Boltzmann CFD in real-world simulations. - [43] arXiv:2405.13971 [pdf, ps, html, other]
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Title: Cellular-resolution X-ray microtomography of an entire mouse brainMattia Humbel, Christine Tanner, Marta Girona Alarcón, Georg Schulz, Timm Weitkamp, Mario Scheel, Vartan Kurtcuoglu, Bert Müller, Griffin RodgersComments: 21 pages, 9 figures, submitted to journalSubjects: Medical Physics (physics.med-ph)
Purpose: Histology is the gold standard for sub-cellular visualization of the mouse brain. It offers excellent in-plane resolution, but a comparably low out-of-plane resolution due to physical sectioning. X-ray microtomography does not require this trade-off. Tomographic imaging of the entire mouse brain with isotropic cellular resolution produces datasets of multiple terabytes in size. These data must be processed and made accessible to domain experts who may have only limited image processing knowledge.
Approach: Extended-field X-ray microtomography covering an entire mouse brain was performed. The 4,495 projections from 8 $\times$ 8 offset acquisitions were stitched to reconstruct a volume of 15,000$^3$ voxels. The microtomography volume was non-rigidly registered to the Allen Mouse Brain Common Coordinate Framework v3 based on a combination of image intensity and landmark pairs.
Results: We present a 3.3 teravoxel dataset covering a full mouse brain with 0.65 $\mu$m voxel size. The data were blockwise transformed to a common coordinate system, then stored in a public repository with a hierarchical format for navigation and overlay with anatomical annotations in online viewers such as Neuroglancer or siibra-explorer.
Conclusions: This study demonstrates X-ray imaging and data processing for a full mouse brain, augmenting current atlases by improving resolution in the third dimension by an order of magnitude. The data are publicly available and easily accessible for domain experts via browser-based viewers. - [44] arXiv:2405.13988 [pdf, ps, html, other]
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Title: Melancholia States of the Atlantic Meridional Overturning CirculationSubjects: Atmospheric and Oceanic Physics (physics.ao-ph); Chaotic Dynamics (nlin.CD)
The Atlantic Meridional Overturning Circulation (AMOC) is a much studied component of the climate system, because its suspected multistability leads to tipping behaviour with large regional and global climatic impacts. In this paper we investigate the global stability properties of the system using an ocean general circulation model. We construct an unstable AMOC state, i.e., an unstable solution of the flow that resides between the stable regimes of a vigorous and collapsed AMOC. Such a solution, also known as a Melancholia or edge state, is a dynamical saddle embedded in the boundary separating the competing basins of attraction. It is physically relevant since it lies on the most probable path of a noise-induced transition between the two stable regimes, and because tipping occurs when one of the attractors and the Melancholia state collide. Its properties may thus give hints towards physical mechanisms and predictability of the critical transition. We find that while the AMOC Melancholia state as viewed from its upper ocean properties lies between the vigorous and collapsed regimes, it is characterized by an Atlantic deep ocean that is fresher and colder compared to both stable regimes. The Melancholia state has higher dynamic enthalpy than either stable state, representing a state of higher potential energy that is in good agreement with the dynamical landscape view on metastability.
- [45] arXiv:2405.13991 [pdf, ps, html, other]
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Title: Flow and Heat Transfer in a Rotating Disc Cavity With Axial Throughflow at High Speed ConditionsSubjects: Fluid Dynamics (physics.flu-dyn)
Flow and heat transfer in a compressor rotating disc cavity with axial throughflow is investigated using wall-modelled large-eddy simulations (WMLES). These are compared to measurements from recently published experiments and used to investigate high Reynolds number effects. The simulations use an open-source CFD solver with high parallel efficiency and employ the Boussinesq approximation for centrifugal buoyancy. Kinetic energy effects (characterised by Eckert number) are accounted for by scaling the thermal boundary conditions from static temperature to rotary stagnation temperature. The WMLES shows very encouraging agreement with experiments up to the highest Reynolds number tested, $Re_\phi=3.0\times10^6$. A further simulation at $Re_\phi=10^7$ extends the investigation to an operating condition more representative of aero engine high pressure compressors. The results support the scaling of shroud heat transfer found at lower $Re_\phi$, but disc heat transfer is higher than expected from a simple extrapolation of lower $Re_\phi$ results. This is associated with transition to turbulence in the disc Ekman layers and is consistent with the boundary layer Reynolds numbers at this condition. The introduction of swirl in the axial throughflow, as may occur at engine conditions, could reduce the boundary layer Reynolds numbers and delay the transition.
- [46] arXiv:2405.14035 [pdf, ps, other]
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Title: Tough Cortical Bone-Inspired Tubular Architected Cement-based MaterialComments: 51 pages, 16 figuresSubjects: Applied Physics (physics.app-ph)
Cortical bone is a tough biological material composed of tube-like osteons embedded in the organic matrix surrounded by weak interfaces known as cement lines. The cement lines provide a microstructurally preferable crack path, hence triggering in-plane crack deflection around osteons due to cement line-crack interaction. Here, inspired by this toughening mechanism and facilitated by a hybrid (3D-printing/casting) process, we engineer architected tubular cement-based materials with a new stepwise cracking toughening mechanism, that enabled a non-brittle fracture. Using experimental and theoretical approaches, we demonstrate the underlying competition between tube size and shape on the stress intensity factor from which engineering stepwise cracking can emerge. Two competing mechanisms, both positively and negatively affected by the growing tube size, arise to significantly enhance the overall fracture toughness by up to 5.6-fold compared to the monolithic brittle counterpart without sacrificing the specific strength. This is enabled by crack-tube interaction and engineering the tube size and shape, which leads to stepwise cracking and promotes rising R-curves. Disorder curves are proposed for the first time to quantitatively characterize the degree of disorder for describing the representation of architected arrangement of materials (using statistical mechanics parameters) in lieu of otherwise inadequate periodicity classification.
- [47] arXiv:2405.14080 [pdf, ps, html, other]
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Title: Fano line shape metamorphosis in resonant two-photon ionizationComments: 5 pages, 3 figuresSubjects: Atomic Physics (physics.atom-ph)
Two-photon atomic ionization driven by time-locked XUV and IR pulses allows to study dynamics of Fano resonances in time and energy domains. Different time evolution of the two interfering pathways leading to a Fano resonance can be exploited to turn the Fano profile of the two-photon XUV/IR ionization into a symmetric Gaussian once the directly ejected photoelectron leaves the parent ion and cannot any longer absorb an IR photon. This line shape transformation allows for the direct determination of the resonant lifetime from the spectroscopic measurements without need for an extremely fine energy resolution. Ubiquitous nature of Fano resonances makes this determination a universal tool in diverse quantum systems ranging from nuclei to nano-fabricated solids.
- [48] arXiv:2405.14081 [pdf, ps, html, other]
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Title: Laboratory-scale Perpendicular Collisionless Shock Generation and Ion Acceleration in Magnetized Head-on Colliding PlasmasSubjects: Plasma Physics (physics.plasm-ph)
Magnetized collisionless shocks drive particle acceleration broadly in space and astrophysics. We perform the first large-scale particle-in-cell simulations with realistic laboratory parameters (density, temperature, and velocity) to investigate the magnetized shock in head-on colliding plasmas with an applied magnetic field of tens of Tesla. It is shown that a perpendicular collisionless shock is formed with about fourfold density jump when two pre-magnetized flows collide. This shock is also characterized by rapid increase of neutron yield, triggered by the beam-beam nuclear reactions between injected deuterons and ones reflected by the shock. Distinct from the shocks arising from the interaction of injected flows with a magnetized background, the self-generated magnetic field in this colliding plasmas experiences a significant amplification due to the increasing diamagnetic current, approximately 30 times of upstream magnetic field. Moreover, we find that ions, regardless of whether they pass through or are reflected by the shock, can gain energy by the shock surfing acceleration, generating a power-law energy spectrum. In addition, we also demonstrate that the shock mediated only by filamentation instability cannot be generated under the prevailing unmagnetized experimental parameters. These results provide a direct connection of astrophysical field amplification to the magnetized shock formation and nonthermal ion generation.
- [49] arXiv:2405.14095 [pdf, ps, html, other]
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Title: Abrupt X-to-O-wave structural field transition in presence of anomalous dispersionSubjects: Optics (physics.optics)
All linear, propagation-invariant, paraxial pulsed beams are spatiotemporally X-shaped (conical waves) in absence of group-velocity dispersion (GVD), or in presence of normal GVD. It is known, however, that such conical waves become O-shaped in presence of anomalous GVD, resulting in a field profile that is circularly symmetric in space and time. To date, experiments generating conical waves in which the wavelength of a high-energy pump laser is tuned across the zero-dispersion wavelength of a nonlinear medium have not revealed the expected X-to-O-wave structural field transition. We report here unambiguous observation of a fixed-wavelength X-to-O-wave structural field transition occurring in linear dispersion-free wave packets in the anomalous GVD regime -- without needing to change the sign or magnitude of the GVD. Instead, by tuning the group velocity of a space-time wave packet (STWP) across a threshold value that we call the `escape velocity', we observe an abrupt transition in the STWP from an O-shaped to an X-shaped spatiotemporal profile. This transition is associated with an abrupt change in the associated spatiotemporal spectrum of the STWP: from closed elliptical spatiotemporal spectra below the escape velocity to open hyperbolic spectra above it. These results may furnish new opportunities for engineering the phase-matching conditions in nonlinear and quantum optics.
- [50] arXiv:2405.14100 [pdf, ps, other]
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Title: Water Management Considerations for a Self-Sustaining MoonbaseComments: 36 pages, 12 Figues, 3 TablesSubjects: Physics and Society (physics.soc-ph); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Popular Physics (physics.pop-ph)
The most pragmatic first step in the all-but-inevitable 3rd-millennium Völkerwanderung of humanity throughout the Solar System is the establishment of a permanent human presence on the Moon. This research examines: 1. the human, agricultural, and technical water needs of a 100-person, 500 m x 100 m x 6 m self-sustaining lunar colony; 2. choosing a strategic location for the moonbase; 3. a heat drill model by which the needed lunar water ice could be sublimated; and 4. the robust water treatment and recovery infrastructure and water management personnel that would be needed for a self-sustaining moonbase.
- [51] arXiv:2405.14102 [pdf, ps, html, other]
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Title: Detailed synthesis and characterization of space-time light sheetsSubjects: Optics (physics.optics)
Space-time wave packets (STWPs) are a new class of pulsed optical beams with many unique and intriguing attributes, including propagation invariance and tunable group velocity in linear optical media. STWPs are a form of spatiotemporally structured light, so their synthesis poses challenges that are not shared by conventional monochromatic structured light fields. We present here a detailed description of the synthesis of STWPs that are localized along one transverse dimension and uniform along the other; i.e., space-time light sheets. We also describe the main characterization schemes needed for benchmarking the unique properties of space-time light sheets.
- [52] arXiv:2405.14155 [pdf, ps, other]
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Title: Room-temperature waveguide-integrated photodetector using bolometric effect for mid-infrared spectroscopy applicationsJoonsup Shim, Jinha Lim, Inki Kim, Jaeyong Jeong, Bong Ho Kim, Seong Kwang Kim, Dae-Myeong Geum, SangHyeon KimComments: 6 figures for the main manuscript and 14 figures for the supplementary informationSubjects: Optics (physics.optics); Applied Physics (physics.app-ph)
Waveguide-integrated mid-infrared (MIR) photodetectors are pivotal components for developing molecular spectroscopy applications, leveraging mature photonic integrated circuit (PIC) technologies. Despite various strategies, critical challenges still remain in achieving broadband photoresponse, cooling-free operation, and large-scale complementary-metal-oxide-semiconductor (CMOS)-compatible manufacturability. To leap beyond these limitations, the bolometric effect - a thermal detection mechanism - is introduced into the waveguide platform. More importantly, we pursue a free-carrier absorption (FCA) process in germanium (Ge) to create an efficient light-absorbing medium, providing a pragmatic solution for full coverage of the MIR spectrum without incorporating exotic materials into CMOS. Here, we present an uncooled waveguide-integrated photodetector based on a Ge-on-insulator (Ge-OI) PIC architecture, exploiting the bolometric effect combined with FCA. Notably, our device exhibits a broadband responsivity of ~12 mA/W across 4030-4360 nm (and potentially beyond), challenging the state of the art, while achieving a noise-equivalent power of 3.4x10^-9 W/Hz^0.5 at 4180 nm. We further demonstrate label-free sensing of carbon dioxide using our integrated photodetector and sensing waveguide on a single chip. This approach to room-temperature waveguide-integrated MIR photodetection, harnessing bolometry with FCA in Ge, not only facilitates the realization of fully integrated lab-on-a-chip systems with wavelength flexibility but also provides a blueprint for MIR PICs with CMOS-foundry-compatibility.
- [53] arXiv:2405.14187 [pdf, ps, other]
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Title: Bifunctional Noble Metal-free Ternary Chalcogenide Electrocatalysts for Overall Water SplittingShantanu Singh, Ahamed Irshad, Germany Diaz De la Cruz, Boyang Zhao, Billal Zayat, Qiaowan Chang, Sri Narayan, Jayakanth RavichandranSubjects: Chemical Physics (physics.chem-ph); Materials Science (cond-mat.mtrl-sci)
Hydrogen has been identified as a clean, zero carbon, sustainable, and promising energy source for the future, and electrochemical water splitting for hydrogen production is an emission-free, efficient energy conversion technology. A major limitation of this approach is the unavailability of efficient, abundant, inexpensive catalysts, which prompts the need for new catalytic materials. Here, we report the synthesis and electrocatalytic properties of a novel transition metal-based ternary chalcogenide family, LaMS$_3$ (M = Mn, Fe, Co, Ni). Powder X-ray diffraction confirms the phase purity of these materials, while composition analysis using energy dispersive spectroscopy (EDS) confirms the presence of the stoichiometric ratio of elements in these compounds. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) were used to study the chemical states on the surface and in bulk, respectively. These materials exhibit bifunctional catalytic activity towards the two half-reactions of the water-splitting process, with LaNiS$_3$ being the most active material for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The LaMS$_3$ compounds show long-term stability with negligible change in the overpotential at a constant current density of 10 mA cm$^{-2}$ over 18 hours of measurements. As compared to the corresponding ternary oxides, the LaMS$_3$ materials exhibit higher activity and significantly lower Tafel slopes. The ability to catalyze both half-reactions of water electrolysis makes these materials promising candidates for bifunctional catalysts and presents a new avenue to search for high-efficiency electrocatalysts for water splitting.
- [54] arXiv:2405.14202 [pdf, ps, other]
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Title: Giant Acoustic Geometric Spin and Orbital Hall EffectSubjects: Classical Physics (physics.class-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Acoustic waves in fluid with spin-0 nature have been long believed not to support spin Hall effect and strong orbital Hall effect that enables experimental observation. Here we report the first theoretical explication and experimental demonstration of giant acoustic geometric spin and orbital Hall effect characterized by a large transverse shift. We reveal that this effect occurs when a vortex beam is observed from a tilted reference frame free of wave-interface interactions or gradient-index media needed for observing conventional ones, and can be amplified by simply binding the beam tightly. Thanks to this mechanism, large transverse shifts proportional to angular momentum are observed in a compact system. Our work provides deeper insights into the physics of angular momentum of classic waves.
- [55] arXiv:2405.14204 [pdf, ps, html, other]
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Title: Multi-instrument analysis of L-band amplitude scintillation observed over the Eastern Arabian PeninsulaSubjects: Atmospheric and Oceanic Physics (physics.ao-ph); Signal Processing (eess.SP); Space Physics (physics.space-ph)
This study investigates the spatial and temporal characteristics of L1 amplitude scintillation-causing ionospheric irregularities over the Eastern Arabian Peninsula during the ascending phase of solar cycle 25 (years 2020--2023). The temporal occurrences of weak and strong scintillation were separated by sunset, with weak scintillation observed predominantly pre-sunset during the winter solstice and strong scintillation observed mainly post-sunset during the autumnal equinox. Strong scintillation was much more pronounced in 2023 compared to the other three years, indicating a strong influence of solar activity. Spatially, weak-scintillation-causing irregularities exhibited a wide distribution in azimuth and elevation, while strong-scintillation-causing irregularities were concentrated southwards. The combined analysis of S4 and rate of total electron content index (ROTI) suggested that small-scale ionospheric irregularities were present in both pre- and post-sunset periods, while large-scale irregularities were only seen during the post-sunset period. Furthermore, the presence of southward traveling ionospheric disturbances (TIDs) during the 2023 autumnal equinox was confirmed with the total electron content anomaly ($\Delta\text{TEC}$), while the Ionospheric Bubble Index (IBI) provided by the Swarm mission was unable to confirm the presence of equatorial plasma bubbles during the same period. Observations from the FORMOSAT-7/COSMIC-2 mission indicated that strong-scintillation-causing irregularities were more prevalent under the F2-layer peak, while the weak-scintillation-causing irregularities were mostly observed at the E-layer, F2-layer, and above the F2-layer.
- [56] arXiv:2405.14240 [pdf, ps, other]
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Title: Stimulated Raman-induced Beam FocusingSubjects: Optics (physics.optics)
Stimulated Raman scattering, employing a pump and a Stokes beam, exhibits itself through both the Raman loss observed in the pump beam and the Raman gain in the Stokes beam. This phenomenon finds application in spectroscopy for chemical analyses and microscopy for label-free bioimaging studies. Recent efforts have been made to implement super-resolution Raman microscopy using a doughnut-shaped pump, Stokes, or depletion beam. In this study, it is shown that the amplitude and phase of the pump or Stokes beam undergo significant modulation through the stimulated Raman process when they are configured as one of the higher-order Laguerre-Gauss modes, achieved using appropriate spiral phase plates or spatial light modulators. The resulting intensity distributions of the pump and Stokes beams are determined by a superposition of multiple Laguerre-Gauss modes that are coupled through nonlinear Raman gain and loss processes. Calculation results are used to elucidate the limitations associated with super-resolution coherent Raman imaging with a toroidal pump or Stokes beam. This stands in contrast with the stimulated emission depletion fluorescence microscopy technique, which lacks a fundamental limit in the spatial resolution enhancement.
- [57] arXiv:2405.14258 [pdf, ps, html, other]
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Title: Target Field Design of Surface Permanent MagnetsComments: 12 pages, 10 figuresSubjects: Applied Physics (physics.app-ph)
We present a target field approach to analytically design magnetic fields using permanent magnets. We assume that their magnetisation is bound to a two-dimensional surface and is composed of a complete basis of surface modes. By posing the Poisson's equation relating the magnetic scalar potential to the magnetisation using Green's functions, we derive simple integrals which determine the magnetic field generated by each mode. This approach is demonstrated by deriving the governing integrals for optimising axial magnetisation on cylindrical and circular-planar surfaces. We approximate the governing integrals numerically and implement them into a regularised least-squares optimisation routine to design permanent magnets that generate uniform axial and transverse target magnetic fields. The resulting uniform axial magnetic field profiles demonstrate more than a tenfold increase in uniformity across equivalent target regions compared to the field generated by an optimally separated axially magnetised pair of rings, as validated using finite element method simulations. We use a simple example to examine how two-dimensional surface magnetisation profiles can be emulated using thin three-dimensional volumes and determine how many discrete intervals are required to accurately approximate a continuously-varying surface pattern. Magnets designed using our approach may enable higher quality bias fields for electric machines, nuclear fusion, fundamental physics, magnetic trapping, and beyond.
- [58] arXiv:2405.14263 [pdf, ps, html, other]
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Title: Optimizing Four-Wave Mixing in Rydberg Atoms for Microwave-Optical ConversionSubjects: Atomic Physics (physics.atom-ph)
We perform a numerical and analytical investigation of microwave-to-optical conversion based on four-wave mixing in Rydberg atoms. Our work demonstrates that both all-resonant and off-resonant frequency-mixing configurations achieve near-unit photon conversion efficiencies. We review the conditions that can lead to the presence of two possible dark states. We find that for both configurations, one of the dark states can be detrimental at high microwave powers, and show that an additional limitation to all-resonant frequency mixing is microwave-induced fluorescence. Finally, we confirm that the off-resonant configuration is more appropriate as it allows for efficient photon conversion on a wider range of input microwave intensities with reduced total power of the auxiliary fields.
- [59] arXiv:2405.14281 [pdf, ps, other]
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Title: A frequency shift compensation method for light shift and vapor-cell temperature shift in atomic clocksComments: 12 pages, 8 figuresSubjects: Atomic Physics (physics.atom-ph); Optics (physics.optics)
Light shift and vapor-cell temperature shift are the two most significant factors dominating the long-term instability of compact atomic clocks. Due to the different physical mechanisms, there is not yet a solution that can effectively suppress the frequency shifts induced by these two effects. Here, we propose a 'resonance-offset' locking approach that compensates for the two physical frequency shifts. In this approach, the additional offset locking shift can effectively counteract the atomic resonance shifts arising from changes in vapor-cell temperature and light power, reducing the net impact on the clock's frequency to nearly zero. We have demonstrated this strategy on the 778 nm Rubidium two-photon optical frequency standard, successfully compensating for light shift and cell-temperature shift, respectively. This general method is particularly appealing for compact vapor-cell microwave and optical atomic clocks designed for the excellent stability rather than accuracy.
- [60] arXiv:2405.14315 [pdf, ps, html, other]
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Title: qtOCT: quantitative transmission optical coherence tomographyComments: 9 pages, 5 figuresSubjects: Optics (physics.optics)
Transmission optical coherence tomography (OCT) enables analysis of biological specimens in vitro through detection of forward scattered light. Up to now, transmission OCT was considered as a technique that cannot directly retrieve quantitative phase and is thus a qualitative method. In this paper, we present qtOCT, a novel quantitative transmission optical coherence tomography method. Unlike existing approaches, qtOCT allows for a direct, easy, fast and rigorous retrieval of 2D integrated phase information from transmission full-field swept-source OCT measurements. Our method is based on coherence gating and allows user-defined temporal measurement range selection, making it potentially suitable for analyzing multiple-scattering samples. We demonstrate high consistency between qtOCT and digital holographic microscopy phase images. This approach enhances transmission OCT capabilities, positioning it as a viable alternative to quantitative phase imaging techniques.
- [61] arXiv:2405.14317 [pdf, ps, html, other]
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Title: Compressible turbulent convection: The role of temperature-dependent thermal conductivity and dynamic viscositySubjects: Fluid Dynamics (physics.flu-dyn); Solar and Stellar Astrophysics (astro-ph.SR)
The impact of variable material properties, such as temperature-dependent thermal conductivity and dynamical viscosity, on the dynamics of a fully compressible turbulent convection flow beyond the anelastic limit are studied in the present work by two series of three-dimensional direct numerical simulations in a layer of aspect ratio 4 with periodic boundary conditions in both horizontal directions. One simulation series is for a weakly stratified adiabatic background, one for a strongly stratified one. The Rayleigh number is $10^5$ and the Prandtl number is 0.7 throughout this study. The temperature dependence of material parameters is imposed as a power law with an exponent $\beta$. It generates a superadiabaticity $\varepsilon(z)$ that varies across the convection layer. Central statistical quantities of the flow, such as the mean superadiabatic temperature, temperature and density fluctuations, or turbulent Mach numbers are compared in the form of horizontal plane-time averaged profiles. It is found that the additional material parameter dependence causes systematic quantitative changes of all these quantities, but no qualitative ones. A growing temperature power law exponent $\beta$ also enhances the turbulent momentum transfer in the weak stratification case by 40\%, it reduces the turbulent heat transfer by up to 50\% in the strong stratification case.
- [62] arXiv:2405.14328 [pdf, ps, html, other]
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Title: Simultaneous measurement of refraction and absorption with an integrated near-infrared Mach-Zehnder interferometerAntonia Torres-Cubillo, Alejandro Sánchez-Postigo, Jana Jágerská, J. Gonzalo Wangüemert-Pérez, Robert HalirJournal-ref: Optics & Laser Technology 177 (2024) 111154Subjects: Optics (physics.optics); Applied Physics (physics.app-ph)
Most integrated evanescent-field photonic sensors measure changes in either the real part or the imaginary part of the complex refractive index of the sample, i.e., refraction or absorption. Here we propose and experimentally demonstrate a near-infrared sensor based on a silicon nitride Mach-Zehnder interferometer which provides a direct measurement of the complex refractive index. Our architecture exhibits a high sensitivity, achieving limits of detection below $2\cdot 10^{-6}\,\mathrm{RIU}$ for both the real and imaginary parts of the refractive index. We furthermore show that our sensor can be employed as an integrated dispersion spectrometer.
- [63] arXiv:2405.14344 [pdf, ps, html, other]
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Title: Local precursors to anomalous dissipation in Navier-Stokes turbulence: Burgers vortex-type models and simulation analysisSubjects: Fluid Dynamics (physics.flu-dyn)
Anomalous dissipation is a dissipation mechanism of kinetic energy which is established by a sufficiently spatially rough velocity field. It implies that the rescaled mean kinetic energy dissipation rate becomes constant with respect to Reynolds number ${\rm Re}$, the dimensionless parameter that characterizes the strength of turbulence, given that ${\rm Re}\gg 1$. The present study aims at bridging this statistical behavior of high-Reynolds-number turbulence to specific structural building blocks of fluid turbulence -- local vortex stretching configurations which take in the simplest case the form of Burgers' classical vortex stretching model from 1948. We discuss the anomalous dissipation in the framework of Duchon and Robert for this analytical solution of the Navier-Stokes equations, apply the same analysis subsequently to a generalized model of randomly oriented Burgers vortices by Kambe and Hatakeyama, and analyse finally direct numerical simulation data of three-dimensional homogeneous, isotropic box turbulence in this respect. We identify local high-vorticity events in fully developed Navier-Stokes turbulence that approximate the analytical models of strong vortex stretching well. They also correspond to precursors of enhanced anomalous dissipation.
- [64] arXiv:2405.14368 [pdf, ps, other]
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Title: Ferri-ionic Coupling in CuInP$_2$S$_6$ Nanoflakes: Polarization States and Controllable Negative CapacitanceAnna N. Morozovska, Sergei V. Kalinin, Eugene. A. Eliseev, Svitlana Kopyl, Yulian Vysochanskii, Dean R. EvansComments: 36 pages, including 6 figures and AppendixSubjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)
We consider nanoflakes of van der Waals ferrielectric CuInP$_2$S$_6$ covered by an ionic surface charge and reveal the appearance of polar states with relatively high polarization ~5 microC/cm$^2$ and stored free charge ~10 microC/cm$%2$, which can mimic "mid-gap" states related with a surface field-induced transfer of Cu and/or In ions in the van der Waals gap. The change in the ionic screening degree and mismatch strains induce a broad range of the transitions between paraelectric phase, antiferroelectric, ferrielectric, and ferri-ionic states in CuInP$_2$S$_6$ nanoflakes. The states' stability and/or metastability is determined by the minimum of the system free energy consisting of electrostatic energy, elastic energy, and a Landau-type four-well potential of the ferrielectric dipole polarization. The possibility to govern the transitions by strain and ionic screening can be useful for controlling the tunneling barrier in thin film devices based on CuInP$_2$S$_6$ nanoflakes. Also, we predict that the CuInP$_2$S$_6$ nanoflakes reveal features of the controllable negative capacitance effect, which make them attractive for advanced electronic devices, such as nano-capacitors and gate oxide nanomaterials with reduced heat dissipation.
- [65] arXiv:2405.14375 [pdf, ps, html, other]
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Title: Generation of mega-gauss axial and azimuthal magnetic fields in a solid plasma by ultrahigh intensity, circularly polarised femtosecond laser pulsesAnandam Choudhary, Laxman Prasad Goswami, C. Aparajit, Amit D. Lad, Ameya Parab, Yash M. Ved, Amita Das, G. Ravindra KumarComments: 9 pages, 10 figuresSubjects: Plasma Physics (physics.plasm-ph)
The interaction of intense linearly polarized femtosecond laser pulses with solids is known to generate azimuthal magnetic fields, while circularly polarized light has been shown to create axial fields. We demonstrate through experiments and particle-in-cell simulations that circularly polarized light can generate both axial and azimuthal fields of comparable magnitude in a plasma created in a solid. Angular distributions of the generated fast electrons at target front and rear show significant differences between the results for the two polarization states, with circular polarization enforcing more axial confinement. The measurement of the spatial distribution of both types of magnetic fields captures their turbulent evolution.
- [66] arXiv:2405.14412 [pdf, ps, other]
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Title: Experimental investigation of an electronegative cylindrical capacitively coupled geometrically asymmetric plasma discharge with an axisymmetric magnetic fieldComments: 18 PagesSubjects: Plasma Physics (physics.plasm-ph)
In this study, we have investigated the production of negative ions by mixing electronegative oxygen gas with electropositive argon gas in a geometrically asymmetric cylindrical capacitively coupled radio frequency plasma discharge. The plasma parameters such as density (electron, positive and negative ion), negative ion fraction, and electron temperature are investigated for fixed gas pressure and increasing axial magnetic field strength. The axisymmetric magnetic field creates an ExB drift in the azimuthal direction, leading to the confinement of high-energy electrons at the radial edge of the chamber, resulting in decreased species density and negative ion fraction in the plasma bulk. However, the electron temperature increases with the magnetic field. It is concluded that low magnetic fields are better suited for negative ion production in such devices. Furthermore, in addition to the percentage ratio of the two gases, the applied axial magnetic field also plays a vital role in controlling negative ion fraction.
- [67] arXiv:2405.14466 [pdf, ps, html, other]
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Title: Ultra-cold atoms quantum tunneling through single and double optical barriersRoy Eid (IOGS, CNRS), Alfred Hammond (IOGS, CNRS), Lucas Lavoine (IOGS, CNRS), Thomas Bourdel (IOGS, CNRS)Subjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
We realize textbook experiments on Bose-Einstein condensate tunnelling through thin repulsive potential barriers. In particular, we demonstrate atom tunnelling though a single optical barrier in the quantum scattering regime where the De Broglie wavelength of the atoms is larger than the barrier width. Such a beam splitter can be used for atom interferometry and we study the case of two barriers creating an atomic Fabry-P{é}rot cavity. Technically, the velocity of the atoms is reduced thanks to the use of a 39K Bose-Einstein condensate with no interactions. The potential barriers are created optically and their width is tunable thanks to the use of a digital micro-mirror device. In addition, our scattering experiments enable in-situ characterization of the optical aberrations of the barrier optical system.
- [68] arXiv:2405.14485 [pdf, ps, html, other]
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Title: Experimental observations of bifurcated power decay lengths in the near Scrape-Off Layer of tokamak plasmasX Zhang (1), C Marsden (1), M Moscheni (1), E Maartensson (1), A Rengle (1), M Robinson (1), T OGorman (1), H F Lowe (1), E Vekshina (1), S Janhunen (1), P F Buxton (1), M Sertoli (1), M Romanelli (1), A Scarabosio (1 and 2), T K Gray (3), N A Lopez (4), the ST40 Team ((1) Tokamak Energy Ltd, Abingdon, United Kingdom, (2) LINK foundation, Italy, (3) Oak Ridge National Laboratory, United States, (4) University of Oxford, Oxford, United Kingdom)Comments: 6 pages, 4 figuresSubjects: Plasma Physics (physics.plasm-ph)
The scrape-off layer parallel heat flux decay lengths measured at ST40, a high field, low aspect ratio spherical tokamak, have been observed to bifurcate into two groups. The wide group matches closely with the scale of ion poloidal Larmour radius and follows existing H-mode scalings, while the narrow group falls up to 10 times below scalings, on the scale of ion total Larmour radius. The onset of the narrow scrape-off layer width is observed to be associated with suppressed magnetic fluctuations, suggesting reduced electromagnetic turbulence levels in the SOL.
- [69] arXiv:2405.14503 [pdf, ps, other]
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Title: Radial analysis and scaling of housing prices in French urban areasSubjects: Physics and Society (physics.soc-ph)
Urban scaling laws summarize how urban attributes evolve with city size. Recent criticism questions notably the aggregate view of this approach, which leads to neglecting the internal structure of cities. This is all the more relevant for housing prices due to their important variations across space. Based on a dataset compiling millions of real estate transactions over the period 2017-2021, we investigate the regularities of the radial (center-periphery) profiles of housing prices across cities, with respect to their size. Results are threefold. First, they corroborate prior findings in the urban scaling literature stating that largest cities agglomerate higher housing prices. Second, we find that housing price radial profiles scale in three dimensions with the power 1/5 of city population. After rescaling, great regularities between radial profiles can be observed, although some locational amenities have a significant impact on prices. Third, it appears that our rescaled profiles approach fails to explain housing price variations in the city center across cities. In fact, prices near the city center rise much faster with city size than those in the periphery. This has strong implications for low-income households seeking homeownership, because prohibitive prices in the center may contribute to pushing them out into peripheral locations.
- [70] arXiv:2405.14542 [pdf, ps, html, other]
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Title: Emergence of metastability in frustrated oscillatory networks: the key role of hierarchical modularitySubjects: Biological Physics (physics.bio-ph); Adaptation and Self-Organizing Systems (nlin.AO)
Oscillatory complex networks in the metastable regime have been used to study the emergence of integrated and segregated activity in the brain, which are hypothesised to be fundamental for cognition. Yet, the parameters and the underlying mechanisms necessary to achieve the metastable regime are hard to identify, often relying on maximising the correlation with empirical functional connectivity dynamics. Here, we propose and show that the brain's hierarchically modular mesoscale structure alone can give rise to robust metastable dynamics and (metastable) chimera states in the presence of phase frustration. We construct unweighted $3$-layer hierarchical networks of identical Kuramoto-Sakaguchi oscillators, parameterized by the average degree of the network and a structural parameter determining the ratio of connections between and within blocks in the upper two layers. Together, these parameters affect the characteristic timescales of the system. Away from the critical synchronization point, we detect the emergence of metastable states in the lowest hierarchical layer coexisting with chimera and metastable states in the upper layers. Using the Laplacian renormalization group flow approach, we uncover two distinct pathways towards achieving the metastable regimes detected in these distinct layers. In the upper layers, we show how the symmetry-breaking states depend on the slow eigenmodes of the system. In the lowest layer instead, metastable dynamics can be achieved as the separation of timescales between layers reaches a critical threshold. Our results show an explicit relationship between metastability, chimera states, and the eigenmodes of the system, bridging the gap between harmonic based studies of empirical data and oscillatory models.
- [71] arXiv:2405.14543 [pdf, ps, other]
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Title: Initial Burst of Disruptive Efforts over Individual Scientific CareersSubjects: Physics and Society (physics.soc-ph); Digital Libraries (cs.DL)
Despite persistent efforts to understand the dynamics of creativity of scientists over careers in terms of productivity, impact, and prize, little is known about the dynamics of scientists' disruptive efforts that affect individual academic careers and drive scientific advance. Drawing on millions of data over six decades and across nineteen disciplines, associating the publication records of individual scientists with the disruption index, we systematically quantify the temporal pattern of disruptive ideas over individual scientific careers, providing a detailed understanding of the macro phenomenon of scientific stagnation from the individual perspective. We start by checking the relationship between disruption-based and citation-based publication profiles. Next, we observe the finite inequality in the disruptive productivity of scientists, diminishing gradually as the level of disruption increases. We then identify the initial burst phenomenon in disruption dynamics. It is further revealed that while early engagement in high disruption frictions away initial productivity, compared to initial advantage in productivity or impact, initial high disruption ensures more subsequent academic viability evidenced by a longer career span and relatively final higher productivity, but does not necessarily guarantee academic success throughout careers. Further analysis shows that increasing disruptive work is uncorrelated to overall productivity but negatively correlated with the overall impact. However, increasing disruptive work in the early career is associated with higher overall productivity, yet lower overall productivity in the later career. Our research underscores the urgent need for a policy shift that encourages a balance between the pursuit of disruptive efforts and the achievement of impactful outcomes.
- [72] arXiv:2405.14550 [pdf, ps, other]
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Title: Non-Euclidean conformal devices with continuously varying refractive index profiles based on bi-spheresComments: 16 pages, 5 figuresSubjects: Optics (physics.optics); Classical Physics (physics.class-ph)
Either conformal transformation optics or geodesic mapping provides a design method to bend light rays in two-dimensional space with a nonuniform refractive index profile. In this paper, we combine both methods above to design a conformal invisible cloak based on bi-spheres with a refractive index profile varying from 0 to 10.7, smaller than 24.6 for the previous case of a single sphere. Moreover, we obtain an omnidirectional retro-reflector and a specular reflector by making position adjustments to mirrors, and achieve similar invisible effect by tuning sizes of the bi-spheres. Our work expands the toolkits for designing conformal devices with continuously-varying index profile.
- [73] arXiv:2405.14560 [pdf, ps, html, other]
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Title: Effect of magnetic field configuration on double layer formation and reverse discharge ignition in bipolar HiPIMSSubjects: Plasma Physics (physics.plasm-ph)
The reverse discharge (RD) phenomenon in bipolar HiPIMS has been observed when a sufficiently long positive pulse is applied to the magnetron. Due to the magnetic field, electrons accumulated behind the magnetic trap are prevented from reaching the positive target. Consequently, a space charge double layer (DL) is formed between the positive target and the plasma behind the magnetic trap, leading to electron acceleration across the DL and RD ignition. This study reveals the significant impact of the magnetic field configuration on RD ignition. Experiments are performed using a Ti target involving magnetic field variation, wire probe measurements of floating potential, and optical emission spectroscopy imaging. It is found that adjusting the magnetic field to a more balanced configuration leads to earlier RD ignition, while a more unbalanced one delays or even prevents it. Specifically, the time of RD ignition decreases with an increase in the magnetic null point distance from the target. Moreover, the size and shape of optical emission in the RD varies with nearby probe placement, suggesting sensitivity to external electrodes.
- [74] arXiv:2405.14579 [pdf, ps, html, other]
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Title: Assessment of the Role and Origin of S* in Orange Carotenoid Protein PhotoconversionJames P. Pidgeon, George A. Sutherland, Matthew S. Proctor, Shuangqing Wang, Dimitri Chekulaev, Sayantan Bhattacharya, Rahul Jayaprakash, Andrew Hitchcock, Ravi Kumar Venkatraman, Matthew P. Johnson, C. Neil Hunter, Jenny ClarkSubjects: Chemical Physics (physics.chem-ph)
The orange carotenoid protein (OCP) is the water-soluble mediator of non-photochemical quenching in cyanobacteria, a crucial photoprotective mechanism in response to excess illumination. OCP converts from a globular, inactive state (OCPo) to an extended, active conformation (OCPr) under high-light conditions, resulting in a concomitant redshift in the absorption of the bound carotenoid. Here, OCP was trapped in either the active or inactive state by fixing each protein conformation in trehalose-sucrose glass. Glass-encapsulated OCPo did not convert under intense illumination and OCPr did not convert in darkness, allowing the optical properties of each conformation to be determined at room temperature. We measured pump wavelength-dependent transient absorption of OCPo in glass films and found that initial OCP photoproducts are still formed, despite the glass preventing completion of the photocycle. By comparison to the pump wavelength dependence of the OCPo to OCPr photoconversion yield in buffer, we show that the long-lived carotenoid singlet-like feature (S*) is associated with ground-state heterogeneity within OCPo, rather than triggering OCP photoconversion.
- [75] arXiv:2405.14618 [pdf, ps, html, other]
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Title: Phase Separations of Strongly Coupled Fine Particles and Fine Particle Mixtures in PlasmasComments: 14 pages, 8 figuresSubjects: Plasma Physics (physics.plasm-ph); Statistical Mechanics (cond-mat.stat-mech)
Phase separations in strongly coupled fine particles in plasmas are discussed and two-component mixtures are simulated by molecular dynamics with the background plasma being treated as continuum. The system size of laboratory experiments is assumed and separations into phases with a common electron density of the background plasma are analyzed. Since the charge on fine particles increases approximately in proportion to the size, we expect the larger component with stronger coupling condensates from the mixture. Results expressed in terms of strengths of Coulomb coupling and screening of the larger component seem to be mostly similar to the one-component case, at least in cases where the ratio of fine particle sizes is 2 and the mixing ratio is in the range from 0.25 to 0.75.
- [76] arXiv:2405.14666 [pdf, ps, html, other]
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Title: Mathematical model of fluid front dynamics driven by porous media pumpsAndreu Benavent-Claró, Yara Alvarez-Braña, Fernando Benito-Lopez, Lourdes Basabe-Desmonts, Aurora Hernandez-MachadoComments: 6 pages, 6 figuresSubjects: Fluid Dynamics (physics.flu-dyn); Soft Condensed Matter (cond-mat.soft)
Air-permeable porous media hosts air within their pores. Upon removal from the material's interior, these porous media have the tendency to replenish the air, effectively acting as a suction pump. Therefore, the technique used to convert a porous media into a pump, consists of degassing the material to remove their air inside. The suction property when recovering the air, can be used to move a liquid through a microfluidic channel, studying the dynamics of the liquid-air front. In this article, we have developed a theoretical mathematical model that precisely characterize the behavior of this kind of pumps and the dynamics of the liquid-air front. This model allows us to use porous media pumps as very accurate devices to move liquids in a completely controlled way, being able to obtain characteristic properties of fluids such as viscosity or the pressure applied to them. We have tested it using experimental data from the literature, and we have been able to observe that the theory fits satisfactorily with the experiments, being able to affirm that the model is correctly satisfied. This type of pump is of great interest to the scientific community because of its small size and the fact that it operates without any external power source.
- [77] arXiv:2405.14675 [pdf, ps, html, other]
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Title: Utilizing indicator functions with computational data to confirm nature of overlap in normal turbulent stresses: logarithmic or quarter-powerSubjects: Fluid Dynamics (physics.flu-dyn)
Indicator functions of the streamwise normal-stress profiles (NSP), based on careful differentiation of some of the best direct numerical simulations (DNS) data from channel and pipe flows, over the range $550<Re_\tau<16,000$, are examined to establish the existence and range in wall distances of either a logarithmic-trend segment or a $1/4$-power region. For the nine out of fifteen cases of DNS data we examined where $Re_\tau<2,000$, the NSP did not contain either of the proposed trends. As $Re_\tau$ exceeds around $2,000$ a $1/4$-power, reflecting the ``bounded-dissipation'' predictions of Chen \& Sreenivasan and data analysis of Monkewitz , develops near $y^+=1,000$ and expands with Reynolds numbers extending to $1,000<y^+<10,000$ for $Re_\tau$ around $15,000$. This range of $1/4$-power NSP corresponds to a range of outer-scaled $Y$ between around $0.3$ and $0.7$. The computational database examined did not include the zero-pressure-gradient boundary layer experiments at higher Reynolds numbers where the logarithmic trend in the NSP has been previously reported around $y^+$ of $1,000$ by Marusic et al. according to a ``wall-scaled eddy model''.
- [78] arXiv:2405.14717 [pdf, ps, html, other]
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Title: The impact of temporal hydrogen regulation on hydrogen exporters and their domestic energy transitionLeon Schumm, Hazem Abdel-Khalek, Tom Brown, Falko Ueckerdt, Michael Sterner, Davide Fioriti, Max ParzenSubjects: Physics and Society (physics.soc-ph)
As global demand for green hydrogen rises, potential hydrogen exporters move into the spotlight. However, the large-scale installation of on-grid hydrogen electrolysis for export can have profound impacts on domestic energy prices and energy-related emissions. Our investigation explores the interplay of hydrogen exports, domestic energy transition and temporal hydrogen regulation, employing a sector-coupled energy model in Morocco. We find substantial co-benets of domestic climate change mitigation and hydrogen exports, whereby exports can reduce domestic electricity prices while mitigation reduces hydrogen export prices. However, increasing hydrogen exports quickly in a system that is still dominated by fossil fuels can substantially raise domestic electricity prices, if green hydrogen production is not regulated. Surprisingly, temporal matching of hydrogen production lowers domestic electricity cost by up to 31% while the effect on exporters is minimal. This policy instrument can steer the welfare (re-)distribution between hydrogen exporting firms, hydrogen importers, and domestic electricity consumers and hereby increases acceptance among actors.
- [79] arXiv:2405.14732 [pdf, ps, html, other]
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Title: The Data Acquisition System of the LZ Dark Matter Detector: FADRJ. Aalbers, D.S. Akerib, A.K. Al Musalhi, F. Alder, C.S. Amarasinghe, A. Ames, T.J. Anderson, N. Angelides, H.M. Araújo, J.E. Armstrong, M. Arthurs, A. Baker, S. Balashov, J. Bang, E.E. Barillier, J.W. Bargemann, K. Beattie, T. Benson, A. Bhatti, A. Biekert, T.P. Biesiadzinski, H.J. Birch, E. Bishop, G.M. Blockinger, B. Boxer, C.A.J. Brew, P. Brás, J.H. Buckley, S. Burdin, M. Buuck, M.C. Carmona-Benitez, M. Carter, A. Chawla, H. Chen, J.J. Cherwinka, Y.T. Chin, N.I. Chott, M.V. Converse, A. Cottle, G. Cox, D. Curran, C.E. Dahl, A. David, J. Delgaudio, S. Dey, L. de Viveiros, L. Di Felice, T. Dimino, C. Ding, J.E.Y. Dobson, E. Druszkiewicz, S.R. Eriksen, A. Fan, N.M. Fearon, S. Fiorucci, H. Flaecher, E.D. Fraser, T.M.A. Fruth, R.J. Gaitskell, A. Geffre, R. Gelfand, J. Genovesi, C. Ghag, R. Gibbons, S. Gokhale, J. Green, M.G.D.van der Grinten, J.J. Haiston, C.R. Hall, S. Han, E. Hartigan-O'Connor, S.J. Haselschwardt, M.A. Hernandez, S.A. Hertel, G. Heuermann, G.J. Homenides, M. Horn, D.Q. Huang, D. Hunt, E. Jacquet, R.S. James, J. Johnson, A.C. Kaboth, A.C. Kamaha, M. Kannichankandy, D. Khaitan, A. Khazov, I. Khurana, J. Kim, Y.D. Kim, J. Kingston, R. Kirk, D. Kodroff, L. Korley, E.V. Korolkova, M. Koyuncu, H. Kraus, S. Kravitz, L. Kreczko, V.A. KudryavtsevComments: 18 pages, 24 figuresSubjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)
The Data Acquisition System (DAQ) for the LUX-ZEPLIN (LZ) dark matter detector is described. The signals from 745 PMTs, distributed across three subsystems, are sampled with 100-MHz 32-channel digitizers (DDC-32s). A basic waveform analysis is carried out on the on-board Field Programmable Gate Arrays (FPGAs) to extract information about the observed scintillation and electroluminescence signals. This information is used to determine if the digitized waveforms should be preserved for offline analysis.
The system is designed around the Kintex-7 FPGA. In addition to digitizing the PMT signals and providing basic event selection in real time, the flexibility provided by the use of FPGAs allows us to monitor the performance of the detector and the DAQ in parallel to normal data acquisition.
The hardware and software/firmware of this FPGA-based Architecture for Data acquisition and Realtime monitoring (FADR) are discussed and performance measurements are described. - [80] arXiv:2405.14733 [pdf, ps, html, other]
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Title: Space-time statistics of 2D soliton gas in shallow water studied by stereoscopic surface mappingComments: Accepted for publication in Experiments in FluidsSubjects: Fluid Dynamics (physics.flu-dyn); Pattern Formation and Solitons (nlin.PS)
We describe laboratory experiments in a 2D wave tank that aim at building up and monitor 2D shallow water soliton gas. The water surface elevation is obtained over a large ($\sim 100\,\text{m}^2$) domain, with centimetre-resolution, by stereoscopic vision using two cameras. Floating particles are seeded to get surface texture and determine the wave field by image correlation. With this set-up, soliton propagation and multiple interactions can be measured with a previously unreachable level of detail. The propagation of an oblique soliton is analysed, the amplitude decay and local incidence are compared to analytical predictions. We further present two cases of 2D soliton gas, emerging from multiple line solitons with random incidence ($|\theta|<30^\circ$) and from irregular random waves forced with a {\sc jonswap} spectrum ($|\theta|<45^\circ$). To our knowledge, those are the first observations of random 2D soliton gas for gravity waves. In both cases Mach reflections and Mach expansions result in solitons that mainly propagate in directions perpendicular to the wave-makers.
- [81] arXiv:2405.14735 [pdf, ps, other]
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Title: Generalized all-optical complex exponential operatorComments: 17 pages, 4 figures, 1 tableSubjects: Optics (physics.optics)
Euler's formula, an extraordinary mathematical formula, establishes a vital link between complex-valued operations and trigonometric functions, finding widespread application in various fields. With the end of Moore's Law, electronic computing methods are encountering developmental bottlenecks. With its enviable potential, optical computing has successfully achieved high-speed operation of designed complex numbers. However, the challenge of processing and manipulating arbitrary complex numbers persists. This study introduces a generalized complex exponential operator (GCEO), utilizing a diffractive optical neural network (DONN) for the computation of the complex exponential through Euler's formula. Experiments validate a series of complex exponential calculations using the GCEO. The GCEO has demonstrated generalizability and can compute inputs of any precision within an appropriate error margin. The proposed operator highlights the immense potential of DONN in optical computation and is poised to significantly contribute to the development of computational methods for optoelectronic integration.
- [82] arXiv:2405.14761 [pdf, ps, html, other]
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Title: Effective & Ethical Mentorship in Physics and Astronomy through Grassroots OrganizationsComments: 30 pages single spaced with appendix of figures, 8 figures, published in BAASJournal-ref: Bulletin of the AAS, 56(1) (2024)Subjects: Physics Education (physics.ed-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Physics and Society (physics.soc-ph)
Effective and ethical mentorship practices are crucial to improving recruitment and retention especially for historically minoritized groups (HMGs). Spectrum is a diversity, inclusion, equity, and accessibility (DEIA) grassroots organization committed to empowering equitable excellence through sustainable change. By improving transparency and DEIA within the fields of physics and astronomy, we can empower the next generation of diverse scientists and increase field retention. Starting within our home department at George Mason University and moving outwards, we ensure our students leave as advocates for DEIA and AJEDI (access, justice, equity, diversity, and inclusion) through education and mentorship. Spectrum is providing professionally trained peer mentors to aid students in all facets of their academic and personal lives. Although the peer mentoring program existed since the creation of Spectrum in Spring 2020, we have recently developed and implemented a formal mentorship training for both student and faculty mentors thus increasing the quality, trustworthiness, and confidence of our mentors. Using the latest mentorship research available, this training is developed by Spectrum for George Mason University, with the ability to implement the training at any institution.
- [83] arXiv:2405.14806 [pdf, ps, html, other]
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Title: Lorentz-Equivariant Geometric Algebra Transformers for High-Energy PhysicsComments: 10+12 pages, 5+2 figures, 2 tablesSubjects: Data Analysis, Statistics and Probability (physics.data-an); Machine Learning (cs.LG); High Energy Physics - Phenomenology (hep-ph); Machine Learning (stat.ML)
Extracting scientific understanding from particle-physics experiments requires solving diverse learning problems with high precision and good data efficiency. We propose the Lorentz Geometric Algebra Transformer (L-GATr), a new multi-purpose architecture for high-energy physics. L-GATr represents high-energy data in a geometric algebra over four-dimensional space-time and is equivariant under Lorentz transformations, the symmetry group of relativistic kinematics. At the same time, the architecture is a Transformer, which makes it versatile and scalable to large systems. L-GATr is first demonstrated on regression and classification tasks from particle physics. We then construct the first Lorentz-equivariant generative model: a continuous normalizing flow based on an L-GATr network, trained with Riemannian flow matching. Across our experiments, L-GATr is on par with or outperforms strong domain-specific baselines.
- [84] arXiv:2405.14814 [pdf, ps, html, other]
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Title: Accelerated First-Principles Exploration of Structure and Reactivity in Graphene OxideZakariya El-Machachi, Damyan Frantzov, A. Nijamudheen, Tigany Zarrouk, Miguel A. Caro, Volker L. DeringerSubjects: Chemical Physics (physics.chem-ph); Materials Science (cond-mat.mtrl-sci)
Graphene oxide (GO) materials are widely studied, and yet their atomic-scale structures remain to be fully understood. Here we show that the chemical and configurational space of GO can be rapidly explored by advanced machine-learning methods, combining on-the-fly acceleration for first-principles molecular dynamics with message-passing neural-network potentials. The first step allows for the rapid sampling of chemical structures with very little prior knowledge required; the second step affords state-of-the-art accuracy and predictive power. We apply the method to the thermal reduction of GO, which we describe in a realistic (ten-nanometre scale) structural model. Our simulations are consistent with recent experimental findings and help to rationalise them in atomistic and mechanistic detail. More generally, our work provides a platform for routine, accurate, and predictive simulations of diverse carbonaceous materials.
- [85] arXiv:2405.14842 [pdf, ps, html, other]
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Title: Dual-comb correlation spectroscopy of thermal lightEugene J. Tsao, Alexander J. Lind, Connor Fredrick, Ryan K. Cole, Peter Chang, Kristina F. Chang, Dahyeon Lee, Matthew Heyrich, Nazanin Hoghooghi, Franklyn Quinlan, Scott A. DiddamsComments: 54 pages, 7 figuresSubjects: Optics (physics.optics); Instrumentation and Methods for Astrophysics (astro-ph.IM)
The detection of light of thermal origin is the principal means by which humanity has learned about our world and the cosmos. In optical astronomy, in particular, direct detection of thermal photons and the resolution of their spectra have enabled discoveries of the broadest scope and impact. Such measurements, however, do not capture the phase of the thermal fields--a parameter that has proven crucial to transformative techniques in radio astronomy such as synthetic aperture imaging. Over the last 25 years, tremendous progress has occurred in laser science, notably in the phase-sensitive, broad bandwidth, high resolution, and traceable spectroscopy enabled by the optical frequency comb. In this work, we directly connect the fields of frequency comb laser spectroscopy and passive optical sensing as applied to astronomy, remote sensing, and atmospheric science. We provide fundamental sensitivity analysis of dual-comb correlation spectroscopy (DCCS), whereby broadband thermal light is measured via interferometry with two optical frequency combs. We define and experimentally verify the sensitivity scaling of DCCS at black body temperatures relevant for astrophysical observations. Moreover, we provide comparison with direct detection techniques and more conventional laser heterodyne radiometry. Our work provides the foundation for future exploration of comb-based broadband synthetic aperture hyperspectral imaging across the infrared and optical spectrum.
New submissions for Friday, 24 May 2024 (showing 85 of 85 entries )
- [86] arXiv:2405.12998 (cross-list from q-bio.OT) [pdf, ps, other]
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Title: The miscalibration of the honeybee odometerComments: 16 pagesSubjects: Other Quantitative Biology (q-bio.OT); Biological Physics (physics.bio-ph)
We examine a series of articles on honeybee odometry and navigation published between 1996 and 2010, and find inconsistencies in results, duplicated figures, indications of data manipulation, and incorrect calculations. This suggests that redoing the experiments in question is warranted.
- [87] arXiv:2405.13069 (cross-list from astro-ph.SR) [pdf, ps, html, other]
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Title: MHD modeling of a geoeffective interplanetary CME with the magnetic topology informed by in-situ observationsComments: 20 pages, 11 figures, 1 table. Submitted to Astrophysical JournalSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)
Variations of the magnetic field within solar coronal mass ejections (CMEs) in the heliosphere depend on the CME`s magnetic structure as it leaves the solar corona and its subsequent evolution through interplanetary space. To account for this evolution, we developed a new numerical model of the inner heliosphere that simulates the propagation of a CME through a realistic background solar wind and allows various CME magnetic topologies. To this end, we incorporate the Gibson-Low CME model within our global MHD model of the inner heliosphere, GAMERA-Helio. We apply the model to study the propagation of the geoeffective CME that erupted on 3 April, 2010 with the aim to reproduce the temporal variations of the magnetic field vector during the CME passage by Earth. Parameters of the Gibson-Low CME are informed by STEREO white-light observations near the Sun. The magnetic topology for this CME - the tethered flux rope - is informed by in-situ magnetic field observations near Earth. We performed two simulations testing different CME propagation directions. For an in-ecliptic direction, the simulation shows a rotation of all three magnetic field components within the CME, as seen at Earth, similar to that observed. With a southward propagation direction, suggested by coronal imaging observations, the modeled By and Bz components are consistent with the ACE data, but the Bx component lacks the observed change from negative to positive. In both cases, the model favors the East-West orientation of the CME flux rope, consistent with the orientation previously inferred from the STEREO/HI heliospheric images.
- [88] arXiv:2405.13180 (cross-list from eess.SP) [pdf, ps, html, other]
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Title: Data Assimilation with Machine Learning Surrogate Models: A Case Study with FourCastNetSubjects: Signal Processing (eess.SP); Machine Learning (cs.LG); Chaotic Dynamics (nlin.CD); Atmospheric and Oceanic Physics (physics.ao-ph); Applications (stat.AP)
Modern data-driven surrogate models for weather forecasting provide accurate short-term predictions but inaccurate and nonphysical long-term forecasts. This paper investigates online weather prediction using machine learning surrogates supplemented with partial and noisy observations. We empirically demonstrate and theoretically justify that, despite the long-time instability of the surrogates and the sparsity of the observations, filtering estimates can remain accurate in the long-time horizon. As a case study, we integrate FourCastNet, a state-of-the-art weather surrogate model, within a variational data assimilation framework using partial, noisy ERA5 data. Our results show that filtering estimates remain accurate over a year-long assimilation window and provide effective initial conditions for forecasting tasks, including extreme event prediction.
- [89] arXiv:2405.13213 (cross-list from cond-mat.mtrl-sci) [pdf, ps, html, other]
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Title: Low-energy pathways lead to self-healing defects in CsPbBr$_3$Kumar Miskin, Yi Cao, Madaline Marland, Jay Rwaka, Farhan Shaikh, David Moore, John Marohn, Paulette ClancySubjects: Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Self-regulation of free charge carriers in perovskites via Schottky defect formation has been posited as the origin of the well-known defect tolerance of metal halide perovskite materials that are promising candidates for photovoltaic applications, like solar cells. Understanding the mechanisms of self-regulation, here for a representative of more commercially viable all-inorganic perovskites, promises to lead to the fabrication of better-performing solar cell materials with higher efficiencies. We investigated different mechanisms and pathways of the diffusion and recombination of interstitials and vacancies (Schottky pairs) in CsPbBr$_3$. We use Nudged Elastic Band calculations and ab initio-derived pseudopotentials within Quantum ESPRESSO to determine energies of formation, migration, and activation for these defects. Our calculations uncover defect pathways capable of producing an activation energy at or below the value of 0.53~eV observed for the slow, temperature-dependent recovery of light-induced conductivity in CsPbBr$_3$. Our work reveals the existence of a low-energy diffusion pathway involving a concerted "domino effect" interstitial mechanism, with the net result that interstitials can diffuse more readily over long distances than expected. Importantly, this observation suggests that defect self-healing can be promoted if the "domino effect" strategy can be engaged.
- [90] arXiv:2405.13227 (cross-list from cs.LG) [pdf, ps, other]
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Title: A rapid approach to urban traffic noise mapping with a generative adversarial networkComments: submitted to Applied Acoustics as a technical noteSubjects: Machine Learning (cs.LG); Applied Physics (physics.app-ph)
With rapid urbanisation and the accompanying increase in traffic density, traffic noise has become a major concern in urban planning. However, traditional grid noise mapping methods have limitations in terms of time consumption, software costs, and a lack of parameter integration interfaces. These limitations hinder their ability to meet the need for iterative updates and rapid performance feedback in the early design stages of street-scale urban planning. Herein, we developed a rapid urban traffic noise mapping technique that leverages generative adversarial networks (GANs) as a surrogate model. This approach enables the rapid assessment of urban traffic noise distribution by using urban elements such as roads and buildings as the input. The mean values for the mean squared error (MSE) and structural similarity index (SSIM) are 0.0949 and 0.8528, respectively, for the validation dataset. Hence, our prediction accuracy is on par with that of conventional prediction software. Furthermore, the trained model is integrated into Grasshopper as a tool, facilitating the rapid generation of traffic noise maps. This integration allows urban designers and planners, even those without expertise in acoustics, to easily anticipate changes in acoustics impacts caused by design.
- [91] arXiv:2405.13236 (cross-list from cond-mat.soft) [pdf, ps, html, other]
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Title: Granular temperature controls local rheology of vibrated granular flowsSubjects: Soft Condensed Matter (cond-mat.soft); Geophysics (physics.geo-ph)
We use numerical simulations to demonstrate a local rheology for sheared, vibrated granular flows. We consider a granular assembly that is subjected to simple shear and harmonic vibration at the boundary. This configuration allows us to isolate the effects of vibration, as parameterized by granular temperature. We find that friction is reduced due to local velocity fluctuations of grains. All data obey a local rheology that relates the material friction coefficient, the granular temperature, and the dimensionless shear rate. We also observe that reduction in material friction due to granular temperature is associated with reduction in fabric anisotropy. We demonstrate that the temperature can be modeled by a heat equation with dissipation with appropriate boundary conditions, which provides complete closure of the system and allows a fully local continuum description of sheared, vibrated granular flows. This success suggests local rheology based on temperature, as suggested previously, combined with the new, empirical heat diffusion equation may provide a general strategy for dense granular flows.
- [92] arXiv:2405.13277 (cross-list from cond-mat.dis-nn) [pdf, ps, html, other]
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Title: Topology Obstructing Anderson Localization of LightComments: 4 pages, supplemental materialSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
Light propagation in random media is notorious for its resilience to (Anderson) wave localization. We here argue that in materials with slow helicity relaxation previously unnoticed principles of topology reinforce delocalization. We show that the effective electromagnetic action is governed by principles, identical to those protecting delocalization at topological insulator surface states. The length scales over which these exert a protective influence depend on the conservation of helicity, leading to the prediction that light scattering in media with, e.g., strong magnetic and electric dipolar resonances evades localization over large scales.
- [93] arXiv:2405.13278 (cross-list from cs.CV) [pdf, ps, html, other]
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Title: Single color virtual H&E staining with In-and-Out NetMengkun Chen, Yen-Tung Liu, Fadeel Sher Khan, Matthew C. Fox, Jason S. Reichenberg, Fabiana C.P.S. Lopes, Katherine R. Sebastian, Mia K. Markey, James W. TunnellSubjects: Computer Vision and Pattern Recognition (cs.CV); Medical Physics (physics.med-ph)
Virtual staining streamlines traditional staining procedures by digitally generating stained images from unstained or differently stained images. While conventional staining methods involve time-consuming chemical processes, virtual staining offers an efficient and low infrastructure alternative. Leveraging microscopy-based techniques, such as confocal microscopy, researchers can expedite tissue analysis without the need for physical sectioning. However, interpreting grayscale or pseudo-color microscopic images remains a challenge for pathologists and surgeons accustomed to traditional histologically stained images. To fill this gap, various studies explore digitally simulating staining to mimic targeted histological stains. This paper introduces a novel network, In-and-Out Net, specifically designed for virtual staining tasks. Based on Generative Adversarial Networks (GAN), our model efficiently transforms Reflectance Confocal Microscopy (RCM) images into Hematoxylin and Eosin (H&E) stained images. We enhance nuclei contrast in RCM images using aluminum chloride preprocessing for skin tissues. Training the model with virtual H\&E labels featuring two fluorescence channels eliminates the need for image registration and provides pixel-level ground truth. Our contributions include proposing an optimal training strategy, conducting a comparative analysis demonstrating state-of-the-art performance, validating the model through an ablation study, and collecting perfectly matched input and ground truth images without registration. In-and-Out Net showcases promising results, offering a valuable tool for virtual staining tasks and advancing the field of histological image analysis.
- [94] arXiv:2405.13280 (cross-list from astro-ph.CO) [pdf, ps, html, other]
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Title: Nucleation regions in the Large-Scale Structure I. A catalogue of cores in nearby rich superclustersComments: This article has been accepted for publication in the Publications of the Astronomical Society of Australia (PASA) journal. The manuscript file with five (17) figures and six (6) tables embeddedSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc); Computational Physics (physics.comp-ph)
We applied a Density-Based Clustering algorithm on samples of galaxies and galaxy systems belonging to 53 rich superclusters from the \textit{Main SuperCluster Catalogue} (MSCC) to identify the presence of ``central regions'', or \emph{cores}, in these large-scale structures. \emph{Cores} are defined here as large gravitationally bound galaxy structures, comprised of two or more clusters and groups, with sufficient matter density to survive cosmic expansion and virialize in the future. We identified a total of 105 galaxy structures classified as \emph{cores}, which exhibit a high density contrast of mass and galaxies. The Density-based \textit{Core} Catalogue (DCC), presented here, includes \emph{cores} that were previously reported in well-known superclusters of the Local Universe, and also several newly identified ones. We found that 83\% of the rich superclusters in our sample have at least one \emph{core}. While more than three \emph{cores} with different dynamical state are possible, the presence of a single \emph{core} in the superclusters is more common. Our work confirms the existence of nucleation regions in the internal structure of most rich superclusters and points to the fact that these \emph{cores} are the densest and most massive features that can be identified in the cosmic web with high probability for future virialization.
- [95] arXiv:2405.13341 (cross-list from econ.GN) [pdf, ps, other]
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Title: Wealth inequality and utility: Effect evaluation of redistribution and consumption morals using macro-econophysical coupled approachComments: 27 pages, 6 figuresSubjects: General Economics (econ.GN); Multiagent Systems (cs.MA); Physics and Society (physics.soc-ph)
Reducing wealth inequality and increasing utility are critical issues. This study reveals the effects of redistribution and consumption morals on wealth inequality and utility. To this end, we present a novel approach that couples the dynamic model of capital, consumption, and utility in macroeconomics with the interaction model of joint business and redistribution in econophysics. With this approach, we calculate the capital (wealth), the utility based on consumption, and the Gini index of these inequality using redistribution and consumption thresholds as moral parameters. The results show that: under-redistribution and waste exacerbate inequality; conversely, over-redistribution and stinginess reduce utility; and a balanced moderate moral leads to achieve both reduced inequality and increased utility. These findings provide renewed economic and numerical support for the moral importance known from philosophy, anthropology, and religion. The revival of redistribution and consumption morals should promote the transformation to a human mutual-aid economy, as indicated by philosopher and anthropologist, instead of the capitalist economy that has produced the current inequality. The practical challenge is to implement bottom-up social business, on a foothold of worker coops and platform cooperatives as a community against the state and the market, with moral consensus and its operation.
- [96] arXiv:2405.13424 (cross-list from cond-mat.stat-mech) [pdf, ps, html, other]
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Title: Emergent behaviour and phase transitions in spatially distributed multi-cellular metabolic networksK. Narayanankutty, J. A. Pereiro-Morejon, A. Ferrero, V. Onesto, S. Forciniti, L. L. del Mercato, R. Mulet, A. De Martino, D. S. Tourigny, D. De MartinoComments: Main(14 pages)+ supporting information(14 pages). Comments are welcomeSubjects: Statistical Mechanics (cond-mat.stat-mech); Biological Physics (physics.bio-ph); Cell Behavior (q-bio.CB)
Overflow metabolism is a ubiquitous phenomenon whereby cells in aerobic conditions excrete byproducts of glycolysis, such as lactate or acetate, into the medium in a seemingly wasteful and polluting fashion. Whilst overflow may confer microbes a fitness advantage by allowing them to overcome a finite oxidative capacity, its occurrence in higher organisms is harder to assess. Important insight was however obtained in recent experiments conducted at single-cell resolution, which revealed that accumulation of overflow products in tumor cell cultures known as the Warburg effect arises from imbalances in the dynamic and heterogeneous inter-cellular exchange network through which cells collectively regulate the microenvironment. Here we provide a quantitative characterization of this scenario by integrating metabolic network modeling with diffusion constraints, statistical physics theory and single-cell experimental flux data. On the theoretical side, we clarify how diffusion-limited exchanges shape the space of viable metabolic states of a multi-cellular system. Specifically, a phase transition from a balanced network of exchanges to an unbalanced overflow regime occurs as the mean cellular glucose and oxygen uptakes vary while single-cell metabolic phenotypes are highly heterogeneous around this transition. We then show that time-resolved data from human tumor-stroma cell co-cultures consistently map to this crossover region, supporting the idea that environmental deterioration reflects a failure of coordination among recurrently interacting cells. In summary, our findings suggest that, rather than deriving from multiple independent cell-autonomous processes, environmental control is an emergent feature of multi-cellular systems.
- [97] arXiv:2405.13434 (cross-list from cond-mat.soft) [pdf, ps, html, other]
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Title: Observation of Brownian elastohydrodynamic forces acting on confined soft colloidsNicolas Fares (LOMA), Maxime Lavaud (LOMA), Zaicheng Zhang (LOMA), Aditya Jha (LOMA), Yacine Amarouchene (LOMA), Thomas Salez (LOMA)Subjects: Soft Condensed Matter (cond-mat.soft); Chemical Physics (physics.chem-ph); Classical Physics (physics.class-ph)
Confined motions in complex environments are ubiquitous in microbiology. These situations invariably involve the intricate coupling between fluid flow, soft boundaries, surface forces and fluctuations. In the present study, such a coupling is investigated using a novel method combining holographic microscopy and advanced statistical inference. Specifically, the Brownian motion of softmicrometric oil droplets near rigid walls is quantitatively analyzed. All the key statistical observables are reconstructed with high precision, allowing for nanoscale resolution of local mobilities and femtonewton inference of conservative or non-conservative forces. Strikingly, the analysis reveals the existence of a novel, transient, but large, soft Brownian force. The latter might be of crucial importance for microbiological and nanophysical transport, target finding or chemical reactions in crowded environments, and hence the whole life machinery.
- [98] arXiv:2405.13441 (cross-list from math.NA) [pdf, ps, html, other]
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Title: An all Mach number semi-implicit hybrid Finite Volume/Virtual Element method for compressible viscous flows on Voronoi meshesSubjects: Numerical Analysis (math.NA); Fluid Dynamics (physics.flu-dyn)
We present a novel high order semi-implicit hybrid finite volume/virtual element numerical scheme for the solution of compressible flows on Voronoi tessellations. The method relies on the flux splitting of the compressible Navier-Stokes equations into three sub-systems: a convective sub-system solved explicitly using a finite volume (FV) scheme, and the viscous and pressure sub-systems which are discretized implicitly at the aid of a virtual element method (VEM). Consequently, the time step restriction of the overall algorithm depends only on the mean flow velocity and not on the fast pressure waves nor on the viscous eigenvalues. As such, the proposed methodology is well suited for the solution of low Mach number flows at all Reynolds numbers. Moreover, the scheme is proven to be globally energy conserving so that shock capturing properties are retrieved in high Mach number flows. To reach high order of accuracy in time and space, an IMEX Runge-Kutta time stepping strategy is employed together with high order spatial reconstructions in terms of CWENO polynomials and virtual element space basis functions. The chosen discretization techniques allow the use of general polygonal grids, a useful tool when dealing with complex domain configurations. The new scheme is carefully validated in both the incompressible limit and the high Mach number regime through a large set of classical benchmarks for fluid dynamics, assessing robustness and accuracy.
- [99] arXiv:2405.13466 (cross-list from cond-mat.mtrl-sci) [pdf, ps, other]
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Title: Novel dielectric resonance of composites containing randomly distributed ZrB2 particles with continuous dual-peak microwave absorptionComments: 19 pages, 5 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)
Substantial efforts have been devoted to the elaborate component and microstructure design of absorbents (inclusions) in microwave absorbing (MA) composite materials. However, mesoscopic architectures of composites also play significant roles in prescribing their electromagnetic properties, which are rarely explored in studies of MA materials. Herein, a composite containing randomly distributed ZrB2 particles is fabricated to offer a mesoscopic cluster configuration, which produces a novel dielectric resonance. The resonance disappears and reoccurs when ZrB2 is coated with the insulating and semiconductive ZrO2 layer respectively, suggesting that it is a plasmon resonance excited by the electron transport between ZrB2 particles in clusters rather than any intrinsic resonances of materials constituting the composite. The resonance strength can be regulated by controlling the quantity of the electron transport between particles, which is accomplished by gradually increasing the insulating ZrO2-coated ZrB2 ratio x to disturb the electron transport in ternary disordered composites containing ZrB2 and insulating ZrO2-coated ZrB2. When x exceeds 0.7, the electron transport is cut off completely and the resonance thus disappears. The resonance induces unusual double quarter-wavelength interference cancellations or resonance absorption coupled with quarter-wavelength interference cancellation, giving rise to continuous dual-peak absorption. This work highlights the significance of mesoscopic architectures of composites in MA material design, which can be exploited to prescribe novel electromagnetic properties.
- [100] arXiv:2405.13468 (cross-list from astro-ph.EP) [pdf, ps, html, other]
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Title: Machine learning for exoplanet detection in high-contrast spectroscopy Combining cross correlation maps and deep learning on medium-resolution integral-field spectraComments: Accepted for publication in A&A on 23/04/2024. Total 15 pages of text, 7 figuresSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Machine Learning (cs.LG); Applied Physics (physics.app-ph); Data Analysis, Statistics and Probability (physics.data-an)
The advent of high-contrast imaging instruments combined with medium-resolution spectrographs allows spectral and temporal dimensions to be combined with spatial dimensions to detect and potentially characterize exoplanets with higher sensitivity. We develop a new method to effectively leverage the spectral and spatial dimensions in integral-field spectroscopy (IFS) datasets using a supervised deep-learning algorithm to improve the detection sensitivity to high-contrast exoplanets. We begin by applying a data transform whereby the IFS datasets are replaced by cross-correlation coefficient tensors obtained by cross-correlating our data with young gas giant spectral template spectra. This transformed data is then used to train machine learning (ML) algorithms. We train a 2D CNN and 3D LSTM with our data. We compare the ML models with a non-ML algorithm, based on the STIM map of arXiv:1810.06895. We test our algorithms on simulated young gas giants in a dataset that contains no known exoplanet, and explore the sensitivity of algorithms to detect these exoplanets at contrasts ranging from 1e-3 to 1e-4 at different radial separations. We quantify the sensitivity using modified receiver operating characteristic curves (mROC). We discover that the ML algorithms produce fewer false positives and have a higher true positive rate than the STIM-based algorithm, and the true positive rate of ML algorithms is less impacted by changing radial separation. We discover that the velocity dimension is an important differentiating factor. Through this paper, we demonstrate that ML techniques have the potential to improve the detection limits and reduce false positives for directly imaged planets in IFS datasets, after transforming the spectral dimension into a radial velocity dimension through a cross-correlation operation.
- [101] arXiv:2405.13508 (cross-list from cond-mat.dis-nn) [pdf, ps, html, other]
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Title: Furutsu-Novikov--like cross-correlation--response relations for systems driven by shot noiseComments: 12 pages, 9 figuresSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Biological Physics (physics.bio-ph)
We consider a dynamic system that is driven by an intensity-modulated Poisson process with intensity $\Lambda(t)=\lambda(t)+\varepsilon\nu(t)$. We derive an exact relation between the input-output cross-correlation in the spontaneous state ($\varepsilon=0$) and the linear response to the modulation ($\varepsilon>0$). This can be regarded as a variant of the Furutsu-Novikov theorem for the case of shot noise. As we show, the relation is still valid in the presence of additional independent noise. Furthermore, we derive an extension to Cox-process input, i.e. to colored shot noise. We discuss applications to particle detection and to neuroscience. Using the new relation, we obtain a fluctuation-response-relation for a leaky integrate-and-fire neuron. We also show how the new relation can be used in a remote control problem in a recurrent neural network. The relations are numerically tested for both stationary and non-stationary dynamics. Lastly, extensions to marked Poisson processes and to higher-order statistics are presented.
- [102] arXiv:2405.13521 (cross-list from cond-mat.stat-mech) [pdf, ps, html, other]
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Title: Run-and-tumble particle with saturating ratesSubjects: Statistical Mechanics (cond-mat.stat-mech); Biological Physics (physics.bio-ph); Cell Behavior (q-bio.CB)
We consider a run-and-tumble particle whose speed and tumbling rate are space-dependent on an infinite line. Unlike most of the previous work on such models, here we make the physical assumption that at large distances, these rates saturate to a constant. For our choice of rate functions, we show that a stationary state exists, and the exact steady state distribution decays exponentially or faster and can be unimodal or bimodal. The effect of boundedness of rates is seen in the mean-squared displacement of the particle that displays qualitative features different from those observed in the previous studies where it approaches the stationary state value monotonically in time; in contrast, here we find that if the initial position of the particle is sufficiently far from the origin, the variance in its position either varies nonmonotonically or plateaus before reaching the stationary state. These results are captured quantitatively by the exact solution of the Green's function when the particle has uniform speed but the tumbling rates change as a step-function in space; the insights provided by this limiting case are found to be consistent with the numerical results for the general model.
- [103] arXiv:2405.13597 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Quantum-fluctuation asymmetry in multiphoton Jaynes-Cummings resonancesComments: 26 pages, 9 figures, 3 appendicesSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
We explore the statistical behavior of the light emanating from a coherently driven Jaynes-Cummings (JC) oscillator operating in the regime of multiphoton blockade with two monitored output channels causing the loss of coherence at equal rates. We do so by adopting an operational approach which draws the particle and wave aspects of the forwards scattered radiation together, building upon the relationship between quantum optical correlation functions and conditional measurements. We first derive an analytical expression of the intensity cross-correlation function at the peak of the two-photon JC resonance to demonstrate the breakdown of detailed balance. The application of quantum trajectory theory in parallel with the quantum regression formula subsequently uncovers various aspects of temporal asymmetry in the quantum fluctuations characterizing the cascaded process through which a multiphoton resonance is established and read out. We find that monitoring different quadratures of the cavity field in conditional homodyne detection affects the times waited between successive photon counter ``clicks'', which in turn trigger the sampling of the homodyne current. Despite the fact that the steady-state cavity occupation is of the order of a photon, monitoring of the developing bimodality also impacts on the ratio between the emissions directed along the two decoherence channels.
- [104] arXiv:2405.13631 (cross-list from cond-mat.other) [pdf, ps, html, other]
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Title: Realization of Singular Topological Edge States in Locally Resonant MetamaterialsSubjects: Other Condensed Matter (cond-mat.other); Applied Physics (physics.app-ph)
We theoretically and experimentally demonstrate singular topological edge states in a locally resonant metamaterial with a configuration based on inversion-symmetric extended Su-Schrieffer-Heeger chains. Such states arise from a topological gap transition from a conventional Bragg-type gap (BG) to a local resonance-induced gap (LRG), accompanied by a topological phase transition. Remarkably, nontrivial topological states can emerge in the vicinity of the singularity in the imaginary parts of the wavenumber within the bandgap, leading to highly localized modes on a scale comparable to a single subwavelength unit cell. We experimentally demonstrate distinct differences in topologically protected modes-highlighted by wave localization-between the BG and the LRG in locally resonant granular-based metamaterials. Our findings suggest the scope of topological metamaterials may be extended via their bandgap nature.
- [105] arXiv:2405.13654 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Programmable quantum circuits in a large-scale photonic waveguide arrayYang Yang, Robert J. Chapman, Akram Youssry, Ben Haylock, Francesco Lenzini, Mirko Lobino, Alberto PeruzzoSubjects: Quantum Physics (quant-ph); Optics (physics.optics)
Over the past decade, integrated quantum photonic technologies have shown great potential as a platform for studying quantum phenomena and realizing large-scale quantum information processing. Recently, there have been proposals for utilizing waveguide lattices to implement quantum gates, providing a more compact and robust solution compared to discrete implementation with directional couplers and phase shifters. We report on the first demonstration of precise control of single photon states on an $11\times 11$ continuously-coupled programmable waveguide array. Through electro-optical control, the array is subdivided into decoupled subcircuits and the degree of on-chip quantum interference can be tuned with a maximum visibility of 0.962$\pm$0.013. Furthermore, we show simultaneous control of two subcircuits on a single device. Our results demonstrate the potential of using this technology as a building block for quantum information processing applications.
- [106] arXiv:2405.13689 (cross-list from quant-ph) [pdf, ps, other]
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Title: Stabilizing classical accelerometers and gyroscopes with a quantum inertial sensorClément Salducci, Yannick Bidel, Malo Cadoret, Sarah Darmon, Nassim Zahzam, Alexis Bonnin, Sylvain Schwartz, Cédric Blanchard, Alexandre BressonSubjects: Quantum Physics (quant-ph); Accelerator Physics (physics.acc-ph); Atomic Physics (physics.atom-ph)
Accurate measurement of inertial quantities is essential in geophysics, geodesy, fundamental physics and navigation. For instance, inertial navigation systems require stable inertial sensors to compute the position and attitude of the carrier. Here, we present the first hybridized cold-atom inertial sensor based on matter wave interferometry where the atomic measurements are used to correct the drift and bias of both an accelerometer and a gyroscope at the same time. We achieve respective bias stabilities of $7 \times 10^{-7}$ m/s$^2$ and $4 \times 10^{-7}$ rad/s after two days of integration, corresponding to a 100-fold and 3-fold increase on the stability of the hybridized sensor compared to the force-balanced accelerometer and Coriolis vibrating gyroscope operated alone. The instrument has been operated under up to 100-times the Earth rotation rate. Compared to state-of-the-art atomic gyroscope, the simplicity and scalability of our architecture make it easily extendable to a compact full six-axis inertial measurement unit, providing a pathway towards autonomous positioning and orientation using cold-atom sensors.
- [107] arXiv:2405.13711 (cross-list from cs.LG) [pdf, ps, html, other]
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Title: VAE-Var: Variational-Autoencoder-Enhanced Variational AssimilationSubjects: Machine Learning (cs.LG); Artificial Intelligence (cs.AI); Dynamical Systems (math.DS); Atmospheric and Oceanic Physics (physics.ao-ph)
Data assimilation refers to a set of algorithms designed to compute the optimal estimate of a system's state by refining the prior prediction (known as background states) using observed data. Variational assimilation methods rely on the maximum likelihood approach to formulate a variational cost, with the optimal state estimate derived by minimizing this cost. Although traditional variational methods have achieved great success and have been widely used in many numerical weather prediction centers, they generally assume Gaussian errors in the background states, which limits the accuracy of these algorithms due to the inherent inaccuracies of this assumption. In this paper, we introduce VAE-Var, a novel variational algorithm that leverages a variational autoencoder (VAE) to model a non-Gaussian estimate of the background error distribution. We theoretically derive the variational cost under the VAE estimation and present the general formulation of VAE-Var; we implement VAE-Var on low-dimensional chaotic systems and demonstrate through experimental results that VAE-Var consistently outperforms traditional variational assimilation methods in terms of accuracy across various observational settings.
- [108] arXiv:2405.13809 (cross-list from cond-mat.quant-gas) [pdf, ps, html, other]
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Title: Self-trapping phenomenon, multistability and chaos in open anisotropic Dicke dimerSubjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Chaotic Dynamics (nlin.CD); Optics (physics.optics)
We investigate semiclassical dynamics of coupled atom-photon interacting system described by a dimer of anisotropic Dicke model in the presence of photon loss, exhibiting a rich variety of non-linear dynamics. Based on symmetries and dynamical classification, we characterize and chart out various dynamical phases in a phase diagram. A key feature of this system is the multistability of different dynamical states, particularly the coexistence of various superradiant phases as well as limit cycles. Remarkably, this dimer system manifests self-trapping phenomena, resulting in a photon population imbalance between the cavities. Such a self-trapped state arises from saddle-node bifurcation, which can be understood from an equivalent Landau-Ginzburg description. Additionally, we identify a unique class of oscillatory dynamics self-trapped limit cycle hosting self-trapping of photons. The absence of stable dynamical phases leads to the onset of chaos, which is diagnosed using the saturation value of the decorrelator dynamics. Moreover, in a narrow region, the self-trapped states can coexist with chaotic attractor, which may have intriguing consequences in quantum dynamics. Finally, we discuss the experimental relevance of our findings, which can be tested in cavity and circuit quantum electrodynamics setups.
- [109] arXiv:2405.13905 (cross-list from cs.CE) [pdf, ps, html, other]
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Title: Calibration of stochastic, agent-based neuron growth models with Approximate Bayesian ComputationComments: 32 pages, 12 FiguresSubjects: Computational Engineering, Finance, and Science (cs.CE); Biological Physics (physics.bio-ph)
Understanding how genetically encoded rules drive and guide complex neuronal growth processes is essential to comprehending the brain's architecture, and agent-based models (ABMs) offer a powerful simulation approach to further develop this understanding. However, accurately calibrating these models remains a challenge. Here, we present a novel application of Approximate Bayesian Computation (ABC) to address this issue. ABMs are based on parametrized stochastic rules that describe the time evolution of small components -- the so-called agents -- discretizing the system, leading to stochastic simulations that require appropriate treatment. Mathematically, the calibration defines a stochastic inverse problem. We propose to address it in a Bayesian setting using ABC. We facilitate the repeated comparison between data and simulations by quantifying the morphological information of single neurons with so-called morphometrics and resort to statistical distances to measure discrepancies between populations thereof. We conduct experiments on synthetic as well as experimental data. We find that ABC utilizing Sequential Monte Carlo sampling and the Wasserstein distance finds accurate posterior parameter distributions for representative ABMs. We further demonstrate that these ABMs capture specific features of pyramidal cells of the hippocampus (CA1). Overall, this work establishes a robust framework for calibrating agent-based neuronal growth models and opens the door for future investigations using Bayesian techniques for model building, verification, and adequacy assessment.
- [110] arXiv:2405.13963 (cross-list from cond-mat.soft) [pdf, ps, html, other]
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Title: Active dynamics of charged macromoleculesComments: 13 pages, 1 figureSubjects: Soft Condensed Matter (cond-mat.soft); Biological Physics (physics.bio-ph); Chemical Physics (physics.chem-ph)
We study the role of active coupling on the transport properties of homogeneously charged macromolecules in an infinitely dilute solution. An enzyme becomes actively bound to a segment of the macromolecule, exerting an electrostatic force on it. Eventually, thermal fluctuations cause it to become unbound, introducing active coupling into the system. We study the mean-squared displacement (MSD) and find a new scaling regime compared to the thermal counterpart in the presence of hydrodynamic and segment-segment electrostatic interactions. Furthermore, the study of segment-segment equal-time correlation reveals the swelling of the macromolecule. Further, we derive the concentration equation of the macromolecule with active binding and study how the cooperative diffusivity of the macromolecules get modified by its environment, including the macromolecules itself. It turns out that these active fluctuations enhance the effective diffusivity of the macromolecules. The derived closed-form expression for diffusion constant is pertinent to the accurate interpretation of light scattering data in multi-component systems with binding-unbinding equilibria.
- [111] arXiv:2405.13973 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Numerical Simulations of 3D Ion Crystal Dynamics in a Penning Trap using the Fast Multipole MethodComments: 23 pages, 6 figuresSubjects: Quantum Physics (quant-ph); Computational Physics (physics.comp-ph); Plasma Physics (physics.plasm-ph)
We simulate the dynamics, including laser cooling, of 3D ion crystals confined in a Penning trap using a newly developed molecular dynamics-like code. The numerical integration of the ions' equations of motion is accelerated using the fast multipole method to calculate the Coulomb interaction between ions, which allows us to efficiently study large ion crystals with thousands of ions. In particular, we show that the simulation time scales linearly with ion number, rather than with the square of the ion number. By treating the ions' absorption of photons as a Poisson process, we simulate individual photon scattering events to study laser cooling of 3D ellipsoidal ion crystals. Initial simulations suggest that these crystals can be efficiently cooled to ultracold temperatures, aided by the mixing of the easily cooled axial motional modes with the low frequency planar modes. In our simulations of a spherical crystal of 1,000 ions, the planar kinetic energy is cooled to several millikelvin in a few milliseconds while the axial kinetic energy and total potential energy are cooled even further. This suggests that 3D ion crystals could be well-suited as platforms for future quantum science experiments.
- [112] arXiv:2405.14011 (cross-list from cond-mat.soft) [pdf, ps, html, other]
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Title: Nonlinear Response Theory of Molecular MachinesSubjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech); Biological Physics (physics.bio-ph)
Chemical affinities are responsible for driving active matter systems out of equilibrium. At the nano-scale, molecular machines interact with the surrounding environment and are subjected to external forces. The mechano-chemical coupling which arises naturally in these systems reveals a complex interplay between chemical and mechanical degrees of freedom with strong impact on their active mechanism. By considering various models far from equilibrium, we show that the tuning of applied forces give rise to a nonlinear response that causes a non-monotonic behaviour in the machines' activity. Our findings have implications in understanding, designing, and triggering such processes by controlled application of external fields, including the collective dynamics of larger non-equilibrium systems where the total dissipation and performance might be affected by internal and inter-particle interactions.
- [113] arXiv:2405.14060 (cross-list from cs.LG) [pdf, ps, html, other]
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Title: Probabilistic Inference in the Era of Tensor Networks and Differential ProgrammingComments: 12 pages, 4 figuresSubjects: Machine Learning (cs.LG); Computational Physics (physics.comp-ph)
Probabilistic inference is a fundamental task in modern machine learning. Recent advances in tensor network (TN) contraction algorithms have enabled the development of better exact inference methods. However, many common inference tasks in probabilistic graphical models (PGMs) still lack corresponding TN-based adaptations. In this work, we advance the connection between PGMs and TNs by formulating and implementing tensor-based solutions for the following inference tasks: (i) computing the partition function, (ii) computing the marginal probability of sets of variables in the model, (iii) determining the most likely assignment to a set of variables, and (iv) the same as (iii) but after having marginalized a different set of variables. We also present a generalized method for generating samples from a learned probability distribution. Our work is motivated by recent technical advances in the fields of quantum circuit simulation, quantum many-body physics, and statistical physics. Through an experimental evaluation, we demonstrate that the integration of these quantum technologies with a series of algorithms introduced in this study significantly improves the effectiveness of existing methods for solving probabilistic inference tasks.
- [114] arXiv:2405.14065 (cross-list from astro-ph.EP) [pdf, ps, html, other]
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Title: Full spectroscopic model and trihybrid experimental-perturbative-variational line list for NHComments: 12 pages, 8 figures, 9 tables, accepted. arXiv admin note: substantial text overlap with arXiv:2308.03922Journal-ref: MNRAS 2024Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Atomic Physics (physics.atom-ph)
Imidogen (NH) is a reactive molecule whose presence in astrochemical environments is of interest due to its role in the formation of nitrogen-containing molecules and as a potential probe of nitrogen abundance. Spectroscopic NH monitoring is useful for Earth-based combustion and photolysis processes of ammonia and other nitrogen-containing species. NH is also relevant to ultracold molecular physics and plasma studies. To enable these diverse applications, high-quality molecular spectroscopic data is required. Here, a new line list with significant advantages over existing data is presented. Most notably, this line list models isotopologue spectroscopy and forbidden transitions (important for NH visible absorption), alongside some overall improvements to accuracy and completeness. This approach takes advantage of existing experimental data (from a previous MARVEL compilation) and perturbative line lists together with new MRCI ab initio electronic data. These are used to produce a novel variational spectroscopic model and trihybrid line list for the main 14N1H isotopologue, as well as isotopologue-extrapolated hybrid line lists for the 14N2H, 15N1H and 15N2H isotopologues. The new 14N1H ExoMol-style trihybrid line list, kNigHt, comprises 4,076 energy levels (1,078 experimental) and 327,014 transitions up to 47,500 cm-1 (211 nm) between five low-lying electronic states (X 3{\Sigma}-, a 1{\Delta}, b 1{\Sigma}+, A 3{\Pi} and c 1{\Pi}). For most anticipated applications aside from far-IR studies, this line list will be of sufficient quality; any improvements should focus on the b 1{\Sigma}+ energies, and the a 1{\Delta} - A 3{\Pi} and b 1{\Sigma}+ - A 3{\Pi} spin-orbit couplings.
- [115] arXiv:2405.14168 (cross-list from cs.SI) [pdf, ps, html, other]
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Title: A generative model for community types in directed networksComments: 13 pages, 6 figuresSubjects: Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)
Large complex networks are often organized into groups or communities. In this paper, we introduce and investigate a generative model of network evolution that reproduces all four pairwise community types that exist in directed networks: assortative, core-periphery, disassortative, and the newly introduced source-basin type. We fix the number of nodes and the community membership of each node, allowing node connectivity to change through rewiring mechanisms that depend on the community membership of the involved nodes. We determine the dependence of the community relationship on the model parameters using a mean-field solution. It reveals that a difference in the swap probabilities of the two communities is a necessary condition to obtain a core-periphery relationship and that a difference in the average in-degree of the communities is a necessary condition for a source-basin relationship. More generally, our analysis reveals multiple possible scenarios for the transition between the different structure types, and sheds light on the mechanisms underlying the observation of the different types of communities in network data.
- [116] arXiv:2405.14253 (cross-list from cs.LG) [pdf, ps, html, other]
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Title: Higher-Rank Irreducible Cartesian Tensors for Equivariant Message PassingViktor Zaverkin, Francesco Alesiani, Takashi Maruyama, Federico Errica, Henrik Christiansen, Makoto Takamoto, Nicolas Weber, Mathias NiepertSubjects: Machine Learning (cs.LG); Computational Physics (physics.comp-ph)
The ability to perform fast and accurate atomistic simulations is crucial for advancing the chemical sciences. By learning from high-quality data, machine-learned interatomic potentials achieve accuracy on par with ab initio and first-principles methods at a fraction of their computational cost. The success of machine-learned interatomic potentials arises from integrating inductive biases such as equivariance to group actions on an atomic system, e.g., equivariance to rotations and reflections. In particular, the field has notably advanced with the emergence of equivariant message-passing architectures. Most of these models represent an atomic system using spherical tensors, tensor products of which require complicated numerical coefficients and can be computationally demanding. This work introduces higher-rank irreducible Cartesian tensors as an alternative to spherical tensors, addressing the above limitations. We integrate irreducible Cartesian tensor products into message-passing neural networks and prove the equivariance of the resulting layers. Through empirical evaluations on various benchmark data sets, we consistently observe on-par or better performance than that of state-of-the-art spherical models.
- [117] arXiv:2405.14274 (cross-list from gr-qc) [pdf, ps, html, other]
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Title: Window and inpainting: dealing with data gaps for TianQinComments: 12 pages, 5 figures, comments welcomeSubjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an)
Space-borne gravitational wave detectors like TianQin might encounter data gaps due to factors like micro-meteoroid collisions or hardware failures. Such glitches will cause discontinuity in the data and have been observed in the LISA Pathfinder. The existence of such data gaps presents challenges to the data analysis for TianQin, especially for massive black hole binary mergers, since its signal-to-noise ratio (SNR) accumulates in a non-linear way, a gap near the merger could lead to significant loss of SNR. It could introduce bias in the estimate of noise properties, and furthermore the results of the parameter estimation. In this work, using simulated TianQin data with injected a massive black hole binary merger, we study the window function method, and for the first time, the inpainting method to cope with the data gap, and an iterative estimate scheme is designed to properly estimate the noise spectrum. We find that both methods can properly estimate noise and signal parameters. The easy-to-implement window function method can already perform well, except that it will sacrifice some SNR due to the adoption of the window. The inpainting method is slower, but it can minimize the impact of the data gap.
- [118] arXiv:2405.14403 (cross-list from stat.AP) [pdf, ps, html, other]
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Title: Representative electricity price profiles for European day-ahead and intraday spot marketsComments: Supplementary information (SI) included; Manuscript: 27 pages, 9 figures, 4 tables; SI: 7 pages, 5 figures, 2 tablesSubjects: Applications (stat.AP); Computational Engineering, Finance, and Science (cs.CE); Physics and Society (physics.soc-ph)
We propose a method to construct representative price profiles of the day-ahead (DA) and the intraday (ID) electricity spot markets and use this method to provide examples of ready-to-use price data sets. In contrast to common scenario generation approaches, the method is deterministic and relies on a small number of degrees of freedom, with the aim to be well defined and easy to use. We thereby target an enhanced comparability of future research studies on demand-side management and energy cost optimization. We construct the price profiles based on historical time series from the spot markets of interest, e.g., European Power Exchange (EPEX) spot. To this end, we extract key price components from the data while also accounting for known dominant mechanisms in the price variation. Further, the method is able to preserve key statistical features of the historical data (e.g., mean and standard deviation) when constructing the benchmark profile. Finally, our approach ensures comparability of ID and DA price profiles by design, as their cumulative (integral) price can be made identical if needed.
- [119] arXiv:2405.14417 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: The hydrogen atom perturbed by a 1-dimensional Simple Harmonic Oscillator (1d-SHO) potentialSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
The hydrogen atom perturbed by a constant 1-dimensional weak quadratic potential $\lambda z^2$ is solved at first-order perturbation theory using the eigenstates of the total angular momentum operator - the coupled basis. Physical applications of this result could be found, for example, in the study of a quadratic Zeeman effect weaker than fine-structure effects, or in a perturbation caused by instantaneous generalised van der Waals interactions.
- [120] arXiv:2405.14523 (cross-list from cond-mat.mes-hall) [pdf, ps, html, other]
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Title: Casimir-Lifshitz force for graphene-covered gratingsComments: 11 pages, 10 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics); Quantum Physics (quant-ph)
We study the Casimir-Lifshitz force (CLF) between a gold plate and a graphene-covered dielectric grating. Using a scattering matrix (S-matrix) approach derived from the Fourier Modal Method (FMM), we find a significant enhancement in the CLF as compared to a mere dielectric slab coated with graphene, over a wide range of temperatures. Additionally, we demonstrate that the CLF depends strongly on the chemical potential of graphene, with maximal effects observed at lower filling fractions. Finally, we analyse the Casimir force gradient between a gold sphere and a graphene-coated dielectric grating, highlighting potential avenues for experimental measurements.
- [121] arXiv:2405.14531 (cross-list from cond-mat.dis-nn) [pdf, ps, html, other]
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Title: Low-resolution descriptions of model neural activity reveal hidden features and underlying system propertiesSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Computational Physics (physics.comp-ph)
The analysis of complex systems such as neural networks is made particularly difficult by the overwhelming number of their interacting components. In the absence of prior knowledge, identifying a small but informative subset of network nodes on which the analysis should focus is a rather difficult task. In this work, we address this problem in the context of a Hopfield model, for which we seek representations given in terms of a subgroup of its neurons with the aim of identifying those that can reveal the largest amount of information about the system. Using a methodology based on concepts from information theory, we reveal that such optimised low-resolution representations are not only informative per se, but rather they also serve as probes of the neural network properties; these results show a tight and potentially fruitful relation between the level of detail at which the network is inspected and the type and amount of information that can be extracted from it.
- [122] arXiv:2405.14551 (cross-list from cond-mat.soft) [pdf, ps, html, other]
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Title: Lattice Boltzmann methods for soft flowing matterComments: 43 pages, 26 figuresSubjects: Soft Condensed Matter (cond-mat.soft); Computational Physics (physics.comp-ph); Fluid Dynamics (physics.flu-dyn)
Over the last decade, the Lattice Boltzmann method has found major scope for the simulation of a large spectrum of problems in soft matter, from multiphase and multi-component microfluidic flows, to foams, emulsions, colloidal flows, to name but a few. Crucial to many such applications is the role of supramolecular interactions which occur whenever mesoscale structures, such as bubbles or droplets, come in close contact, say of the order of tens of nanometers. Regardless of their specific physico-chemical origin, such near-contact interactions are vital to preserve the coherence of the mesoscale structures against coalescence phenomena promoted by capillarity and surface tension, hence the need of including them in Lattice Boltzmann schemes. Strictly speaking, this entails a complex multiscale problem, covering about six spatial decades, from centimeters down to tens of nanometers, and almost twice as many in time. Such a multiscale problem can hardly be taken by a single computational method, hence the need for coarse-grained models for the near-contact interactions. In this review, we shall discuss such coarse-grained models and illustrate their application to a variety of soft flowing matter problems, such as soft flowing crystals, strongly confined dense emulsions, flowing hierarchical emulsions, soft granular flows, as well as the transmigration of active droplets across constrictions. Finally, we conclude with a few considerations on future developments in the direction of quantum-nanofluidics, machine learning, and quantum computing for soft flows applications.
- [123] arXiv:2405.14557 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: High fidelity distribution of triggered polarization-entangled telecom photons via a 36km intra-city fiber networkTim Strobel1, Stefan Kazmaier1, Tobias Bauer2, Marlon Schäfer2, Ankita Choudhary3, Cornelius Nawrath1, Jonas H. Weber1, Weijie Nie3, Ghata Bhayani3, Lukas Wagner1, André Bisquerra1, Marc Geitz4, Ralf-Peter Braun4, Caspar Hopfmann3, Simone L. Portalupi1, Christoph Becher2, Peter Michler1Subjects: Quantum Physics (quant-ph); Optics (physics.optics)
Fiber-based distribution of triggered, entangled, single-photon pairs is a key requirement for the future development of terrestrial quantum networks. In this context, semiconductor quantum dots (QDs) are promising candidates for deterministic sources of on-demand polarization-entangled photon pairs. So far, the best QD polarization-entangled-pair sources emit in the near-infrared wavelength regime, where the transmission distance in deployed fibers is limited. Here, to be compatible with existing fiber network infrastructures, bi-directional polarization-conserving quantum frequency conversion (QFC) is employed to convert the QD emission from \unit[780]{nm} to telecom wavelengths. We show the preservation of polarization entanglement after QFC (fidelity to Bell state $F_{\phi^+, conv}=0.972\pm0.003$) of the biexciton transition. As a step towards real-world applicability, high entanglement fidelities ($F_{\phi^+, loop}=0.945\pm0.005$) after the propagation of one photon of the entangled pair along a \unit[35.8]{km} field installed standard single mode fiber link are reported. Furthermore, we successfully demonstrate a second polarization-conversing QFC step back to \unit[780]{nm} preserving entanglement ($F_{\phi^+, back}=0.903\pm0.005$). This further prepares the way for interfacing quantum light to various quantum memories.
- [124] arXiv:2405.14624 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Quantum Simulation of Spin-Boson Models with Structured BathKe Sun, Mingyu Kang, Hanggai Nuomin, George Schwartz, David N. Beratan, Kenneth R. Brown, Jungsang KimComments: 11 pages, 7 figuresSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
The spin-boson model, involving a spin interacting with a bath of quantum harmonic oscillators, is a widely used representation of open quantum systems. Trapped ions present a natural platform for the quantum simulation of such models; however, previous experiments have been limited to simulating a scenario where a spin is coherently coupled to bosonic modes, which neglects capturing the dissipation of the bath. In our work, we perform quantum simulations of spin-boson models with structured baths using the motional states of trapped ions. We demonstrate the capability for adjusting the bath's temperature and continuous spectral density by adding randomness to the control parameters. Subsequently, we simulate the dynamics of various spin-boson models with spectral densities composed of up to three Lorentzian peaks. The experimental outcomes closely align with theoretical predictions, suggesting the advantage of adding the trapped-ion system's experimental noise for simulating open quantum systems.
- [125] arXiv:2405.14649 (cross-list from cond-mat.mtrl-sci) [pdf, ps, html, other]
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Title: Leveraging Machine Learning for Advanced Nanoscale X-ray Analysis: Unmixing Multicomponent Signals and Enhancing Chemical QuantificationSubjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Data Analysis, Statistics and Probability (physics.data-an); Instrumentation and Detectors (physics.ins-det)
Energy dispersive X-ray (EDX) spectroscopy in the transmission electron microscope is a key tool for nanomaterials analysis, providing a direct link between spatial and chemical information. However, using it for precisely determining chemical compositions presents challenges of noisy data from low X-ray yields and mixed signals from phases that overlap along the electron beam trajectory. Here, we introduce a novel method, non-negative matrix factorisation based pan-sharpening (PSNMF), to address these limitations. Leveraging the Poisson nature of EDX spectral noise and binning operations, PSNMF retrieves high quality phase spectral and spatial signatures via consecutive factorisations. After validating PSNMF with synthetic datasets of different noise levels, we illustrate its effectiveness on two distinct experimental cases: a nano-mineralogical lamella, and supported catalytic nanoparticles. Not only does PSNMF obtain accurate phase signatures, datasets reconstructed from the outputs have demonstrably lower noise and better fidelity than from the benchmark denoising method of principle component analysis.
- [126] arXiv:2405.14687 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Quantum thermodynamic derivation of the energy resolution limit in magnetometrySubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
It was recently demonstrated that a large number of magnetic sensing technologies satisfy the energy resolution limit, which connects a quantity composed by the variance of the magnetic field estimate, the sensor volume and the measurement time, and having units of action, with $\hbar$. A first-principles derivation of the energy resolution limit is still elusive. We here present such a derivation based on quantum thermodynamic arguments. We show that the energy resolution limit is a result of quantum thermodynamic work associated with quantum measurement and Landauer erasure, the work being exchanged with the magnetic field. We apply these considerations to atomic magnetometers and SQUIDS. Regarding the former, we unravel a new spin correlation effect relevant to the magnetic noise produced by atomic vapors.
- [127] arXiv:2405.14693 (cross-list from astro-ph.EP) [pdf, ps, html, other]
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Title: Interpolation and synthesis of sparse samples in exoplanet atmospheric modelingComments: Accepted for publication in the Planetary Science JournalSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Atmospheric and Oceanic Physics (physics.ao-ph); Geophysics (physics.geo-ph)
This paper highlights methods from geostatistics that are relevant to the interpretation, intercomparison, and synthesis of atmospheric model data, with a specific application to exoplanet atmospheric modeling. Climate models are increasingly used to study theoretical and observational properties of exoplanets, which include a hierarchy of models ranging from fast and idealized models to those that are slower but more comprehensive. Exploring large parameter spaces with computationally-expensive models can be accomplished with sparse sampling techniques, but analyzing such sparse samples can pose challenges for conventional interpolation functions. Ordinary kriging is a statistical method for describing the spatial distribution of a data set in terms of the variogram function, which can be used to interpolate sparse samples across any number of dimensions. Variograms themselves may also be useful diagnostic tools for describing the spatial distribution of model data in exoplanet atmospheric model intercomparison projects. Universal kriging is another method that can synthesize data calculated by models of different complexity, which can be used to combine sparse samples of data from slow models with larger samples of data from fast models. Ordinary and universal kriging can also provide a way to synthesize model predictions with sparse samples of exoplanet observations and may have other applications in exoplanet science.
- [128] arXiv:2405.14762 (cross-list from cs.LG) [pdf, ps, html, other]
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Title: Neural Pfaffians: Solving Many Many-Electron Schr\"odinger EquationsSubjects: Machine Learning (cs.LG); Chemical Physics (physics.chem-ph); Computational Physics (physics.comp-ph); Quantum Physics (quant-ph)
Neural wave functions accomplished unprecedented accuracies in approximating the ground state of many-electron systems, though at a high computational cost. Recent works proposed amortizing the cost by learning generalized wave functions across different structures and compounds instead of solving each problem independently. Enforcing the permutation antisymmetry of electrons in such generalized neural wave functions remained challenging as existing methods require discrete orbital selection via non-learnable hand-crafted algorithms. This work tackles the problem by defining overparametrized, fully learnable neural wave functions suitable for generalization across molecules. We achieve this by relying on Pfaffians rather than Slater determinants. The Pfaffian allows us to enforce the antisymmetry on arbitrary electronic systems without any constraint on electronic spin configurations or molecular structure. Our empirical evaluation finds that a single neural Pfaffian calculates the ground state and ionization energies with chemical accuracy across various systems. On the TinyMol dataset, we outperform the `gold-standard' CCSD(T) CBS reference energies by 1.9m$E_h$ and reduce energy errors compared to previous generalized neural wave functions by up to an order of magnitude.
- [129] arXiv:2405.14787 (cross-list from cond-mat.mtrl-sci) [pdf, ps, html, other]
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Title: Construction and sampling of alloy cluster expansions -- A tutorialComments: 18 pages; 12 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Crystalline alloys and related mixed systems make up a large family of materials with high tunability which have been proposed as the solution to a large number of energy related materials design problems. Due to the presence of chemical order and disorder in these systems, neither experimental efforts nor ab-initio computational methods alone are sufficient to span the inherently large configuration space. Therefore, fast and accurate models are necessary. To this end, cluster expansions have been widely and successfully used for the past decades. Cluster expansions are generalized Ising models designed to predict the energy of any atomic configuration of a system after training on a small subset of the available configurations. Constructing and sampling a cluster expansion consists of multiple steps that have to be performed with care. In this tutorial, we provide a comprehensive guide to this process, highlighting important considerations and potential pitfalls. The tutorial consists of three parts, starting with cluster expansion construction for a relatively simple system, continuing with strategies for more challenging systems such as surfaces and closing with examples of Monte Carlo sampling of cluster expansions to study order-disorder transitions and phase diagrams.
- [130] arXiv:2405.14837 (cross-list from cs.LG) [pdf, ps, html, other]
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Title: Analysis of Atom-level pretraining with QM data for Graph Neural Networks Molecular property modelsComments: 6 pages + 10 Supplement MaterialsSubjects: Machine Learning (cs.LG); Chemical Physics (physics.chem-ph); Quantum Physics (quant-ph)
Despite the rapid and significant advancements in deep learning for Quantitative Structure-Activity Relationship (QSAR) models, the challenge of learning robust molecular representations that effectively generalize in real-world scenarios to novel compounds remains an elusive and unresolved task. This study examines how atom-level pretraining with quantum mechanics (QM) data can mitigate violations of assumptions regarding the distributional similarity between training and test data and therefore improve performance and generalization in downstream tasks. In the public dataset Therapeutics Data Commons (TDC), we show how pretraining on atom-level QM improves performance overall and makes the activation of the features distributes more Gaussian-like which results in a representation that is more robust to distribution shifts. To the best of our knowledge, this is the first time that hidden state molecular representations are analyzed to compare the effects of molecule-level and atom-level pretraining on QM data.
Cross submissions for Friday, 24 May 2024 (showing 45 of 45 entries )
- [131] arXiv:1709.09508 (replaced) [pdf, ps, other]
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Title: Quantum Mechanical Foundations of EpistemologyComments: Reconceptualization with major revisions. 33 pagesSubjects: History and Philosophy of Physics (physics.hist-ph); Quantum Physics (quant-ph)
Scholars of the history and philosophy of science have asked what would decolonized science would look like. This paper develops an answer by interrogating the assumption that observations need to be recorded and communicated using the language of classical physics. Niels Bohr held this assumption even though he recognized the fact that quantum phenomena cannot be analyzed on classical lines. Classical analysis requires the objectification of whatever is being observed so that it can be objectively described. Inherent in this analysis is the intellectual creation of a transcendental verity, a view from nowhere. In contrast, knowledge systems that predate European colonialism make use of the quantum nature of nature without constructing an objective model of it. This paper concludes that uncolonized knowledge systems differ from classical ones in that they are epistemically plural, accepting multiple true observations of the same phenomenon.
- [132] arXiv:2110.12592 (replaced) [pdf, ps, html, other]
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Title: Collective plasma effects of electron-positron pairs in beam-driven QED cascadesComments: 15 pages, 14 figuresSubjects: Plasma Physics (physics.plasm-ph)
Understanding the interplay of strong-field QED and collective plasma effects is important for explaining extreme astrophysical environments like magnetars. It has been shown that QED pair plasmas is possible to be produced and observed by passing a relativistic electron beam through an intense laser field. This paper presents in detail multiple sets of 3D QED-PIC simulations to show the creation of pair plasmas in the QED cascade. The beam driven method enables a high pair particle density and also a low particle gamma factor, which both play equal rolls on exhibiting large collective plasma effects. Finite laser frequency upshift is observed with both ideal parameters (24 PW laser laser colliding with 300 GeV electron beam) and with existing technologies (3 PW laser laser colliding with 30 GeV electron beam).
- [133] arXiv:2307.01098 (replaced) [pdf, ps, other]
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Title: Automated identification and quantification of myocardial inflammatory infiltration in digital histological images to diagnose myocarditisComments: 21 pages,5 figures,6 Tables, 25 referencesSubjects: Medical Physics (physics.med-ph); Artificial Intelligence (cs.AI)
This study aims to develop a new computational pathology approach that automates the identification and quantification of myocardial inflammatory infiltration in digital HE-stained images to provide a quantitative histological diagnosis of myocarditis.898 HE-stained whole slide images (WSIs) of myocardium from 154 heart transplant patients diagnosed with myocarditis or dilated cardiomyopathy (DCM) were included in this study. An automated DL-based computational pathology approach was developed to identify nuclei and detect myocardial inflammatory infiltration, enabling the quantification of the lymphocyte nuclear density (LND) on myocardial WSIs. A cutoff value based on the quantification of LND was proposed to determine if the myocardial inflammatory infiltration was present. The performance of our approach was evaluated with a five-fold cross-validation experiment, tested with an internal test set from the myocarditis group, and confirmed by an external test from a double-blind trial group. An LND of 1.02/mm2 could distinguish WSIs with myocarditis from those without. The accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) in the five-fold cross-validation experiment were 0.899 plus or minus 0.035, 0.971 plus or minus 0.017, 0.728 plus or minus 0.073 and 0.849 plus or minus 0.044, respectively. For the internal test set, the accuracy, sensitivity, specificity, and AUC were 0.887, 0.971, 0.737, and 0.854, respectively. The accuracy, sensitivity, specificity, and AUC for the external test set reached 0.853, 0.846, 0.858, and 0.852, respectively. Our new approach provides accurate and reliable quantification of the LND of myocardial WSIs, facilitating automated quantitative diagnosis of myocarditis with HE-stained images.
- [134] arXiv:2311.01539 (replaced) [pdf, ps, html, other]
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Title: Influence of ion-to-electron temperature ratio on tearing instability and resulting subion-scale turbulence in a low-$\beta_e$ collisionless plasmaSubjects: Plasma Physics (physics.plasm-ph)
A two-field gyrofluid model including ion finite Larmor radius (FLR) corrections, magnetic fluctuations along the ambient field and electron inertia is used to study two-dimensional reconnection in a low $\beta_e$ collisionless plasma, in a plane perpendicular to the ambient field. Both moderate and large values of the ion-to-electron temperature ratio $\tau$ are considered. The linear growth rate of the tearing instability is computed for various values of $\tau$, confirming the convergence to reduced electron magnetodynamics (REMHD) predictions in the large $\tau$ limit. Comparisons with analytical estimates in several limit cases are also presented. The nonlinear dynamics leads to a fully-developed turbulent regime that appears to be sensitive to the value of the parameter $\tau$. For $\tau = 100$, strong large-scale velocity shears trigger Kelvin-Helmholtz instability, leading to the propagation of the turbulence through the separatrices, together with the formation of eddies of size of the order of the electron skin depth. In the $\tau = 1$ regime, the vortices are significantly smaller and their accurate description requires that electron FLR effects be taken into account.
- [135] arXiv:2311.05728 (replaced) [pdf, ps, html, other]
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Title: A Physics-Informed, Deep Double Reservoir Network for Forecasting Boundary Layer VelocitySubjects: Fluid Dynamics (physics.flu-dyn); Applications (stat.AP)
When a fluid flows over a solid surface, it creates a thin boundary layer where the flow velocity is influenced by the surface through viscosity, and can transition from laminar to turbulent at sufficiently high speeds. Understanding and forecasting the fluid dynamics under these conditions is one of the most challenging scientific problems in fluid dynamics. It is therefore of high interest to formulate models able to capture the nonlinear spatio-temporal velocity structure as well as produce forecasts in a computationally efficient manner. Traditional statistical approaches are limited in their ability to produce timely forecasts of complex, nonlinear spatio-temporal structures which are at the same time able to incorporate the underlying flow physics. In this work, we propose a model to accurately forecast boundary layer velocities with a deep double reservoir computing network which is capable of capturing the complex, nonlinear dynamics of the boundary layer while at the same time incorporating physical constraints via a penalty obtained by a Partial Differential Equation (PDE). Simulation studies on a one-dimensional viscous fluid demonstrate how the proposed model is able to produce accurate forecasts while simultaneously accounting for energy loss. The application focuses on boundary layer data on a water tunnel with a PDE penalty derived from an appropriate simplification of the Navier-Stokes equations, showing forecasts improved by 33.7% and 80.0% in terms of mass conservation and variability of velocity fluctuation, respectfully, against non physics-informed methods.
- [136] arXiv:2311.17070 (replaced) [pdf, ps, html, other]
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Title: Quantum Entanglement without nonlocal causation in (3,2)-dimensional spacetimeComments: 23 pages, 3 figures. Changes in the new version: additional comments in the text, added referencesSubjects: General Physics (physics.gen-ph)
This work aims at exploring whether the nonlocal correlations due to quantum entanglement could exist without nonlocal causation. This is done with the aid of a toy model to investigate whether the ability of two quantum entangled particles to "correlate" their behaviors even at very large distances and in the absence of any physical connection can be seen as due to an exchange of information through an extra-temporal dimension. Since superluminal information exchange is forbidden in our (3,1) spacetime, an extra-temporal dimension is needed to recover the physical picture of finite velocity information exchange between entangled entities. Assuming that the geometry of space-time of dimension (3,2) is described by a metric containing a warping factor, the confinement of the massive particles in the extra time dimension follows. Therefore, why we do not experience an infinitely large extra time dimension can be explained. The toy model proposed here is defined by borrowing Bohm-Bub's proposal to describe the wavefunction collapse using nonlinear (non-unitary) dynamical equations and then elaborating this approach for an entangled system. The model so obtained is just speculative without any claim of being robust against any criticism, nevertheless, it satisfies the purpose of giving the possibility to the hypotheses formulated above to be verified experimentally; in fact, it proposes an experiment potentially interesting which would otherwise be immediately dismissed as manifestly trivial. The proposed experiment would consist of checking the possible violation of Bell's inequality between two identical but independent systems under appropriate conditions. Beyond its theoretical interest, entanglement is a key topic in quantum computing and quantum technologies, so any attempt to gain a deeper understanding of it could be useful.
- [137] arXiv:2312.01891 (replaced) [pdf, ps, html, other]
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Title: A Christmas Story about Quantum TeleportationComments: 11 + 8 pages, 3 figures, v2: as publishedJournal-ref: Phys. Educ. 59, 035021 (2024)Subjects: Physics Education (physics.ed-ph); Popular Physics (physics.pop-ph); Quantum Physics (quant-ph)
Quantum teleportation is a concept that fascinates and confuses many people, in particular, given that it combines quantum physics and the concept of teleportation. With quantum teleportation likely to play a key role in several communication technologies and the quantum internet in the future, it is imperative to create learning tools and approaches that can accurately and effectively communicate the concept. Recent research has indicated the importance of teachers enthusing students about the topic of quantum physics. Therefore, educators at both high school and early university level need to find engaging and perhaps unorthodox ways of teaching complex, yet interesting topics such as quantum teleportation. In this paper, we present a paradigm to teach the concept of quantum teleportation using the Christmas gift-bringer Santa Claus. Using the example of Santa Claus, we use an unusual context to explore the key aspects of quantum teleportation, and all without being overly abstract. In addition, we outline a worksheet designed for use in the classroom setting which is based on common naive conceptions from quantum physics. This worksheet will be evaluated as a classroom resource to teach quantum teleportation in a subsequent study.
- [138] arXiv:2312.03861 (replaced) [pdf, ps, html, other]
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Title: Data-driven analysis of annual rain distributionsComments: 26 pages, 18 figuresJournal-ref: Phys. Rev. Research 6, 023187 (2024)Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Statistical Mechanics (cond-mat.stat-mech); Data Analysis, Statistics and Probability (physics.data-an)
Rainfall is an important component of the climate system and its statistical properties are vital for prediction purposes. In this study, we have developed a statistical method for constructing the distribution of annual precipitation. The method is based on the convolution of the measured monthly rainfall distributions and does not depend on any presumed annual rainfall distribution. Using a simple statistical model, we demonstrate that our approach allows for a better prediction of extremely dry or wet years with a recurrence time several times longer than the original time series. The method that has been proposed can be utilized for other climate variables as well.
- [139] arXiv:2312.04878 (replaced) [pdf, ps, html, other]
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Title: Response of Non-premixed Jet Flames to Blast WavesSubjects: Fluid Dynamics (physics.flu-dyn); Applied Physics (physics.app-ph)
The work investigates the response dynamics of non-premixed jet flame to blast waves that are incident along the jet axis. In the present study, blast waves, generated using the wire-explosion technique, are forced to sweep across a non-premixed jet flame that is stabilised over a nozzle rim positioned at a distance of 264 mm from the source of blast generation. The work spans a wide range of fuel jet Reynolds numbers ($Re$) and incident blast wave Mach numbers ($M_{s,r}$). The interaction imposes a characteristic flow field over the jet flame, marked by a sharp discontinuity followed by a decaying profile and a delayed second spike. The second spike in the flow field profile corresponds to the induced flow that follows the blast front. While the response of the flame to the blast front was minimal, it was found to detach from the nozzle rim and lift off following the interaction with the induced flow. Subsequently, the lifted flame was found to re-attach back at the nozzle or extinguish, contingent on the operating $Re$ and $M_{s,r}$. Alongside flame lift-off, flame tip flickering was aggravated under the influence of the induced flow. A simplified theoretical model extending the vorticity transport equation was developed to estimate the change in flickering timescales and length scales owing to the interaction with the induced flow. The observed experimental trends were further compared against theoretical predictions from the model.
- [140] arXiv:2312.11161 (replaced) [pdf, ps, other]
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Title: Comparative simulations of Kelvin-Helmholtz induced magnetic reconnection at the Earth's magnetospheric flanksJournal-ref: Phys. Plasmas 1 May 2024; 31 (5): 052902Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph)
This study presents three-dimensional (3D) resistive Hall-magnetohydrodynamic simulations of the Kelvin-Helmholtz instability (KHI) dynamics at Earth's magnetospheric flanks during northward interplanetary magnetic field periods. By comparing two simulations with and without initial magnetic shear, we analyze the impact of distinct magnetic field orientations on plasma dynamics and magnetic reconnection events taking into account 3D mechanisms, such as KHI high latitude stabilization. The identical nature of the simulations, except for the presence/absence of an initial magnetic shear, enables, for the first time, a complete and coherent comparative analysis of the latitudinal distribution of KH vortices, current sheets, reconnection events, and the evolution of the mixing layer. In one configuration, a uniform magnetic field leads to double mid-latitude reconnection (MLR), while in the other, magnetic shear induces both type I vortex-induced reconnection (VIR) and MLR. Notably, the type I VIR observed in this second scenario results from the combined action of line advection and vortex-induced current sheet pinching (the classic mechanism driving two-dimensional type I VIR). Of particular importance is our quantification of newly closed field lines that experienced double reconnection, ultimately becoming embedded in solar wind plasma at low latitudes while remaining connected to magnetospheric plasma at high latitudes. The varying abundance of such lines in the two simulations holds implications for plasma transport at the magnetopause.
- [141] arXiv:2312.12548 (replaced) [pdf, ps, html, other]
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Title: Double diffraction imaging of X-ray induced structural dynamics in single free nanoparticlesM. Sauppe, T. Bischoff, C. Bomme, C. Bostedt, A. Colombo, B. Erk, T. Feigl, L. Flückiger, T. Gorkhover, A. Heilrath, K. Kolatzki, Y. Kumagai, B. Langbehn, J. P. Müller, C. Passow, D. Ramm, D. Rolles, D. Rompotis, J. Schäfer-Zimmermann, B. Senfftleben, R. Treusch, A. Ulmer, J. Zimbalski, T. Möller, D. RuppSubjects: Atomic and Molecular Clusters (physics.atm-clus); Instrumentation and Detectors (physics.ins-det); Optics (physics.optics)
Because of their high photon flux, X-ray free-electron lasers (FEL) allow to resolve the structure of individual nanoparticles via coherent diffractive imaging (CDI) within a single X-ray pulse. Since the inevitable rapid destruction of the sample limits the achievable resolution, a thorough understanding of the spatiotemporal evolution of matter on the nanoscale following the irradiation is crucial. We present a technique to track X-ray induced structural changes in time and space by recording two consecutive diffraction patterns of the same single, free-flying nanoparticle, acquired separately on two large-area detectors opposite to each other, thus examining both the initial and evolved particle structure. We demonstrate the method at the extreme ultraviolet (XUV) and soft X-ray Free-electron LASer in Hamburg (FLASH), investigating xenon clusters as model systems. By splitting a single XUV pulse, two diffraction patterns from the same particle can be obtained. For focus intensities of about $2\cdot10^{12}\,\text{W/cm}^2$ we observe still largely intact clusters even at the longest delays of up to 650 picoseconds of the second pulse, indicating that in the highly absorbing systems the damage remains confined to one side of the cluster. Instead, in case of five times higher flux, the diffraction patterns show clear signatures of disintegration, namely increased diameters and density fluctuations in the fragmenting clusters. Future improvements to the accessible range of dynamics and time resolution of the approach are discussed.
- [142] arXiv:2401.05084 (replaced) [pdf, ps, html, other]
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Title: Statistical Reproducibility of Selective Area Grown InAs Nanowire DevicesDāgs Olšteins, Gunjan Nagda, Damon J. Carrad, Daria V. Beznasyuk, Christian E. N. Petersen, Sara Martí-Sánchez, Jordi Arbiol, Thomas Sand JespersenSubjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
New approaches such as selective area growth, where crystal growth is lithographically controlled, allow the integration of bottom-up grown semiconductor nanomaterials in large-scale classical and quantum nanoelectronics. This calls for assessment and optimization of the reproducibility between individual components. We quantify the structural and electronic statistical reproducibility within large arrays of nominally identical selective area growth InAs nanowires. The distribution of structural parameters is acquired through comprehensive atomic force microscopy studies and transmission electron microscopy. These are compared to the statistical distributions of the cryogenic electrical properties of 256 individual SAG nanowire field effect transistors addressed using cryogenic multiplexer circuits. Correlating measurements between successive thermal cycles allows distinguishing between the contributions of surface impurity scattering and fixed structural properties to device reproducibility. The results confirm the potential of SAG nanomaterials, and the methodologies for quantifying statistical metrics are essential for further optimization of reproducibility.
- [143] arXiv:2401.09469 (replaced) [pdf, ps, html, other]
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Title: Mixed Convection From an Isothermal Rough PlateComments: 33 pages; 39 figures; 12 tables; 19 referencesSubjects: Fluid Dynamics (physics.flu-dyn)
While there are studies of mixed convection heat transfer from a smooth plate, studies of this phenomenon from an external rough plate are absent.
The derivation by Jaffer (2023) of the heat transfer formula for natural convection from an external plate implies a simple relation between heat transfer and fluid velocity. This relation leads to formulas for mixed convection from horizontal and vertical rough plates; these formulas are then combined to predict the mixed convection heat transfer at any plate inclination.
Heat transfer measurements of a 30.5 cm square rough plate with forced air velocities between 0.1 m/s and 2.5 m/s were made in each orthogonal combination of plate and airflow direction, and of a tilted downward-facing plate. Each data-set matches the present theory with root-mean-squared relative error between 1.4% and 4%. - [144] arXiv:2401.16046 (replaced) [pdf, ps, html, other]
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Title: A Triplet Track Trigger for the FCC-hh to improve the measurement of Di-Higgs production and the Higgs self-couplingComments: 25 pages, 26 figuresSubjects: Instrumentation and Detectors (physics.ins-det)
A new concept, the Triplet Track Trigger (TTT), is proposed for stand-alone tracking at the first trigger level of the FCC-hh detector. The concept is based on a highly scalable monolithic pixel sensor technology and uses a very simple and fast track reconstruction algorithm that can be easily implemented in hardware processors. The goal is to suppress the enormous pileup of ~1000 minimum bias collisions expected at the FCC-hh experiment and to identify the hard-interaction vertex and the corresponding tracks as a basis for a trigger decision. In the barrel region, the TTT consists of three closely stacked, highly granular pixel detector layers at radii of ~1m. An extension of the TTT to the endcap region increases the geometrical acceptance.
We present full Geant4 simulations and reconstruction performance of a modified FCC-hh reference tracker that includes TTT barrel and endcap detector layers. The stacking of TTT layers results in excellent track purity, and the large lever arm ensures very good momentum resolution. Additionally, sub-mm $z$-vertex resolution is achieved, which allows for very efficient pileup suppression. By reconstructing pileup suppressed track-jets, the primary vertex of the hard interaction is successfully identified, even at a pileup rate of $<\mu>=1000$ and at trigger level.
The multi-jet signature, pp->HH->4b, is used as a showcase to study the trigger performance of the TTT and compare it to an emulated calorimeter trigger (calo-trigger). The TTT allows for significantly lower trigger thresholds and higher trigger efficiencies than a calo-trigger. Furthermore, the TTT is very robust against fluctuations in the pileup rate compared to the calo-trigger. As a result, a significant increase in the statistics of di-Higgs events is expected, in particular at low transverse momentum, where the sensitivity to the Higgs self-coupling ($\lambda$) is the highest. - [145] arXiv:2402.02153 (replaced) [pdf, ps, other]
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Title: Talbot-like pattern evolution in complex structured light from unitary transformationComments: 7 pages, 5 figuresSubjects: Optics (physics.optics)
Astigmatic unitary transformations allow for the adiabatic connections of all feasible states of paraxial Gaussian beams on the same modal sphere, i.e., Hermite-Laguerre-Gaussian (HLG) modes. Here, we present a comprehensive investigation into the unitary modal evolution of complex structured Gaussian beams, comprised by HLG modes from disparate modal spheres, via astigmatic transformation. The non-synchronized higher-order geometric phases in cyclic transformations originates a Talbot-effect-like modal evolution in the superposition state of these HLG modes, resulting in pattern variations and revivals in transformations with specific geodesic loops. Using Ince-Gaussian modes as an illustrative example, we systematically analyze and experimentally corroborate the beamforming mechanism behind the pattern evolution. Our results outline a generic modal conversion theory of structured Gaussian beams via astigmatic unitary transformation, offering a new approach for shaping spatial modal structure. These findings may inspire a wide variety of applications based on structured light.
- [146] arXiv:2402.02994 (replaced) [pdf, ps, html, other]
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Title: Extreme statistics and extreme events in dynamical models of turbulenceXander M. de Wit, Giulio Ortali, Alessandro Corbetta, Alexei A. Mailybaev, Luca Biferale, Federico ToschiSubjects: Fluid Dynamics (physics.flu-dyn); Chaotic Dynamics (nlin.CD)
We present a study of the intermittent properties of a shell model of turbulence with unprecedented statistics, about $\sim 10^7$ eddy turn over time, achieved thanks to an implementation on a large-scale parallel GPU factory. This allows us to quantify the inertial range anomalous scaling properties of the velocity fluctuations up to the 24th order moment. Through a careful assessment of the statistical and systematic uncertainties, we show that none of the phenomenological and theoretical models previously proposed in the literature to predict the anomalous power-law exponents in the inertial range is in agreement with our high-precision numerical measurements. We find that at asymptotically high order moments, the anomalous exponents tend towards a linear scaling, suggesting that extreme turbulent events are dominated by one leading singularity. We found that systematic corrections to scaling induced by the infrared and ultraviolet (viscous) cut-offs are the main limitations to precision for low-order moments, while high orders are mainly affected by the finite statistical samples. The unprecedentedly high fidelity numerical results reported in this work offer an ideal benchmark for the development of future theoretical models of intermittency in dynamical systems for either extreme events (high-order moments) or typical fluctuations (low-order moments). For the latter, we show that we achieve a precision in the determination of the inertial range scaling exponents of the order of one part over ten thousand (5th significant digit), which must be considered a record for out-of-equilibrium fluid-mechanics systems and models.
- [147] arXiv:2402.05026 (replaced) [pdf, ps, html, other]
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Title: Characterization and Optimization of a Cryogenic Pure CsI Detector with Remarkable Light Yield and Unprecedented Energy Resolution for CLOVERS ExperimentSubjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)
In this study, we conducted a comprehensive characterization and optimization of a cryogenic pure CsI (pCsI) detector. We utilized a \SI{2}{\centi\metre} cubic crystal coupled with a HAMAMATSU R11065 photomultiplier tube (PMT), achieving a remarkable light yield of \SI{35.2}{PE/\keV_{ee}} and an unprecedented energy resolution of \SI{6.9}{\%} at \SI{60}{\keV}. Additionally, we measured the scintillation decay time of pCsI, which proved to be significantly faster than that of CsI(Na) at room temperature. Furthermore, we investigated the impact of temperature, surface treatment, and crystal shape on the light yield. Notably, the light yield peaked at approximately \SI{20}{\K} and remained stable within the range of \SI{70}-\SI{100}{\K}. We observed that the light yield of polished crystals was approximately 1.5 times greater than that of ground crystals, while the crystal shape exhibited minimal influence on the light yield. These results are crucial for the design of the \SI{10}{\kg} pCsI detector for the future CLOVERS (Coherent eLastic neutrinO(V)-nucleus scattERing at China Spallation Neutron Source (CSNS)) experiment.
- [148] arXiv:2402.06419 (replaced) [pdf, ps, html, other]
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Title: Radiationless decay spectrum of O 1s double core holes in liquid waterFlorian Trinter, Ludger Inhester, Ralph Püttner, Sebastian Malerz, Stephan Thürmer, Tatiana Marchenko, Maria Novella Piancastelli, Marc Simon, Bernd Winter, Uwe HergenhahnComments: Main manuscript: 28 pages, 8 figures. Supplementary Material: 16 pages, 9 figuresJournal-ref: J. Chem. Phys. 160, 194503 (2024)Subjects: Chemical Physics (physics.chem-ph)
We present a combined experimental and theoretical investigation of the radiationless decay spectrum of an O 1s double core hole in liquid water. Our experiments were carried out using liquid-jet electron spectroscopy from cylindrical microjets of normal and deuterated water. The signal of the double-core-hole spectral fingerprints (hypersatellites) of liquid water is clearly identified, with an intensity ratio to Auger decay of singly charged O 1s of 0.0014(5). We observe a significant isotope effect between liquid H$_2$O and D$_2$O. For theoretical modeling, the Auger electron spectrum of the central water molecule in a water pentamer was calculated using an electronic-structure toolkit combined with molecular-dynamics simulations to capture the influence of molecular rearrangement within the ultrashort lifetime of the double core hole. We obtained the static and dynamic Auger spectra for H$_2$O, (H$_2$O)$_5$, D$_2$O, and (D$_2$O)$_5$, instantaneous Auger spectra at selected times after core-level ionization, and the symmetrized oxygen-hydrogen distance as a function of time after double core ionization for all four prototypical systems. We consider this observation of liquid-water double core holes as a new tool to study ultrafast nuclear dynamics.
- [149] arXiv:2402.09114 (replaced) [pdf, ps, other]
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Title: Non-Volatile Analog Control and Reconfiguration of a Vortex Nano-Oscillator FrequencyComments: 15 pages, 10 figuresSubjects: Applied Physics (physics.app-ph)
Magnetic tunnel junctions are nanoscale devices which have recently attracted interested in the context of frequency multiplexed spintronic neural networks, due to their interesting dynamical properties, which are defined during the fabrication process, and depend on the material parameters and geometry. This paper proposes an approach to extending the functionality of a standard magnetic tunnel junction (MTJ) by introducing an additional ferromagnet/antiferromagnet (FM/AFM) storage layer (SL) vertically integrated with the standard Vortex MTJ stack into the nanopillar. The magnetostatic field created by this storage layer acts on the free layer and can be used to change its static and dynamic properties. To tune the magnitude and direction of this magnetostatic field, magnetic reconfiguration is carried out through a thermally assisted switching mechanism using a voltage pulse that heats the AFM layer in the SL above the Neel temperature in the presence of an external field. It is experimentally shown that using an MTJ based on a 600 nm diameter nanopillar with a vortex in the free layer, reconfiguration of the SL allows to continuously change the core precession frequency in the 15 MHz range. The reconfigurable analogue storage layer locally affects both the static and dynamic properties of the MTJ free layer, demonstrating vertical 3D integration of additional functionalities into a single MTJ nanopillar.
- [150] arXiv:2402.10766 (replaced) [pdf, ps, html, other]
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Title: Live magnetic observation of parahydrogen hyperpolarization dynamicsSubjects: Chemical Physics (physics.chem-ph); Quantum Physics (quant-ph)
Hyperpolarized nuclear spins in molecules exhibit high magnetization that is unachievable by classical polarization techniques, making them widely used as sensors in physics, chemistry, and medicine. The state of a hyperpolarized material, however, is typically only studied indirectly and with partial destruction of magnetization, due to the nature of conventional detection by resonant-pickup nuclear magnetic resonance spectroscopy or imaging. Here we establish atomic magnetometers with sub-pT sensitivity as an use an alternative modality to detect in real time the complex dynamics of hyperpolarized materials without disturbing or interrupting the magnetogenesis process. As an example of dynamics that are impossible to detect in real time by conventional means, we examine parahydrogen-induced $^{1}$H and $^{13}$C magnetization during adiabatic eigenbasis transformations at \si{\micro\tesla}-field avoided crossings. Continuous but nondestructive magnetometry reveals previously unseen spin dynamics, fidelity limits, and magnetization back-action effects. As a second example, we apply magnetometry to observe the chemical-exchange-driven $^{13}$C hyperpolarization of [1--$^{13}$C]-pyruvate -- the most important spin tracer for clinical metabolic imaging. Our approach can be readily combined with other high-sensitivity magnetometers and is applicable to a broader range of general observation scenarios involving production, transport and systems interaction of hyperpolarized compounds.
- [151] arXiv:2402.13266 (replaced) [pdf, ps, html, other]
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Title: Single electron charge spectra of 8-inch high-collection-efficiency MCP-PMTsSubjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)
The atomic layer deposition(ALD) coating lengthens the lifetime of microchannel plates(MCP), which are used as the electron amplifier of the photomultiplier tubes(PMT). In the Jinping Neutrino Experiment, the newly developed 8-inch MCP-PMT achieves high collection efficiency by coating with high secondary emission materials. The resulting single electron response(SER) charge distribution deviates from the Gaussian distribution in large charge this http URL understand the nature of the jumbo-charged SER, we designed a voltage-division experiment to quantify the dependence of the MCP gain on the energy of incident electrons. Combining the relationship with the Furman probabilistic model, we reproduced the SER charge spectra by an additional amplification stage on the input electrode of the first MCP. Our results favor a Gamma-Tweedie mixture to describe the SER charge spectra of the MCP-PMTs.
- [152] arXiv:2402.14678 (replaced) [pdf, ps, html, other]
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Title: Zeptonewton and Attotesla per Centimeter Metrology With Coupled OscillatorsComments: 13 pages, 17 figuresSubjects: Applied Physics (physics.app-ph)
We present the coupled oscillator: a new mechanism for signal amplification with widespread application in metrology. We introduce the mechanical theory of this framework, and support it by way of simulations. We present a particular implementation of coupled oscillators: a microelectromechanical system (MEMS) that uses one large (~100mm) N52 magnet coupled magnetically to a small (~0.25mm), oscillating N52 magnet, providing a force resolution of 200zN measured over 1s in a noiseless environment. We show that the same system is able to resolve magnetic gradients of 130aT/cm at a single point (within 500um). This technology therefore has the potential to revolutionize force and magnetic gradient sensing, including high-impact areas such cardiac and brain imaging.
- [153] arXiv:2402.16209 (replaced) [pdf, ps, html, other]
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Title: Cold Beam of $^7$Li$^4$He DimersComments: Added a figure of the experimental apparatus, longitudinal fluorescence results, and simulation results including exchange collisions with helium dimersSubjects: Atomic Physics (physics.atom-ph)
We demonstrate an approach for producing a high flux beam of $^7$Li$^4$He dimers by performing post-nozzle seeding of a lithium beam into a supersonic helium expansion. The molecular beam has a longitudinal temperature of 13(6) mK and a continuous flux on the order of $10^{11}$ dimers/s. Monte Carlo simulations of molecular formation based on ab-initio quantum scattering calculations are carried out and compared to the experimentally observed molecular flux. Extensions of this work could lead towards a more quantitative understanding of few-body collision processes of alkali and helium atoms.
- [154] arXiv:2402.19157 (replaced) [pdf, ps, html, other]
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Title: Broken detailed balance and entropy production in directed networksRamón Nartallo-Kaluarachchi, Malbor Asllani, Gustavo Deco, Morten L. Kringelbach, Alain Goriely, Renaud LambiotteComments: 36 pages, 14 figuresSubjects: Physics and Society (physics.soc-ph); Statistical Mechanics (cond-mat.stat-mech); Neurons and Cognition (q-bio.NC)
The structure of a complex network plays a crucial role in determining its dynamical properties. In this work, we show that the the degree to which a network is directed and hierarchically organised is closely associated with the degree to which its dynamics break detailed balance and produce entropy. We consider a range of dynamical processes and show how different directed network features affect their entropy production rate. We begin with an analytical treatment of a 2-node network followed by numerical simulations of synthetic networks using the preferential attachment and Erdös-Renyi algorithms. Next, we analyse a collection of 97 empirical networks to determine the effect of complex real-world topologies. Finally, we present a simple method for inferring broken detailed balance and directed network structure from multivariate time-series and apply our method to identify non-equilibrium dynamics and hierarchical organisation in both human neuroimaging and financial time-series. Overall, our results shed light on the consequences of directed network structure on non-equilibrium dynamics and highlight the importance and ubiquity of hierarchical organisation and non-equilibrium dynamics in real-world systems.
- [155] arXiv:2403.01161 (replaced) [pdf, ps, html, other]
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Title: Droplet dynamics in homogeneous isotropic turbulence with the immersed boundary-lattice Boltzmann methodSubjects: Fluid Dynamics (physics.flu-dyn)
We develop a numerical method for simulating the dynamics of a droplet immersed in a generic time-dependent velocity gradient field. This approach is grounded on the hybrid coupling between the lattice Boltzmann (LB) method, employed for the flow simulation, and the immersed boundary (IB) method, utilized to couple the droplet with the surrounding fluid. We show how to enrich the numerical scheme with a mesh regularization technique, allowing droplets to sustain large deformations. The resulting methodology is adapted to simulate the dynamics of droplets in homogeneous and isotropic turbulence, with the characteristic size of the droplet being smaller than the characteristic Kolmogorov scale of the outer turbulent flow. We report on statistical results for droplet deformation and orientation, collected from an ensemble of turbulent trajectories, as well as comparisons with theoretical models in the limit of small deformation.
- [156] arXiv:2403.04527 (replaced) [pdf, ps, html, other]
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Title: Geometric Phase-Driven Scattering EvolutionsComments: Wei Liu acknowledges many illuminating correspondences with Sir Michael Berry, whose monumental paper on geometric phase was published 40 years ago todaySubjects: Optics (physics.optics)
Conventional approaches for scattering manipulations rely on the technique of field expansions into spherical harmonics (electromagnetic multipoles), which nevertheless is non-generic (expansion coefficients depend on the position of the coordinate system's origin) and more descriptive than predictive. Here we explore this classical topic from a different perspective of controlled excitations and interferences of quasi-normal modes (QNMs) supported by the scattering system. Scattered waves are expanded into not spherical harmonics but radiations of QNMs, among which the relative amplitudes and phases are crucial factors to architect for scattering manipulations. Relying on the electromagnetic reciprocity, we provide full geometric representations based on the Poincaré sphere for those factors, and identify the hidden underlying geometric phases of QNMs that drive the scattering evolutions. Further synchronous exploitations of the incident polarization-dependent geometric phases and excitation amplitudes enable efficient manipulations of both scattering intensities and polarizations. Continuous geometric phase spanning $2\pi$ is directly manifest through scattering variations, even in the rather elementary configuration of an individual particle scattering waves of varying polarizations. We have essentially established a profoundly all-encompassing framework for the calculations of geometric phase in scattering systems, which will greatly broaden horizons of many disciplines not only in photonics but also in general wave physics where geometric phase is generic and ubiquitous.
- [157] arXiv:2403.07155 (replaced) [pdf, ps, html, other]
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Title: A Real-time Dyson Expansion Scheme: Efficient Inclusion of Dynamical Correlations in Non-equilibrium Spectral PropertiesComments: 7 pages, 3 figures, 14 page supplemental information with 7 additional figuresSubjects: Computational Physics (physics.comp-ph)
Time-resolved photoemission spectroscopy is the key technique to probe the real-time non-equilibrium dynamics of electronic states. Theoretical predictions of the time dependent spectral function for realistic systems is however, a challenge. Employing the Kadanoff-Baym equations to find this quantity results in a cubic scaling in the total number of time steps, quickly becoming prohibitive and often fail quantitatively and even qualitatively. In comparison, mean-field methods have more favorable numerical scaling both in the number of time steps and in the complexity associated with the cost of evolving for a single time step, however they miss key spectral properties such as emergent spectral features. Here we present a scheme that allows for the inclusion of dynamical correlations to the spectral function while maintaining the same scaling in the number of time steps as for mean-field approaches, while capturing the emergent physics. Further, the scheme can be efficiently implemented on top of equilibrium real-time many-body perturbation theory schemes and codes. We see excellent agreement with exact results for test systems. Furthermore we exemplify the method on a periodic system and demonstrate clear evidence that our proposed scheme produces complex spectral features including excitonic band replicas, features that are not observed using static mean-field approaches.
- [158] arXiv:2403.13559 (replaced) [pdf, ps, html, other]
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Title: Mechanism of circular polarization in giant pulses and fast radio burstsSubjects: Plasma Physics (physics.plasm-ph); High Energy Astrophysical Phenomena (astro-ph.HE)
Some giant pulses and fast radio bursts exhibit notable circular polarization, which remains inexplicable and carries significant implications for their emission mechanisms. In this study, we unveil the presence of multiple nanoshot pairs uniformly spaced by approximately 21 $\mu$s within a giant pulse emitted by the Crab pulsar. Among these pairs, a subset displays left-hand and right-hand circular polarization in two distinct nanoshots. We propose that the occurrence of such nanoshot pairs with dual circular polarizations arises from the fragmentation of a linearly-polarized nanoshot under the extreme Faraday effect, leveraging highly-asymmetrical pair plasma and the ultra-intense field of nanoshots. The asymmetry in pair plasmas is likely linked to discharge activities in pulsars. Moreover, the intense field of nanoshots induces cyclotron resonance within the magnetosphere, effectively slowing down the propagation velocity of the circularly polarized mode. Our findings suggest that giant pulses originate within the inner magnetosphere and lend support to a magnetospheric origin for fast radio bursts.
- [159] arXiv:2403.14239 (replaced) [pdf, ps, html, other]
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Title: Physical insights from the aspect ratio dependence of turbulence in negative triangularity plasmasAlessandro Balestri, Justin Ball, Stefano Coda, Diego Jose Cruz-Zabala, Manuel Garcia-Munoz, Eleonora ViezzerSubjects: Plasma Physics (physics.plasm-ph)
In this work, we study the impact of aspect ratio A = R0 /r (the ratio of major radius R0 to minor radius r) on the confinement benefits of Negative Triangularity (NT) plasma shaping. We use high-fidelity flux tube gyrokinetic GENE simulations and consider several different scenarios: four of them inspired by TCV experimental data, a scenario inspired by DIII-D experimental data and a scenario expected in the new SMART spherical tokamak. The present study reveals a surprising and non-trivial dependence. NT improves confinement at any value of A for ITG turbulence, while for TEM turbulence confinement is improved only in the case of large and conventional aspect ratios. Additionally, through a detailed study of a large aspect ratio case with pure ITG drive, we develop an intuitive physical picture that explains the beneficial effect of NT at large and conventional aspect ratios. This picture does not hold in TEM-dominated regimes, where a complex synergistic effect of many factors is found. Finally, we performed the first linear gyrokinetic simulations of SMART, finding that both NT and PT scenarios are dominated by micro-tearing-mode (MTM) turbulence and that NT is more susceptible to MTMs at tight aspect ratio. However, we found that a regime where ITG dominates in SMART can be found, and in this regime NT is more linearly stable.
- [160] arXiv:2404.00754 (replaced) [pdf, ps, html, other]
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Title: Imitation dynamics and the replicator equationSubjects: Physics and Society (physics.soc-ph); Adaptation and Self-Organizing Systems (nlin.AO); Populations and Evolution (q-bio.PE)
Evolutionary game theory has impacted many fields of research by providing a mathematical framework for studying the evolution and maintenance of social and moral behaviors. This success is owed in large part to the demonstration that the central equation of this theory - the replicator equation - is the deterministic limit of a stochastic imitation (social learning) dynamics. Here we offer an alternative elementary proof of this result, which holds for the scenario where players compare their instantaneous (not average) payoffs to decide whether to maintain or change their strategies, and only more successful individuals can be imitated.
- [161] arXiv:2404.01056 (replaced) [pdf, ps, html, other]
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Title: Detangling the quantum tapestry of intra-channel interference in below-threshold nonsequential double ionization with few-cycle laser pulsesComments: 34 pages, 24 figures; in the revised version, some references have been added, the introduction has been slightly altered and the conclusions have been considerably extendedSubjects: Atomic Physics (physics.atom-ph)
We perform a systematic analysis of single-channel quantum interference in laser-induced nonsequential double ionization with few-cycle pulses, using the strong-field approximation. We focus on a below-threshold intensity for which the recollision-excitation with subsequent ionization (RESI) mechanism is prevalent. We derive and classify several analytic interference conditions for single-channel RESI in arbitrary driving fields, and address specific issues for few-cycle pulses. Since the cycles in a short pulse are no longer equivalent, there are several events whose dominance varies. We quantify this dominance for single excitation channels by proposing a dominance parameter. Moreover, there will be many more types of superimposed interference fringes that must be taken into consideration. We find an intricate tapestry of patterns arising from phase differences related to symmetrization, temporal shifts and a combination of exchange and event interference.
- [162] arXiv:2404.04307 (replaced) [pdf, ps, other]
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Title: PREDIS-MHI Thermal DataSeun Osonuga (G2Elab-MAGE, G2ELab), Ali Chouman (G2ELab, CSTB), Muhammad-Salman Shahid (G2ELab), Benoit Delinchant (G2ELab), Frederic Wurtz (G2ELab)Journal-ref: Conf{\'e}rence Francophone de l'International Building Performance Simulation Association (IBPSA -- France) 2024, le Laboratoire des Sciences de l'Ing{\'e}nieur pour l'Environnement (LaSIE) de l'Universit{\'e} de La Rochelle; IBPSA France, May 2024, La Rochelle - Ile d'Ol{\'e}ron, France. pp.489 - 496Subjects: Physics and Society (physics.soc-ph); Classical Physics (physics.class-ph)
Tertiary buildings could be an important lever to meet the goals necessitated by the energy transition. The availability of high-quality datasets from this sector will be a crucial enabler in meeting these goals by developing and testing new energy management approaches in the buildings. In this paper, we present the thermal energy datasets available and published online for the PREDIS-MHI zone of the GreEn-ER building, a tertiary building with more than a thousand sensors used for research, teaching, and administrative activities in Grenoble. PREDIS-MHI platform is a net-zero sub-section that is energetically isolated from the rest of the building. Its data has been used in a wide range of applications from indoor temperature forecasting, thermal simulation calibration, and even occupant comfort experiments
- [163] arXiv:2404.05346 (replaced) [pdf, ps, html, other]
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Title: On the relevance of lift force modelling in turbulent wall flows with small inertial particlesComments: Accepted for publication in Journal of Fluid MechanicsSubjects: Fluid Dynamics (physics.flu-dyn)
In particle-laden turbulent wall flows, lift forces can influence the near-wall turbulence. This has been recently observed in particle-resolved simulations, which, however, are too expensive to be used in upscaled models. Instead, point-particle simulations have been the method of choice to simulate the dynamics of these flows during the last decades. While this approach is simpler, cheaper, and physically sound for small inertial particles in turbulence, some issues remain. In the present work, we address challenges associated with lift force modelling in turbulent wall flows and the impact of lift forces in the near-wall flow. We performed direct numerical simulations (DNS) of small inertial point particles in turbulent channel flow for fixed Stokes number and mass loading while varying the particle size. Our results show that the particle dynamics in the buffer region, causing the apparent particle-to-fluid slip velocity to vanish, raises major challenges for accurately modelling lift forces. While our results confirm that lift forces have little influence on particle dynamics for sufficiently small particle sizes, for inner-scaled diameters of order one and beyond, lift forces become quite important near the wall. The different particle dynamics under lift forces results in the modulation of streamwise momentum transport in the near-wall region. We analyze this lift-induced turbulence modulation for different lift force models, and the results indicate that realistic models are critical for particle-modelled simulations to correctly predict turbulence modulation by particles in the near-wall region.
- [164] arXiv:2405.02856 (replaced) [pdf, ps, html, other]
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Title: A tale of two emergent games: opinion dynamics in dynamical directed networksComments: arXiv admin note: substantial text overlap with arXiv:2307.05511Subjects: Physics and Society (physics.soc-ph)
Uni-directional social interactions are ubiquitous in real social networks whereas undirected interactions are intensively studied. We establish a voter model in a dynamical directed network. We analytically obtain the degree distribution of the evolving network at any given time. Furthermore, we find that the average degree is captured by an emergent game. On the other hand, we find that the fate of opinions is captured by another emergent game. Beyond expectation, the two emergent games are typically different due to the unidirectionality of the evolving networks. The Nash equilibrium analysis of the two games facilitates us to give the criterion under which the minority opinion with few disciples initially takes over the population eventually for in-group bias. Our work fosters the understanding of opinion dynamics ranging from methodology to research content.
- [165] arXiv:2405.04240 (replaced) [pdf, ps, html, other]
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Title: Exploring relaxation dynamics in warm dense plasmas by tailoring non-thermal electron distributions with a free electron laserSubjects: Plasma Physics (physics.plasm-ph)
Knowing the characteristic relaxation time of free electrons in a dense plasma is crucial to our understanding of plasma equilibration and transport. However, experimental investigations of electron relaxation dynamics have been hindered by the ultra-fast, sub-femtosecond time scales on which these interactions typically take place. Here we propose a novel approach that uses x-rays from a free electron laser to generate well-defined non-thermal electron distributions, which can then be tracked via emission spectroscopy from radiative recombination as they thermalize. Collisional radiative simulations reveal how this method can enable the measurement of electron relaxation time scales {\it in situ}, shedding light on the applicability and accuracy of the Coulomb Logarithm framework for modelling collisions in dense plasmas.
- [166] arXiv:2405.04430 (replaced) [pdf, ps, html, other]
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Title: Intrinsic Current Concentration of Buffer Layer Material for Cable Ablation Failure: Role of Random Fiber NetworksComments: 8 pages, 12 figuresSubjects: Applied Physics (physics.app-ph)
In recent years, the buffer layer ablation failures of high voltage cables are frequently reported by the power systems. Previous studies have dominantly regarded the buffer layer as the continuous homogeneous medium, whereas neglects its microstructures. In this paper, the current distribution within the random fiber networks of buffer layer are investigated. Experiment results of our self-designed platform revealed an uneven current distribution in buffer layer at the moment of bearing current. This phenomenon is named as the intrinsic current concentration where the current density concentrates at certain sites inner the buffer layer. And the degree of current concentration will be suppressed by compressing the sample. Then, a 2D simulation model of the random fiber networks was constructed based on the Mikado model. The simulation results also presented an uneven current distribution in the networks whose every fiber can be viewed as a micro-resistor. Two types of dimensionless current concentration factors were defined to describe the degree of current concentration, finding their values decreasing with the rise of fiber density. Meanwhile, it is equivalent of compressing the buffer layer and increasing the fiber density of model. We believe that the intrinsic current concentration phenomenon is mainly related with the inhomogeneity of geometry structure of buffer layer. The ablation traces and fracture fibers observed by the X-ray micro-computed tomography test supported this point. In addition, the non-ideal surface of sample can also induce this phenomenon. The intrinsic current concentration can aggravate the degree of originally existed macroscopic current concentration in cables, thus causing the ablation failure. Our work may unveil a deeper understanding on the cable ablation failure and the electrical response of the similar fibrous materials.
- [167] arXiv:2405.06894 (replaced) [pdf, ps, other]
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Title: Dual-grating single-shot pump-probe techniqueComments: 10 pages, 2 figuresSubjects: Optics (physics.optics); Applied Physics (physics.app-ph)
A simple and effective single-shot pump-probe technique is reported. Using only two commercial gratings, a large time window of ~ 95.58 ps is spatially encoded in a single probe pulse, and single-shot time-resolved measurements are implemented. The time window exceeds the maximum reported values for single-shot pump-probe techniques using the echelon or angle beam encoding strategy. The phase difference problem in the echelon encoding strategies is also eliminated and a customized echelon is not needed in this technique. The measurements of the ultrafast dynamics of ZnSe at a wavelength of 650 nm verify the effectiveness of this technique.
- [168] arXiv:2405.09117 (replaced) [pdf, ps, html, other]
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Title: Complex-valued 3D atomic spectroscopy with Gaussian-assisted inline holographyComments: 20 pages, 7 figures; small corrections, with reference format updatedSubjects: Atomic Physics (physics.atom-ph); Optics (physics.optics); Quantum Physics (quant-ph)
When a laser-cooled atomic sample is optically excited, the envelope of coherent forward scattering can often be decomposed into a few complex Gaussian profiles. The convenience of Gaussian propagation helps addressing key challenges in digital holography. In this work, we theoretically develop and experimentally demonstrate a Gaussian-decomposition-assisted approach to inline holography, for single-shot, simultaneous measurements of absorption and phase shift of small atomic samples sparsely distributed in 3D. Experimentally, we image a sparse lattice of $^{87}$Rb samples on the D2 line, to resolve their axial positions with micrometer precision, and to retrieve their complex-valued spectroscopic images. With the phase-angle readouts that are highly insensitive to atom-number and interaction-strength uncertainties, we achieve hundred-kHz-level single-shot-resolution to the transition frequency with merely hundreds of atoms. We further demonstrate 3D sensing of local light shift with micrometer spatial resolution.
- [169] arXiv:2405.11052 (replaced) [pdf, ps, html, other]
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Title: Progress in Electron Energy Modeling for Hypersonic Plasma FlowsComments: 34 pages, 10 figuresSubjects: Plasma Physics (physics.plasm-ph)
A novel formulation of the electron energy relaxation terms is presented here, which is applicable to high-speed plasma flows and discharges wherein the electron temperature could be higher or lower than the gas temperature. It is demonstrated that the electron energy losses due to inelastic collisions can be expressed as a function of only two species-dependent parameters: the reduced electric field and the reduced electron mobility. This formulation is advantageous over previous ones, being simpler to implement and more accurate when experimental data of the reduced electric field and reduced mobility are available. Curve fits to empirical data of these two properties are outlined here for all important air molecular species. The approach accounts for all inelastic electron energy relaxation processes without needing individual cross-sections or rates, reducing potential errors associated with independently handling each process. Several test cases are presented to validate the proposed electron energy source terms including hypersonic plasma flows for which the electron temperature is less than the gas temperature, as well as discharges in which the electron temperature reaches values in excess of 30 eV. In all cases, the agreement with experimental data is observed to be very good to excellent, significantly surpassing prior electron energy models for high-speed flows.
- [170] arXiv:2405.12090 (replaced) [pdf, ps, html, other]
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Title: Two-dimensional Synchrotron Beam Characterisation from a Single InterferogramComments: 5 pages, 5 figures, submitted to PRLSubjects: Accelerator Physics (physics.acc-ph); Optics (physics.optics)
Double-aperture Young interferometry is widely used in accelerators to provide a one-dimensional beam measurement. We improve this technique by combining and further developing techniques of non-redundant aperture masking and self-calibration from astronomy. Using visible synchrotron radiation, tests at the ALBA synchrotron show that this method provides an accurate two-dimensional beam transverse characterisation, even from a single 1ms interferogram. The technique is resistant to phase fluctuations that might be introduced by vibration of optical components, or in the laboratory atmosphere.
- [171] arXiv:2405.12411 (replaced) [pdf, ps, html, other]
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Title: Decomposing causality into its synergistic, unique, and redundant componentsComments: arXiv admin note: text overlap with arXiv:2310.20544Subjects: Data Analysis, Statistics and Probability (physics.data-an); Fluid Dynamics (physics.flu-dyn)
Causality lies at the heart of scientific inquiry, serving as the fundamental basis for understanding interactions among variables in physical systems. Despite its central role, current methods for causal inference face significant challenges due to nonlinear dependencies, stochastic interactions, self-causation, collider effects, and influences from exogenous factors, among others. While existing methods can effectively address some of these challenges, no single approach has successfully integrated all these aspects. Here, we address these challenges with SURD: Synergistic-Unique-Redundant Decomposition of causality. SURD quantifies causality as the increments of redundant, unique, and synergistic information gained about future events from past observations. The formulation is non-intrusive and applicable to both computational and experimental investigations, even when samples are scarce. We benchmark SURD in scenarios that pose significant challenges for causal inference and demonstrate that it offers a more reliable quantification of causality compared to previous methods.
- [172] arXiv:2405.12834 (replaced) [pdf, ps, html, other]
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Title: Effect of Synthetic Jets Actuator Parameters on Deep Reinforcement Learning-Based Flow Control Performance in a Square CylinderSubjects: Fluid Dynamics (physics.flu-dyn)
We utilize deep reinforcement learning (DRL) algorithms to precisely control the mass flow rates of synthetic jets located on the upper and lower surfaces of a square cylinder for active flow control. Through DRL-based active flow control (AFC) technology, we significantly reduce the lift and drag coefficients of the square cylinder at Reynolds number (Re) = 100 and Re=500, while completely suppressing vortex shedding in the wake flow field. Additionally, we conduct a sensitivity analysis of the position and width parameters of the synthetic jets regarding flow control performance. Our observations indicate that positioning the synthetic jets near the trailing edge corners of the square cylinder, rather than the leading edge corners, can completely suppress vortex shedding, resulting in more stable lift and drag coefficients in the controlled flow. When the synthetic jets are positioned at the trailing edge corners, flow control reduces the mean drag coefficient by 14.4% and the standard deviation of the lift coefficient by 86.1% for the baseline flow at Re=100. For the baseline flow at Re=500, flow control reduces the mean drag coefficient by 51.4% and the standard deviation of the lift coefficient by 90.5%. At both Reynolds numbers, vortex shedding in the wake flow field is completely suppressed. Furthermore, using narrower synthetic jets results in a lower reduction rate of the standard deviations of the lift and drag coefficients, while increasing the mean and standard deviation of the mass flow rate of the jets used for flow control. This study provides guidance on optimizing the width and position of synthetic jets for DRL-based active flow control.
- [173] arXiv:2106.05330 (replaced) [pdf, ps, html, other]
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Title: Complete Realization of Energy Landscape and Non-equilibrium Trapping Dynamics in Spin Glass and Optimization ProblemSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Computational Physics (physics.comp-ph)
Energy landscapes are high-dimensional surfaces representing the dependence of system energy on variable configurations, which determine crucially the system's emergent behavior but are difficult to be analyzed due to their high-dimensional nature. In this article, we introduce an approach to reveal the complete energy landscapes of small spin glasses and Boolean satisfiability problems, which also unravels their non-equilibrium dynamics at an arbitrary temperature for an arbitrarily long time. In contrary to our common belief, our results show that it can be less likely to identify the ground states when temperature decreases, due to trapping in individual local minima, which ceases at different time, leading to multiple abrupt jumps with time in the ground-state probability. Simulations agree well with theoretical predictions on these remarkable phenomena. Finally, for large systems, we introduce a variant approach to extract partially the energy landscapes and observe both analytically and in simulations similar phenomena. This work introduces new methodology to unravel the non-equilibrium dynamics of glassy systems, and provides us with a clear, complete and new physical picture on their long-time behaviors inaccessible by modern numerics.
- [174] arXiv:2204.13777 (replaced) [pdf, ps, html, other]
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Title: A geometric perspective: experimental evaluation of the quantum Cramer-Rao boundComments: 13 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Applied Physics (physics.app-ph)
The power of quantum sensing rests on its ultimate precision limit, quantified by the quantum Cramer-Rao bound (QCRB), which can surpass classical bounds. In multi-parameter estimation, the QCRB is not always saturated as the quantum nature of associated observables may lead to their incompatibility. Here we explore the precision limits of multi-parameter estimation through the lens of quantum geometry, enabling us to experimentally evaluate the QCRB via quantum geometry measurements. Focusing on two- and three-parameter estimation, we elucidate how fundamental quantum uncertainty principles prevent the saturation of the bound. By linking a metric of "quantumness" to the system geometric properties, we investigate and experimentally extract the attainable QCRB for three-parameter estimations.
- [175] arXiv:2209.03844 (replaced) [pdf, ps, html, other]
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Title: Fast, high-order numerical evaluation of volume potentials via polynomial density interpolationSubjects: Numerical Analysis (math.NA); Computational Physics (physics.comp-ph)
This article presents a high-order accurate numerical method for the evaluation of singular volume integral operators, with attention focused on operators associated with the Poisson and Helmholtz equations in two dimensions. Following the ideas of the density interpolation method for boundary integral operators, the proposed methodology leverages Green's third identity and a local polynomial interpolant of the density function to recast the volume potential as a sum of single- and double-layer potentials and a volume integral with a regularized (bounded or smoother) integrand. The layer potentials can be accurately and efficiently evaluated everywhere in the plane by means of existing methods (e.g. the density interpolation method), while the regularized volume integral can be accurately evaluated by applying elementary quadrature rules. Compared to straightforwardly computing corrections for every singular and nearly-singular volume target, the method significantly reduces the amount of required specialized quadrature by pushing all singular and near-singular corrections to near-singular layer-potential evaluations at target points in a small neighborhood of the domain boundary. Error estimates for the regularization and quadrature approximations are provided. The method is compatible with well-established fast algorithms, being both efficient not only in the online phase but also to set-up. Numerical examples demonstrate the high-order accuracy and efficiency of the proposed methodology; applications to inhomogeneous scattering are presented.
- [176] arXiv:2303.16490 (replaced) [pdf, ps, html, other]
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Title: Quantum algorithm for collisionless Boltzmann simulation of self-gravitating systemsComments: 12 pages, 10 figuresSubjects: Quantum Physics (quant-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Computational Physics (physics.comp-ph); Plasma Physics (physics.plasm-ph)
The collisionless Boltzmann equation (CBE) is a fundamental equation that governs the dynamics of a broad range of astrophysical systems from space plasma to star clusters and galaxies. It is computationally expensive to integrate the CBE directly in a multi-dimensional phase space, and thus the applications to realistic astrophysical problems have been limited so far. Recently, Todorova & Steijl (2020) proposed an efficient quantum algorithm to solve the CBE with significantly reduced computational complexity. We extend the algorithm to perform quantum simulations of self-gravitating systems, incorporating the method to calculate gravity with the major Fourier modes of the density distribution extracted from the solution-encoding quantum state. Our method improves the dependency of time and space complexities on Nv , the number of grid points in each velocity coordinate, compared to the classical simulation methods. We then conduct some numerical demonstrations of our method. We first run a 1+1 dimensional test calculation of free streaming motion on 64*64 grids using 13 simulated qubits and validate our method. We then perform simulations of Jeans collapse, and compare the result with analytic and linear theory calculations. It will thus allow us to perform large-scale CBE simulations on future quantum computers.
- [177] arXiv:2305.13445 (replaced) [pdf, ps, html, other]
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Title: Quantum state manipulation and cooling of ultracold moleculesComments: 5 figuresJournal-ref: Nature Physics (2024)Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
An increasingly large variety of molecular species are being cooled down to low energies in recent years, and innovative ideas and powerful techniques continue to emerge to gain ever more precise control of molecular motion. In this brief review we focus our discussions on two widely employed cooling techniques that have brought molecular gases into the quantum regime: association of ultracold atomic gases into quantum gases of molecules and direct laser cooling of molecules. These advances have brought into reality our capability to prepare and manipulate both internal and external states of molecules quantum mechanically, opening the field of cold molecules to a wide range of scientific explorations.
- [178] arXiv:2305.18548 (replaced) [pdf, ps, other]
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Title: I/O-efficient iterative matrix inversion with photonic integrated circuitsSubjects: Emerging Technologies (cs.ET); Optics (physics.optics)
Photonic integrated circuits have been extensively explored for optical processing with the aim of breaking the speed bottleneck of digital electronics. However, the input/output (IO) bottleneck remains one of the key barriers. Here we report a novel photonic iterative processor (PIP) for matrix-inversion-intensive applications. The direct reuse of inputted data in the optical domain unlocks the potential to break the IO bottleneck. We demonstrate notable IO advantages with a lossless PIP for real-valued matrix inversion and integral-differential equation solving, as well as a coherent PIP with optical loops integrated on-chip, enabling complex-valued computation and a net inversion time of 1.2 ns. Furthermore, we estimate at least an order of magnitude enhancement in IO efficiency of a PIP over photonic single-pass processors and the state-of-the-art electronic processors for reservoir training tasks and MIMO precoding tasks, indicating the huge potential of PIP technology in practical applications.
- [179] arXiv:2306.07787 (replaced) [pdf, ps, html, other]
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Title: Quantum coherent feedback control of an N-level atom with multiple excitationsComments: 16 pages, 6 figuresSubjects: Quantum Physics (quant-ph); Systems and Control (eess.SY); Atomic Physics (physics.atom-ph)
The purpose of this paper is to study the dynamics of a quantum coherent feedback network, where an $N$-level atom is coupled with a cavity and the cavity is also coupled with single or multiple parallel waveguides. When the atom is initialized at the highest energy level, it can emit multiple photons into the cavity, and the photons can be further transmitted to the waveguides and re-interact with the cavity quantum electrodynamics (cavity-QED) system. The transmission of photons in the waveguide can construct a feedback channel with a delay determined by the length of the waveguide. We model the dynamics of the atomic and photonic states of the cavity-QED system as a linear control system with delay. By tuning the control parameters such as the coupling strengths among the atom, cavity and waveguide, the eigenstates of the quantum system can be exponentially stable or unstable, and the exponential stability of the linear quantum control system with delay is related with the generation of single- and multi-photon states. Besides, when the cavity-QED system is coupled with multiple parallel waveguides, the emitted photons oscillate among different waveguides and the stability of quantum states is influenced by the feedback loop length and coupling strengths among waveguides.
- [180] arXiv:2307.04922 (replaced) [pdf, ps, html, other]
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Title: Programmable XY-type couplings through parallel spin-dependent forces on the same trapped ion motional modesNikhil Kotibhaskar, Chung-You Shih, Sainath Motlakunta, Anthony Vogliano, Lewis Hahn, Yu-Ting Chen, Rajibul IslamSubjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other); Soft Condensed Matter (cond-mat.soft); Superconductivity (cond-mat.supr-con); Atomic Physics (physics.atom-ph)
We propose and experimentally demonstrate an analog scheme for generating XY-type ($J_{ij}^x \sigma_x^i \sigma_x^j \;$ + $J_{ij}^y \sigma_y^i \sigma_y^j \;$) Hamiltonians on trapped ion spins with independent control over the $J_{ij}^x$ and $J_{ij}^y$ terms. The Ising-type interactions $\sigma_x^i \sigma_x^j \;$ and $\sigma_y^i \sigma_y^j \;$ are simultaneously generated by employing two spin-dependent forces operating in parallel on the same set of normal modes. We analytically calculate the region of validity of this scheme, and provide numerical and experimental validation with $^{171}\rm{Yb}^+\;$ ions. This scheme inherits the programmability and scalability of the Ising-type interactions with trapped ions that have been explored in numerous quantum simulation experiments. Our approach extends the capabilities of existing trapped ion quantum simulators to access a large class of spin Hamiltonians relevant for exploring exotic quantum phases such as superfluidity and spin liquids.
- [181] arXiv:2307.06110 (replaced) [pdf, ps, html, other]
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Title: Quantum field theory for multipolar composite bosons with mass defect and relativistic correctionsComments: 35 pages, 8 figures, 6 tablesJournal-ref: PRX Quantum 5, 020322 (2024)Subjects: Quantum Physics (quant-ph); High Energy Physics - Theory (hep-th); Atomic Physics (physics.atom-ph)
Atomic high-precision measurements have become a competitive and essential technique for tests of fundamental physics, the Standard Model, and our theory of gravity. It is therefore self-evident that such measurements call for a consistent relativistic description of atoms that eventually originates from quantum field theories like quantum electrodynamics. Most quantum-metrological approaches even postulate effective field-theoretical treatments to describe a precision enhancement through techniques like squeezing. However, a consistent derivation of interacting atomic quantum gases from an elementary quantum field theory that includes both the internal structure as well as the center of mass of atoms, has not yet been addressed. We present such a subspace effective field theory for interacting, spin carrying, and possibly charged ensembles of atoms composed of nucleus and electron that form composite bosons called cobosons, where the interaction with light is included in a multipolar description. Relativistic corrections to the energy of a single coboson, light-matter interaction, and the scattering potential between cobosons arise in a consistent and natural manner. In particular, we obtain a relativistic coupling between the coboson's center-of-mass motion and internal structure encoded by the mass defect. We use these results to derive modified bound-state energies, including the motion of ions, modified scattering potentials, a relativistic extension of the Gross-Pitaevskii equation, and the mass defect applicable to atomic clocks or quantum clock interferometry.
- [182] arXiv:2307.15626 (replaced) [pdf, ps, other]
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Title: A quantitative phase-field model for void evolution in defect supersaturated environments: a novel introduction of defect reaction asymmetryComments: We have developed a much better version of this work. The derivation of the phase-field model in the arxiv version is incorrect. Also, we did not expand on the different contributions to the heat flux. Moreover, we have now developed a new numerical strategy to solve the equations using the KKS model. So, for the aforementioned reasons, we request the arxiv to withdraw this articleSubjects: Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Voids develop in crystalline materials under energetic particle irradiation, as in nuclear reactors. Understanding the underlying mechanisms of void nucleation and growth is of utmost importance as it leads to dimensional instability of the metallic materials. In the past two decades, researchers have adopted the phase-field approach to study the phenomena of void evolution under irradiation. The approach involves modeling the boundary between the void and matrix with a diffused interface. However, none of the existing models are quantitative in nature. This work introduces a thermodynamically consistent, quantitative diffuse interface model based on KKS formalism to describe the void evolution under irradiation. The model concurrently considers both vacancies and self-interstitials in the description of void evolution. Unique to our model is the presence of two mobility parameters in the equation of motion of the phase-field variable. The two mobility parameters relate the driving force for vacancy and self-interstitial interaction to the interface motion, analogous to dislocation motion through climb and glide processes. The asymptotic matching of the phase-field model with the sharp-interface theory fixes the two mobility parameters in terms of the material parameters in the sharp-interface model. The Landau coefficient, which controls the height of the double-well function in the phase field variable, and the gradient coefficient of the phase field variable are fixed based on the interfacial energy and interface width of the boundary. With all the parameters in the model determined in terms of the material parameters, we thus have a new phase field model for void evolution. Simple test cases will show the void evolution under various defect supersaturation to validate our new phase-field model.
- [183] arXiv:2307.16876 (replaced) [pdf, ps, html, other]
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Title: Quantum coherent and measurement feedback control based on atoms coupled with a semi-infinite waveguideComments: 25 pages, 5 figuresSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
In this paper, we show that quantum feedback control may be applied to generate desired states for atomic and photonic systems based on a semi-infinite waveguide coupled with multiple two-level atoms. In this set-up, an initially excited atom can emit one photon into the waveguide, which can be reflected by the terminal mirror or other atoms to establish different feedback loops via the coherent interactions between the atom and photon. When there are at most two excitations in the waveguide quantum electrodynamics (waveguide QED) system, the evolution of quantum states can be interpreted using random graph theory. While this process is influenced by the environment, and we clarify that the environment-induced dynamics can be eliminated by measurement-based feedback control or coherent drives. Thus, in the open system atom-waveguide interactions, measurement-based feedback can modulate the final steady quantum state, while simultaneously, the homodyne detection noise in the measurement process can induce oscillations, which is treated by the coherent feedback designs.
- [184] arXiv:2308.02958 (replaced) [pdf, ps, html, other]
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Title: K-band: Self-supervised MRI Reconstruction via Stochastic Gradient Descent over K-space SubsetsSubjects: Image and Video Processing (eess.IV); Computer Vision and Pattern Recognition (cs.CV); Machine Learning (cs.LG); Signal Processing (eess.SP); Medical Physics (physics.med-ph)
Although deep learning (DL) methods are powerful for solving inverse problems, their reliance on high-quality training data is a major hurdle. This is significant in high-dimensional (dynamic/volumetric) magnetic resonance imaging (MRI), where acquisition of high-resolution fully sampled k-space data is impractical. We introduce a novel mathematical framework, dubbed k-band, that enables training DL models using only partial, limited-resolution k-space data. Specifically, we introduce training with stochastic gradient descent (SGD) over k-space subsets. In each training iteration, rather than using the fully sampled k-space for computing gradients, we use only a small k-space portion. This concept is compatible with different sampling strategies; here we demonstrate the method for k-space "bands", which have limited resolution in one dimension and can hence be acquired rapidly. We prove analytically that our method stochastically approximates the gradients computed in a fully-supervised setup, when two simple conditions are met: (i) the limited-resolution axis is chosen randomly-uniformly for every new scan, hence k-space is fully covered across the entire training set, and (ii) the loss function is weighed with a mask, derived here analytically, which facilitates accurate reconstruction of high-resolution details. Numerical experiments with raw MRI data indicate that k-band outperforms two other methods trained on limited-resolution data and performs comparably to state-of-the-art (SoTA) methods trained on high-resolution data. k-band hence obtains SoTA performance, with the advantage of training using only limited-resolution data. This work hence introduces a practical, easy-to-implement, self-supervised training framework, which involves fast acquisition and self-supervised reconstruction and offers theoretical guarantees.
- [185] arXiv:2308.09782 (replaced) [pdf, ps, html, other]
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Title: Velocity-gauge real-time time-dependent density functional tight-binding for large-scale condensed matter systemsComments: 23 pages, 6 figuresJournal-ref: J. Chem. Theory Comput., 19, 22, 7989-7997 (2024)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Computational Physics (physics.comp-ph)
We present a new velocity-gauge real-time, time-dependent density functional tight-binding (VG-rtTDDFTB) implementation in the open-source DFTB+ software package (this https URL) for probing electronic excitations in large, condensed matter systems. Our VG-rtTDDFTB approach enables real-time electron dynamics simulations of large, periodic, condensed matter systems containing thousands of atoms with a favorable computational scaling as a function of system size. We provide computational details and benchmark calculations to demonstrate its accuracy and computational parallelizability on a variety of large material systems. As a representative example, we calculate laser-induced electron dynamics in a 512-atom amorphous silicon supercell to highlight the large periodic systems that can be examined with our implementation. Taken together, our VG-rtTDDFTB approach enables new electron dynamics simulations of complex systems that require large periodic supercells, such as crystal defects, complex surfaces, nanowires, and amorphous materials.
- [186] arXiv:2308.11279 (replaced) [pdf, ps, html, other]
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Title: Thermocapillary Thin Films: Periodic Steady States and Film RuptureComments: 31 pages, 8 figures; we added a remark regarding the instability of positive solutions with additional referencesSubjects: Analysis of PDEs (math.AP); Pattern Formation and Solitons (nlin.PS); Fluid Dynamics (physics.flu-dyn)
We study stationary, periodic solutions to the thermocapillary thin-film model
\begin{equation*}
\partial_t h + \partial_x \Bigl(h^3(\partial_x^3 h - g\partial_x h) + M\frac{h^2}{(1+h)^2}\partial_xh\Bigr) = 0,\quad t>0,\ x\in \mathbb{R},
\end{equation*} which can be derived from the Bénard-Marangoni problem via a lubrication approximation. When the Marangoni number $M$ increases beyond a critical value $M^*$, the constant solution becomes spectrally unstable via a (conserved) long-wave instability and periodic stationary solutions bifurcate. For a fixed period, we find that these solutions lie on a global bifurcation curve of stationary, periodic solutions with a fixed wave number and mass. Furthermore, we show that the stationary periodic solutions on the global bifurcation branch converge to a weak stationary periodic solution which exhibits film rupture. The proofs rely on a Hamiltonian formulation of the stationary problem and the use of analytic global bifurcation theory. Finally, we show the instability of the bifurcating solutions close to the bifurcation point and give a formal derivation of the amplitude equation governing the dynamics close to the onset of instability. - [187] arXiv:2309.07063 (replaced) [pdf, ps, html, other]
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Title: Real-time quantum dynamics of thermal states with neural thermofieldsSubjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other); Computational Physics (physics.comp-ph)
Solving the time-dependent quantum many-body Schrödinger equation is a challenging task, especially for states at a finite temperature, where the environment affects the dynamics. Most existing approximating methods are designed to represent static thermal density matrices, 1D systems, and/or zero-temperature states. In this work, we propose a method to study the real-time dynamics of thermal states in two dimensions, based on thermofield dynamics, variational Monte Carlo, and neural-network quantum states. To this aim, we introduce two novel tools: (i) a procedure to accurately simulate the cooling down of arbitrary quantum variational states from infinite temperature, and (ii) a generic thermal (autoregressive) recurrent neural-network (ARNNO) Ansatz that allows for direct sampling from the density matrix using thermofield basis rotations. We apply our technique to the transverse-field Ising model subject to an additional longitudinal field and demonstrate that the time-dependent observables, including correlation operators, can be accurately reproduced for a 4x4 spin lattice. We provide predictions of the real-time dynamics on a 6x6 lattice that lies outside the reach of exact simulations.
- [188] arXiv:2311.18647 (replaced) [pdf, ps, html, other]
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Title: Long-term temporal stability of the DarkSide-50 dark matter detectorThe DarkSide-50 Collaboration: P. Agnes, I.F.M. Albuquerque, T. Alexander, A.K. Alton, M. Ave, H.O. Back, G. Batignani, K. Biery, V. Bocci, W.M. Bonivento, B. Bottino, S. Bussino, M. Cadeddu, M. Cadoni, F. Calaprice, A. Caminata, M.D. Campos, N. Canci, M. Caravati, N. Cargioli, M. Cariello, M. Carlini, V. Cataudella, P. Cavalcante, S. Cavuoti, S. Chashin, A. Chepurnov, C. Cicalò, G. Covone, D. D'Angelo, S. Davini, A. De Candia, S. De Cecco, G. De Filippis, G. De Rosa, A.V. Derbin, A. Devoto, M. D'Incecco, C. Dionisi, F. Dordei, M. Downing, D. D'Urso, M. Fairbairn, G. Fiorillo, D. Franco, F. Gabriele, C. Galbiati, C. Ghiano, C. Giganti, G.K. Giovanetti, A.M. Goretti, G. Grilli di Cortona, A. Grobov, M. Gromov, M. Guan, M. Gulino, B.R. Hackett, K. Herner, T. Hessel, B. Hosseini, F. Hubaut, T. Hugues, E.V. Hungerford, An. Ianni, V. Ippolito, K. Keeter, C.L. Kendziora, M. Kimura, I. Kochanek, D. Korablev, G. Korga, A. Kubankin, M. Kuss, M. Kuźniak, M. La Commara, M. Lai, X. Li, M. Lissia, G. Longo, O. Lychagina, I.N. Machulin, L.P. Mapelli, S.M. Mari, J. Maricic, A. Messina, R. Milincic, J. Monroe, M. Morrocchi, X. Mougeot, V.N. Muratova, P. Musico, A.O. Nozdrina, A. Oleinik, F. Ortica, L. Pagani, M. Pallavicini, L. Pandola, E. Pantic, E. PaoloniComments: 13 pages, 5 figuresJournal-ref: JINST 19 P05057 (2024)Subjects: High Energy Physics - Experiment (hep-ex); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Detectors (physics.ins-det)
The stability of a dark matter detector on the timescale of a few years is a key requirement due to the large exposure needed to achieve a competitive sensitivity. It is especially crucial to enable the detector to potentially detect any annual event rate modulation, an expected dark matter signature. In this work, we present the performance history of the DarkSide-50 dual-phase argon time projection chamber over its almost three-year low-radioactivity argon run. In particular, we focus on the electroluminescence signal that enables sensitivity to sub-keV energy depositions. The stability of the electroluminescence yield is found to be better than 0.5%. Finally, we show the temporal evolution of the observed event rate around the sub-keV region being consistent to the background prediction.
- [189] arXiv:2312.11072 (replaced) [pdf, ps, html, other]
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Title: Waveform Simulation in PandaX-4TJiafu Li, Abdusalam Abdukerim, Chen Cheng, Zihao Bo, Wei Chen, Xun Chen, Yunhua Chen, Zhaokan Cheng, Xiangyi Cui, Yingjie Fan, Deqing Fang, Changbo Fu, Mengting Fu, Lisheng Geng, Karl Giboni, Linhui Gu, Xuyuan Guo, Chencheng Han, Ke Han, Changda He, Jinrong He, Di Huang, Yanlin Huang, Zhou Huang, Ruquan Hou, Xiangdong Ji, Yonglin Ju, Chenxiang Li, Mingchuan Li, Shu Li, Shuaijie Li, Qing Lin, Jianglai Liu, Xiaoying Lu, Lingyin Luo, Yunyang Luo, Wenbo Ma, Yugang Ma, Yajun Mao, Nasir Shaheed, Yue Meng, Xuyang Ning, Ningchun Qi, Zhicheng Qian, Xiangxiang Ren, Changsong Shang, Xiaofeng Shang, Guofang Shen, Lin Si, Wenliang Sun, Andi Tan, Yi Tao, Anqing Wang, Meng Wang, Qiuhong Wang, Shaobo Wang, Siguang Wang, Wei Wang, Xiuli Wang, Zhou Wang, Yuehuan Wei, Mengmeng Wu, Weihao Wu, Jingkai Xia, Mengjiao Xiao, Xiang Xiao, Pengwei Xie, Binbin Yan, Xiyu Yan, Jijun Yang, Yong Yang, Chunxu Yu, Jumin Yuan, Ying Yuan, Zhe Yuan, Xinning Zeng, Dan Zhang, Minzhen Zhang, Peng Zhang, Shibo Zhang, Shu Zhang, Tao Zhang, Yingxin Zhang, Yuanyuan Zhang, Li Zhao, Qibin Zheng, Jifang Zhou, Ning Zhou, Xiaopeng Zhou, Yong Zhou, Yubo ZhouJournal-ref: Chin. Phys. C 48, no.7,073001 (2024)Subjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Signal reconstruction through software processing is a crucial component of the background and signal models in the PandaX-4T experiment, which is a multi-tonne dark matter direct search experiment. The accuracy of signal reconstruction is influenced by various detector artifacts, including noise, dark count of photomultiplier, impurity photoionization in the detector, and other relevant considerations. In this study, we present a detailed description of a semi-data-driven approach designed to simulate the signal waveform. This work provides a reliable model for the efficiency and bias of the signal reconstruction in the data analysis of PandaX-4T. By comparing critical variables which relate to the temporal shape and hit pattern of the signals, we demonstrate a good agreement between the simulation and data.
- [190] arXiv:2401.05260 (replaced) [pdf, ps, html, other]
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Title: A Novel ES-BGK Model for Non-Polytropic Gases with Internal State Density Independent of the TemperatureSubjects: Statistical Mechanics (cond-mat.stat-mech); Fluid Dynamics (physics.flu-dyn)
A novel ES-BGK-based model of non-polytropic rarefied gases in the framework of kinetic theory is presented. Key features of this model are: an internal state density function depending only on the microscopic energy of internal modes (avoiding the dependence on temperature seen in previous reference studies); full compliance with the H-theorem; feasibility of the closure of the system of moment equations based on the maximum entropy principle, following the well-established procedure of Rational Extended Thermodynamics.
The structure of planar shock waves in carbon dioxide (CO$_2$) obtained with the present model is in general good agreement with that of previous results, except for the computed internal temperature profile, which is qualitatively different with respect to the results obtained in previous studies, showing here a consistently monotonous behavior across the shock structure, rather than the non monotonous behavior previously found. - [191] arXiv:2401.08361 (replaced) [pdf, ps, html, other]
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Title: Adjoint Monte Carlo MethodComments: 39 pages, 7 figuresSubjects: Numerical Analysis (math.NA); Computational Physics (physics.comp-ph)
This survey explores the development of adjoint Monte Carlo methods for solving optimization problems governed by kinetic equations, a common challenge in areas such as plasma control and device design. These optimization problems are particularly demanding due to the high dimensionality of the phase space and the randomness in evaluating the objective functional, a consequence of using a forward Monte Carlo solver. To overcome these difficulties, a range of ``adjoint Monte Carlo methods'' have been devised. These methods skillfully combine Monte Carlo gradient estimators with PDE-constrained optimization, introducing innovative solutions tailored for kinetic applications. In this review, we begin by examining three primary strategies for Monte Carlo gradient estimation: the score function approach, the reparameterization trick, and the coupling method. We also delve into the adjoint-state method, an essential element in PDE-constrained optimization. Focusing on applications in the radiative transfer equation and the nonlinear Boltzmann equation, we provide a comprehensive guide on how to integrate Monte Carlo gradient techniques within both the optimize-then-discretize and the discretize-then-optimize frameworks from PDE-constrained optimization. This approach leads to the formulation of effective adjoint Monte Carlo methods, enabling efficient gradient estimation in complex, high-dimensional optimization problems.
- [192] arXiv:2401.08539 (replaced) [pdf, ps, html, other]
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Title: Mapping low-resolution edges to high-resolution paths: the case of traffic measurements in citiesComments: arXiv admin comment: This version has been removed by arXiv administrators as the submitter did not have the rights to agree to the license at the time of submissionJournal-ref: In: Botta, F., Macedo, M., Barbosa, H., Menezes, R. (eds) Complex Networks XV. CompleNet-Live 2024. Springer Proceedings in Complexity. Springer, ChamSubjects: Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)
We consider the following problem : we have a high-resolution street network of a given city, and low-resolution measurements of traffic within this city. We want to associate to each measurement the set of streets corresponding to the observed traffic. To do so, we take benefit of specific properties of these data to match measured links to links in the street network. We propose several success criteria for the obtained matching. They show that the matching algorithm generally performs very well, and they give complementary ways to detect data discrepancies that makes any matching highly dubious.
- [193] arXiv:2402.00972 (replaced) [pdf, ps, html, other]
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Title: Closure Discovery for Coarse-Grained Partial Differential Equations Using Grid-based Reinforcement LearningComments: 23 pages, 12 figuresSubjects: Machine Learning (cs.LG); Multiagent Systems (cs.MA); Computational Physics (physics.comp-ph)
Reliable predictions of critical phenomena, such as weather, wildfires and epidemics often rely on models described by Partial Differential Equations (PDEs). However, simulations that capture the full range of spatio-temporal scales described by such PDEs are often prohibitively expensive. Consequently, coarse-grained simulations are usually deployed that adopt various heuristics and empirical closure terms to account for the missing information. We propose a novel and systematic approach for identifying closures in under-resolved PDEs using grid-based Reinforcement Learning. This formulation incorporates inductive bias and exploits locality by deploying a central policy represented efficiently by a Fully Convolutional Network (FCN). We demonstrate the capabilities and limitations of our framework through numerical solutions of the advection equation and the Burgers' equation. Our results show accurate predictions for in- and out-of-distribution test cases as well as a significant speedup compared to resolving all scales.
- [194] arXiv:2402.03070 (replaced) [pdf, ps, html, other]
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Title: Bound impurities in a one-dimensional Bose lattice gas: low-energy properties and quench-induced dynamicsComments: Submission to SciPost. 29 pages, 17 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
We study two mobile bosonic impurities immersed in a one-dimensional optical lattice and interacting with a bosonic bath. We employ the exact diagonalization method for small periodic lattices to study stationary properties and dynamics. We consider the branch of repulsive interactions that induce the formation of bound impurities, akin to the bipolaron problem. A comprehensive study of ground-state and low-energy properties is presented, including an examination of the interaction strengths which induce the formation of a bound dimer of impurities. We also study the dynamics induced after an interaction quench to examine the stability of the bound dimers. We reveal that after large interaction quenches from strong to weak interactions the system can show large oscillations over time with revivals of the dimer states. We find that the oscillations are driven by selected eigenstates with phase-separated configurations.
- [195] arXiv:2402.11186 (replaced) [pdf, ps, html, other]
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Title: Low-Dose CT Reconstruction Using Dataset-free LearningSubjects: Image and Video Processing (eess.IV); Medical Physics (physics.med-ph)
Low-Dose computer tomography (LDCT) is an ideal alternative to reduce radiation risk in clinical applications. Although supervised-deep-learning-based reconstruction methods have demonstrated superior performance compared to conventional model-driven reconstruction algorithms, they require collecting massive pairs of low-dose and norm-dose CT images for neural network training, which limits their practical application in LDCT imaging. In this paper, we propose an unsupervised and training data-free learning reconstruction method for LDCT imaging that avoids the requirement for training data. The proposed method is a post-processing technique that aims to enhance the initial low-quality reconstruction results, and it reconstructs the high-quality images by neural work training that minimizes the $\ell_1$-norm distance between the CT measurements and their corresponding simulated sinogram data, as well as the total variation (TV) value of the reconstructed image. Moreover, the proposed method does not require to set the weights for both the data fidelity term and the plenty term. Experimental results on the AAPM challenge data and LoDoPab-CT data demonstrate that the proposed method is able to effectively suppress the noise and preserve the tiny structures. Also, these results demonstrate the rapid convergence and low computational cost of the proposed method. The source code is available at \url{this https URL}.
- [196] arXiv:2402.17660 (replaced) [pdf, ps, html, other]
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Title: TorchMD-Net 2.0: Fast Neural Network Potentials for Molecular SimulationsRaul P. Pelaez, Guillem Simeon, Raimondas Galvelis, Antonio Mirarchi, Peter Eastman, Stefan Doerr, Philipp Thölke, Thomas E. Markland, Gianni De FabritiisComments: Version accepted in Journal of Chemical Theory and ComputationSubjects: Machine Learning (cs.LG); Biological Physics (physics.bio-ph); Chemical Physics (physics.chem-ph); Computational Physics (physics.comp-ph)
Achieving a balance between computational speed, prediction accuracy, and universal applicability in molecular simulations has been a persistent challenge. This paper presents substantial advancements in the TorchMD-Net software, a pivotal step forward in the shift from conventional force fields to neural network-based potentials. The evolution of TorchMD-Net into a more comprehensive and versatile framework is highlighted, incorporating cutting-edge architectures such as TensorNet. This transformation is achieved through a modular design approach, encouraging customized applications within the scientific community. The most notable enhancement is a significant improvement in computational efficiency, achieving a very remarkable acceleration in the computation of energy and forces for TensorNet models, with performance gains ranging from 2-fold to 10-fold over previous iterations. Other enhancements include highly optimized neighbor search algorithms that support periodic boundary conditions and the smooth integration with existing molecular dynamics frameworks. Additionally, the updated version introduces the capability to integrate physical priors, further enriching its application spectrum and utility in research. The software is available at this https URL.
- [197] arXiv:2403.01052 (replaced) [pdf, ps, other]
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Title: Long-Distance Signal Propagation in AC-LGADCasey Bishop, Ayan Das, Jane Ding, Matthew Gignac, Forest Martinez-McKinney, Simone M. Mazza, Adam Molnar, Noah Nagel, Mohammad Nizam, Jennifer Ott, Hartmut F.-W. Sadrozinski, Bruce Schumm, Abraham Seiden, Taylor Shin, Andrew Summerell, Max Wilder, Yuzhan ZhaoComments: 9 pages, 7 figures, 13th Hiroshima Symposium HSTD13Subjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
We investigate the signal propagation in AC-LGAD (aka RSD), which are LGAD with a common N+ layer and segmented AC-coupled readout contacts, by measuring response to IR laser TCT on a large selection of AC-LGAD with strip readout. The interest for this topic derives from the realization that while large charge sharing between neighboring strips is essential for good position resolution, large sharing beyond the next neighbor generates background signals which in general are detrimental to the sensor goal of low occupancy. Using AC-LGAD with strip readout produced by Hamamatsu Photonics (HPK), we evaluate the effects of a variety of sensor properties, including geometrical parameters (strip length, width), process parameters like the N+ layer resistivity, the coupling capacitance, and the thickness of the bulk on the signal sharing and the position resolution.
- [198] arXiv:2403.05443 (replaced) [pdf, ps, html, other]
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Title: Simulating dynamics of ellipsoidal particles using lattice Boltzmann methodSubjects: Soft Condensed Matter (cond-mat.soft); Fluid Dynamics (physics.flu-dyn)
Anisotropic particles are often encountered in different fields of soft matter and complex fluids. In this work, we present an implementation of the coupled hydrodynamics of solid ellipsoidal particles and the surrounding fluid using the lattice Boltzmann method. A standard link-based mechanism is used to implement the solid-fluid boundary conditions. We develop an implicit method to update the position and orientation of the ellipsoid. This exploits the relations between the quaternion which describes the ellipsoid's orientation and the ellipsoid's angular velocity to obtain a stable and robust dynamic update. The proposed algorithm is validated by looking at four scenarios: (i) the steady translational velocity of a spheroid subject to an external force in different orientations, (ii) the drift of an inclined spheroid subject to an imposed force, (iii) three-dimensional rotational motions in a simple shear flow (Jeffrey's orbits), and (iv) developed fluid flows and self-propulsion exhibited by a spheroidal microswimmer. In all cases the comparison of numerical results showed good agreement with known analytical solutions, irrespective of the choice of the fluid properties, geometrical parameters, and lattice Boltzmann model, thus demonstrating the robustness of the proposed algorithm.
- [199] arXiv:2403.15855 (replaced) [pdf, ps, html, other]
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Title: Initialisation and Topology Effects in Decentralised Federated LearningSubjects: Machine Learning (cs.LG); Artificial Intelligence (cs.AI); Distributed, Parallel, and Cluster Computing (cs.DC); Physics and Society (physics.soc-ph)
Fully decentralised federated learning enables collaborative training of individual machine learning models on distributed devices on a communication network while keeping the training data localised. This approach enhances data privacy and eliminates both the single point of failure and the necessity for central coordination. Our research highlights that the effectiveness of decentralised federated learning is significantly influenced by the network topology of connected devices. We propose a strategy for uncoordinated initialisation of the artificial neural networks, which leverages the distribution of eigenvector centralities of the nodes of the underlying communication network, leading to a radically improved training efficiency. Additionally, our study explores the scaling behaviour and choice of environmental parameters under our proposed initialisation strategy. This work paves the way for more efficient and scalable artificial neural network training in a distributed and uncoordinated environment, offering a deeper understanding of the intertwining roles of network structure and learning dynamics.
- [200] arXiv:2404.00721 (replaced) [pdf, ps, html, other]
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Title: Designing robust trajectories by lobe dynamics in low-dimensional Hamiltonian systemsComments: 5 pages, 4 figures + Supplemental Material (5 pages, 6 figures)Subjects: Chaotic Dynamics (nlin.CD); Dynamical Systems (math.DS); Optimization and Control (math.OC); Classical Physics (physics.class-ph)
Modern space missions with uncrewed spacecraft require robust trajectory design to connect multiple chaotic orbits by small controls. To address this issue, we propose a control scheme to design robust trajectories by leveraging a geometrical structure in chaotic zones, known as a {\it lobe}. Our scheme shows that appropriately selected lobes reveal possible paths to traverse chaotic zones in a short time. The effectiveness of our method is demonstrated through trajectory design in both the standard map and Hill's equation.
- [201] arXiv:2405.03797 (replaced) [pdf, ps, html, other]
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Title: Tensor Network Computations That Capture Strict Variationality, Volume Law Behavior, and the Efficient Representation of Neural Network StatesComments: 4+9 pages, 13 figuresSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Strongly Correlated Electrons (cond-mat.str-el); Computational Physics (physics.comp-ph)
We introduce a change of perspective on tensor network states that is defined by the computational graph of the contraction of an amplitude. The resulting class of states, which we refer to as tensor network functions, inherit the conceptual advantages of tensor network states while removing computational restrictions arising from the need to converge approximate contractions. We use tensor network functions to compute strict variational estimates of the energy on loopy graphs, analyze their expressive power for ground-states, show that we can capture aspects of volume law time evolution, and provide a mapping of general feed-forward neural nets onto efficient tensor network functions. Our work expands the realm of computable tensor networks to ones where accurate contraction methods are not available, and opens up new avenues to use tensor networks.
- [202] arXiv:2405.05674 (replaced) [pdf, ps, other]
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Title: TransAnaNet: Transformer-based Anatomy Change Prediction Network for Head and Neck Cancer Patient RadiotherapySubjects: Computer Vision and Pattern Recognition (cs.CV); Medical Physics (physics.med-ph)
Early identification of head and neck cancer (HNC) patients who would experience significant anatomical change during radiotherapy (RT) is important to optimize patient clinical benefit and treatment resources. This study aims to assess the feasibility of using a vision-transformer (ViT) based neural network to predict RT-induced anatomic change in HNC patients. We retrospectively included 121 HNC patients treated with definitive RT/CRT. We collected the planning CT (pCT), planned dose, CBCTs acquired at the initial treatment (CBCT01) and fraction 21 (CBCT21), and primary tumor volume (GTVp) and involved nodal volume (GTVn) delineated on both pCT and CBCTs for model construction and evaluation. A UNet-style ViT network was designed to learn spatial correspondence and contextual information from embedded CT, dose, CBCT01, GTVp, and GTVn image patches. The model estimated the deformation vector field between CBCT01 and CBCT21 as the prediction of anatomic change, and deformed CBCT01 was used as the prediction of CBCT21. We also generated binary masks of GTVp, GTVn, and patient body for volumetric change evaluation. The predicted image from the proposed method yielded the best similarity to the real image (CBCT21) over pCT, CBCT01, and predicted CBCTs from other comparison models. The average MSE and SSIM between the normalized predicted CBCT to CBCT21 are 0.009 and 0.933, while the average dice coefficient between body mask, GTVp mask, and GTVn mask are 0.972, 0.792, and 0.821 respectively. The proposed method showed promising performance for predicting radiotherapy-induced anatomic change, which has the potential to assist in the decision-making of HNC Adaptive RT.
- [203] arXiv:2405.07441 (replaced) [pdf, ps, html, other]
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Title: Reducing Spatial Discretization Error on Coarse CFD Simulations Using an OpenFOAM-Embedded Deep Learning FrameworkSubjects: Machine Learning (cs.LG); Fluid Dynamics (physics.flu-dyn)
We propose a method for reducing the spatial discretization error of coarse computational fluid dynamics (CFD) problems by enhancing the quality of low-resolution simulations using a deep learning model fed with high-quality data. We substitute the default differencing scheme for the convection term by a feed-forward neural network that interpolates velocities from cell centers to face values to produce velocities that approximate the fine-mesh data well. The deep learning framework incorporates the open-source CFD code OpenFOAM, resulting in an end-to-end differentiable model. We automatically differentiate the CFD physics using a discrete adjoint code version. We present a fast communication method between TensorFlow (Python) and OpenFOAM (c++) that accelerates the training process. We applied the model to the flow past a square cylinder problem, reducing the error to about 50% for simulations outside the training distribution compared to the traditional solver in the x- and y-velocity components using an 8x coarser mesh. The training is affordable in terms of time and data samples since the architecture exploits the local features of the physics while generating stable predictions for mid-term simulations.
- [204] arXiv:2405.08580 (replaced) [pdf, ps, html, other]
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Title: Importance of hyper-parameter optimization during training of physics-informed deep learning networksSubjects: Materials Science (cond-mat.mtrl-sci); Data Analysis, Statistics and Probability (physics.data-an)
Incorporating scientific knowledge into deep learning (DL) models for materials-based simulations can constrain the network's predictions to be within the boundaries of the material system. Altering loss functions or adding physics-based regularization (PBR) terms to reflect material properties informs a network about the physical constraints the simulation should obey. The training and tuning process of a DL network greatly affects the quality of the model, but how this process differs when using physics-based loss functions or regularization terms is not commonly discussed. In this manuscript, several PBR methods are implemented to enforce stress equilibrium on a network predicting the stress fields of a high elastic contrast composite. Models with PBR enforced the equilibrium constraint more accurately than a model without PBR, and the stress equilibrium converged more quickly. More importantly, it was observed that independently fine-tuning each implementation resulted in more accurate models. More specifically, each loss formulation and dataset required different learning rates and loss weights for the best performance. This result has important implications on assessing the relative effectiveness of different DL models and highlights important considerations when making a comparison between DL methods.
- [205] arXiv:2405.11542 (replaced) [pdf, ps, html, other]
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Title: From Fourier to Neural ODEs: Flow Matching for Modeling Complex SystemsSubjects: Machine Learning (cs.LG); Physics Education (physics.ed-ph)
Modeling complex systems using standard neural ordinary differential equations (NODEs) often faces some essential challenges, including high computational costs and susceptibility to local optima. To address these challenges, we propose a simulation-free framework, called Fourier NODEs (FNODEs), that effectively trains NODEs by directly matching the target vector field based on Fourier analysis. Specifically, we employ the Fourier analysis to estimate temporal and potential high-order spatial gradients from noisy observational data. We then incorporate the estimated spatial gradients as additional inputs to a neural network. Furthermore, we utilize the estimated temporal gradient as the optimization objective for the output of the neural network. Later, the trained neural network generates more data points through an ODE solver without participating in the computational graph, facilitating more accurate estimations of gradients based on Fourier analysis. These two steps form a positive feedback loop, enabling accurate dynamics modeling in our framework. Consequently, our approach outperforms state-of-the-art methods in terms of training time, dynamics prediction, and robustness. Finally, we demonstrate the superior performance of our framework using a number of representative complex systems.
- [206] arXiv:2405.12054 (replaced) [pdf, ps, html, other]
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Title: Solvent Selectivity controls Micro- versus Macro-phase Separation in Multiblock ChainsSubjects: Soft Condensed Matter (cond-mat.soft); Chemical Physics (physics.chem-ph)
Monte Carlo simulations in the grand canonical ensemble were used to obtain critical parameters and conditions leading to microphase separation for block copolymers with solvophilic and solvophobic segments. Solvent selectivity was systematically varied to distinguish between systems that undergo macrophase separation to ones that microphase separate in the dilute phase, prior to macrophase separating. Finite-size scaling was used to obtain the critical parameters. Interestingly, corrections to scaling increase significantly for systems that form finite aggregates. The threshold value of solvent selectivity for aggregation was determined for symmetric diblock chains of varying length. The results indicate that long diblock copolymers form micelles in the dilute phase prior to macrophase separation, even in marginally selective solvents. The dependence of critical temperature on solvent selectivity was obtained for triblock, multiblock, and alternating chains. For highly selective solvents, strong structuring of both dilute and dense phases makes it harder to reach equilibrium.
- [207] arXiv:2405.12822 (replaced) [pdf, ps, html, other]
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Title: Open-Path Detection of Organic Vapors via Quantum Infrared SpectroscopySimon Neves, Adimulya Kartiyasa, Shayantani Ghosh, Geoffrey Gaulier, Luca La Volpe, Jean-Pierre WolfComments: 8 pages, 7 figures, 1 table. For associated gif file, see this https URLSubjects: Quantum Physics (quant-ph); Optics (physics.optics)
In recent years, quantum Fourier transform infrared (QFTIR) spectroscopy emerged as an alternative to conventional spectroscopy in the mid-infrared region of the spectrum. By harnessing induced coherence and spectral entanglement, QFTIR offers promising potential for the practical detection of organic gasses. However, little research was conducted to bring QFTIR spectrometers closer to domestic or in-field usage. In this work, we present the first use of a QFTIR spectrometer for open-path detection of multiple interfering organic gases in ambient air. The accurate identification of mixtures of acetone, methanol, and ethanol vapors is demonstrated with a QFTIR spectrometer. We achieved this breakthrough by building a nonlinear Michelson interferometer with 1.7m-long arms to increase the absorption length, coupled with analysis techniques from differential absorption spectroscopy. The evolution of different gasses' concentrations in ambient air was measured through time. These results constitute the first use-case of a QFTIR spectrometer as a detector of organic gasses, and thus represent an important milestone towards the development of such detectors in practical situations.