Plasma Physics
Quantifying resonant drive in resistive perturbed tokamak equilibria
Matthew Pharr, Nikolas Logan, Carlos Paz-Soldan et al. (+1 more)
Resonant drive in tokamaks is routinely quantified using a variety of different metrics that target different aspects of a resonant response to an external perturbation. Two of the most direct metrics, $\Delta_{mn}$ and $b_{pen}$, are widely used but their relative behavior was previously uncharacterized. This work examines how these metrics representing the shielding current and penetrated field relate in resistive perturbed tokamak
equilibria using asymptotically matched solutions with a resistive MHD inner layer model in GPEC. $b_{pen}$ scales with Lundquist number as $S^{-2/3}$ until saturation at low $S$, and $\Delta_{mn}$ remains consistent with its ideal definition but is affected by global kink structure. Both metrics are shown to yield closely similar dominant coupling modes within the same resistive model. However, the resistive physics shifts this dominant mode spectrum to lower poloidal mode numbers $m$ in a low-rotation ITER
equilibrium. This alteration is predicted to be observable in experiment in the form of optimal relative phasings of resonant
magnetic perturbation coils.
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All authors Matthew Pharr, Nikolas Logan, Carlos Paz-Soldan, Jong-Kyu Park
Plasma Physics
STAR_Lite: A stellarator designed to experimentally validate non-resonant divertors
Georg Friedrich Harrer, Andrew Giuliani, Misha Padidar et al. (+3 more)
The non-resonant divertor (NRD) offers a promising exhaust solution for stellarators, combining topological simplicity with resilience to
magnetic field perturbations. To experimentally validate the robustness of non-resonant divertors in a quasi-axisymmetric (QA) configuration, we introduce
STAR_Lite, a new stellarator experiment at Hampton University. This paper details the design and analysis of the first
STAR_Lite coil configuration,
STAR_Lite-A. The two field-period configuration manifests an NRD through X-points with zero rotational transform, at the top and bottom of the device. The divertor legs extruding from the X-points are topologically similar to the poloidal divertors of tokamaks. To expand the experimental range,
STAR_Lite-A is optimized for experimental flexibility, producing a wide range of distinct QA configurations by only varying the currents in the modular coils. The NRDs not only persist across these configurations, but numerical strike-line simulations confirm that heat exhaust remains resilient to changes in coil currents, with
plasma following the divertor legs and creating a toroidal, discontinuous, strike pattern. We further examine the resilience of the NRD to
magnetic perturbations caused by manufacturing errors in the modular coils. We find that quasisymmetry and the existence of X-points is well-preserved under these
magnetic field changes, but the rotational transform may vary substantially and displacements of the divertor X-points may lead to one X-point having a dominant effect on edge transport. Overall, our analysis indicates a compact, modular design can likely generate a resilient NRD structure while satisfying the practical constraints of a university-scale experiment.
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All authors Georg Friedrich Harrer, Andrew Giuliani, Misha Padidar, Robert Davies, Shibabrat Naik, Calvin Lowe
Data Analysis and Statistics · Cross-listed from astro-ph.IM
ALABI: Active Learning for Accelerated Bayesian Inference
Jessica Birky and Rory K. Barnes
We present Active Learning for Accelerated
Bayesian Inference (alabi): an open-source Python package for performing
Bayesian inference with computationally expensive models. Given a forward model and observational data to construct a likelihood and priors, alabi\ uses a Gaussian Process (GP) surrogate model trained to predict posterior probability as a function of input parameters, and employs active learning to iteratively improve GP predictive performance in high-likelihood regions where the GP is most uncertain. alabi\ provides a uniform interface for using Markov chain Monte Carlo (MCMC) with different packages, including the affine-invariant sampler emcee, and nested samplers dynesty, multinest, and ultranest. This approach facilitates accurate estimation of the desired posterior distribution, while reducing the number of computationally expensive model evaluations required by factors of thousands. We demonstrate the performance of alabi\ on a variety of test cases, including where inference is challenging due to complex posterior structure or high dimensionality. We show that alabi\ offers a substantial improvement for likelihood functions with evaluation times $\gtrsim 1$\,s, speeding up MCMC computations by a factor of $10-1000\times$ when tested on problems with up to 64 dimensions.
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Optics
Direct observation of ultrafast defect-bound and free exciton dynamics in defect-engineered WS$_2$ monolayers
Tae Gwan Park, Xufan Li, Kyungnam Kang et al. (+7 more)
Defects in two-dimensional transition metal dichalcogenides (TMDCs) broadly affect their optical and electronic properties. Directly capturing the ultrafast processes of
exciton trapping and defect-bound
exciton formation is crucial for understanding and advancing defect-mediated optoelectronics and
quantum technologies. However, the weak transient optical absorption of defect-bound
excitons has limited their experimental observation to date. Here, we report the direct observation of the ultrafast dynamics of defect-bound
excitons in monolayer WS$_2$
crystals with a high density of mono-sulfur vacancies (V$_S$) and W-site defect complexes (S$_W$V$_S$) resulting from synthesis by alkali metal halide-assisted chemical vapor deposition. The dynamics of
excitons bound to these defects, along with their coherent interactions with free
excitons, are elucidated using ultrafast optical spectroscopy. Using above band-edge photoexcitation, we find that both free and defect-bound
excitons simultaneously form within 300 fs from hot carrier relaxation. The defect-bound
excitons exhibit shorter lifetimes than free
excitons, leading to a population difference of the corresponding excitonic states and free
exciton trapping within a 1–100 ps window. Band-edge photoexcitation of free and defect-bound
exciton states reveals ultrafast interconversion within ~150 fs (comparable to our temporal resolution), indicating possible coherent coupling between these states. We further demonstrate efficient up-conversion of defect-bound
excitons to free
excitons with
photon energies up to ~300 meV below the free
exciton resonance. These findings provide insights into the ultrafast dynamics of defect-bound
excitons in TMDCs and their coupling with free
excitons, which are relevant to defect-engineered optoelectronic,
quantum photonic, and valleytronic applications.
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All authors Tae Gwan Park, Xufan Li, Kyungnam Kang, Austin Houston, Liam Collins, Gerd Duscher, David B. Geohegan, Christopher M. Rouleau, Kai Xiao, Alexander A. Puretzky
Chemical Physics
Spin-Flip Configuration Interaction for Strong Static Correlation in Quantum Electrodynamics
Braden M. Weight, Zheng Pei and Sergei Tretiak
In computational chemistry of molecular materials, strong static correlation effects appear when electronic states, often involving the ground state, become quasi-degenerate, as occurs, for example, in bond-breaking processes. Such situations present significant challenges for accurate theoretical treatment. In these regimes, many-body methods involving a single-determinant description, such as Hartree-Fock theory and its time-dependent extension, fail to reproduce the correct
topology of the ground and excited state potential energy surfaces (e.g., near conical intersections). When strongly correlated electronic systems are further strongly coupled to a quantized radiation field within the framework of non-relativistic cavity
quantum electrodynamics, an additional photonic degree of freedom introduces both new complexity and new opportunities to control. Excited cavity
photons can modify bond-breaking processes and enable tunability of geometrical and
spin-phase transitions, for instance, in organometallic complexes. To overcome this bottleneck, in this work, we extend the well-studied
spin-flip configuration interaction singles (SF-CIS) approach to explicitly include quantized cavity
photons leading to QED-SF-CIS method. We derive the
spin-flip
Hamiltonian and find that the double excitation subspace of the system (single with respect to electronic excitation) must be included in the configurations to properly describe singlet electronic states interacting with cavity
photons. We then illustrate, through representative molecular examples, how cavity coupling can provide additional tunability in bond-breaking processes. We finally generalize this approach to include higher numbers of photonic excitations, which are required in the strong coupling regime.
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Optics
Temperature in Glass Slides: measurement using Phase Sensitive Optical Coherence Tomography and Computational Modeling
Jose M. Folgueiras, Lucas G. Chej, Luis L. Zurdo et al. (+4 more)
Phase-sensitive optical coherence
tomography (PhS-OCT) enables precise, contactless measurements of temperature-dependent changes in transparent solids. In this work, we used a common-path spectral-domain OCT system to measure optical path differences (OPD) in a 1-mm-thick soda-lime glass slide immersed in a thermal bath. The OPD variation showed a strong linear correlation with temperature in the range of 20-52{\deg}C, with an experimentally determined sensitivity of 12.4 +- 1.9 nm/{\deg}C. A theoretical model incorporating the thermo-optic and thermal expansion coefficients of glass was proposed to interpret the measurements, and numerical simulations based on finite volume methods were performed to account for spatial temperature gradients in the system. The simulations showed agreement with experimental results within 5% error, validating the approach. Additionally, repeatability tests using lateral scans at constant temperature demonstrated sub-10 nm stability, supporting future extensions to spatially resolved thermal mapping. This technique provides a low-cost platform for localized temperature sensing in solid transparent materials.
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All authors Jose M. Folgueiras, Lucas G. Chej, Luis L. Zurdo, Alejandro G. Monastra, Eneas N. Morel, Maria F. Carusela, Jorge R. Torga
Computational Physics · Cross-listed from quant-ph
An HHL-Based Quantum-Classical Solver for the Incompressible Navier-Stokes Equations with Approximate QST
Moshe Inger and Steven Frankel
In computational fluid dynamics (CFD), the numerical integration of the Navier-Stokes equations is frequently constrained by the Poisson equation to determine the pressure. Discretization of this equation often results in the need to solve a system of linear algebraic equations. This step typically represents the primary computational bottleneck.
Quantum linear system
algorithms such as Harrow-Hassidim-Lloyd (HHL) offer the potential for exponential speedups for solving sparse linear systems, such as those that arise from the discretized Poisson equation. In this work, we successfully couple HHL to a discretized formulation of the incompressible Navier-Stokes equations and demonstrate both accurate lid-driven cavity flow simulations as a fully integrated
benchmark problem, and accurate flow of the Taylor-Green
vortex. To address the readout limitation, we utilize a recent novel
quantum state
tomography (QST) approach based on Chebyshev
polynomials and
Quantum Amplitude Estimation (QAE), which enables approximate statevector extraction without full state reconstruction. Together, these results clarify the algorithmic structure required for
quantum CFD, explicitly confront the measurement bottleneck, and establish
benchmark problems for future
quantum fluid simulations. We implement the solver using IBM's Qiskit framework and validate the hybrid
quantum-classical simulation against standard classical numerical methods. Our results demonstrate that the hybrid solver successfully captures the global
vortex dynamics of the lid-driven cavity problem and the Taylor-Green
vortex, offering a robust pathway for integrating
quantum subroutines into more practical higher-Reynolds number CFD workflows.
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Optics · Cross-listed from quant-ph
High-dimensional quantum communication with scalable photonic entanglement in time and frequency
Kai-Chi Chang, Murat Can Sarihan, Nicky Kai Hong Li et al. (+13 more)
High-dimensional photonic
entanglement holds significant promise for advancing
quantum communication, computation, and metrology. For example, large-alphabet
quantum communication protocols are known to benefit from enhanced noise resilience and information capacity via multi-bit time-bin encoding. Yet, characterizing high-dimensional entangled states is challenging, as full state
tomography becomes prohibitively costly and often requires unrealizable measurements. Here, we demonstrate a scan-free method to characterize high-dimensional
entanglement in the time-frequency domain. Our reconstruction achieves a record $5.70\pm0.07$ ebits and a fidelity of $65.4\pm0.4\%$ with the maximally entangled state of local dimension $1021$, certifying the presence of $668$-dimensional
entanglement. We further prove the attainability of a secure key rate of $15.6$ kB/s in a composable finite-size,
entanglement-based protocol, and show that in continuous operation, the setup can quickly approach asymptotic key rates. Using commercial telecom components and state-of-the-art low-jitter single-
photon detectors, our scalable architecture offers a practical path towards high-rate, noise-resilient
quantum communication testbeds.
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All authors Kai-Chi Chang, Murat Can Sarihan, Nicky Kai Hong Li, Florian Kanitschar, Kemal Enes Akyuz, Yujie Chen, Dong-Il Lee, Jin Ho Kang, Alwaleed Aldhafeeri, Andrew Mueller, Matthew D. Shaw, Boris Korzh, Maria Spiropulu, Paul Erker, Marcus Huber, Chee Wei Wong
Applied Physics
Resonance-enhanced integrated acousto-optic beam steering
Yue Yu, Qixuan Lin, Shucheng Fang et al. (+8 more)
Optical beam steering is a key technology for free-space optical communication, sensing, and imaging. Mechanical beam steering systems suffer from limited scanning speed and bulky form factors, while existing solid-state solutions rely on pixelated synthetic aperture that requires complex fabrication and control architectures. Integrated acousto-optic beam steering (AOBS) is an emerging technology that enables continuous one-dimensional beam steering using integrated acoustic transducers and fixed-wavelength
laser sources. Here, we integrate AOBS with an optical ring resonator on the same thin-film lithium niobate (TFLN) platform to significantly enhance beam steering efficiency and system functionality. The resulting device achieves a resonance-enhanced beam steering efficiency of up to $26\%$ and a field of view of $18^\circ$. Moreover, by leveraging integrated electro-optic control, we dynamically lock the ring-resonator's resonance to a chirped
laser frequency, enabling frequency-modulated continuous-wave (FMCW)
LiDAR operation. By combining lithium niobate's piezoelectric and electro-optic properties, this work establishes a compact, efficient, and scalable beam-steering platform with co-integrated acousto-optic modulation and electro-optic control for multifunctional applications.
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All authors Yue Yu, Qixuan Lin, Shucheng Fang, Joseph G. Thomas, Yibing Zhou, Zichen Xi, Jun Ji, Yizheng Zhu, Linbo Shao, Bingzhao Li, Mo Li
Atomic Physics · Cross-listed from quant-ph
Dissipative Phase Transitions in an Open Quantum Rabi Model with Two-Photon Processes
Mingjian Zhu and Han Pu
We demonstrate a novel mechanism driving complex critical phenomena in open light-atom interacting systems by investigating a parametrically amplified
quantum Rabi model (QRM) subject to both single- and two-
photon decay. In the classical oscillator limit, four composite phases emerge, arising from the possible normal or superradiant regimes across the upper and lower
spin branches. A mean-field analysis reveals that the two-
photon decay activates the intrinsic nonlinearity of the QRM. The synergy of the coherent and dissipative two-
photon processes, together with the
spin-
boson coupling, constitutes an “inverted" regime where superradiance emerges exclusively at weak coupling. This regime features first- and second-order superradiant DPTs separated by a tricritical point. Utilizing an adiabatic approach and the semi-classical Langevin formalism, we further study the steady-state structure beyond the mean-field level. The universality classes of the DPTs are identified, with the corresponding critical and finite-size scaling exponents derived and a scaling ansatz proposed to describe the critical behavior.
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Applied Physics · Cross-listed from quant-ph
Fully selective charging of a quantum battery by a purely quantum charger
Yohan Vianna and Marcelo F. Santos
In this paper we discuss a protocol for charging a two-level
quantum battery using a bipartite charger composed of two
quantum harmonic oscillators. As one of its features, it allows us to fully charge the battery and is universally optimal in the regime of a single excitation added as energy input. We also make use of a selective interaction to extend the protocol for a different class of
quantum states and show that, in this case, the presence of
quantum coherence can be harnessed as energetic resource to charge multiple similar batteries. Among these, we also explore
symmetries of the derived effective dynamics to quickly discuss how the same protocol can be adapted to the task of active state resetting, a task which is particularly useful in the
quantum computation area.
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Physics and Society · Cross-listed from cond-mat.dis-nn
Statistical Mechanics of Random Hyperbolic Graphs within the Fermionic Maximum-Entropy Framework
M. Ángeles Serrano
The intricate relations between elements in natural and human-made systems sustain the complex processes that shape our world, forming multiscale networks of interactions. These networks can be represented as graphs composed of nodes connected by links and, regardless of their domain, they share a set of fundamental structural properties. The family of network models in
hyperbolic space constitutes one of the most advanced frameworks accounting for such properties, including sparsity, the small-world property, heterogeneity and hierarchical organization, high clustering, and scale invariance under network renormalization transformations. These
geometric models also exhibit other intriguing phenomena, such as an anomalous, temperature-dependent phase transition between a
geometric and a non-
geometric phase. In simple graph representations, where network links are unweighted, the model can be derived within a statistical-mechanics framework by maximizing the Gibbs
entropy of the graph ensemble subject to constraints imposed by observations, with links effectively behaving as fermionic particles. In this topical review, I revisit these derivations previously scattered across different sources and complement them, in order to properly contextualize and consolidate
hyperbolic random graphs within the broad framework of the maximum-
entropy principle in the statistical mechanics of complex networks. The approach presented here represents the least-biased prediction of the fundamental set of core network properties and establishes a principled framework for analyzing network structure, offering new perspectives and powerful analytical tools for both theoretical and empirical studies.
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Computational Physics · Cross-listed from cond-mat.str-el
Removing nodal and support-mismatch pathologies in Variational Monte Carlo via blurred sampling
Zhou-Quan Wan, Roeland Wiersema and Shiwei Zhang
Variational Monte Carlo (VMC) is a powerful and fast-growing method for optimizing and evolving parameterized many-body wave functions, especially with modern neural-network
quantum states. In practice, however, the
stochastic estimators that form the backbone of the method can become unstable or biased due to the presence of nodes, a ubiquitous feature of
quantum wave functions. In the continuum, this results in heavy-tailed
estimators with potentially divergent variances, while in discrete
Hilbert spaces the sampling distribution can miss parts of the support needed to form unbiased
estimators. These statistical pathologies lead to unreliable optimization trajectories in
stochastic reconfiguration or incorrect variational dynamics in time-dependent Variational Monte Carlo (t-VMC), and severely limit the power of the numerical simulations. We introduce blurred sampling to address these difficulties. The method has a number of rigorous properties that make it well-behaved, effective and computationally efficient. Additionally, it is a post-processing approach that can be used without modifying the underlying sampler and incurs only minimal overhead. We demonstrate its effectiveness in a broad range of problems – including ground state optimization in both continuum and discrete settings, as well as in time-dependent variational Monte Carlo, where it resolves previously identified failure modes – and further apply it to large-scale problems in
spin dynamics. This work establishes a broadly applicable framework for robust VMC and t-VMC calculations.
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Physics and Society
Myopic Best Response as a Double-Edged Mechanism in Networked Social Dilemmas with Individual Solutions
Hirofumi Takesue
Myopic best-response dynamics (MBRD) capture
agents' bounded rationality and can generate evolutionary outcomes that differ from those produced by widely examined imitation dynamics. In this study, we apply MBRD to a three-strategy social dilemma – the snowdrift game with an individual solution – in which not only defection but also an individual solution that guarantees a safe, constant payoff can undermine cooperation. Monte Carlo simulations show that, on a square
lattice, the evolutionary dynamics result in distinct
equilibria, including the dominance of the individual solution, the coexistence of cooperators and defectors, or all-strategy coexistence. By combining simulations with a simple heuristic that approximates the transition condition between the dominance of the individual solution and the all-strategy coexistence, the analysis reveals a dual role of neighborhood size. Specifically, smaller neighborhoods can promote cooperation even when the individual solution is relatively inexpensive; however, achieving cooperation under these conditions requires greater benefits from cooperation. Notably, this hindrance to cooperation contrasts with evolutionary outcomes observed under imitation dynamics. Analysis of local strategy configurations explains the transition between the all-strategy coexistence and the coexistence of cooperators and defectors while showing that this transition is absent in a one-dimensional
lattice. These observations indicate that the persistent availability of individual solutions constitutes an additional inhibiting factor of cooperation in populations of boundedly rational
agents.
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Physics and Society
A geometric scaling between collective organizations and interaction-space dimension
Arturo Tozzi
The number of stable macroscopic organizations in complex systems is often much smaller than the large number of microscopic degrees of freedom would suggest. Yet theoretical approaches rarely address whether general limits constrain the diversity of admissible macroscopic organizations. We develop a
geometric framework in which interactions among system components define a coarse-grained interaction space endowed with a metric structure. When this space has finite intrinsic dimensionality,
geometric packing constraints impose bounds on the number of mutually distinguishable collective organizations. We derive a dimension-dependent scaling law showing that the number of stable macroscopic regimes grows polynomially with exponent equal to the intrinsic dimensionality of the interaction space. This implies that increasing microscopic complexity alone does not necessarily expand the range of macroscopic organizations. Instead, diversification requires an increase in the dimensionality of effective interactions. To illustrate our approach, we analyze an interacting system in which collective regimes correspond to regions of a low-dimensional parameter space describing effective interactions. In this setting,
geometric packing constrains the number of robust organizations that the system can support. Overall, we argue that dimensionality of interaction space may act as a control parameter governing a variety of collective organization across physical and biological systems.
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Chemical Physics · Cross-listed from cs.AR
A Survey of Neural Network Variational Monte Carlo from a Computing Workload Characterization Perspective
Zhengze Xiao, Xuanzhe Ding, Yuyang Lou et al. (+2 more)
Neural Network Variational Monte Carlo (NNVMC) has emerged as a promising paradigm for solving
quantum many-body problems by combining variational Monte Carlo with expressive neural-network wave-function ansätze. Although NNVMC can achieve competitive accuracy with favorable asymptotic scaling, practical deployment remains limited by high runtime and
memory cost on modern graphics processing units (GPUs). Compared with
language and
vision workloads, NNVMC execution is shaped by physics-specific stages, including Markov-Chain Monte Carlo sampling, wave-function construction, and derivative/
Laplacian evaluation, which produce heterogeneous kernel behavior and nontrivial bottlenecks. This paper provides a workload-oriented survey and empirical GPU characterization of four representative ansätze: PauliNet, FermiNet, Psiformer, and Orbformer. Using a unified profiling protocol, we analyze model-level runtime and
memory trends and kernel-level behavior through family breakdown, arithmetic intensity, roofline positioning, and hardware utilization counters. The results show that end-to-end performance is often constrained by low-intensity elementwise and data-movement kernels, while the compute/
memory balance varies substantially across ansätze and stages. Based on these findings, we discuss
algorithm–hardware co-design implications for scalable NNVMC systems, including phase-aware scheduling,
memory-centric optimization, and heterogeneous acceleration.
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All authors Zhengze Xiao, Xuanzhe Ding, Yuyang Lou, Lixue Cheng, Chaojian Li
History and Philosophy of Physics · Cross-listed from gr-qc
On the concept of simultaneity in relativity
Justo Pastor Lambare
In this comment, we demonstrate that the claim by Spavieri et al., asserting that Wang et al.'s interferometric experiment disproves the special theory of relativity by revealing that simultaneity must be an absolute concept independent of the observer's state of motion, is based on circular
reasoning and therefore constitutes a logical fallacy.
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Computational Physics · Cross-listed from q-bio.BM
Generative Replica-Exchange: A Flow-based Framework for Accelerating Replica Exchange Simulations
Shengjie Huang, Sijie Yang, Jianqiao Yi et al. (+6 more)
Replica exchange (REX) is one of the most widely used enhanced sampling methodologies, yet its efficiency is limited by the requirement for a large number of intermediate temperature replicas. Here we present Generative Replica Exchange (GREX), which integrates deep generative models into the REX framework to eliminate this temperature ladder. Drawing inspiration from reservoir replica exchange (res-REX), GREX utilizes trained normalizing flows to generate high-temperature configurations on demand and map them directly to the target distribution using the potential energy as a constraint, without requiring target-temperature training data. This approach reduces production simulations to a single replica at the target temperature while maintaining thermodynamic rigor through Metropolis exchange acceptance. We validate GREX on three
benchmark systems of increasing complexity, highlighting its superior efficiency and practical applicability for molecular simulations.
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All authors Shengjie Huang, Sijie Yang, Jianqiao Yi, Rui Zheng, Haocong Liao, Muzammal Hussain, Yaoquan Tu, Xiaoyun Lu, Yang Zhou
Fluid Dynamics
SIREN Residual Error as a Regularity Diagnostic for Navier-Stokes Equations
Jason Burton
We introduce a method for detecting regularity loss in solutions to the three-dimensional Navier-Stokes equations using the approximation error of Sinusoidal Representation Networks (SIRENs). SIRENs use sin() activations, producing C-infinity outputs that cannot represent non-smooth features. By classical spectral approximation theory, the SIREN error is bounded by O(N^{-s}) where s is the local Sobolev regularity. At a singularity (s to 0), the error is O(1) and localizes via the Gibbs phenomenon. We decompose the velocity field into a cheap analytical baseline (advection-
diffusion) and a learned residual (pressure correction), training a compact SIREN (4,867 parameters). We validate on the 3D Taylor-Green
vortex, where error concentration increases from 4.9x to 13.6x as viscosity decreases from 0.01 to 0.0001, localizing to the stagnation point – the geometry matching the singularity proven by Chen and Hou (2025) for 3D Euler. On axisymmetric equations, we reproduce blowup signatures (T* converging across resolutions) and identify a critical viscosity nu_c = 0.00582 for the regularization transition.
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Optics · Cross-listed from cond-mat.mes-hall
Comment on: "Coherent perfect absorption: Zero reflection without linewidth suppression"
Rui-Chang Shen and Jie Li
A recent paper, Phys. Rev. Research 8, 013261 (2026), claims that the polaromechanical normal-mode splitting (NMS) measured in Nat. Commun. 16, 5652 (2025) is not true based on their two results: $i$) there is no true splitting in the linear-scale spectrum; $ii$) the total or intrinsic decay rate of the cavity-
magnon polariton, set by the imaginary part of the pole of the total output spectrum, remains unchanged under the coherent-perfect-absorption (CPA) condition. In this comment, we indicate that $i$) there is NMS in both the linear and logarithmic scales of our spectra in a narrow frequency range around the CPA frequency; $ii$) the total decay rate defined via the pole of the spectrum cannot characterize the vanishing effective decay rate at the CPA frequency (known as the monochromaticity of the CPA), and thus this parameter is irrelevant to the NMS measured in our experiment in a narrow frequency range around the CPA frequency. Consequently, their results above are either false or irrelevant, and thus cannot support their claim on the polaromechanical strong coupling measured in our experiment.
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Optics
Interfacial optical absorptance of air-water interfaces
Preston Bohm, Mingjun Li, Akanksha K. Menon et al. (+1 more)
The photomolecular effect has been hypothesized to enhance evaporation of water at visible wavelengths. This study develops a measurement technique to investigate its presence and magnitude at the
liquid-vapor interface of water. The experiment detects surface absorptance by comparing polarized reflectance for substrates with and without a water layer. The reflectance ratio is used as an indicator of interfacial absorptance or attenuation. Lightly doped silicon and platinum were used as dielectric and metal substrates, and their pseudo-optical properties were measured using ellipsometry. Experimental results were compared to a multilayer reflectance model to determine theoretical sensitivity and guide angle selection. Measurements showed close agreement with a classical model assuming zero surface absorptance. The model was then extended to include surface absorptance using a spectral response based on Lorentzian-distributed Feibelman parameters derived from a recent estimate of 0.84% interfacial absorption. Although this model predicted a 1-2% reduction in reflectance near resonant frequencies, no such spectral features were observed experimentally. These results suggest that under ambient conditions, interfacial absorption is well below 1%, indicating that the optical signature of the photomolecular effect is either much weaker than previously reported or strongly dependent on conditions not present in this experiment.
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All authors Preston Bohm, Mingjun Li, Akanksha K. Menon, Zhuomin M. Zhang
Physics Education
Investigating students' gender expression and its relation to sense of belonging in introductory physics courses
Noah Leibnitz and Yangqiuting Li
Despite nation efforts to promote diversity and inclusion, women and gender minorities remain underrepresented in physics. One common approach to studying gender in physics contexts treats gender as a categorical identity variable (e.g. "man," "woman"). In contrast, approaches that center gender expression focus on the nuanced and context-dependent ways in which gender is socially enacted and interpreted. They are therefore well-suited for exploring how gender permeates the small-scale interactions that ultimately shape students' persistence and perceptions of inclusivity. In the present study, we utilized gender expression as a lens to investigate gendered patterns in introductory undergraduate physics students' sense of belonging in the discipline. Specifically, this qualitative investigation expands on our previous quantitative work to investigate why students may feel misperceived by their peers in physics and how that experience influences their belonging. Results indicated that students' sense of belonging may be impacted by perceived pressures to alter their gender expression in physics contexts. Many interviewees expressed a felt need to present themselves more "masculinely" to fit in. Contrastingly, pressure to present "femininely" was most often associated with standing out. Implications for supporting students' authentic self-ex in physics contexts are discussed.
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Instrumentation and Detectors
Low Energy Phonon Bursts Created By Fast Neutron Damage
A. Armatol, C. Augier, L. Bergé et al. (+67 more)
Solid state athermal
phonon calorimeters used in the search for low mass dark matter or coherent
neutrino-
nucleus interactions have long observed a large excess of events below several hundred eV. The relaxation of damage created by the interaction of fast
cosmic ray
neutrons with the detector has been proposed as a source of these excess events. By comparing
neutron exposed detectors to control detectors, we report the first measurement of
phonon bursts caused by damage created by fast
neutrons. Differences in the spectral shape, the rate dependence on thermal history, and the observed spectral rate scaled to the
neutron exposure between irradiated and control detectors suggest that our observed LEE backgrounds are not dominated by
neutron damage-induced
phonon bursts.
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All authors A. Armatol, C. Augier, L. Bergé, J. Billard, H.J. Birch, J. Blé, C.L. Chang, Y.-Y. Chang, L. Chaplinsky, G. Cline, A. Cochard, I. Cojocari, J. Colas, M. De Jesus, P. de Marcillac, K. Dwinger, R. Faure, S. Fiorucci, M. Garcia-Sciveres, J. Gascon, C. Girard-Carillo, W. Guo, L. Haegel, S.J. Haselschwardt, S.A. Hertel, K. Hunter, L. Juigne, A. Juillard, A. Kavner, J. Lamblin, T. Le-Bellec, X. Li, J. Lin, R. Mahapatra, S. Marnieros, C. Marrache, N. Martini, W. Matava, D.N. McKinsey, J. Menu, K. Moraa, V. Novati, E. Olivieri, B. Penning, M. Platt, M. Pyle, D. Poda, Y. Qi, M. Reed, R.K. Romani, I. Rydstrom, B. Sadoulet, S. Scorza, B. Serfass, P. Sorensen, S. Steinfeld, H. Su, A. Suzuki, R.L. Vaughn II, C. Veihmeyer, V. Velan, G. Wang, P. Vittaz, Y. Wang, M.R. Williams, J. Wuko, K. E. J. Myers, L. Bernstein, M. Potts, J. Orrell
Biological Physics · Cross-listed from cond-mat.soft
Physical Approaches to Metabolic Scaling in Living Systems
Efe Ilker, Michael Hinczewski, Xingbo Yang et al. (+1 more)
Living systems continuously transform matter and energy through the chemical processes that constitute their metabolism. The overall metabolic rate of an organism correlates positively with its body mass, however both the exact scaling behavior and possible explanations for this behavior have been under intense debate for two centuries. This review synthesizes empirical findings and theoretical frameworks on the energetics of living systems from an interdisciplinary perspective, with a focus on physical concepts. A general thermodynamic framework to study metabolism is laid out, together with a coarse-grained description of metabolic biochemistry. The rich history of experimental work in this field is surveyed, revealing a variety of metabolic scaling patterns at different levels of biological organization, from individual
cells to whole populations. Several biophysical models proposed to explain the sublinear scaling of metabolic rate with body mass are summarized. Though the traditional focus has been on adult organisms, the review also highlights recent advances that probe metabolism during development. Improvements in experimental techniques, extensive
datasets, and a host of open questions, suggest the field will continue gaining momentum in the near term. The review concludes with an outlook for this future progress: an interdisciplinary approach to elucidate metabolic scaling across different developmental stages and organism sizes.
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All authors Efe Ilker, Michael Hinczewski, Xingbo Yang, Frank Jülicher
Atomic Physics
Rotational excitation of asymmetric-top molecular ions by electron impact: application to H$_2$O$^+$, HDO$^+$, and D$_2$O$^+$
Joshua Forer
The rotational excitation of the three asymmetric-top molecular ion isotopologues H$_2$O$^+$, HDO$^+$, and D$_2$O$^+$ is studied theoretically using a combined framework of electron-molecule R-
matrix scattering theory, multichannel
quantum-defect theory, frame transformation theory, and the Coulomb-Born approximation. The latter two have been adapted here for asymmetric-top rotors. State-resolved cross sections and kinetic rate coefficients for transitions from the rotational ground state of the ions are presented. State-resolved rate coefficients for all calculated transitions $N=0\ldotstwo4$ are included as supplementary material and will be made available through the EMAA database.
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Fluid Dynamics · Cross-listed from math.NA
Decoupled Divergence-Free Neural Networks Basis Method for Incompressible Fluid Problems
Jinbao Cheng, Jianguo Huang, Haoqin Wang et al. (+1 more)
We propose a decoupled divergence-free neural networks basis (Decoupled-DFNN) method for solving incompressible flow problems, including the Stokes and Navier-Stokes equations. To ensure the divergence free property exactly, the velocity field is represented as the curl of a stream function in two dimensions and as the curl of a vector potential in three dimensions. Beyond classical stream-function or velocity-vorticity formulations, we further utilize the properties of the curl operator to derive two specific decoupled subproblems for the velocity (through the stream function or vector potential) and the pressure, respectively. The proposed formulations enable a sequential solution strategy, in which the velocity and pressure are solved independently. To resolve the inherent nonlinearity of the Navier-Stokes equations, we employ a Gauss-Newton linearization strategy, transforming the nonlinear velocity subproblem into a sequence of linear subproblems. These decoupled subproblems for velocity and pressure are subsequently solved using the TransNet framework. Compared with existing methods, the proposed approach reduces computational cost while strictly preserving the incompressibility constraint.
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All authors Jinbao Cheng, Jianguo Huang, Haoqin Wang, Tao Zhou
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Mechanistic Insights into Enhanced Alkaline Oxygen Evolution on Zn-Al Alloy Electrodes
Abdul Ahad Mamun, Rokon Uddin Mahmud, Shahin Aziz et al. (+3 more)
Electrochemical water electrolysis, which produces clean energy carriers to mitigate carbon emissions, lacks suitable, low-cost electrodes for efficient oxygen
evolution reaction (OER) in alkaline water splitting. To address this challenge, we developed Zn-Al
alloy electrodes with varying Al contents up to 20 wt.% via powder metallurgy method and conducted electrochemical measurements of the OER in alkaline solution to investigate their catalytic performance. We also performed first-principles calculations to examine their thermodynamic phase stability and electronic structures. Both theoretical and experimental results indicated that incorporating $\geq 20$ wt.% Al into Zn led to thermodynamic phase instability and secondary-phase segregation in Al-rich regions, limiting reaction kinetics and reducing catalytic efficiency. Although the Al content of 5 wt.% into Zn exhibited favorable thermodynamic and electronic characteristics, but its electrochemical performance was inefficient and poor due to inadequate reaction active sites on the surface. In contrast, the 10 wt.% and 15 wt.% Al into Zn showed approximately three- and two-fold increases in anodic exchange current density relative to pure Zn, respectively. Additionally, the anodic overpotential losses ($\eta_{0,a}$) measured at a current density of 12 mAcm$^{-2}$ were 0.240 V for Zn$_{0.9}$Al$_{0.1}$ and 0.5603 V for Zn$_{0.85}$Al$_{0.15}$, significantly lower than that of pure Zn ($\eta_{0,a} = 1.086$ V). While Zn$_{0.9}$Al$_{0.1}$ and Zn$_{0.85}$Al$_{0.15}$ showed similar charge transfer resistance ($R_{\rm CT}$), Zn$_{0.9}$Al$_{0.1}$ demonstrated superior reaction kinetics and lower $\eta_{0,a}$ across all samples tested. Furthermore, the improved kinetics and reduced overpotential of the Zn-Al
alloys favorably compare with those of other transition-metal-based catalysts, including Fe-Co-Ni-Mo
alloys and Fe-doped CuO.
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All authors Abdul Ahad Mamun, Rokon Uddin Mahmud, Shahin Aziz, Muhammad Shahriar Bashar, Ahmed Sharif, Muhammad Anisuzzaman Talukder
Plasma Physics
A Deterministic Ionization Algorithm for the OSIRIS Particle-in-Cell Framework
Stephen DiIorio, Ricardo Fonseca, Frank Tsung et al. (+2 more)
Ionization is critical in the formation and
evolution of
plasma dynamics; collisional ionization, in particular, is an often overlooked source of electrons when dealing with
laser-
plasma interactions. Ionization plays a crucial role in understanding the complex
plasma kinetics, ranging from cold and sparse astrophysical settings to hot and dense fusion systems. In this paper, we describe the underlying theory for and development, validation, and verification of an extension to the standard particle-in-
cell method to include a deterministic
algorithm for collisional ionization physics. This
algorithm offers improved accuracy, achieving up to two orders of magnitude decrease in the error of the ionization rate calculations, scales linearly in execution time with the number of macro-particles per
cell, has been tested for physical correctness and benchmarked against several codes.
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All authors Stephen DiIorio, Ricardo Fonseca, Frank Tsung, Benjamin J. Winjum, Alec G. R. Thomas
Space Physics
Compressive Structures in the Foreshock of Collisionless Shocks
Savvas Raptis, Domenico Trotta, Drew L. Turner et al. (+11 more)
Collisionless shocks are fundamental accelerators of energetic particles; yet, the observations of nonlinear foreshock structures, which are essential in acceleration processes, differ significantly between Interplanetary (IP) shocks and planetary bow shocks. We present a direct comparison of two high-Mach-number, quasi-parallel shocks: an IP shock observed by
Solar Orbiter and the Earth's bow shock measured by the Magnetospheric Multiscale (MMS) mission during the 2024-2025 “string-of-pearls” campaign. We show that Foreshock Compressive Structures (FCSs) initiate upstream of both shocks at similar normalized distances ($\lesssim$50 ion inertial lengths, $d_i$) when the suprathermal ($>10$ keV) ion density exceeds $\sim$1% of the background. However, the IP shock lacks the fully evolved, high-amplitude Short Large Amplitude
Magnetic Structures (SLAMS) characteristic of the terrestrial foreshock. We demonstrate that the “growth zone” capable of sustaining these structures is spatially limited ($\sim$135 $d_i$), which, due to the high speed of the propagating IP shock, corresponds to a brief observational window of $<10$ s. Beyond this observational constraint, we suggest an additional physical mechanism that can inhibit foreshock maturity at IP shocks. The lack of global
curvature prevents the lateral supply (“cross-talk”) of energetic ions from different shock regions. These findings suggest that while the fundamental physics of FCS initiation is unified across collisionless shocks, the achievement of full nonlinearity can be regulated by the unique shock geometry and upstream properties, while ultimately remaining observationally challenging to identify.
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All authors Savvas Raptis, Domenico Trotta, Drew L. Turner, Xóchitl Blanco-Cano, Heli Hietala, Tomas Karlsson, Immanuel Christopher Jebaraj, Ivan Y. Vasko, Adnane Osmane, Kazue Takahashi, David Lario, Lynn B. Wilson III, Gregory G. Howes, Robert F. Wimmer-Schweingruber
Optics
Reconfigurable Resonant Multimode Nonlinear Coupling for UV-to-infrared Frequency Generation
Samantha Sbarra, Ji Zhou, Boris Zabelich et al. (+6 more)
On-chip coherent visible and near-infrared (NIR) light generation has broad applications in metrology, bio-sensing, and
quantum information. High-Q microresonators are ideal candidates for generating light across such broad wavelength ranges via efficient second- ($\chi^{(2)}$) and third-order ($\chi^{(3)}$) nonlinear optical processes. However, harnessing these diverse nonlinearities simultaneously in a single microresonator remains elusive yet highly attractive both fundamentally and technologically. Here, we demonstrate coherent light generation from the ultraviolet to NIR in a silicon nitride microresonator pumped by a single continuous-wave telecom
laser. This broad frequency generation arises from the interplay of $\chi^{(2)}$ and $\chi^{(3)}$ nonlinear processes. A cascade of nonlinear processes, including harmonic generation and optical parametric oscillation (OPO), is initiated by the photoinduced second harmonic generation enabled by all-optical poling. The dynamic reconfigurability of this $\chi^{(2)}$ nonlinearity enables access to different transverse spatial modes at the second harmonic, enabling highly tunable OPO processes triggered by hybrid modal phase matching conditions and yielding milliwatt-level NIR light. This work sheds new insights into the fundamental physics of cooperative nonlinear multimode interactions in resonant systems and provides a versatile approach for reconfigurable OPOs, highlighting their potential to generate light at wavelengths beyond the reach of photonic integrated
lasers.
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All authors Samantha Sbarra, Ji Zhou, Boris Zabelich, Marco Clementi, Christian Lafforgue, Ozan Yakar, Junqiu Liu, Tobias J. Kippenberg, Camille-Sophie Brès