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Physics Physics

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Sunday 28 June

Geophysics

Two kinds of robustness are not the same: disentangling fault tolerance and low-SNR robustness in multi-domain event detection on real data

Isao Kurosawa

Reliable event detection underpins induced-seismicity monitoring for Carbon dioxide Capture and Storage (CCS) and geothermal operations, distributed acoustic sensing (DAS), and industrial condition monitoring. In each setting a detector must stay reliable both when sensors fail and when the signal is buried in noise. These two failure modes are routinely conflated, and architectural complexity is often credited with robustness it may not deserve. We assemble a unified binary event-detection benchmark from three physically distinct real sources – Hi-net seismic waveforms, Utah FORGE 2024 borehole DAS, and MAFAULDA industrial vibration – each mapped to a common 8-channel, 256-sample representation, and evaluate a fault-tolerant detector (CEPHALON) trained with per-sample sensor-dropout against standard detectors (a 1D convolutional network, a temporal convolutional network, and a compact Transformer) trained with an identical recipe. On clean data every model is near-perfect (AUC ~ 0.99). Under progressive sensor loss, simple models with sensor-dropout are already robust and CEPHALON holds no advantage. Under additive noise, however, CEPHALON degrades far more gracefully: at -2.5 dB its overall AUC is 0.939 versus 0.532-0.572 for the convolutional baselines. Same-architecture ablations isolate the cause: disabling internal redundancy at inference reduces the low-SNR advantage only modestly, whereas removing sensor-dropout training collapses it (0.899 to 0.603 at -5 dB). The training recipe is therefore the dominant cause and parallel redundancy only secondary. We release a complete, numbered, reproducible pipeline so that every figure can be regenerated.
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Optics · Cross-listed from cond-mat.mes-hall

Emergent energy scales in magnonic systems with relative motion

Daigo Oue

Relative motion between interacting systems can generate emergent energy scales that are absent in isolated systems. While uniform motion can be eliminated by a Galilean transformation, relative motion between interacting systems generally cannot. By coupling to an excitation's spatial structure, relative motion generates a Doppler frequency determined by its wavevector and the relative velocity, providing a mechanism for driving nonequilibrium phenomena. In this tutorial, we illustrate these ideas using magnonic systems as a concrete platform. We first discuss motion-induced magnon transport between relatively moving ferromagnets, in which the Doppler frequency serves as an effective nonequilibrium bias in the perturbative regime. This mechanism produces magnon currents even without conventional driving forces such as temperature gradients or chemical potential differences. We then introduce motion-induced parametric instabilities. When the emergent scale becomes sufficiently large to resonantly create magnon pairs, the perturbative description breaks down, and the magnonic vacuum becomes unstable. This instability occurs above a critical velocity threshold and leads to spontaneous magnon-pair creation. Connections to related phenomena, including quantum friction, Cherenkov emission, and Zel'dovich superradiance, are also highlighted. The concept of an emergent energy scale provides a unifying framework for understanding transport phenomena and instabilities in quantum systems with relative motion.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci

Multiphysical impedance spectroscopy of porous electrodes based on linear irreversible thermodynamics

Junning Jiao and Juner Zhu

Porous electrodes couple electrical, chemical, mechanical, hydraulic, and thermal fields, yet conventional frequency-domain diagnostics interrogate only one of them: electrochemical impedance spectroscopy (EIS) the electrical response and dynamic mechanical analysis (DMA) the mechanical. Each reads a diagonal entry of the multiphysical constitutive matrix and is blind to the cross-couplings that govern structural evolution and degradation. Starting from linear irreversible thermodynamics, we formulate a general theory of multiphysical impedance spectroscopy, in which perturbing one field and measuring the conjugate response of another probes an off-diagonal entry of the constitutive matrix, recovering the static coupling coefficient and resolving its relaxation dynamics across frequency. Specializing to the electro-chemo-mechanical pathway yields a closed-form theory of mechano-electrochemical impedance spectroscopy (MEIS), in which a small harmonic current is applied and the stack stress is measured; the impedance factorizes into a chemical-accumulation term multiplying the sum of a chemo-mechanical and a poro-mechanical kernel. The porosity-accommodation bridge function is derived from a Helmholtz free energy – following from a microstructural stiffness and viscosity rather than a fitted form – and a three-phase (solid-fluid-void) closure interpolates continuously between unsaturated and Biot-saturated limits through a void-accommodation fraction. Non-dimensionalization reduces the spectrum to five groups, identifies the phase angle as the discriminator of the chemo-mechanical parameters, and locates the onset of second-quadrant behavior, which in a full cell arises from the competition between an expanding and a contracting electrode. MEIS emerges as one member of a family of cross-coupled spectroscopies the same framework brings within reach.
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Atomic Physics

Low-energy positron scattering from metastable helium

Ning-Ning Gao, Hui-Li Han, Ting-Yun Shi et al. (+1 more)

Low-energy positron scattering from singlet and triplet metastable He($1s2s$) is investigated using the $R$-matrix propagation method in hyperspherical coordinates. Elastic and positronium-formation cross sections are reported, and near-threshold resonance structures are analyzed in terms of eigenphase sums and the time-delay matrix. For the triplet target, the calculated cross sections are in agreement with available convergent-close-coupling results and display the expected threshold behavior. Beyond the known $S$-wave features, Feshbach resonance series in higher partial waves extending up to highly excited atomic thresholds are systematically identified. The time-delay matrix further uncovers hidden resonances that produce obvious structures in the positronium-formation cross sections.
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All authors Ning-Ning Gao, Hui-Li Han, Ting-Yun Shi, Li-Yan Tang

Computational Physics

Latent Genetic Algorithm for Crystal Structure Prediction

Kaixin Zheng, Wanjian Yin, Hongyu Yu et al. (+1 more)

Predicting crystal structures requires navigating rugged energy landscapes in which favorable local motifs must be inherited across candidates with incompatible cells, densities, and symmetries. Conventional real-space crossover often destroys these motifs when parent structures are geometrically mismatched. Here we show that latent representations learned by pretrained universal interatomic potentials can serve as continuous evolutionary coordinates for crystal structure prediction. In the Latent Genetic Algorithm (LGA), offspring are generated by inverse optimization of atomic positions and lattice vectors to match a target latent representation, which is constructed via interpolation of the parent latent vectors. LGA suppresses high-energy and short-contact offspring, increases the HfO$_2$ ground-state recovery rate from 20-35% to 60-95%, and enables a unified variable-supercell search over 16 perovskites with a nearly tenfold reduction in search cost. Applied to (PbTiO$_3$)$_n$/(PbZrO$_3$)$_n$ superlattices, LGA reveals $\sqrt{2} \times 3\sqrt{2} \times 1$ long-period ground-state structures characterized by a common in-plane finite-$q$ modulation $q{_\parallel} = (1/6,1/6)$ and layer-coupled sidebands. To our knowledge, this in-plane periodicity has not been reported in any related oxide perovskite superlattice studies. Altogether, LGA offers a powerful representation-guided paradigm for ground-state structure prediction and provides a practical, decoder-free route toward materials inverse design.
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All authors Kaixin Zheng, Wanjian Yin, Hongyu Yu, Hongjun Xiang

Plasma Physics

Detecting Quantum Stochastic Effects in Radiation Reaction via Laser-Produced Surface QED Plasmas

Junhua Zhang, Xianshu Wu, Luyao Zhang et al. (+2 more)

We propose a method to detect quantum stochastic effects in radiation reaction by irradiating a V-shaped plasma cavity with an ultra-intense laser pulse. The pulse accelerates GeV electrons along the inner surface and simultaneously drives strong-field surface wave near the cavity apex. The accelerated electron bunches then collide with the surface wave, the latter acts as an effective counter-propagating ultra-intense electromagnetic wave, triggering significant radiation reaction. Importantly, because the surface wave is confined to an ultra-thin QED plasma layer (on the scale of the skin depth) where the expected number of hard photon emissions per electron is of order unity, stochastic effects are expected. Three-dimensional particle-in-cell simulations with different QED models show that radiation reaction strongly reshapes the angular distribution of high-energy electrons. In particular, electrons deflected by the surface wave experience strong radiation loss. However, compared with the semi-classical model, the stochastic QED model preserves a higher-energy component in the deflected beam, producing a clear angular-spectral signature, which potentially opens a pathway for experimental study of quantum stochastic effects in radiation reaction.
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All authors Junhua Zhang, Xianshu Wu, Luyao Zhang, Yao Meng, Longqing Yi

Classical Physics · Cross-listed from nlin.CD

Stable Ballistic Prograde Cyclers in the Three-Body Problem

Shane D. Ross and Michael Roberts-Tsoukkas

We report the first continuous families of stable, ballistic, prograde cycler orbits in the circular restricted three-body problem: periodic trajectories that alternately undergo temporary capture and orbit each primary. We construct continuous families of symmetric cyclers from intersections of the stable and unstable manifold tubes of the $L_1$ Lyapunov orbit and exhibit stable examples across more than two orders of magnitude in mass ratio, from the Sun–Jupiter regime to the equal-mass limit. Linear stability separates naturally into planar and out-of-plane components. A planar-stable branch of every computed family is created simultaneously with a hyperbolic branch in a saddle-center bifurcation of the return map at the family's maximal Jacobi constant, while out-of-plane instability occurs only through isolated parametric resonances. Every computed family contains a subfamily that is linearly stable to both planar and out-of-plane perturbations. These stable cyclers persist into the full three-body problem for sufficiently small third mass. We conjecture that saddle-center birth is universal among cycler families, suggesting that stable cyclers are a generic feature of three-body dynamics.
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Atmospheric and Oceanic Physics

CORDEX-ML-Bench: A Benchmark for Data-Driven Regional Climate Downscaling -Experiment Design and Overview

Neelesh Rampal, José González-Abad, Henry Addison et al. (+34 more)

Machine learning (ML) has emerged as a cost-effective approach to complement dynamical downscaling for producing high-resolution regional climate projections. However, the absence of standardised training and evaluation protocols, applied consistently across multiple domains, continues to hinder meaningful model intercomparison. We introduce CORDEX-ML-Bench, a benchmark aligned with CORDEX, which constitutes the first phase of a community initiative to advance data-driven downscaling toward operational readiness, and complement future dynamical downscaling efforts under CMIP7. The framework targets downscaled daily maximum temperature and precipitation to ~10 km resolution (20x increase) across three pilot regions; European Alps, New Zealand, and Southern Africa. Using a perfect-model experimental design, we evaluate 40 ML configurations developed independently, spanning traditional ML, convolutional U-Nets, vision transformers, graph neural networks, and generative models based on diffusion, flow matching, and generative adversarial networks. Models are trained under two experimental periods, an empirical-statistical downscaling pseudo-reality (historical period only) and Emulator (historical and future periods) -and are evaluated against a core set of metrics developed specifically for assessing downscaling skill. Generative models consistently outperform deterministic approaches for precipitation, better capturing fine-scale variability and extremes. For temperature, the generative advantage narrows and deterministic architectures remain competitive. Models trained solely on the historical period systematically underestimate future climate-change signals while those additionally trained on a future period perform better. These findings raise concerns about historically trained models widely used in an operational setting, underscoring the need for rigorous extrapolation testing.
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All authors Neelesh Rampal, José González-Abad, Henry Addison, Jorge Baño-Medina, Maria Laura Bettolli, Valentina Blasone, Ben Booth, Erika Coppola, Serafina Di Gioia, Joshua Oldham-Dorrington, Antoine Doury, Francois Engelbrecht, Ramón Fuentes-Franco, Peter B. Gibson, Luca Glawion, Caroline Hardy, Mikhail Ivanov, Hugo Kyo Lee, Mikel N. Legasa, Matias Olmo, Andrew Orr, Julius Polz, Martin S. J. Rogers, Maybritt Schillinger, Shivani Sharma, Pedro M. M. Soares, Stefan Sobolowski, Jessica Steinkopf, Wenchang Tang, Jr-Ben Tian, Ricardo Tomé, Ko-Chih Wang, Yi-Chi Wang, Peter A. G. Watson, Tom Wetherell, Martin Widmann, José M. Gutiérrez

Chemical Physics · Cross-listed from quant-ph

Shadow tomography for classical tensor network simulations

Jiace Sun and Garnet Kin-Lic Chan

Shadow tomography has appeared as a powerful tool for estimating observables on quantum computers from a small number of samples. We show that shadow-tomography-inspired ideas can offer similarly improved sample scaling for estimating observables on tensor network states on classical computers after proper adaptation. We develop strategies for both spin (bosonic) and fermionic systems, tailored to the contraction requirements of tensor networks, and generate scaling improvements of factors of $O(N)$ to $O(N^{3})$ (where $N$ is system size), depending on the specific task and system type. For the important and difficult task of evaluating the expectation value of long-range interacting Hamiltonians, we achieve the optimal $O(1)$ overall scaling (up to logarithmic factors) for an arbitrarily fixed relative Monte Carlo error in both spin and fermionic systems. Additionally, we show that shadow estimators offer more stable gradients of observables in variational optimization tasks than standard Monte Carlo estimators. We demonstrate practical advantage by simulating systems with long-range interactions, including the 2D long-range Heisenberg model and an ab-initio quantum chemistry Hamiltonian.
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Optics

Peculiarities Of High-Speed Dynamics Of Two-Photon Absorption In Si Nanowire Waveguides

Vadym Zayets, Siim Heinsalu and Akihiro Noriki

We investigate the complete dynamical pathway of photon-electron interactions involved in two-photon absorption (TPA) in a silicon nanowire waveguide using three independent high-speed measurement techniques. These methods probe different stages of the process: nonlinear photon absorption, electron excitation from the valence to the conduction band, and free-carrier generation. According to the conventional model of TPA, these three processes should occur at identical rates. However, our measurements reveal significant discrepancies between them. The measured nonlinear photon absorption is more than twice the value required to account for the measured TPA transitions, indicating the presence of additional absorption pathways or nontrivial TPA dynamics. Furthermore, the number of measured TPA transitions substantially exceeds the measured free-carrier density, indicating that long-lifetime free carriers represent only a small fraction of the TPA-excited electrons, while the majority recombine rapidly back to the valence band on a timescale shorter than 13 ps. In addition, the three stages of the TPA pathway exhibit distinct saturation behaviors at different photon densities, further indicating that the TPA process in silicon is more complex than described by the conventional model. These findings provide new insight into the physical mechanisms governing TPA, suggesting the existence of multiple competing pathways for this optical transition. A major obstacle to a complete understanding of TPA is the unclear physical origin of the virtual midgap level. The potential strategies for minimizing unwanted nonlinear losses in high-speed silicon photonic circuits, as well as for exploiting TPA in high-speed optical switching and photonic signal processing are investigated.
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Saturday 27 June

Geophysics

An Agentic Interface for End-to-End Probabilistic Seismic Hazard and Risk Analysis

Sreenath Vemula, Pierre Jehel, Fabrice Cotton et al. (+1 more)

Probabilistic seismic hazard and risk analyses are backbone to building codes, insurance pricing, and disaster management. Yet their open-engine pipelines remain accessible primarily to experts. We present the first agentic interface to the end-to-end probabilistic seismic hazard and risk chain via an open-source server, addressable through the Model Context Protocol (MCP). MCP wraps the OpenQuake engine and the 2020 European Seismic Hazard and Risk Models using twenty-four typed endpoints. Here, an agent is defined as a large language model (LLM) with tools. LLM is confined to the role of an orchestrator so it plans, translates, and explains, while the OpenQuake engine and custom codes compute hazard values, damage probability, and loss. Each response carries source-model, ground-motion model (GMM), and certified data provenance for transparency. Results are benchmarked against ESHM20 at seventy-three cities, the replicated 475-year spectral accelerations match official values within a median of 5 %, and a full hazard-to-loss estimate runs in minutes. The interface additionally accepts a user-supplied empirical or machine-learning GMM on any tectonic region type of the published tree, and adds additional features that existing web services omit: conditional spectra, deterministic scenarios, surface hazard, per-building loss, retrofit comparison, and record selection with waveform retrieval. The proposed design layers transfer to other regional models, and to other hazards.
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All authors Sreenath Vemula, Pierre Jehel, Fabrice Cotton, Filippo Gatti

Atmospheric and Oceanic Physics

Evolution of Thunderstorm Charge Structure Revealed by Particle Composition and Near-Surface Electric Field

A.Chilingarian and B.Sarsyan

Thunderstorm Ground Enhancements (TGEs) provide a direct particle-physics diagnostic of accelerating electric fields within thunderclouds. During 12 15 May 2026, Aragats detectors recorded a compact sequence of TGEs under closely related meteorological and electric field conditions. Ten statistically resolved TGEs were selected for quantitative analysis using STAND3 and SEVAN Light gamma and electron proxy channels. The events were classified into negative (N), transition/disturbed negative (TD N), and positive (P) states based on the stability of the near surface electric field (NSEF). The results show that TGEs occur during both comparatively stable and rapidly evolving charge states. Stable negative events correspond to sustained exposure of the Main Negative (MN) charge region, whereas positive and TD N events reflect Lower Positive Charge Region (LPCR) screening and rapid restructuring of the lower thundercloud dipole during End Of Storm Oscillation (EOSO) like evolution. The analysis demonstrates that the electron/gamma composition depends primarily on the persistence and geometry of the lower accelerating field structure rather than solely on the instantaneous sign or magnitude of the NSEF. Rapid electric field impulses, frequently associated with nearby lightning activity, mark active restructuring of the lower dipole and strongly influence electron transport to the detector level. All analyzed events occurred during persistent low cloud base conditions favorable for electron TGEs at Aragats.
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Atmospheric and Oceanic Physics

Positron acceleration in thunderstorms

A.Chilingarian and B. Sargsyan

Thunderstorm Ground Enhancements (TGEs) are known manifestations of relativistic runaway electron avalanches (RREAs) developing inside thunderclouds. However, the role of positrons in TGEs and their relationship to thundercloud charge structure remain poorly understood. We report time resolved observations of intense positron fluxes detected at the Aragats Observatory on 16 17 May 2026 during strong thunderstorms. Two of the three events were characterized by a positive near surface electric field (NSEF), graupel precipitation, a low cloud base, and low-to-moderate enhancement of gamma ray and electron fluxes measured by SEVAN and STAND3 detectors. The third event is a classical electron TGE considered for comparative purposes. All events show moderate to strong enhancement of the 511 keV annihilation line, along with enhanced radon progeny gamma ray lines. We observe a temporal separation between the electron and gamma ray TGE peak and the positron flux maximum. To explain these observations, we introduce a dual dipole electrodynamic model. The large scale electron dipole comprises the main negative thundercloud layer and its broad positive mirror charge induced at the Earths surface, producing ordinary TGEs. Simultaneously, a localized positron dipole forms from the LPCR, with its negative mirror charge directly beneath the LPCR footprint. This lower dipole accelerates positrons downward while decelerating electrons entering the same region. These results establish positron TGEs as a new subclass of atmospheric high energy phenomena and provide direct evidence of localized positron acceleration in the lower atmosphere.
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Atmospheric and Oceanic Physics

Direct Observation of Wilsonian Electrons in Thunderstorms

A.Chilingarian, T.Karapetyan and B.Sargsyan

We analyze electron rich Thunderstorm Ground Enhancements (TGEs) detected at Aragats using the SEVAN Light spectrometer, which can separate charged and neutral particles and reconstruct their energy spectra. The events exhibit large electron fluxes, with reconstructed energies extending to 45 MeV. Simultaneous meteorological observations reveal that all events occurred within a remarkably narrow atmospheric regime characterized by exceptionally low cloud-base heights, temperatures near 0{\deg}C, strong electric-field disturbances, and lightning. Comparisons with the complete Aragats TGE archive demonstrate that the direct detection of runaway electrons becomes possible only when the active acceleration region approaches within several tens of meters of detector altitude, allowing electrons to survive atmospheric attenuation. These results provide an experimental explanation for the century long rarity of observations of Wilsonian electrons. The findings establish the atmospheric conditions required for direct observation of runaway electrons and contribute to the understanding of particle acceleration in natural electric fields.
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General Physics

Varying Gravity from a Modified Fractional Model: Observational Constraints and Slow-Fast Dynamics

Rami Ahmad El-Nabulsi, Genly Leon, Esteban González et al. (+1 more)

We investigate a fractional gravity model in which both the Hubble parameter and the gravitational constant evolve dynamically due to fractional renormalization-group effects. The model incorporates a scalar field coupled to a time-varying $G$, generating nonlocal corrections characteristic of fractional–action cosmology. Analytical and numerical solutions reveal oscillatory regimes, cyclic phases, and rapid variations with implications for BBN and early-universe evolution. A robust numerical framework is developed to integrate the regularized system and compare the resulting $H(z)$ evolution with observational data from the Hubble parameter, baryon acoustic oscillations, type Ia supernovae, gravitational lensing, and black hole shadows, thereby enabling a consistent reconstruction of cosmographic quantities. A Bayesian analysis shows that the Fractional model with $\mu=0$ is the only statistically viable variant. The inferred Hubble parameter is stable across models ($h\simeq 0.72$), while the fractional parameters are significantly better constrained in the $\mu=0$ case ($\alpha=1.20^{+0.25}_{-0.14}$, $\zeta=0.43^{+0.39}_{-0.29}$). The dynamical sector yields $m=30.8^{+28.0}_{-20.9}$ and $\Gamma=108.3\pm1.1$, leading to a positive discriminant and a well-determined relaxation timescale $\tau_{\rm rel}\simeq 9$ Gyr, confirming an overdamped regime. Although the $\mu=0$ model attains a slightly lower $\chi^2_{\min}$ than $\Lambda$CDM, the BIC strongly favors $\Lambda$CDM due to its smaller parameter space. Overall, the model reproduces late-time acceleration and mimics $\Lambda$CDM while introducing distinctive cosmographic signatures. The dynamical systems analysis clarifies the stability structure and parameter dependence, indicating that fractional nonlocal corrections may offer new pathways toward addressing the $H_0$ and $S_8$ tensions.
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All authors Rami Ahmad El-Nabulsi, Genly Leon, Esteban González, Kevin Marroquín

General Physics

Scalar Photon Coupling and Modified Photon Evolution: CMB Signatures and Cosmological Constraints

Y. Bisabr

We investigate the constant-$\epsilon$ limit of a photon-sector modification derived from an early-time interaction between a scalar field and radiation. Starting from the underlying scalar–photon coupling, the parameter $\epsilon$ quantifies the departure of the photon energy density from the standard adiabatic scaling, leading in the constant-$\epsilon$ limit to $\rho_{\gamma}\propto a^{-4+\epsilon}$ and to the modified CMB temperature–redshift relation $T(z)=T_{0}(1+z)^{1-\epsilon/4}$. The standard photon sector is recovered for $\epsilon=0$. We implement the corresponding constant-$\epsilon$ background evolution in CLASS and verify that the numerical photon-density evolution reproduces the analytic scaling. We then examine the resulting changes in the recombination history, visibility function and CMB temperature-anisotropy spectrum. These CMB spectra are used only as diagnostic outputs since the coupled scalar–photon perturbation equations are not implemented self-consistently in the numerical calculation and a full CMB likelihood analysis is beyond the scope of the present work. As a preliminary statistical application, we interface the modified CLASS implementation with MontePython and analyze the Pantheon+SH0ES supernova likelihood together with BAO measurements. Within the adopted constant-$\epsilon$ framework, prior choices, data combination and fixed early Universe parameter setup, we obtain $\epsilon=0.0230\pm0.0065$. The posterior is therefore centered on a positive value within this restricted analysis. Because the BAO predictions depend on the model-dependent drag scale and several early-Universe quantities are held fixed, this result should be interpreted as a conditional and preliminary constraint rather than as a full CMB-level determination or evidence for a resolution of the Hubble tension.
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Optics

$4\pi$ Combination of Gaussian Laser Beams

Hocine.Djellout

This work is a generalization of our previous study [arXiv:2406.17944], which dealt with the coherent and incoherent combination of linearly polarized Gaussian laser beams operating in continuous-wave mode under a $2\pi$ focusing configuration. In the present work, the laser beams are focused within a solid angle that can reach $4\pi$ by using two opposing source planes, where all the lasers from both planes are focused onto the same point in the focal plane. Our results show that the focal spot area obtained with either one or two source planes remains unchanged, despite the fact that, in the two-source-plane configuration, the numerical aperture (NA) of the system is twice that of the $2\pi$ focusing scheme. However, the intensity at the focal point is four times greater than that obtained with a single source plane. In addition, the longitudinal resolution is significantly improved, yielding a focal volume smaller than $0.5 \lambda^3$ for a numerical aperture of NA = 0.895. For incoherent beam combination, the focal volume remains practically the same in both the $2\pi$ and $4\pi$ focusing configurations, while the intensity at the focal point is twice that obtained in the $2\pi$ case. Furthermore, in the incoherent configuration, we observe a depth of focus reaching up to 30,000 $\lambda$ for a system with a low numerical aperture.
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Optics · Cross-listed from cs.CV

From Fog Chamber to Aircraft Window: Pixel-Registered Imaging and Synthetic Fine-Tuning Enable Cross-Domain Defogging

Alexander Ingold, Sabina D. Menon, Manya Yellepeddy et al. (+5 more)

A deep defogging pipeline pretrained on controlled laboratory fog and fine-tuned with domain-randomized synthetic fog applied to clear outdoor scenes generalizes across a graded sequence of out-of-distribution settings with no target-domain training, from chamber-free free-flowing fog to iPhone video recorded through an aircraft cabin window in flight, an entirely unseen sensor, scene, and optical path. This directly addresses an open transfer limitation reported for real-world binocular defogging. Two design choices support the transfer. First, a single-camera fog imager photographs a flat-panel display through an artificial-fog enclosure with a fixed 114~mm scattering path, producing 5{,}495 pixel-aligned foggy/clear pairs. Exact registration permits a paired Laplacian ratio that predicts per-image restoration quality far better than single-image proxies (Spearman $\rho = 0.632$ versus $0.399$) and supports pixel-exact $L_1$ reconstruction training that avoids adversarial hallucination. Second, the fog-chamber checkpoint is fine-tuned on Mapillary Vistas crops overlaid with on-the-fly randomized synthetic fog spanning a broad range of strengths, spatial variations, airlights, and noise conditions. On a 552-image held-out split, a uniform comparison of 30 restoration backbones places NAFNet at the top (24.33~dB~/~0.7912~SSIM), with a compact alternative within 1.29~dB at 3% of the parameter count, and a ResNet-50 classifier confirms that the restoration preserves semantic content rather than only pixel-level structure. On unpaired aircraft-window video, NIQE decreases from a mean of 6.22 to 4.97 after fine-tuning, with temporally stable output across full-motion sequences. The same backbone, under paired supervision, also reaches 20.71~dB~/~0.683~SSIM on a non-overlapping O-HAZE/NH-HAZE split (a transferability check rather than a competitive ranking).
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All authors Alexander Ingold, Sabina D. Menon, Manya Yellepeddy, Alec Ikei, John D. Hodges, Jordan Baker, Syed N. Qadri, Rajesh Menon

Instrumentation and Detectors · Cross-listed from eess.IV

Complete virtual unwrapping and reading of a rolled Herculaneum papyrus

Giorgio Angelotti, Stephen Parsons, Federica Nicolardi et al. (+24 more)

The carbonized papyri from Herculaneum preserve the only large-scale library to survive from classical antiquity, but many unopened rolls remain unread because physical opening risks irreversible damage. X-ray computed microtomography ($\mu$CT) and virtual unwrapping offer a non-invasive route to their texts, yet previous work on sealed Herculaneum scrolls has recovered only localized readings or limited surface regions. Here, using high-resolution phase-contrast $\mu$CT acquired on the BM18 beamline at the European Synchrotron Radiation Facility (ESRF), together with improved computational unrolling and machine learning, we achieve the complete virtual unwrapping and reading of PHerc. 1667 under explicit coverage and papyrological-review criteria. This makes PHerc. 1667 the first Herculaneum papyrus to be fully digitally unrolled and read for extended scholarly study without physical opening. In PHerc. Paris 4, the optimized scan protocol makes ink directly visible in the tomographic volume, allowing three-dimensional ink segmentation and independent validation of surface-conditioned ink recovery. In PHerc. 139, we recover title and author-attribution evidence identifying the scroll as Philodemus, On Gods, Book 8. These results move virtual unwrapping of the Herculaneum scrolls beyond isolated demonstrations towards a scalable framework for systematic recovery of the still-unopened library.
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All authors Giorgio Angelotti, Stephen Parsons, Federica Nicolardi, Youssef Nader, Sean Johnson, David Josey, Paul Henderson, Hendrik Schilling, Johannes Rudolph, Forrest McDonald, Elian Rafael Dal Prá, Paul Tafforeau, Alessandro Mirone, Clifford Seth Parker, Jan Paul Posma, Benjamin Kyles, Claudio Vergara, Alessia Lavorante, Rossella Villa, Maria Chiara Robustelli, Marzia D'Angelo, Gianluca Del Mastro, Michael McOsker, Kilian Fleischer, Christy Chapman, Nat Friedman, William Brent Seales

Medical Physics

An Optimal Contact-Mechanically Consistent and Flow-Separation Adapted Modeling of Vocal Fold Dynamics

Sardar Nafis Bin Ali, Maryam Naghibolhosseini and Mohsen Zayernouri

Single mass-spring-damper models of vocal folds have been effective in simulating vocal fold vibrations without added complexity. However, single-degree-of-freedom models cannot sustain oscillation in the presence of structural damping unless source-tract interaction is considered. Moreover, existing lumped models struggle to accurately simulate vocal fold closure during phonation. This study aims to develop a reliable and simplified single-degree-of-freedom model of phonation that can simulate sustained oscillation in a damped system without incorporating a vocal tract model. Additionally, the proposed model maintains vocal fold closure in a manner consistent with the physics of phonation, addressing a longstanding challenge in existing lumped models. High-speed videoendoscopy (HSV) data from four normophonic subjects producing sustained vowel /i/ were used to extract glottal area waveforms (GAWs) via deep learning-based image segmentation for particle swarm optimization of the model parameters. An additional resistance force was incorporated to compensate for flow separation and generate the force imbalance required for sustained oscillation. An external structural force was also added during closure to sustain the closed phase. The 4th-order Runge-Kutta method was used to solve the governing equations with enhanced numerical stability and accuracy. The model parameters were optimized for individual subjects, resulting in normalized errors below 3% between experimental and simulated GAWs. The proposed model accurately reproduced subject-specific vocal fold vibrations and vocal fold closure in agreement with experimental data. Overall, the proposed model provides a computationally efficient framework for simulating sustained phonation without requiring complex source-tract coupling while capturing the key biomechanical and aerodynamic mechanisms of phonation.
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Computational Physics · Cross-listed from cond-mat.mtrl-sci

Dislocation-loop formation is a first-order phase transition

Xiaoya Chang, Arsalan Hashemi, Nima Ghafari Cherati et al. (+3 more)

Dislocation loops are the elementary product of radiation damage in crystals, limiting reactor-component lifetimes, power-electronics reliability and the coherence of solid-state qubits. Their nucleation has been simulated for six decades but never reduced to a thermodynamic law. We show that dislocation-loop formation is a first-order phase transition, and construct its Ginzburg–Landau free energy, with the loop area as order parameter, entirely from atomistic simulation. In diamond, carbon self-interstitials condense into planar precursors that collapse abruptly into a prismatic $\tfrac{1}{2}\langle110\rangle$ loop across a 3.7-electronvolt barrier, with pressure–volume work supplying only 2% of the energy released. The reduced free energy proves material-independent: the vacancy platelet-to-loop collapse in body-centred-cubic iron falls on the same one-parameter family, placing loop nucleation on a transferable thermodynamic footing.
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All authors Xiaoya Chang, Arsalan Hashemi, Nima Ghafari Cherati, Mikko Karttunen, Adam Gali, Tapio Ala-Nissila

Fluid Dynamics · Cross-listed from cs.CE

Weak Dominant Balance for Robust Identification of Dynamically Consistent Fluid Flow Structure

Samuel Ahnert, Esther Lagemann, H. Jane Bae et al. (+4 more)

Extracting interpretable, localized physical mechanisms from complex spatiotemporal data is a foundational challenge across physics, biology, and engineering, but has remained out of reach on real measurements. The central obstacle is obtaining high-quality gradients of data via numerical differentiation, which amplifies noise, diverges for high-order equations, and falters on irregular geometries, limiting the scope of existing approaches to clean simulations of low-order systems. Here, we present weak dominant balance, a derivative-free framework that projects governing equations into a weak (integral) formulation, offloading differentiation onto smooth analytical test functions and leaving the data untouched. The method sustains accurate regime identification under severe noise where existing approaches categorically fail, delivers the first data-driven decomposition of a third-order partial differential equation applied to turbulent duct flow, and produces matching decompositions across direct numerical simulation and particle-image velocimetry measurements of a wavy channel flow, uncovering a previously uncharacterized dynamical regime. Weak dominant balance brings mechanism-level analysis out of simulation and onto measured data, and opens complex physical systems to direct, equation-grounded interpretation.
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All authors Samuel Ahnert, Esther Lagemann, H. Jane Bae, Kunihiko Taira, Ricardo Vinuesa, Christian Lagemann, Steven L. Brunton

Optics

Optically dense nanowire metamaterials are transparent to polarization

Shravan Raghunathan, Ad Lagendijk and Willem L.Vos

We study the transport of light through dense opaque anisotropic metamaterials consisting of oriented nanowires. The nanowires consist of polymer photoresist that is structured by direct laser writing (DLW) with two-photon induced polymerization, with radii between $a = 0.5$ and $1~\mu \text{m}$. Our flat samples have a thickness up to 9 layers, from $L = 3~\mu \text{m}$ to $20~\mu \text{m}$. Within each layer, the nanowires are parallel and spaced with random nearest-neighbor distances; nanowires in adjacent layers are perpendicular. The diffuse optical transmission at $\lambda = 633~$nm is as low as $T = 12 \%$, typical of optically dense, multiple scattering metamaterials, with a mean free path down to $\ell = 1.1~\mu \text{m}$, much less than the sample thickness. It is striking that the linear polarization of the input light is maintained at the output of the dense nanowire samples, and not scrambled as in dense nanosphere arrays. Moreover, the linear output polarization faithfully tracks the input polarization. We propose that the polarization is maintained in our optically thick samples, since light is predominantly transported perpendicularly to the nanowire layers. The polarization vector then lies in the nanowire plane, consisting of a linear combination of parallel and perpendicular vectors that are both conserved upon subsequent scattering. Hence, the polarization remains independent of nanowire orientation, even after multiple scattering events. We propose that anisotropic scattering samples may find practical uses in white LEDs and its applications in lighting luminaires, optical communication, and encryption systems.
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Physics and Society · Cross-listed from math.CO

Impartial Combinatorial Games and the Nuclear Escalation Ladder

Arnav Garg

We model Herman Kahn's escalation ladder as an impartial combinatorial game. Reindexing each rung by its distance to the nuclear threshold turns the ladder into a subtraction game, the most tractable class in combinatorial game theory, and the doctrinal fact that no side wishes to fire first selects the misere convention. We prove that single-ladder stability is governed by a congruence (Theorem 4.1) and derive a ladder-design corollary that makes the burden of first escalation a function of ladder length and escalation granularity (Corollary 4.2). For simultaneous theaters we show, under normal play, that joint stability is the Nim-sum of the theater-wise escalation distances (Theorem 5.2), a condition that is neither additive nor dominated by the most dangerous theater. We then show the Nim-sum reduction fails under misere play, introduce the misere quotient as its replacement, and prove by exhaustive backward induction that for two-step escalation the quotient is the order-six monoid with generators a, b satisfying a^2=1 and b^3=b, with loss set {a,b^2} (Theorem 6.3). To our knowledge, impartial combinatorial game theory has not previously been applied to nuclear escalation ladders; the existing game-theoretic literature on escalation is classical and payoff-based.
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Accelerator Physics

Thermal and electromechanical response of ultra-thin carbon-strip polarimeter targets in relativistic bunched beams

F. Rathmann, O. Eyser, M. Sangroula et al. (+2 more)

Thin carbon-strip targets provide fast relative hadron beam polarimetry, but their response in intense relativistic bunched beams is not governed by local stopping-power heating alone. We develop a coupled response model that combines beam-target overlap, secondary-electron escape, retained heat, target motion, transient heat transport, RF-induced strip-end heating, beam-induced forces, resistance changes, and slack-strip deformation. RHIC target observations constrain the relevant motion, force, and nonlocal-heating scales and show that target survival depends on both beam-center heating and electromagnetic boundary conditions near the strip ends. Applying the model to Booster, AGS, RHIC, and EIC proton and $^{3}\mathrm{He}$ cases shows that the RHIC proton lifetime scale is reproduced at the order-of-magnitude level, while the RHIC target-holder fin results require the additional RF/end-heating mechanism. For EIC proton flattop operation, carbon-strip polarimetry may remain viable only with reduced dwell time, sufficient detector acceptance, and suppression of RF-induced end heating. For cooled-emittance $^{3}\mathrm{He}$, the calculated sublimation-loss scale is far beyond a straightforward RHIC-like carbon-strip extrapolation. Conventional carbon strips are therefore unlikely to remain viable for the most demanding EIC light-ion cases without major changes in target motion, target technology, or diagnostic concept.
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All authors F. Rathmann, O. Eyser, M. Sangroula, P. Shanmuganathan, V. Shmakova

Computational Physics · Cross-listed from eess.SP

Two-Dimensional Method-of-Moments Analysis of TMz and TEz Scattering from PEC Cylinders

Sabrina Saima

This paper presents a two-dimensional method-of-moments (MoM) solver for electromagnetic scattering from infinitely long perfectly electrically conducting (PEC) cylinders. Both TMz and TEz polarizations are considered. Starting from the scalar Helmholtz equation, the electric field integral equation (EFIE) is derived for TMz scattering and the magnetic field integral equation (MFIE) is derived for TEz scattering. The induced surface current on the PEC boundary is expanded using pulse basis functions, and the boundary integral equations are discretized using point matching at the segment centers. Circular cylinders with radii $R = {\lambda}$ and $R = 2{\lambda}$ are used as validation cases because analytical series solutions are available. The MoM-computed surface currents, total near fields, scattered near fields, and field-error distributions are compared against the analytical solutions. After validation, the same solver is applied to a square PEC cylinder, for which no simple closed-form analytical solution is used. The results show strong agreement between the MoM and analytical circular-cylinder solutions and demonstrate the geometry-dependent scattering behavior of the square cylinder.
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Optics

Continuous modal spectrum in nonreciprocal cavities

Filipa R. Prudêncio, David E. Fernandes and Mário G. Silveirinha

Nonreciprocal systems enable asymmetric energy transport and suppress backscattering, giving rise to unconventional wave phenomena. Here, we show that nonreciprocal cavities based on unidirectional waveguides exhibit a continuous modal spectrum, in contrast to conventional cavities with discrete eigenmodes. Using a ferrite-loaded microwave cavity as an example, we demonstrate that enforcing unidirectionality, by tailoring the waveguide geometry, drives a transition from discrete to continuous spectra, accompanied by strong spatial localization of electromagnetic fields. Our results reveal that dissipation alone fails to regularize these singular responses, highlighting the need for additional mechanisms to control localization in nonreciprocal systems.
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Atomic Physics · Cross-listed from nucl-ex

Dineutron clusters

Takashi Nakamura, Kouichi Hagino and Yosuke Kondo

The dineutron is a spatially compact two-neutron cluster, which is expected to appear in a low-density part of nuclei. In recent years, there has been rapid progress in experimental and theoretical research on dineutron clusters, particularly on neutron-rich rare isotopes. Experimentally, evidence for dineutron in two-neutron halo nuclei, such as $^{11}$Li, has been obtained using Coulomb breakup, measurements of charge radii, and quasi-free proton scattering. Specific unbound nuclei just beyond the neutron drip line, which decay by emitting two neutrons, are also candidates for having a dineutron correlation. For instance, the dineutron structure has recently been investigated for $^{16}$Be, focusing on its decay into the core and the two neutrons. Theoretically, it is shown that the dineutron is partially due to the admixture of different-parity configurations for the two valence neutrons. Few-body theories, including dynamical effects of the decay process, play important roles in interpreting three-body decays. We also discuss the four-neutron clusters, showing the experimental results of recent tetraneutron experiments and observation of $^{28}$O. Possible relevance of these states to dineutron correlation is discussed. Finally, we discuss future perspectives on dineutron clusters in neutron-rich nuclei and their relation to the universal features in few-body physics.
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Applied Physics

Vertical $\beta$-Ga$_2$O$_3$ Schottky Diodes with Deep-Etch Field Termination using Plasma-free Ga-assisted Etching

Saleh Ahmed Khan, Ahmed Ibreljic and Anhar Bhuiyan

A deep-etch field termination strategy using a Ga-assisted plasma-free etching technique in a low-pressure chemical vapor deposition (LPCVD) system is demonstrated for $\beta$-Ga$_2$O$_3$ Schottky barrier diodes (SBDs). The thermally activated etching method provides a plasma-free approach for forming deep mesa terminations while maintaining excellent device integrity. The fabricated diodes exhibit excellent forward conduction characteristics with a turn-on voltage of 1.14~V, a Schottky barrier height (SBH) of 1.15~eV, an ideality factor of 1.20, and a specific on-resistance of 3.72~m$\Omega\cdot$cm$^2$, all closely matching those of the unetched planar devices. Capacitance-voltage analysis further confirms a uniform carrier concentration of $2\times10^{16}$~cm$^{-3}$ and an SBH of 1.23~eV, indicating stable electrical characteristics after deep mesa formation. Temperature-dependent electrical measurements from 25 to 250$^\circ$C demonstrate stable thermionic-emission transport behavior, with a gradual increase in on-resistance at elevated temperatures due to phonon-limited carrier mobility. Over this temperature range, the SBH decreases from 1.16 to 1.12~eV, while the ideality factor increases from 1.21 to 1.33. The leakage current remains low throughout the entire temperature range, and the rectification ratio remains above $10^{5}$ even at 250$^\circ$C. Under reverse bias, the diodes exhibit an increase in breakdown voltage from 287V to 500V, confirming the effectiveness of geometric electric-field redistribution achieved by the deep-etched mesa structure. Silvaco TCAD simulations corroborate these experimental observations by showing significant suppression of electric-field crowding near the anode edge. These results establish Ga-assisted plasma-free etching as a reliable, damage-free field termination technique for high-performance $\beta$-Ga$_2$O$_3$ power devices.
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Computational Physics · Cross-listed from cs.LG

MALOQ: Massively Accelerated Learning of Operators for Quantum Transport

Manasa Kaniselvan, Alexander Maeder, Denghui Lu et al. (+2 more)

Machine-learned (ML) operator models can be trained to predict density functional theory (DFT) Hamiltonian/density matrices at significantly reduced computational cost, thus extending electronic-structure calculations to previously unfeasible scales. Here, we introduce MALOQ (Massively Accelerated Learning of Operators for Quantum Transport), an application built to train on and predict electronic-structure matrices for systems made of few to 100k atoms, described by large basis sets, and covering a wide range of atomic elements. Based on a state-of-the-art, SO(2)-equivariant backbone architecture, MALOQ provides (i) custom data-processing kernels to handle high-rank Hamiltonian matrix data and (ii) a scalable edge-wise distribution of atomic graph(s). Trained on the largest molecular Hamiltonian datasets available today, it reduces time-per-epoch by over 30% compared to a molecule-wise-distributed framework, and enables inference on material graphs of arbitrary size. We demonstrate scalable training and inference for 3,000-12,000 atoms on the Alps supercomputer, up to 192 GPUs and 256 GPUs, respectively.
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All authors Manasa Kaniselvan, Alexander Maeder, Denghui Lu, Alexandros Nikolaos Ziogas, Mathieu Luisier