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Physics Physics

physics Watch Physics

Tuesday 10 March

Atmospheric and Oceanic Physics · Cross-listed from astro-ph.SR

Joint Diagnostics of Circumsolar Sky Brightness Using Coronagraphic Measurements and Aerosol Optical Inversions at Mauna Loa

Thomas A. Schad, Paul Bryans, Andre Fehlmann et al. (+5 more)

Atmospheric aerosols strongly influence daytime sky quality for solar coronal imaging, yet few studies directly link aerosol properties and sky-brightness measurements within ~2{\deg} of the Sun. Here we compare externally occulted coronagraphic measurements of near-Sun radiance with aerosol-constrained inferences derived from direct-Sun and sky photometry. Our analysis focuses on Mauna Loa Observatory, a well-characterized high-altitude site for atmospheric and solar observations. We present coronagraphic measurements of near-Sun radiance at 1.54 +/- 0.77{\deg} from solar disk center acquired between 2006 and 2007 by an ATST Sky Brightness Monitor (SBM). These data are directly compared with circumsolar radiances inferred at 1.54{\deg} using AERONET almucantar measurements and aerosol optical retrievals. We find quantitative agreement between these two approaches, enabling extension to multi-decadal analyses of circumsolar radiance and its relationship to aerosol properties and related proxies (e.g., the Angstrom exponent) using AERONET data from 2000-2025. Near-Sun radiances are expressed relative to the solar disk-center radiance, facilitating direct comparison with related studies. Finally, we synthesize physically based true-color images of the circumsolar sky under representative aerosol conditions as an observational aid, in part to illustrate that visually enhanced solar aureoles do not necessarily imply poor infrared coronal observing conditions. This methodology provides an extended framework for assessing daytime coronal sky quality at existing and future observing sites.
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All authors Thomas A. Schad, Paul Bryans, Andre Fehlmann, Sarah Gibson, David M. Harrington, Lucas A. Tarr, Steven Tomczyk, Jeffrey G. Yepez

Applied Physics

Non-Hermitian-induced higher-order topological phases in acoustic fractal lattices

Shuanghuizhi Li, Bowei Wu, Tingfeng Ma et al. (+3 more)

For fractal (non-integer-dimension) geometries in Hermitian system, high-order topological phases were realized in the past few years, for which, it is difficult to tune the energy concentration degree of topological states flexibly and smoothly. Non-Hermiticity method is expected to solve this problem. However, in non-integer-dimension system, the non-Hermitian-fractal coupled topological mechanism is unclear and topological phases induced by non-Hermiticity remain unrealized. By introducing a loss contrast in a fractal lattice, this study proposes a non-Hermitian route to realize higher-order topological phases in acoustic fractal lattices with good tunability. Based on the tight-binding approximation, calculations on the Hamiltonian of the system yield the wave-function distribution of the zero-energy modes, revealing the formation mechanisms and conditions for the topological phase transitions induced by non-Hermiticity in acoustic fractal lattices. We numerically and experimentally realize non-Hermitian-induced topological edge and corner states in a fractal structure. Furthermore, a tunable acoustic energy concentrator has been realized, namely, the degree of acoustic energy localization can be tuned conveniently by merely adjusting the loss contrast, rather than redesigning the structure parameters. This work not only establishes an effective mechanism for manipulating higher-order topology in complex fractal geometries through non-Hermiticity but also provides a theoretical framework for exploring exotic topological states of matter in non-integer dimensions.
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All authors Shuanghuizhi Li, Bowei Wu, Tingfeng Ma, Haixiao Wang, Jiaqi Zhang, Chenbowen Lou

Optics

Sensing coherent phonon dynamics in solids with delayed even harmonics

Jinbin Li, Ulf Saalmann, Hongchuan Du et al. (+1 more)

High harmonics have emerged as a powerful ultrafast probe of phonon dynamics and electron-phonon interactions in solids, with most studies focusing on odd harmonics. Here, in a pump-probe setup with variable delay, we theoretically investigate how even harmonics reveal coherent phonon dynamics. If pump and probe pulses overlap temporally, the spatial interference effect resulting from a non-coaxial pump-probe setup suppresses harmonic yields. At longer delays, odd-harmonic yields oscillate in phase at the optical phonon frequency, whereas even harmonics exhibit order-dependent phase-shifted oscillations. We identify a responsive range of even harmonic orders, in which the delay of yield oscillations is highly sensitive to subtle features of phonon dynamics and electron-electron interactions. Our findings highlight the potential of even harmonics to elucidate microscopic effects in systems with dynamically broken inversion symmetry.
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All authors Jinbin Li, Ulf Saalmann, Hongchuan Du, Jan Michael Rost

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Ultralight High-Entropy Nanowire Scaffolds for Extreme-Temperature Functionality

Cameron S. Jorgensen, Corisa Kons, William Stallions et al. (+3 more)

High-entropy alloys (HEAs) combine compositional disorder with exceptional functional tunability, yet their inherently high-density limits use in lightweight systems. Here, we introduce entropy-architected nanowire metamaterials, a class of materials that couple configurational entropy with structural porosity to achieve metal-like functionality at ultralow density. FeCoNiCrCu HEA nanowires were electrodeposited into porous templates and freeze-cast into three-dimensional “bird`s-nest“ scaffolds with densities below 1 $\%$ of the bulk metal. The resulting architectures retain a disordered face-centered-cubic phase, exhibit Curie temperatures exceeding 1000 K, and deliver thermal diffusivity ($\approx0.211$ mm$^2$ s$^{-1}$) comparable to titanium alloys. Structural and spectroscopic analyses reveal nanoscale Cu segregation that enhances magnetic ordering and thermal stability. These findings demonstrate that configurational entropy and architectural hierarchy can be co-engineered to yield lightweight, high-temperature functional materials for extreme-environment applications.
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All authors Cameron S. Jorgensen, Corisa Kons, William Stallions, Austin C. Houston, Gerd Duscher, Dustin A. Gilbert

Optics

Geometric Realism Without Angular Resolution Structural Classification of Multilayer Kubelka-Munk Theory within Radiative Transport

Claude Zeller

Kubelka-Munk (KM) theory provides a two-flux description of radiative transport in layered scattering and absorbing media. Despite its wide use in the coatings, paper, paint, and textile industries, the theory has often been regarded as a phenomenological model whose connection to the full radiative transfer equation (RTE) remains unclear. Under the standard steady-state, plane-parallel, azimuthally symmetric assumptions, we show that multilayer KM theory is exactly a rank-2 Galerkin projection of the RTE onto hemispherical basis functions. The projection is idempotent with an infinite-dimensional kernel, and its rank is preserved under multilayer composition – so no amount of layer stacking can recover angular information discarded by the projection. We derive the KM coefficients as hemispherical moments of the transport operator and compute the projection error for representative scattering media (g from 0 to 0.85), finding that the reduced optical thickness tau* = tau(1-g) governs KM accuracy. The projection-error framework explains the well-documented accuracy of compositional multilayer models in printed media and shows where higher-order methods become necessary. The result places KM theory on rigorous footing as a legitimate – if low-resolution – transport approximation rather than an ad hoc phenomenology.
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Fluid Dynamics

Droplet impact on a superhydrophobic surface under shear airflow: Lattice Boltzmann simulations and scaling analyses

Yang Liu, Xuan Zhang, Yiqing Guo et al. (+2 more)

Droplet impact in airflow environments is ubiquitous in nature and industry, making the understanding of this multiphase behavior crucial for technologies such as anti-icing and spray cooling. In this study, the dynamics of droplet impact on a superhydrophobic surface under shear airflow are numerically investigated using the pseudopotential multiphase lattice Boltzmann method. This three-dimensional model employs a non-orthogonal multiple-relaxation-time scheme to enhance numerical stability and a contact angle hysteresis window to effectively capture dynamic wetting. Specifically, the kinetic energy supplied by the airflow enhances streamwise spreading and significantly expands the final contact footprint due to continuous horizontal sliding. To describe the nonlinear dependence of these contact-line characteristics on the impact Weber number (We) and the airflow Reynolds number (Re), a set of composite scaling laws is developed based on a modified Weber number (We*) that incorporates the airflow contribution. Moreover, the aerodynamic effect leads to a higher velocity restitution coefficient and a deflected take-off angle. Based on an energy partition analysis at detachment, a refined power law is derived to scale the vertical restitution coefficient under shear airflow, while the streamwise restitution coefficient is formulated via the sliding velocity approximation. Integrating these two directional components enables accurate quantitative predictions of the total restitution coefficient and the take-off angle governed by the interplay of We and Re. Overall, this study clarifies the underlying mechanisms of droplet-airflow-surface interactions, providing practical insights for predicting droplet behaviors and guiding surface design under aerodynamic conditions.
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All authors Yang Liu, Xuan Zhang, Yiqing Guo, Xiaomin Wu, Jingchun Min

Optics

Meta-cavity Quantum Electrodynamics

Xueshi Li, Ziwei Wang, Yan Chen et al. (+13 more)

Cavity quantum electrodynamics (cQED) harnesses light-matter interactions to produce nonclassical light states. However, a fundamental challenge lies in simultaneously achieving Purcell enhancement and tailored wavefront control within a single cavity, due to conflicting resonator requirements. Here, we overcome this limitation by demonstrating triggered single-photon emission with customizable wavefronts from semiconductor quantum dots embedded in geometric-phase metacavities. These monolithic devices - only 200 nm thick - deliver Purcell-enhanced emission alongside spin-momentum-locked radiation, vortex beams, and holographic patterns. The meta-atom lattice provides high-Q optical confinement, while spatially modulated orientations enable efficient outcoupling of photons with designed states. This work establishes a new paradigm for intrinsically multiplexing metasurface-based wavefront shaping with cQED, enabling high-performance quantum light sources from subwavelength-scale monolithic platforms.
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All authors Xueshi Li, Ziwei Wang, Yan Chen, Dong Liu, Kaili Xiong, Guangfeng Wang, Jiantao Ma, Ying Yu, Jiawei Wang, Zhanling Wang, Xiao Li, Xianfeng Chen, Erez Hasman, Bo Wang, Jin Liu, Tian Jiang

Atomic Physics

Observation of Strong Electron Correlation in Planetary Atomic Structure

Xinglong Yu, Yongyan Han, Zhenjie Shen et al. (+10 more)

Unravelling two-electron correlation is a long-standing challenge at the heart of few-body quantum physics, underlying correlated phenomena across atomic, molecular and condensed-matter science. In prototypical three-body Coulomb systems, such strong correlation in doubly excited states (DESs) of planetary atomic systems leaves distinct signatures in nonsequential above-threshold double ionization (NS-ATDI) driven by coherent laser fields, yet such targeted study has long remained elusive. Here we present kinematically complete measurements of multi-photon double ionization in cold strontium atoms. Our results reveal a dominant NS-ATDI channel exhibiting well-defined band structures that encode pronounced energy and angular correlations between the two emitted electrons. Autoionization spectra confirm the presence of DESs as transition states that effectively promote the NS-ATDI process. These observations provide direct evidence that both electrons are synchronously excited and ionized via resonant high-lying DES transitions, meaning the structure-linked two-electron correlation of DES is preserved and propagated in the laser-driven time-dependent three-body system. Our work transcends the traditional paradigm of multi-photon double ionization, and fundamentally reshapes the core understanding of intrinsic electron correlation governing many-body systems in nature.
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All authors Xinglong Yu, Yongyan Han, Zhenjie Shen, Yong-Kang Fang, Shushu Ruan, Jie Liu, Zhixian Wu, Xincheng Wang, Ahai Chen, Wei-Chao Jiang, Kiyoshi Ueda, Liang-You Peng, Yuhai Jiang

Atomic Physics

Recent advances in Ultralong-range Rydberg molecules

Jingxu Bai, Yuechun Jiao, Xiao-Qiang Shao et al. (+2 more)

Rydberg molecule, formed by one or more Rydberg atoms, exhibits remarkable properties, including an exceptionally large spatial extent, rich rovibrational level structures, permanent electric dipole moments, and a pronounced sensitivity to external fields. Based on the underlying binding mechanisms, Rydberg molecules can be divided into three categories, the ground-Rydberg molecule that is bound via a low-energy electron-atom scattering interaction between ground atom and Rydberg electron, the Rydberg-Rydberg molecule that is bound via a long-range electrostatic interaction between Rydberg atoms, and the ion-Rydberg molecule that is bound via single- or multi-polar interactions between Rydberg atom and ion. This review focuses on recent theoretical and experimental advances in diatomic Rydberg molecules, covering their formation and binding mechanisms, potential energy curves, experimental observations, and spectroscopic properties, with the aim of providing a comprehensive overview of the current state and future prospects of this rapidly developing field.
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All authors Jingxu Bai, Yuechun Jiao, Xiao-Qiang Shao, Weibin Li, Jianming Zhao

Computational Physics

A multi-phase-field model for fiber-reinforced composite laminates based on puck failure theory

Pavan Kumar Asur Vijaya Kumar, Rafael Fleischhacker, Aamir Dean et al. (+1 more)

This article proposes a multi-phase-field model using the Puck failure theory to predict the failure in fiber-reinforced composites (FRCs) laminates. Specifically, this work proposes a two-dimensional multi-field model in conjunction with a mesh overlay method to compute in-plane damage in the FRCs laminates with various ply orientations. The formulation considers the two independent phase-field variables to trigger fiber and inter-fiber-dominated failure separately, thereby accessing the interrelation between the damage. Furthermore, the model considers two characteristic length scales and two structural tensors to describe the damage modes accurately. Each ply in the laminate is represented using a separate mesh and is combined using the mesh overlay method. Four benchmark examples are utilized to demonstrate the predictive capability of the proposed model. Specifically, coupon tests in tensile and compressive loading, open-hole tension, compact tension, and double-edged notched tension examples are presented along with the comparison with the experimental results from the literature. Furthermore, results regarding cross-ply laminates and isotropic laminates show the model's ability to mimic the experimental results both qualitatively and quantitatively.
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All authors Pavan Kumar Asur Vijaya Kumar, Rafael Fleischhacker, Aamir Dean, Heinz E Pettermann

Plasma Physics

Mode-Selective Laser Propagation and Absorption in Strongly Magnetized Inhomogeneous Plasma

Kun Li, Wuhan Wu, Yuxi Li et al. (+1 more)

We systematically investigate the field-aligned propagation and collisional absorption of normally incident laser light in a strongly magnetized inhomogeneous plasma. Analytical expressions for electric fields in both vacuum and plasma are derived. Using analytical modelling and particle-in-cell simulations, we establish the cutoff conditions, absorption efficiencies, and scaling laws for the right-hand (R) and left-hand (L) circularly polarized waves. The dependence of collisional absorption coefficient on magnetic field strength, plasma scale length and laser intensity are quantified. In particular, L waves reflect at cutoff density, with absorption strongly enhanced as the magnetic field increases. For the R-waves, the absorption decreases with increasing magnetic field when the normalized electron cyclotron frequency is less than unity. However, when it exceeds unity, the R-waves propagate as whistler modes without a cutoff, allowing penetration into overdense plasma. This enables deep energy deposition inside overdense plasma. These results provide a framework for understanding laser-plasma energy coupling through collisional absorption in strongly magnetized inhomogeneous plasma.
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All authors Kun Li, Wuhan Wu, Yuxi Li, Mingyang Yu

Applied Physics

A Stable, High-Order Time-Stepping Scheme for the Drift-Diffusion Model in Modern Solar Cell Simulation

Jun Du and Jun Yan

This paper presents a one-dimensional transient drift-diffusion simulator for advanced solar cells, integrating a structure-preserving finite-volume spatial discretization with Scharfetter-Gummel-type fluxes and a high-order, L-stable implicit Runge-Kutta (Radau IIA) temporal integrator. The scheme ensures local charge conservation, handles sharp material interfaces, achieves second-order spatial and fifth-order temporal convergence, and exhibits excellent computational efficiency and numerical stability. Its accuracy is verified against the classical depletion approximation in p-n junction and validated against four independent software implementations for an organic photovoltaic device under a common protocol. The framework's extensibility is demonstrated by incorporating exciton kinetics in organic solar cells, capturing multi-timescale dynamics, and by modeling mobile ions in perovskite solar cells, reproducing characteristic J-V hysteresis without empirical parameters. This work provides a robust, high-order numerical foundation for simulating coupled charge, exciton, and ion transport in next-generation photovoltaic devices.
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Monday 9 March

Computational Physics

Tensor Train Representation of High-Dimensional Unsteady Flamelet Manifolds

Sinan Demir, Pierson Guthrey, Jason Burmark et al. (+3 more)

This study, for the first time, investigates the use of tensor trains (TTs) to represent high-dimensional unsteady flamelet progress variable (UFPV) manifolds in chemically reacting computational fluid dynamics (CFD). The UFPV framework captures the thermochemical state of reacting flows using a reduced set of parameters and pre-computed manifolds, avoiding the need to transport all species or solve large stiff reaction systems. High-dimensional manifolds enhance accuracy by resolving coupled thermochemical effects critical in high-speed reacting flows but impose substantial memory demands. Here, a five-dimensional UFPV manifold is constructed and stored in the TT format to address this limitation. Several chemical mechanisms and table sizes are examined to evaluate TT compression performance and accuracy. The TT representation achieves significant memory reduction while preserving manifold fidelity and combustion behavior. A one-dimensional reacting-flow case using the discontinuous Galerkin (DG)-based JENRE Multiphysics Framework confirms that TT-compressed manifolds are interchangeable with standard UFPV tables. In addition to memory reduction, benchmark tests show that TT-based manifold sampling can achieve up to 2.4X speedup relative to dense tensor evaluation. Although demonstrated for UFPV combustion models, the proposed TT framework is broadly applicable to other tabulation-based combustion methodologies and provides a scalable alternative to machine learning (ML)-based approaches for representing high-dimensional combustion manifolds.
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All authors Sinan Demir, Pierson Guthrey, Jason Burmark, Matthew Blomquist, Brian T. Bojkod, Ryan F. Johnson

Chemical Physics

Micropatterning photopolymerizable hydrogels for diffusion studies using pillar arrays or photomasks

Sevgi Onal, Edmondo Battista, Hilal Nasir et al. (+4 more)

In situ polymerization and micropatterning of hydrogels on-chip opens the potential for many applications such as tracking and controlling the diffusion of molecules, stimulants, inhibitors, as well as nutrients and drugs, from their source to a target. To enable such applications, we developed hydrogel-on chip platforms for molecular diffusion studies by refining PEGDA-PEG hydrogel in terms of micropatterning and diffusion properties. In the first platform that we introduce here, the design has multiple adjacent microfluidic channels separated with pillar arrays shaping the flow of our custom-prepared photopolymerizable hydrogels and thus enabling the localization of photopolymerization. In the second platform, a photomask formation has been achieved by coupling the micro-milling of 250-\textmu m thickness of PMMA substrate with Platinum (Pt)-coating onto the PMMA mask. In this way the design was obtained to have opaque and transparent regions for light-based polymerization of the PEGDA-PEG hydrogels. The developed method of in situ polymerization of the hydrogel on-chip through photomask has enabled direct transfer of the design of interest to the pre-hydrogel in channel. Next, the developed platforms will be further used to test various compositions of photopolymerizable hydrogels and track and control the diffusion of molecules across hydrogel interfaces. The micropatterning methods and platforms developed here could be tailored to device design and development needs in various application fields from molecular transport to biosensing to electronic devices.
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All authors Sevgi Onal, Edmondo Battista, Hilal Nasir, Fabio Formiggini, Valentina Mollo, Raffaele Vecchione, Paolo Netti

Classical Physics

Extended Structural Dynamics and the Lorentz Abraham Dirac Equation: A Deformable Charge Interpretation

Patrick BarAvi

Radiation reaction in classical electrodynamics is traditionally described by the Lorentz Abraham Dirac equation (LAD), whose point particle formulation leads to well known difficulties including runaway solutions, pre acceleration, and the ambiguous status of the Schott term. We analyze radiation reaction within the framework of Extended Structural Dynamics (ESD), in which charged particles are modeled as finite systems possessing internal dynamical structure. In the present formulation the particle is represented as a finite, deformable sphere with a single radial breathing mode describing internal charge redistribution. This internal degree of freedom introduces a finite response time and ensures that changes in the charge distribution propagate at finite speed. Starting from the full particle field Hamiltonian, we derive the retarded self force for such a deformable charge and obtain a delay kernel that depends on both the past motion and the past internal configuration. In the adiabatic regime the kernel reduces to an effective causal form that is free of pre acceleration and exhibits a band pass frequency response, suppressing high frequency instabilities associated with runaway behavior. The Schott term is shown to correspond to reversible energy stored in the internal deformation mode, providing a direct mechanical interpretation of this contribution. The LAD dynamics are recovered only in the double limit of vanishing spatial extent and frozen internal dynamics, where the causal delay structure collapses to the familiar point particle approximation. Within this framework radiation reaction arises as the leading order effective dynamics of a finite deformable charge, while higher order corrections encode finite size and internal structural effects without modifying Maxwell's equations or introducing ad hoc regularization.
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Chemical Physics

Matlantis-PFP v8: Universal Machine Learning Interatomic Potential with Better Experimental Agreements via r2SCAN Functional

Chikashi Shinagawa, So Takamoto, Daiki Shintani et al. (+7 more)

Universal Machine Learning Interatomic Potentials (uMLIPs) enable atomistic simulations and high-throughput screening at scales far beyond those accessible with density functional theory (DFT). However, most existing uMLIPs are trained on Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA) data and are therefore fundamentally limited by PBE-level accuracy. In this paper, we argue that better zero-shot predictions versus experiments must be an explicit design target for uMLIPs and present PFP v8, a uMLIP available on the Matlantis service that overcomes the inherent limitations of the PBE functional by being trained to reproduce the regularized-restored strongly constrained and appropriately normed (r2SCAN) meta-GGA potential-energy surface across a wide range of chemical domains. Without requiring domain-specific fine-tuning, PFP v8 delivers systematically improved agreement with experimental data or high-accuracy references for crystals, molecules, and surfaces, outperforming PBE-based DFT calculations. Crucially, in long-time molecular dynamics simulations that are computationally impractical with DFT, PFP v8 predicts melting points with an average error of approximately 130 K, halving the error relative to PBE-trained models. These results establish that uMLIPs can move beyond the limitations of their training approximations and achieve substantially improved agreement with experiment across diverse chemical domains, further narrowing the gap between simulation and reality.
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All authors Chikashi Shinagawa, So Takamoto, Daiki Shintani, Yong-Bin Zhuang, Yuta Tsuboi, Katsuhiko Nishimra, Kohei Shinohara, Shigeru Iwase, Yuta Tanaka, Ju Li

Chemical Physics

Hybrid Quantum-Classical Encoding for Accurate Residue-Level pKa Prediction

Van Le and Tan Le

Accurate prediction of residue-level pKa values is essential for understanding protein function, stability, and reactivity. While existing resources such as DeepKaDB and CpHMD-derived datasets provide valuable training data, their descriptors remain primarily classical and often struggle to generalize across diverse biochemical environments. We introduce a reproducible hybrid quantum-classical framework that enriches residue-level representations with a Gaussian kernel-based quantum-inspired feature mapping. These quantum-enhanced descriptors are combined with normalized structural features to form a unified hybrid encoding processed by a Deep Quantum Neural Network (DQNN). This architecture captures nonlinear relationships in residue microenvironments that are not accessible to classical models. Benchmarking across multiple curated descriptor sets demonstrates that the DQNN achieves improved cross-context generalization relative to classical baselines. External evaluation on the PKAD-R experimental benchmark and an A$\beta$40 case study further highlights the robustness and transferability of the quantum-inspired representation. By integrating quantum-inspired feature transformations with classical biochemical descriptors, this work establishes a scalable and experimentally transferable approach for residue-level pKa prediction and broader applications in protein electrostatics.
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General Physics

An axially symmetric stationary N-center solution of Einstein's vacuum equations

Aleksandr A. Shaideman, Jesus D. Arias H and Kirill V. Golubnichiy

Using the Euclidon method, a stationary solution of Einstein's vacuum equations was obtained, describing N rotating axially symmetric masses, which in the absence of rotation describes N arbitrary axially symmetric static masses, for example, N Zipoy masses on the axis of symmetry, and in the absence of distortion, N Kerr-NUT solutions.
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Medical Physics

Controlled kHz laser-driven electron irradiations for pre-clinical applications

C.M.Lazzarini, M.Favetta, E.R.Szabo et al. (+20 more)

We report the first in-air irradiations of biological samples with kHz laser-driven electrons with beam energy 20 MeV, high-energy tail extending to 40 MeV, and average dose rate up to 30 Gy/min. An in-house procedure has been developed to characterize and deliver on-demand (i.e. pre-agreed date and time) the target electron beam energy, dose and dose uniformity. We present a tolerance analysis on the laser electron parameters, highlighting the importance of beam stability for precise irradiations of in vivo zebrafish embryos and in vitro U251 glioblastoma cell line. The observed improvement in the survival rate of the zebrafish embryos, combined with unchanged cytotoxicity in the cell cultures, indicates promising results for normal tissue sparing while maintaining anticancer efficacy. The pre-clinical results of this work represent an important milestone towards the clinical translation of laser-plasma accelerators.
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All authors C.M.Lazzarini, M.Favetta, E.R.Szabo, I.Zymak, L.V.N.Goncalves, M.Jech, S.Lorenz, M.Nevrkla, J.Sisma, A.Spadova, F.Vitha, R.Antipenkov, P.Bakule, A.Grenfell, V.Sobr, W.Szuba, J.Dudas, A.Ebert, R.Molnar, R.Polanek, S.V.Bulanov, K.Hideghety, G.M.Grittani

Physics and Society · Cross-listed from q-fin.PM

Spectral Portfolio Theory: From SGD Weight Matrices to Wealth Dynamics

Anders G Frøseth

We develop spectral portfolio theory by establishing a direct identification: neural network weight matrices trained on stochastic processes are portfolio allocation matrices, and their spectral structure encodes factor decompositions and wealth concentration patterns. The three forces governing stochastic gradient descent (SGD) - gradient signal, dimensional regularisation, and eigenvalue repulsion - translate directly into portfolio dynamics: smart money, survival constraint, and endogenous diversification. The spectral properties of SGD weight matrices transition from Marchenko-Pastur statistics (additive regime, short horizon) to inverse-Wishart via the free log-normal (multiplicative regime, long horizon), mirroring the transition from daily returns to long-run wealth compounding. We unify the cross-sectional wealth dynamics of Bouchaud and Mezard (2000), the within-portfolio dynamics of Olsen et al. (2025), and the scalar Fokker-Planck framework via a common spectral foundation. A central result is the Spectral Invariance Theorem: any isotropic perturbation to the portfolio objective preserves the singular-value distribution up to scale and shift, while anisotropic perturbations produce spectral distortion proportional to their cross-asset variance. We develop applications to portfolio design, wealth inequality measurement, tax policy, and neural network diagnostics. In the tax context, the invariance result recovers and generalises the neutrality conditions of Froseth (2026).
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Atomic Physics

High-optical-depth, sub-Doppler-width absorption lines at telecom wavelengths in hot, optically driven rubidium vapor

Inna Kviatkovsky, Lucas Pache, Viola-Antonella Zeilberger et al. (+4 more)

Doppler broadening presents a major limitation for high-resolution spectroscopy and nonlinear optics in room-temperature atomic vapors. Here, we demonstrate the suppression of Doppler broadening accompanied by pronounced absorption on the upper transition of a three-level ladder system, achieved by dressing the intermediate state with a strong control field. As a concrete realization, we study a hot vapor of $^{87}$Rb where the lower transition is driven by a strong control field resonant with the D2 line at a wavelength of 780 nm, while a weak counter-propagating probe field at the telecom C-band wavelength of 1529 nm ($5P_{(3/2)}\leftrightarrow 4D_{(5/2)}$) interrogates the dressed states. We observe absorption features with a resonant optical depth of approximately 4 and a full width at half maximum of about 17 MHz. Remarkably, this corresponds to an order-of-magnitude reduction relative to the Doppler width, while the optical depth on the upper transition of the ladder scheme exceeds that of the Doppler-broadened lower transition. The measured spectra are in good agreement with theoretical modeling. Combining high optical density with sub-Doppler-width absorption lines typically requires laser-cooled atoms, while our approach profits from the experimental simplicity of a hot-vapor platform.
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All authors Inna Kviatkovsky, Lucas Pache, Viola-Antonella Zeilberger, Philipp Schneeweiss, Jürgen Volz, Arno Rauschenbeutel, Leonid Yatsenko

Applied Physics · Cross-listed from cond-mat.mtrl-sci

3D Mapping of Intragranular Residual Strain and Microstructure in Recrystallized Iron Using Dark-Field X-ray Microscopy

Virginia Sanna, Yubin Zhang, Wolfgang Ludwig et al. (+4 more)

Grain growth is a key process in the thermomechanical treatment of metals. Recently, the presence of local residual stresses within fully recrystallized grains has attracted increasing interest in connection with shear-coupled grain boundary migration mechanisms. In this work, we provide the first direct experimental measurements of residual elastic strain variations in fully recrystallized commercial-purity iron, on the order of $10^{-4}$. Using dark-field X-ray microscopy (DFXM), we performed non-destructive three-dimensional measurements of strain and orientation variations within individual grains. Our results reveal heterogeneous strain distributions across all measured grains. In one case, we observed several isolated dislocations accommodating two second-phase particles, exhibiting a localized strain signature with no detectable long-range effect. The formation mechanisms of intragranular residual strains and their potential influence on grain boundary migration during subsequent grain growth are discussed. This work highlights the importance of accounting for such residual elastic strains in future grain growth models.
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All authors Virginia Sanna, Yubin Zhang, Wolfgang Ludwig, Aditya Shukla, Abderrahmane Benhadjira, Marilyn Sarkis, Can Yildirim

Plasma Physics

Nonlinear generation of global zonal structures in gyrokinetic simulations of TCV and ASDEX Upgrade magnetic configurations

I. Novikau, A. Biancalani, A. Bottino et al. (+6 more)

In tokamaks, turbulence is responsible not only for the anomalous transport of heat and particles from the core to the edge, which reduces heating efficiency, but also for the generation of zonal structures (ZSs). Examples of ZSs are those with characteristic sound frequency, like the geodesic acoustic modes (GAMs). Developing a theoretical model of ZS is essential, as they contribute to the turbulence saturation and thus indirectly influence transport. In this paper, we investigate the radial structure of ZS in the frequency range of GAMs, by means of numerical simulations using the gyrokinetic particle-in-cell code ORB5. We find that radially extended coherent ZSs (labelled here as global ZSs) are non-linearly generated by the high-n part of the turbulence spectrum (with n being the toroidal mode number) by means of self-consistent simulations. We also reproduce this generation by mimicking the turbulence modes with an antenna, thus isolating the nonlinear generation mechanism.
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All authors I. Novikau, A. Biancalani, A. Bottino, E. Poli, G. D. Conway, P. Manz, L. Villard, N. Ohana, ASDEX Upgrade Team

Accelerator Physics

Synchrotron radiation leveling at future circular hadron colliders

Frank Zimmermann

Luminosity leveling to limit the event pile up is a key ingredient of the LHC luminosity upgrade, the High-Luminosity LHC (HL-LHC). For a future circular hadron collider, such as the FCC-hh, operating at a centre-of-mass energy of 70-90 TeV, synchrotron radiation becomes significant, with radiation damping times of the order of one or a few hours. The rapid shrinkage of the emittance may call for a leveling of the beam-beam tune shift or of the event pile up, as previously explored. However, the strong synchrotron radiation emitted inside the cold superconducting magnets also represents a significant heat load and is likely to limit the total beam current. In this article, we discuss a new approach, namely synchrotron radiation power leveling, where the beam energy is adjusted during a physics store, either continually or in a few discrete steps, while the beam current decreases, so as to keep the synchrotron radiation power at or below a certain limiting value. In this way, both peak and integrated luminosity of the FCC-hh are increased, compared with operation at a fixed beam energy. The FCC-hh detectors, and in particular the physics event analysis, need to be prepared for this novel mode of operation. This article presents two example running scenarios for synchrotron radiation leveling at the FCC-hh. While not greatly reducing the integrated luminosity at highest collision energy, synchrotron-radiation leveling can significantly increase the number of events for key processes already occurring at lower energy. As an example, we show that it raises the number of di-Higgs production events by 60% or more.
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Computational Physics · Cross-listed from cond-mat.soft

When velocity autocorrelations mirror force autocorrelations: Exact noise-cancellation in interacting Brownian systems

Anton Lüders, Suvendu Mandal and Thomas Franosch

Resolving the mean-squared displacement (MSD) and velocity autocorrelation function (VACF) of interacting Brownian particles remains a central challenge in simulations of soft-matter systems, especially at low densities where particle-particle interactions are sparse and signals are dominated by thermal noise. A recently proposed noise-cancellation (NC) algorithm [Mandal et al. Phys. Rev. Lett. 123, 168001 (2019)] addresses this by decomposing particle trajectories into two components: free Brownian motion and interaction-induced displacements. The NC approximation enhances signal clarity by neglecting cross-correlations between the total particle displacements and the extracted interaction-induced contributions of the trajectories - an assumption that has so far lacked rigorous theoretical justification. In this work, we establish an exact theoretical relation between the VACF, the force autocorrelation function (FACF) characterizing the interaction-induced contributions, and these cross-correlations, which is valid for Brownian systems. We show that in thermal equilibrium, the cross-correlations vanish for Brownian systems because the VACF is strictly proportional to the negative FACF, which establishes the NC algorithm as an exact method. In contrast, for Brownian nonequilibrium systems, the cross-correlations remain finite, providing a direct fingerprint of nonequilibrium physics in such systems and a criterion to distinguish equilibrium from nonequilibrium states. Here, suitable corrections must be applied for the NC method to remain accurate. Our results expand the scope of the NC algorithm to a broad range of soft-matter systems in and out of equilibrium, where it has the potential to strongly enhance the resolution of VACF data obtained through simulations in future studies.
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Instrumentation and Detectors

Isotopic Measurements of SNM using a Portable Neutron Resonance Transmission System for Arms Control

Mital A. Zalavadia, Ethan A. Klein, Michael E. Moore et al. (+4 more)

Neutron Resonance Transmission Analysis (NRTA) was explored as an arms control verification approach to support potential future nuclear weapon limiting treaties. A compact and portable neutron Time of Flight (ToF) system was developed to enable proof-of-concept NRTA measurements of special nuclear material (SNM). Using a short 2-meter flight path, the NRT system is sensitive to cross-section resonances of isotopes such as 235U, 238U, 239Pu and 240Pu between 1-100 eV incident neutron energies due to their physical nuclear structure. The detected neutron ToF spectrum exhibits transmission dips at resonance energies that are characteristic of SNM isotopic composition in the inspected item. The proof-of-concept measurements of Highly Enriched Uranium (HEU), Depleted Uranium (DU), and Reactor Grade Plutonium (RGPu) confirmed the characteristic resonance features within two hours of data collection time. Analysis via the REFIT resonance fitting tool accurately predicted the 235U enrichment and Pu isotopic composition within 5% and 6% of the known values, respectively.
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All authors Mital A. Zalavadia, Ethan A. Klein, Michael E. Moore, Jonathan A. Kulisek, Farheen Naqvi, Glen A. Warren, Areg Danagoulian

Plasma Physics

Spherical compression of an applied magnetic field in inertial confinement fusion

R. Spiers, A. Bose, C. A. Frank et al. (+4 more)

Applying an external magnetic field to laser-driven inertial confinement fusion implosions is a promising approach for enhancing fusion yield. The field is compressed with the plasma, producing a magnetized hotspot that anisotropically suppresses thermal losses and traps alpha particles, making performance sensitive to the compressed field orientation. We derive a simple, readily applicable analytic model that enables rapid evaluation of the compressed field topology and show that ablation into the hotspot amplifies the central field, while the ablated ice near the hotspot edge develops a decaying, radially bent field, with a discontinuity in the field direction. The radially bent field renders thermal insulation at the hotspot edge negligible and largely independent of the applied field strength, whereas insulation in the hotspot core still depends strongly on the applied field. Applying the model to non-axial initial field configurations, we find that an initially applied mirror field provides the greatest suppression, followed by the standard axial field.
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All authors R. Spiers, A. Bose, C. A. Frank, D. J. Strozzi, J. D. Moody, C. A. Walsh, B. A. Hammel

Medical Physics · Cross-listed from cs.CV

Multi-Kernel Gated Decoder Adapters for Robust Multi-Task Thyroid Ultrasound under Cross-Center Shift

Maziar Sabouri, Nourhan Bayasi and Arman Rahmim

Thyroid ultrasound (US) automation couples two competing requirements: global, geometry-driven reasoning for nodule delineation and local, texture-driven reasoning for malignancy risk assessment. Under cross-center domain shift, these cues degrade asymmetrically, yet most multi-task pipelines rely on a single shared backbone, often inducing negative transfer. In this paper, we characterize this interference across CNN (ResNet34) and medical ViT (MedSAM) backbones, and observe a consistent trend: ViTs transfer geometric priors that benefit segmentation, whereas CNNs more reliably preserve texture cues for malignancy discrimination under strong shift and artifacts. Motivated by this failure mode, we propose a lightweight family of decoder-side adapters, the Multi-Kernel Gated Adapter (MKGA) and a residual variant (ResMKGA), which refine multi-scale skip features using complementary receptive fields and apply semantic, context-conditioned gating to suppress artifact-prone content before fusion. Across two US benchmarks, the proposed adapters improve cross-center robustness: they strengthen out-of-domain segmentation and, in the CNN setting, yield clear gains in clinical TI-RADS diagnostic accuracy compared to standard multi-task baselines. Code and models will be released.
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Chemical Physics · Cross-listed from math.CO

Degree-based weighted adjacency matrices: spectra, integrality, and edge deletion effects

Bilal Ahmad Rather and Hilal Ahmad Ganie

We study degree-based weighted adjacency matrices associated with symmetric edge-weight functions $\phi(d_u,d_v)$, with emphasis on complete multipartite graphs and spectral changes caused by edge modification. We characterize its families with three distinct eigenvalues and identifies integral matrices. For complete graphs, an exact threshold is obtained that determines whether deleting one edge increases, preserves, or decreases both the spectral radius and the weighted energy; the generalized Randić family is classified completely, thereby correcting and refining earlier published results in [Bilal and Munir, Int. J. Quantum Chem. (2024)]. We further determine the $ISI$ spectrum under edge deletion from regular complete multipartite graphs, derive the complete weighted spectrum, energy, and inertia of crown multipartite graphs, and prove that adding an edge between two leaves of $S_n$ strictly increases its $ISI$ energy.
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Fluid Dynamics

Aliasing and phase shifting in pseudo-spectral simulations of the incompressible Navier-Stokes equations

Clovis Lambert, Jason Reneuve and Pierre Augier

Pseudo-spectral methods are widely used for direct numerical simulations of turbulence, but the standard 2/3 truncation rule for dealiasing is computationally expensive – accounting for up to 80% of the total cost in three dimensions. Phase shifting methods provide a more efficient alternative by canceling aliasing errors the combination of nonlinear terms evaluated on shifted grids, allowing the same physical resolution to be achieved on a coarser numerical grid. Despite their use in high-resolution turbulence codes, these methods remain poorly documented in the literature and no open-source implementation exists. This paper presents a comprehensive analysis of phase-shifting dealiasing for pseudo-spectral simulations of the incompressible Navier-Stokes equations. We derive the aliasing mechanism from quadratic nonlinearities in discrete Fourier space and explain how phase-shifting cancels aliasing contributions exactly or approximately depending on the time-stepping scheme. We describe and compare several algorithms – including the exact and approximate RK2 phase-shifting schemes of Patterson Jr and Orszag (1971) and Rogallo (1981), and an extension to forced flows – and discuss their interaction with different truncation geometries in three dimensions. All algorithms are implemented in the open-source framework Fluidsim, providing the first publicly available implementation of phase-shifting dealiasing for pseudo spectral Navier-Stokes solvers. We evaluate the methods on two test cases: the transition to turbulence of Taylor-Green vortices and forced homogeneous isotropic turbulence at $Re_\lambda = 200$. Phase-shifting methods achieve speedups of up to a factor of 3 compared to RK4 with 2/3 truncation at the same maximum wavenumber, with small accuracy loss.
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