Applied Physics · Cross-listed from math-ph
Disentangling Measurement Protocol from Material Physics in Isotypic and Anisotypic SiC/Si Heterojunctions: A Metrology-Driven Study for Betavoltaic Energy Conversion
Mikhail V. Dolgopolov
We compare isotypic (n-SiC/n-Si) and anisotypic (n-SiC/p-Si) heterojunctions using Kelvin probe force microscopy, scanning tunnelling spectroscopy, precision electrical measurements with a Keithley 2450 SourceMeter, and a 0.1 farad supercapacitor charge-storage test. Two-wire probing shows an enhanced low-bias current in the isotypic structures; four-wire Kelvin sensing removes the voltage-drop contribution of external leads and contacts and collapses this current to a much lower bulk and interface limited level. The high density of interface states detected by KPFM and STS, up to five times ten to the twelfth per square centimetre per electronvolt in dislocation-rich regions, provides a plausible origin for the enhanced local response. Anisotypic junctions exhibit a genuine diode-like current-voltage characteristic and an open-
circuit voltage of about 1.2 volts under beta irradiation. In the capacitor test with the patented charge-pump converter, the anisotypic structure reaches 0.25 volts versus 0.05 volts for the isotypic one after 30 minutes, giving an energy ratio of about 25. We formulate a measurement-interpretation framework based on four-wire Kelvin sensing, generator polarity with cathode to LO, and high-impedance output-off state. Our results show that anisotypic SiC/Si heterojunctions are the preferred platform for betavoltaic conversion when measured correctly.
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Fluid Dynamics · Cross-listed from cs.CE
Compositional Aeroelastic Operators for Morphing Flexible Multibody Aircraft: A Geometric Framework with Structural Verification
Gelin Chen, Chen Song and Chao Yang
Morphing flexible multibody aircraft require structural strain, aerodynamic geometry, surface velocity, and generalized loading to remain compatible as joints and flexible components change configuration. A compositional formulation is developed around an assumed material attachment between each lifting surface and a geometrically exact beam. Separating the component root pose from the section field shows that the body strain and elastic potential of a component depend on its own elastic coordinates, while upstream motion enters kinetic terms and external-load pullbacks. At element level, an exact relative logarithm $d$ supplies strain and potential energy, whereas a reference-anchored section coordinate $\sigma$ supplies deformed section geometry. Finite-order expansions retain the finite reference geometry exactly and truncate only endpoint perturbations. The attachment map then generates surface points, tangents, normals, velocities, and force Jacobians from common section kinematics. Euler–Poincare beam balance, moving-surface potential-flow relations, graph cotangent assembly, and the associated semidiscrete power identity are stated in a common twist–wrench convention. Collocation, pressure, equivalent-load, and structural-station sites are distinguished to expose their approximation errors. Verification gives the expected $N_d+1$ convergence order for degree-$N_d$ relative-log expansions. In a geometrically nonlinear cantilever comparison, a cubic static-
manifold correction reduces mean full-record displacement error from $0.479$ to $0.255$ over four completed load cases. These results provide structural and interface-level evidence rather than validation of a complete aircraft aeroelastic prediction.
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General Physics
Odd-Parity Perturbations of Geometrically Regular Black Holes with Hedgehog Scalar Hair
G.G.L. Nashed
In this paper, we study linear perturbations of a geometrically regular black hole supported by a constrained $\mathrm{SO}(3)$ scalar triplet in the hedgehog configuration. Since the individual background scalars depend explicitly on the angular coordinates, the decoupling of polar and axial perturbations cannot be concluded from the spherical form of the metric or the energy–momentum tensor alone. To settle this point, we introduce the polar and axial metric and triplet amplitudes simultaneously and derive the corresponding projections of the radiative linearized Einstein–matter equations for $\ell\geq2$. The polar equations contain only polar amplitudes, whereas the axial equations contain only axial amplitudes; hence, the two off-diagonal blocks vanish at linear order. The resulting odd-parity sector forms a closed Einstein–scalar system in which a tangent perturbation of the scalar triplet is coupled to the Regge–Wheeler metric amplitudes. We show that its scalar equation has a second-order
hyperbolic principal part whenever $K_Y\neq0$, and that, for the nonlinear kinetic function supporting the background, $K_Y>0$ throughout the black-hole exterior. The coefficient of the direct metric–scalar mixing is largest at the event horizon and decreases as $r^{-4}$ at large distance, while the metric block in the
vacuum limit reproduces the standard Regge–Wheeler equation and potential; the scalar kinetic coefficient simultaneously vanishes, so the full operator changes rank. These results establish linear parity decoupling and the consistency of the closed axial equations. They do not, however, constitute a proof of mode stability, which requires the reduction of the complete quadratic action.
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Biological Physics · Cross-listed from q-bio.NC
The effect of the excitatory feedback in anticipated synchronization and phase bistability regimes in neuronal populations
Julio N. Machado, Joana M. G. L. Silva, Katiele V. Brito et al. (+2 more)
Anticipated synchronization (AS), in which the receiver leads the sender and the phase lag is negative, can emerge in unidirectionally coupled dynamical systems when the receiver has faster internal dynamics than the sender. In cortical-like population models, AS and bistability between AS and delayed synchronization (DS) have been reported mainly in unidirectional motifs and have been proposed as possible explanations for phase relations observed in electrophysiological recordings. Because cortical areas are often connected bidirectionally, it is important to understand how excitatory feedback from the receiver to the sender affects the emergence and persistence of anticipatory synchronization and phase-bistable regimes. Here, we investigate the effect of the excitatory feedback on the phase relations between two cortical-like neuronal populations. We show that AS and phase bistability are not restricted to strictly unidirectional architectures, but remain robust in the presence of reciprocal coupling. In addition, we find that the transition from AS to DS can occur through different routes within the same motif, either via a bistable regime or via zero-lag synchronization, depending on the inhibitory coupling. More generally, the model exhibits a rich repertoire of phase relations, including: positive, negative, and zero-lag phase-lockings, as well as phase bistability, and phase-drift regimes. These results are consistent with the diversity of phase relations reported in electrophysiological experiments and suggest that fixed structural connectivity may support rapid reconfiguration of functional dynamics without requiring structural rewiring.
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All authors Julio N. Machado, Joana M. G. L. Silva, Katiele V. Brito, Rodrigo Pena, Fernanda Selingardi Matias
Computational Physics
Scalable dynamical inference of phase-field fracture from sparse and partial measurements
Hanfeng Zhai and Zisheng Zhang
Evolving crack fields in structural health monitoring and fracture assessment must often be inferred from sparse mechanical measurements rather than dense full-field observations. We develop CNN2D–ConvGRU, a convolutional-recurrent framework for measurement-conditioned reconstruction of time-dependent phase-field brittle fracture. At each load step, the model maps a fixed-length history of phase and displacement fields and sparse current-step displacement measurements to the current full-field state. New measurements are assimilated during sequential deployment, making the framework a state-inference surrogate rather than an autonomous time integrator. It reproduces crack paths, damage
evolution, and bulk displacement response, with the largest errors near propagating crack tips and steep displacement gradients and some drift at late stages. Without retraining, weights learned on a $256 \times 256$ raster are evaluated on a $512 \times 512$ raster of the same physical domain and finite-element discretization using a proportionally refined measurement grid. This empirical raster-and-sensing transfer preserves the principal damage
topology and global damage
evolution, although fine-scale displacement errors increase near crack tips. Comparisons with alternative spatial and temporal architectures show that CNN2D–ConvGRU offers a favorable balance between reconstruction accuracy and computational cost. Relative to repeated finite-element solutions, sequential reconstruction achieves mean speedups of $175\times$ on CPU and $253\times$ on GPU. These results demonstrate efficient full-field fracture-state reconstruction from sparse observations while retaining the spatial structure and history dependence of phase-field fracture.
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Fluid Dynamics · Cross-listed from cond-mat.stat-mech
Nonequilibrium Maxwell-Demon NEMD formalism for transport: I. Extrapolating shear viscosity to the hydrodynamic limit
Hesam Arabzadeh and Brad Lee Holian
The Maxwell-Demon nonequilibrium molecular dynamics method for measuring the shear viscosity divides the fluid simulation
cell into two regions of width w in the $x$-direction, with the particles allowed to move freely between the two sides. The Demon maintains equal and opposite regional average particle velocities in the $y$-direction by applying an acceleration needed to sustain the nonequilibrium steady state (NESS), which includes both total force balance and an instantaneous correction for
diffusion of particles across boundaries. We show that the driven velocity profile in x is a natural hydrodynamic response and not imposed by the constraint. For the present shear geometry, the measured NESS profile in Eulerian slabs is represented accurately by a piecewise
parabolic form, reminiscent of planar Poiseuille flow. The
parabolic profile gives an estimate of the kinematic viscosity from work done on the shearing fluid, as well as an
entropy production estimate, derived from heat removal by the Nosé-Hoover thermostat that keeps each regional average temperature constant. We show that the mechanical work supplied by the Demon equals the heat removed by the thermostat. Once NESS driving is removed, the
parabolic velocity profile relaxes exponentially in short order to sinusoidal, the natural transverse momentum-
diffusion eigenmode. Our Maxwell-Demon shear method provides a direct NEMD formalism for obtaining shear viscosity from momentum
diffusion, work, and
entropy balances. Our results in three dimensions for increasing system size $N$ (the number of particles) demonstrate that shear viscosity approaches an asymptote (the so-called hydrodynamic limit) as $N^{-1/3}$.
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Medical Physics
Proposal of a consistent value for the mean excitation energy of liquid water using advanced modeling, detailed simulations and precission proton Bragg curves
Pablo de Vera, Isabel Abril, Flávio Matias et al. (+3 more)
Protontherapy precision depends on accurately knowing the stopping power of
liquid water, as it is the most abundant component of soft body tissues. Difficulties when working with volatile
liquids have led to a long-standing debate regarding the values of the stopping power and the mean excitation energy $I$ of
liquid water. The equivalence between the stopping power of
liquid water and amorphous ice per unit mass density across all clinically relevant
proton energies opens the possibility to obtain a reliable estimation of the $I$-value of
liquid water. In this work, we employ two complementary theoretical methodologies to assess the
proton stopping power of water. The MELF-GOS (Mermin Energy Loss Function - Generalized Oscillator Strengths) approach, based on the perturbative dielectric formalism, serves as an accurate reference for sufficiently high energies, while the novel non-perturbative TDDFT-Penn (time-dependent density functional theory - Penn) method ensures accuracy for energies even below the stopping maximum. These stopping-power values were incorporated into the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids) to evaluate
proton Bragg curves from $1$ to $230$ MeV. Comparisons with available precise depth-dose measurements provide critical insights that help establish the consistent value $I = 79.4$ eV for
liquid water, providing robust physical grounds for improving range prediction for treatment planning.
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All authors Pablo de Vera, Isabel Abril, Flávio Matias, Julian M. B. Shorto, Hélio Yoriyaz, Rafael Garcia-Molina
Data Analysis and Statistics · Cross-listed from astro-ph.SR
Determining low-$\ell$ p-mode frequency shifts in Sun-like stars: Enhancing the cross-correlation technique with filters
Samarth G. Kashyap, Laurent Gizon, Jesper Schou et al. (+1 more)
Acoustic mode frequencies in the Sun and Sun-like
stars change due to
magnetic activity, on time-scales much larger than the
star's rotation and much smaller than its
evolution. Given the poor S/N of the observed
stellar p-modes, it is challenging to measure the changes of individual mode frequencies. Typically, power spectra of different time series segments are cross-correlated to estimate a mean p-mode frequency change, which ends up averaging over the individual mode contributions. We seek to enhance the cross-correlation method, by introducing a novel and computationally cheap method, thus enabling us to disentangle p-mode frequency changes for different spherical harmonic degree $\ell$. Assuming that the inclination angle and rotation rate are already measured, filters are designed, which enable the isolation of $\delta\omega_\ell$, frequency changes of modes with a given $\ell$, while preventing bias creeping in from neighbouring modes. Monte-Carlo simulations are performed to quantify uncertainty in the estimation of $\delta\omega_\ell$. We validate our method against well-studied
solar data (SOHO/VIRGO and BiSON) and demonstrate its applicability to the
solar-like Kepler
star KIC 8006161.
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All authors Samarth G. Kashyap, Laurent Gizon, Jesper Schou, Rachel Howe
Computational Physics
Conforming and nonconforming Trefftz approximations for two-dimensional scalar electromagnetic problems
Igor Tsukerman
Trefftz functions satisfy the differential equation locally and exactly; quasi-Trefftz functions do so approximately to prescribed high order. This paper considers (quasi-)Trefftz approximations for two-dimensional scalar electromagnetic problems. Established discretizations include the Flexible Local Approximation MEthod (FLAME), Trefftz elements ($T$-elements), and Trefftz discontinuous Galerkin (Trefftz-DG) methods. New developments are gradient-enriched FLAME (GEFLAME), conforming Trefftz–FLAME finite elements (TFF), and a full-field Bloch-wavevector-vs-frequency solution with Schur–DtN reduction. Applications cover electrostatics, scattering, singular fields, and Bloch waves in periodic structures. These methods make different compromises between conformity and flexibility. FLAME and GEFLAME incorporate Trefftz functions directly into local difference schemes; TFF uses elementwise FLAME schemes to lift
polynomial traces into element interiors; $T$-elements match elementwise Trefftz spaces weakly to such traces; and Trefftz-DG couples broken Trefftz spaces through fluxes and penalties. In the reported wave-scattering examples, GEFLAME gives field and gradient errors several orders of magnitude below those of the quadratic finite-element discretization at comparable algebraic cost. Localized singular-function enrichment removes the dominant reentrant-corner error. Conforming TFF and quasi-conforming $T$-elements admit standard finite-element assembly but expose
polynomial edge traces as an accuracy bottleneck. For periodic media, the bilinear Trefftz-DG formulation gives an analytic
polynomial wavenumber-vs-frequency eigenproblem without restricting the Bloch multiplier to the unit circle. Schur–DtN reduction yields compact boundary-response problems.
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Medical Physics
Whole Blood-Based Point-of-Care Assay for Single-Tier Lyme Disease Testing
Mihye Lee, Rajesh Ghosh, Artem Goncharov et al. (+10 more)
Rapid point-of-care diagnostics that operate directly on whole blood can accelerate clinical decision-making by bypassing complex sample preprocessing and centralized laboratory infrastructure. However, most serologic assays still require serum or
plasma, limiting near-patient deployment. This challenge is particularly evident for Lyme disease, whose diagnosis relies on centralized two-tier serology. Here, we present a whole-blood multiplexed vertical flow assay (WB-xVFA) that performs single-tier Lyme serology directly from 50 microliter of whole blood. The assay combines multilayer blood filtration with a peptide-patterned nitrocellulose membrane to separate cellular components and detect Lyme-associated IgM/IgG responses on a cartridge. Coupled with smartphone-based imaging and machine-learning analysis, the WB-xVFA provides results in 20 min. The assay remained robust across hematocrits up to 60% and sample volumes ranging from 25 to 100 microliter. In blinded testing of 62 whole-blood measurements, it achieved ~97% sensitivity and specificity, demonstrating the feasibility of rapid, near-patient whole-blood Lyme serology.
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All authors Mihye Lee, Rajesh Ghosh, Artem Goncharov, Rui-Chian Tang, Barath Palanisamy, Gyeo-Re Han, Adrian Anaya, Elizabeth J. Horn, Paul M. Arnaboldi, Raymond J. Dattwyler, Omai B. Garner, Aydogan Ozcan, Dino Di Carlo
Optics · Cross-listed from quant-ph
Transitions to super-radiance in ensembles of incoherently pumped emitters
Laszlo Rassaert and Tommaso Roscilde
Super-radiance is a striking phenomenon resulting from the collective interaction of emitters with light, and it is fundamentally related to the appearance of long-range correlations between the dipole moments of the emitters. As such, it represents a distinct phase of dissipative many-body systems compared to the case of independent emitters, similarly to how ferromagnetism stands out in
magnetic materials in contrast to paramagnetism. In this work we address the conditions under which the transition to super-radiance can occur in ensembles of emitters subject to dephasing and individual decay – a situation which is particularly relevant to the case of emitters in the solid state. The simplifying assumption of an ensemble of permutationally invariant emitters allows for the efficient solution of both the dissipative dynamics after a pulsed excitation, as well as of the steady state under incoherent pumping. This exact solution allows us to
benchmark a truncated cumulant expansion approach, which can give predictions for arbitrarily big system sizes. We show that super-radiance is fundamentally robust to sizable dephasing and non-radiative decay rates, both under a pulsed excitation, as well as under continuous pumping. This robustness is the result of the collective acceleration effect of super-radiant emission with respect to the individual coupling to a local environment. We establish the universal critical scaling laws at the transition between normal radiance and super-radiance; and we show that, in the super-radiant phase, significant finite-size crossovers can be observed before reaching the asymptotic scaling regime. Our results pave the way for future experiments to provide a quantitative characterization of the scaling properties of super-radiance, seen as a distinct non-
equilibrium many-body phase in ensembles of incoherently pumped emitters.
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Fluid Dynamics
The Geometry of Stochastic Fluid Dynamics
Darryl D. Holm
Stochastic geometric mechanics (SGM) is known for its potential utility in quantifying uncertainty in global
climate modelling of the Earth's ocean and atmosphere while also preserving the fundamental advective transport properties of ideal fluid flow. This paper is a pedagogical review of the recent developments of the mathematical framework of
stochastic geometric mechanics obtained from Lie group-invariant
stochastic variational principles in the context of model building for upper ocean dynamics, The paper is divided into the following five parts. Part I discusses the origins of
geometric mechanics applications in deterministic fluid dynamics. Part II focuses on the example of the deterministic 3D Euler Boussinesq (EB) equations. Part III adds
stochastic transport to the 3D Euler Boussinesq (EB) and derives its SALT equations. (SALT is the abbreviation of
Stochastic Advection by Lie Transport.) Part IV focuses on Lagrangian Averaged
Stochastic Lie Transport, abbreviated as LA-SALT. LA-SALT treats atmospheric `
climate' as the ensemble expectation, while the atmospheric `weather' is treated as a field of pathwise fluctuations, as discussed in Ed Lorenz's famous 1995 lecture. Part V applies SALT and LA-SALT to create
stochastic Ocean–Atmosphere Models, abbreviated as SOAM.. The SOAM approach brings us back to Hasselmann's 1976 paradigm, which decomposes a general
climate model into its deterministic and
stochastic parts.
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Data Analysis and Statistics
The geometry of uncertainty decomposition in profile-likelihood fits
Rafael Coelho Lopes de Sá
Uncertainty decompositions in profile-likelihood fits are commonly reported through nuisance-parameter impacts, although shifting a fitted parameter and fluctuating the observation that constrains it answer different questions. Recently, Pinto et al. provided an explicit construction for uncertainty decomposition based on fluctuating the observations and argued that such a construction allows for a cleaner interpretation of systematic uncertainties in terms of physical sources. We provide a
geometric description of the distinction between the two methods by using a coupled pair of fiber bundles. The geometrical approach clarifies the relationship between several methods traditionally used to estimate systematic uncertainties in high-energy physics. By describing the profiling as an information-orthogonal horizontal lift and the Schur complement as the induced metric on the parameter-of-interest
manifold, physical-source uncertainties arise by mapping observation fluctuations to score covectors, raising them with the inverse total information, and pushing the resulting
estimator covariance forward to the parameters of interest. This construction clarifies why nuisance-parameter impacts do not generally coincide with repeated-experiment source variances.
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Biological Physics · Cross-listed from cs.LG
Earth Observation Foundation Models for Terrestrial Ecohydrology: From Representation Learning to Process Inference
Yi Yu, Jian Peng, Yucheng Lin et al. (+2 more)
Earth observation foundation models (EOFMs) are emerging as reusable representation frameworks for data-driven
retrieval, prediction and process modelling within ecohydrology, which integrate EO, meteorological forcing and process models to characterise coupled water, energy and carbon dynamics in vegetation and soil across scales. However, there is yet to be an ecohydrology-specific synthesis assessing the EOFM relevance, application evidence or evaluation requirements under uncertain reference data, scale mismatch and temporal dependence. Here, we develop a framework for determining when EOFMs support interpretable inference and identify a mismatch between EOFMs and ecohydrological requirements. Firstly, an observation-to-inference hierarchy shows that relevance depends on target-specific sensing pathways, spatial-temporal support and traceable uncertainty. Secondly, a meta-analysis shows that pretraining is dominated by reflected optical and active-microwave data, with sparse thermal coverage and no passive-microwave-emission sources. Thirdly, our synthesis of ecohydrological applications finds strongest support for spatial context, label-efficient adaptation and hybrid workflows. Evidence declines with inference depth; independent validation of fluxes, coupled dynamics, event trajectories, calibrated uncertainty and decision benefits remains sparse. Fourthly, our
benchmark audit finds stronger coverage of fair adaptation and reproducibility in general EOFM suites, and of process targets, direct reference evidence and distribution shifts in ecohydrological evaluations; physical consistency and uncertainty remain weakly assessed. These findings motivate a process-aware framework aligning EOFM design and evaluation with the target variable, observation pathway and process timescale, supporting trustworthy monitoring and interpretation of coupled water, energy and carbon dynamics.
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All authors Yi Yu, Jian Peng, Yucheng Lin, Trevor F. Keenan, Thomas F. A. Bishop
Accelerator Physics
Relative and absolute dosimetric commissioning of the ELIMAIA–ELIMED laser-driven proton beamline at 23.4 MeV
G.A.P. Cirrone, G. Petringa, A. Kurmanova et al. (+12 more)
The development of
laser-driven
proton beamlines for biomedical and radiobiological applications requires traceable dosimetry and reliable online monitoring at the irradiation point. In this work, we report the relative and absolute dosimetric commissioning of the ELIMAIA–ELIMED
laser-driven
proton beamline at ELI Beamlines using an energy-selected
proton beam with an average energy of about 24~MeV. Radiochromic-film measurements were used to characterize the transverse dose distribution, the depth–dose profile, and the
proton energy spectrum at the irradiation point. The reconstructed spectrum was centred at $23.45~\mathrm{MeV}$ with a FWHM of $2.60~\mathrm{MeV}$, while the transverse dose distribution showed an approximately $5.5~\mathrm{mm}$ field size with a millimetre-scale homogeneous region. The Faraday Cup was used as the absolute reference detector for dose to water determination and for cross-calibrating the Dual-Gap Ionization Chamber, which was operated as the primary online dose monitor. The Integrating Current
Transformer and Secondary Electron Monitor were evaluated as upstream relative beam monitors. An independent RCF–FC dose comparison performed over fifty consecutive shots yielded $30.45 \pm 3.5~\mathrm{cGy}$ from the FC and $36.46 \pm 1.8~\mathrm{cGy}$ from the EBT3 film. Dedicated G4ELIMED Monte Carlo simulations showed that the RCF positioned upstream of the FC perturbs the FC measurement through
proton losses outside the FC acceptance and through an increase in the effective beam area at the FC entrance. Applying the resulting correction factor, $C_{\mathrm{MC}}=1.109$, reduced the residual difference between the FC- and RCF-derived doses to about $7\%$. These results establish the dosimetric chain of the ELIMAIA–ELIMED beamline under the present low-fluence commissioning conditions and identify the operational limits of the online monitoring system.
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All authors G.A.P. Cirrone, G. Petringa, A. Kurmanova, R. Catalano, A. Amato, A. Pappalardo, M.G. Guarrera, F. Schillaci, P. Blaha, F. Grepl, M. Tryus, A. Velyhan, L. Giuffrida, D. Margarone, G. Cuttone
Plasma Physics
Yinjian Zhao, Zhongping Zhao, Zhe Liu et al. (+9 more)
AlgoPlasma is an open-source library in which core numerical
algorithms for
plasma modeling are implemented as modular, well-documented, and independently testable components. Rather than offering a complete simulation code, it allows researchers to select, adapt, and assemble the required components into application-specific workflows. The current release is centered on particle-based simulation, while AlgoPlasma is designed to encompass a broader range of approaches to
plasma modeling. It provides components for particle initialization and advancement, particle-grid coupling, field solution, collision modeling, neutral transport, selected continuity updates, probe signal analysis, and input/output, together with Message Passing Interface (MPI) exchange routines and selected Open Multi-Processing (OpenMP) kernels. Documentation links mathematical formulations to source implementations, interfaces, and usage, while verification and validation cases evaluate numerical accuracy and physical behavior. AlgoPlasma thus establishes a shared algorithmic foundation for
plasma modeling, transforming repeatedly reimplemented numerical methods into open, reusable, tested, and explainable components for research, verification, education, and collaborative development.
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All authors Yinjian Zhao, Zhongping Zhao, Zhe Liu, Baisheng Wang, Zilong Peng, Xin Luo, Lihuan Xie, Xi Chen, Zhijun Zhou, Kunpeng Zhong, Yingjie Chen, Changzheng Hu
Accelerator Physics
Towards Cavity-Based X-ray Free-Electron Lasers: Milestones and Challenges
Kai Li, Patrick Rauer, Nanshun Huang et al. (+1 more)
Cavity-based X-ray free-electron
lasers (CBXFELs) could advance X-ray science by delivering fully coherent radiation with high spectral brightness and enhanced pulse control, addressing the limitations of conventional self-amplified spontaneous emission paradigms. Recent experiments at the European XFEL have demonstrated spectral narrowing and proof-of-concept multi-pass amplification, marking the first experimental signature of the tightly coupled three-body interaction between relativistic electron beams, FEL gain dynamics, and high-finesse Bragg cavities. This review consolidates advances in CBXFEL theory built on this framework, global R$\&$D efforts, and outstanding technical challenges arising from the coupled system. CBXFELs support applications in X-ray spectroscopy,
quantum optics, and precision metrology. Future directions prioritize CBXFEL stabilization, X-ray comb generation, and applications in coherent
quantum control of
nuclear transitions.
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All authors Kai Li, Patrick Rauer, Nanshun Huang, Haixiao Deng
Geophysics · Cross-listed from hep-ex
Deep Earth imaging through neutrino and seismic tomography
Sanjib Kumar Agarwalla, Arjun Datta, Amol Dighe et al. (+2 more)
This article is a report on the Deep Earth
Neutrino + Seismic Imaging and
TomographY (DENSITY 2026) mini-workshop, held on 23–24 February 2026 in the Department of Earth and
Climate Science at the Indian Institute of Science Education and Research (IISER), Pune. The workshop was jointly organised by IISER Pune and the Institute of Physics (IOP), Bhubaneswar. Researchers from Earth Sciences and
Neutrino Physics participated in the workshop to explore multipronged approaches for studying the deep interior of the Earth. Since the participants came from diverse scientific disciplines (seismology, geochemistry, mineral physics, and
neutrino physics), the programme featured a series of overview talks introducing all participants to the basic concepts of each field and highlighting how these concepts may be applied to the study of the deep Earth.
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All authors Sanjib Kumar Agarwalla, Arjun Datta, Amol Dighe, Vinod Kumar Gaur, Anuj Kumar Upadhyay
Plasma Physics · Cross-listed from astro-ph.SR
A self-consistent solar coronal heating model by Alfvenic waves
Hidetaka Kuniyoshi and Richard J. Morton
Alfvenic waves are prevalent throughout the
solar atmosphere and are believed to play an essential role in coronal heating, classified as alternating current (AC) heating in contrast to direct current (DC) heating associated with quasi-static
magnetic field line braiding. The relative importance of AC versus DC heating depends on the details of the photospheric driver and on the configuration of the
magnetic field. Moreover, even if AC heating prevails, several wave dissipation mechanisms have been proposed, and which of them dominates remains unclear, as its efficiency depends on
plasma compressibility and density inhomogeneity. We address these issues by performing three-dimensional radiative magnetohydrodynamic (MHD) simulations of a coronal loop spanning from the upper convection zone to the corona, which self-consistently capture many relevant physical processes. We find that the corona is predominantly heated by AC heating, with Alfven wave
turbulence providing the primary contribution, accounting for at least 80% of the entire coronal heating in the present simulation. Our results strongly support the use of Alfven wave
turbulence-based models employed in space weather and
stellar activity research, such as the Alfven Wave
Solar Model (AWSoM) and the Magnetohydrodynamic
Algorithm outside a Sphere (MAS).
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Physics and Society · Cross-listed from q-fin.RM
Is the medium the message? Social disclosure channels and firm risk
Andreas G. F. Hoepner, Blerita Korca, Frank Schiemann et al. (+1 more)
Investors interpret social disclosures from a risk perspective, yet relevant information can reach them through channels that differ sharply in regulatory enforcement and materiality: SEC filings, sustainability reports, or financial reports. We analyse how social disclosure via each channel relates to idiosyncratic risk. Studying S&P 1,500 constituents, we distinguish between initiated and continued disclosure along the three disclosure channels. We find first-time disclosure of social issues via SEC filings is related to increased idiosyncratic firm risk, highlighting that unexpected information is published. Continuous disclosure of social issues is related to lower idiosyncratic risk for sustainability and financial reports, which is in line with the literature. The SEC filing effect is robust for downside idiosyncratic risk measures, the separation of social disclosure into human capital, product liabilities, and stakeholder engagement, and for propensity score matching. Our findings suggest that the risk impacts of sustainability disclosure depend on the newness of information and disclosure channels.
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All authors Andreas G. F. Hoepner, Blerita Korca, Frank Schiemann, Fabiola I. Schneider
Optics
Driven Time Crystal in Low-Symmetry ENZ Conductors
Mario G. Silveirinha
In recent years, epsilon-near-zero (ENZ) materials have attracted a great deal of
attention in nonlinear optics, as they combine field enhancement with strong, ultrafast nonlinearities. In particular, transparent conducting
oxides, such as ITO, have emerged as a promising class of materials and have been extensively exploited to achieve temporal optical responses varying on the femtosecond scale using an optical pump. Most of the solutions discussed so far in the literature rely on effective $\chi^{(3)}$ modulations, wherein the dominant material response is controlled by the envelope of the optical pump. Here, it is shown that low-
symmetry conductors can provide an interesting alternative to transparent conducting
oxides and a more natural implementation of time-crystalline behavior in optical systems with optical-cycle modulation. I demonstrate that ENZ confinement, combined with the strong anomalous-velocity nonlinearity of low-
symmetry conductors, enables a subwavelength nanoparticle to develop a time-crystalline response under optical pumping. For sufficiently strong pumping, this response can overcome dissipative losses and lead to parametric amplification. Furthermore, the pump can strongly tailor the scattering and extinction of a weak probe and, in extreme cases, render the extinction negative. In this regime, the driven nanoparticle effectively amplifies the probe beam.
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Computational Physics · Cross-listed from stat.ML
Identifying parameter couplings and uncertainties of mixed-noise stochastic systems via full-covariance Gaussian mixture network
Xiaolong Wang, Xiangwen Hao, Jing Feng et al. (+2 more)
Parameter identification of
stochastic dynamical systems driven by mixed noises is challenging due to intractable likelihood functions. We propose PENN-GMD, a parameter estimation neural network that maps partially observed trajectories to a Gaussian mixture distribution (GMD) over the system parameters. Unlike conventional uncertainty estimates, the GMD employs full covariance
matrices to explicitly reveal parameter couplings and multi-modal likelihood structures. The network is trained by minimizing the negative log-likelihood via a surjective parameterization that hard-encodes all GMD constraints, thereby approximating the true likelihood. We validate the method on five numerical examples with increasing complexity, including systems driven by fractional Gaussian and Lévy noises, oscillators with colored noise, coupled
neurons under different observability, and an aeroelastic airfoil with unidentifiable
stochastic disturbances. Results demonstrate that PENN-GMD accurately recovers likelihood distributions, captures parameter couplings, and naturally diagnoses non-identifiability through variance broadening or mode splitting. These capabilities establish PENN-GMD as a practical tool for uncertainty-aware parameter identification in complex
stochastic systems where conventional likelihood-based methods are infeasible.
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All authors Xiaolong Wang, Xiangwen Hao, Jing Feng, Yuanyuan Liu, Yong Xu
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe
Peng Kang, Wei Yin, Da Wan et al. (+9 more)
Moiré superlattices reshape
lattice dynamics without altering chemical composition, yet how
crystal anisotropy modifies this control remains unclear. We combine density-functional-theory (DFT)-calibrated
lattice-dynamical calculations with angle-matched untwisted controls to study puckered
bilayer SnSe across seven commensurate twist angles ($3.18^\circ$–$8.77^\circ$). At 300 K, twisting suppresses the band-path heat-capacity-weighted mean-square group velocity to 2.6–8.4% of the control values; the suppression spans a broad frequency range rather than a few soft branches. The velocity response crosses over between $4.78^\circ$ and $3.82^\circ$ into a regime where the relaxed stacking textures and frequency-resolved velocity profiles become self-similar, with the normalized mean-square velocity ratio spanning only 11.1% of its mean across the three smallest angles—a finite anisotropic crossover, not a singular-angle condition. Direct DFT–MACE force-constant agreement ($r=0.996$), uniform $4\times4\times1$ stability scans, and acoustic-sum-rule and path-density tests support the trend. The
equilibrium trend is defined by six structures after excluding one relaxation-sensitive case. These results extend
phonon twistronics to low-
symmetry layered materials and identify
crystal anisotropy as a key determinant of finite-angle
phonon crossover behavior.
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All authors Peng Kang, Wei Yin, Da Wan, Shulin Bai, Sirui Fan, Qi Zou, Hongfeng Li, Xiao Xiang, Zhen Li, Yu Liu, Lei Zheng, Li-Dong Zhao
Computational Physics
Plasolver: Physics-Informed Neural Operators for Elastoplasticity
Yizheng Wang, Mohammad Sadegh Eshaghi, Huadong Zhang et al. (+3 more)
Elastoplastic analysis is computationally demanding because its nonlinear, path-dependent constitutive behavior requires incremental loading and repeated iterative solutions. To address this challenge, we propose Plasolver, a physics-informed neural operator framework that combines the efficiency of operator learning with the accuracy and robustness of classical numerical solvers. Plasolver consists of a physics-informed pretraining stage and an optional warm-start stage. During pretraining, the neural operator is trained solely by minimizing the incremental potential energy of elastoplasticity formulated by Simo, without requiring any labeled solution data. It operates directly on unstructured point clouds by encoding spatial coordinates, loading histories, and material properties as unified point-wise
prompts. This formulation provides dual invariance to spatial and loading-path discretizations, enabling consistent predictions across different spatial resolutions and different numbers of increments representing the same loading trajectory. The pretrained Plasolver achieves relative errors on the order of 1% while providing approximately two orders of magnitude acceleration over conventional finite element simulations. In the warm-start stage, the pretrained prediction is supplied as the initial solution to a classical iterative solver, preserving its numerical accuracy, robustness, and convergence properties while substantially accelerating convergence. Numerical results show that Plasolver reduces the required number of iterations by approximately 50% compared with conventional zero-initialized solvers and converges to solutions at any prescribed tolerance. Plasolver thus provides an efficient, accurate, and discretization-invariant computational framework for nonlinear, path-dependent elastoplastic problems.
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All authors Yizheng Wang, Mohammad Sadegh Eshaghi, Huadong Zhang, Xiaoying Zhuang, Timon Rabczuk, Yinghua Liu
Optics
Robust inverse design of non-periodic Bloch surface wave sensors
Riccardo Bollati, Giovanni Pellegrini, Paolo Biagioni et al. (+1 more)
One-dimensional photonic
crystals supporting Bloch surface waves (BSWs) have emerged as highly sensitive platforms for label-free refractometric sensing. However, the practical performance of these sensors is limited by their vulnerability to fabrication-induced thickness variations. In this Letter, we address this challenge by introducing a robust inverse design framework based on multi-objective genetic optimization. This framework jointly maximizes intensity sensitivity and resilience against manufacturing errors, demonstrating that non-periodic multilayers achieve inherently superior sensitivity-robustness trade-offs, with a pronounced gain in device resilience over conventional periodic designs. By analyzing the optimized designs, we uncover an intrinsic compensation mechanism that physically governs the trade-off and effectively stabilizes the sensor response against structural perturbations. By unlocking the expanded design space of non-periodic multilayers, our optimization strategy paves the way for the practical realization of next-generation BSW sensors.
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All authors Riccardo Bollati, Giovanni Pellegrini, Paolo Biagioni, Jonathan Barolak
Atomic Physics · Cross-listed from quant-ph
Stochastic Liouville-transport theory of light-atom interaction noise in thermal atomic vapors
Shaoxin Yuan, Bin Wu, Mingyong Jing et al. (+11 more)
Atom-light interaction noise can limit thermal-vapor sensing. Existing theories often treat internal-state dynamics, finite-mode atomic motion, and
stochastic renewal separately, obscuring their coupled contributions to measured noise. We develop a general
stochastic Liouville-transport theory, tested against polarization-resolved resonant Cs D$_2$ spectra. Joint experiment-theory analysis identifies atom-light noise below approximately 100 kHz as transit-dominated. Ballistic motion through the finite Gaussian mode modulates both the coupling-weighted effective atom number and trajectory-dependent Rabi coupling, producing predominantly common-mode noise. Boundary renewal introduces atoms with independently sampled ground-state sublevels, generating differential population fluctuations with opposite effects on the circular channels. Under an applied longitudinal
magnetic field, experiment and theory show the same qualitative nonmonotonic change in common-mode suppression, supporting Zeeman redistribution of the channel responses. The framework can analyze noise in other thermal-atom sensors, including Rydberg-atom electric-field measurements.
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All authors Shaoxin Yuan, Bin Wu, Mingyong Jing, Chaoyang Hu, Yan Peng, Tingting Li, Xingya Li, Wenguang Yang, Junyao Xie, Zongkai Liu, Hao Zhang, Linjie Zhang, Liantuan Xiao, Suotang Jia