Physics and Society
Poverty Mapping: Data, Models and Applications
Suoyi Tan, Mengning Wang, Yixiu Kong et al. (+5 more)
Poverty mapping is increasingly important for monitoring Sustainable Development Goal 1 (SDG 1) of the United Nations 2030 Agenda, which aims to end poverty in all its forms everywhere. Yet timely and fine-resolution poverty estimation remains difficult because conventional census- and survey-based approaches are costly, infrequent, and often sparse precisely where deprivation is most severe. As poverty emerges from complex socioeconomic systems shaped by human mobility, social interactions, infrastructure, and economic activities, emerging computational methods and nontraditional data sources have created new opportunities for poverty estimation and mapping. At the intersection of statistical physics, complex systems science, and data science, these approaches enable poverty estimation at finer spatial and temporal resolutions. This review summarizes the main concepts of poverty and the principal frameworks used to measure it, and examines recent advances on poverty estimation and mapping using satellite imagery, mobile phone data, social media data, and multisource data fusion. The review also discusses persistent challenges related to representativeness, transferability across regions, interpretability, and uncertainty quantification. Finally, the review clarifies both the analytical promise and the practical limits of contemporary poverty mapping.
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All authors Suoyi Tan, Mengning Wang, Yixiu Kong, Huimin Bai, Jianguo Liu, Dirk Brockmann, Yicheng Zhang, Xin Lu
Data Analysis and Statistics
Discovery Sensitivity for a Counting Experiment with Background Uncertainty
Enzo Canonero and Glen Cowan
In Particle Physics, a search for a new signal process is often based on observing a Poisson-distributed number of events, whose mean contains contributions from background and, if it exists, the hypothesised signal. The discovery significance can be expressed as an equivalent number of standard deviations derived from the $p$-value of the background-only hypothesis. To characterise the experimental sensitivity, one may report the median, assuming a nominal signal strength, of the discovery significance. In this paper, approximate expressions for the median significance are derived both when the expected number of background events is known and when the background rate is uncertain but constrained by a Poisson control measurement. The formulae are based on a test statistic using the profile likelihood ratio, and the median significance is approximated using the Asimov data set. Higher-order asymptotic corrections, based on the Barndorff-Nielsen $r^\ast$ statistic, are incorporated for both the observed and expected discovery significance. The validity of the resulting expressions is compared with Monte Carlo results and with other formulae for expected significance often used in particle physics. The higher-order corrections are found to provide meaningful improvements at small event yields. The results are important for obtaining an accurate assessment of the sensitivity of a planned experiment and for the optimal choice of cuts that determine the expected numbers of signal and background events.
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Instrumentation and Detectors · Cross-listed from astro-ph.IM
Persistence characteristics of H4RG-15 detectors for ESO instruments
Elizabeth M. George, Domingo Alvarez Mendez, Nagaraja Naidu Bezawada et al. (+3 more)
As a part of the ESO Instrumentation Program, we already ordered 23 H4RG-15 (2.5 um cut-off) detectors for the instruments MOONS, MICADO, and HARMONI, with more of these detectors planned for future instruments on the ELT as well as possibly other ESO
telescopes. As part of our comprehensive detector testing program, we characterize detector persistence at different temperatures between 40 and 85 K, allowing the best-informed choice of operating temperature for the science focal planes. We report the characteristics of persistence as a function of temperature for the 5 MOONS detectors and 10 MICADO detectors that have already been tested between 2019 and 2025. These detectors show a rich variety of persistence behaviour that can be fit with a single persistence model with varying parameters. We produce persistence trap maps and a model for persistence decay for each device, allowing automatic pipeline correction of persistence and also simulation of persistence behaviour of individual detectors using the Pyxel detector simulator. Each detector was unique and had different optimal operation temperatures for reduced persistence. We therefore recommend implementing a flexible thermal interface in the instrument design phase allowing for the detector operating temperature to be optimized after the science detectors have been fully characterized.
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All authors Elizabeth M. George, Domingo Alvarez Mendez, Nagaraja Naidu Bezawada, Derek J. Ives, Mark Neeser, Benoit Serra
Computational Physics · Cross-listed from cond-mat.stat-mech
Entropy production of active matter systems as indicator for computing performance
Patrick Egenlauf, Hannes A. Kröninger, Arnulf Kung et al. (+2 more)
Physical systems can process information through their natural dynamics, offering alternatives to conventional digital computing. Reservoir computing offers a basic framework by using a nonlinear substrate to map inputs into rich dynamical states read out by a simple linear layer. Active matter substrates are striking examples; they continuously consume energy and produce
entropy. Theoretically,
entropy production (EP) can describe the irreversibility and distance from
equilibrium. But it remains unclear whether it can track computational capabilities. We address this conceptual gap by analyzing a driven swarm reservoir model. The system EP is computed from phase-space contraction and the bath EP from heat flow, separately, and put in direct association to prediction performance on a Lorenz-63 task. Via force parameter scans, we show that dynamical regimes with the strongest response to a driver as well as dissipation coincide with peak performance. Therein, the dynamical discrepancy between innate (minimal dissipation) and driven transferred heat (maximal dissipation) is sharpest. Generally, driver work and relative differences of driven and undriven EP closely mirror the performance landscape. The system EP, derived from a generalized Liouville-equation
estimator, and heat flow provide complementary diagnostics and metrics, which are most robust in the best-performing regime. These results extend prior expectations that dissipation matters for computation by identifying when and how it becomes predictive. They also relate inference power to innate dynamics, pointing to generic principles for physical computing and where EP offers a screening metric for reservoirs and other base substrates.
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All authors Patrick Egenlauf, Hannes A. Kröninger, Arnulf Kung, Mario U. Gaimann, Miriam Klopotek
Applied Physics
Impact of Structural Design on Magneto-Mechanical Resonators: The Case of a Jewel Bearing Variant
David Conrad, Jan-Philipp Scheel, Frauke H. Niebel et al. (+6 more)
Magneto-mechanical resonators (MMRs) are passive, wirelessly read sensors whose small size, miniaturizability, and low cost make them attractive for tracking and for sensing physical and chemical quantities. Their operation relies on a permanent-magnet rotor whose mechanical resonance encodes the sensing and tracking information. The bearing suspending this rotor is therefore decisive both for in-operation performance and for manufacturability. The original design suspends the rotor on a thin thread, which is nontrivial to assemble. This work investigates the impact of that structural design choice by introducing an alternative bearing in which the spherical rotor magnet rests in a cup-shaped industrial jewel. A dynamic model of this Jewel-MMR is derived, including the angle-dependent dry friction torque at the jewel contact. From it, a
geometric trade-off between friction torque and resilience against unwanted oscillation modes is identified. Since the conventional quality factor loses its meaning under dominant dry friction, a two-tiered framework is proposed that compares MMR variants by estimation precision at equal magnet size and natural frequency. Both variants are characterized at a fixed pose on a Helmholtz-coil detection platform. The Jewel-MMR is self-aligning, requires fewer adhesive bonds and
alignment steps, and the prototypes built here were assembled in less than half the time. Its response signal decays faster, so that under laboratory noise conditions the natural frequency and the orientation are recovered more precisely from the thread variant; these orientation figures quantify repeatability, not absolute accuracy. The jewel bearing, however, tolerates larger deflection angles and thus a stronger signal, which reverses this relation above a noise level determined in a simulation-based robustness analysis, indicating an advantage at reduced signal-to-noise ratio.
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All authors David Conrad, Jan-Philipp Scheel, Frauke H. Niebel, Hossein Shabanalinezhad, Nora Timm, Sarah Reiss, Fabian Mohn, Tobias Knopp, Matthias Graeser
Optics
Ascorbic acid mitigates oxidative structural degradation in bovine spermatozoa: a label-free quantitative phase microscopy study
Harpreet Kaur, Shubham Tiwari, Aman Kumar et al. (+3 more)
Oxidative stress is a key factor in low fertility outcomes during assisted reproduction technology (ART) and contributes to poor sperm quality. Conventional assessment relies on bright-field microscopy, which lacks the quantitative sensitivity to resolve subcellular structural and biophysical changes without exogenous contrast
agents, a requirement that can introduce cytotoxic effects and compromise
cell viability. This study uses QPM as a label-free, high-throughput method to demonstrate how ascorbic acid reduces the impact of oxidative structural degradation in Sahiwal bovine spermatozoa. To illustrate this pathology, severe oxidative stress was experimentally induced using hydrogen peroxide (H2O2), and two doses of ascorbic acid (1 mg/ml and 8 mg/ml) were tested to evaluate dose-dependent antioxidant recovery in structurally damaged sperm. QPM was used to quantify structural changes in key biophysical parameters, including dry mass, optical thickness, volume, surface area, sphericity, and surface area-to-volume ratio, as well as intracellular texture parameters. Under acute oxidative stress, bovine spermatozoa exhibited significant reductions in optical thickness and dry mass, alongside measurable changes in intracellular structural organization, collectively indicative of oxidative stress-induced morphological degradation. Co-treatment with ascorbic acid resulted in partial, dose-dependent structural preservation, with the 8 mg/ml formulation demonstrating statistically significant attenuation of these structural changes compared to the 1 mg/ml treatment group. These findings suggest that QPM-derived biophysical parameters may serve as promising, label-free structural indicators for characterizing oxidative damage in bovine spermatozoa. Future studies should incorporate functional validation to determine whether this structural preservation translates to improved outcomes in ART.
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All authors Harpreet Kaur, Shubham Tiwari, Aman Kumar, Sandeep Kumar Jha, Satish Kumar Dubey, Dalip Singh Mehta
Optics
Coating-free monolithic fused silica resonator via total internal reflection for precision laser stabilization
Swadha Pandey, Rodica Martin, Peter Fritschel et al. (+2 more)
Brownian noise in the thin-film mirror coatings of optical reference cavities is a fundamental limitation in precision metrology, including gravitational-wave detectors and optical atomic clocks. We demonstrate a monolithic fused silica resonator that eliminates the use of thin-film coatings by operating via total internal reflection (TIR), achieving a finesse of 1225 and an optical mode volume of \qty{50}{mm^3}. To our knowledge, this is the largest mode volume reported for any coating-free monolithic resonator, comparable to state-of-the-art reference cavities. We use the cavity to frequency-stabilize an Nd:YAG
laser, and demonstrate its application to precision metrology by operating it in a passive ring gyroscope configuration. This platform circumvents the dominant noise source of conventional reference cavities and provides a pathway toward cryogenic silicon TIR resonators that could surpass current frequency stabilization limits.
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All authors Swadha Pandey, Rodica Martin, Peter Fritschel, Matthew Evans, Evan D. Hall
Chemical Physics · Cross-listed from nucl-th
Revisiting the Equation-of-Motion Method: A Universal Framework for Correlated Quantum Systems
Andrea Porro
A general implementation of the equation-of-motion (EOM) formalism for correlated many-body states is presented and applied to the description of collective excitations in atomic
nuclei. While EOM approaches are traditionally formulated on top of independent-particle reference states, the present work extends the method to correlated reference states generated by modern many-body solvers. This formulation enables a consistent treatment of ground-state correlations and excited-state dynamics within a unified framework. Particular emphasis is placed on collective
nuclear excitations employing
chiral nuclear Hamiltonians in an ab initio context. The approach is motivated by the renewed interest in EOM techniques across several fields, including
quantum chemistry and
quantum computing, where they provide efficient and systematically improvable descriptions of excitation spectra. The present results demonstrate that the EOM framework offers a flexible and powerful tool for the microscopic description of
nuclear spectroscopy beyond the traditional mean-field paradigm.
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Physics Education
Students' Epistemological Beliefs and their Chatbot Preferences in AI-mediated Physics Learning
Amogh Sirnoorkar and Omkar Mamidpalliwar
Evolving technologies have traditionally influenced pedagogical practices and Generative AI is one such technology that promises to transform higher education. In this study, we investigate the association between introductory students' preferences for chatbot behavior and their epistemological beliefs surrounding physics. Our context involves a custom built online module on waves containing simulations integrated with a chatbot. While students' chatbot preferences were captured through three provided options (guided-inquiry, direct answer, and a combination of inquiry and answer), their epistemological beliefs were captured through the standardized Epistemological Beliefs Assessment for Physical Sciences (EBAPS) survey. Results highlight that students who preferred chatbots that initially engage them in guided-inquiry but provide answers when explicitly sought (`Combination'), demonstrated sophisticated epistemological beliefs than those who preferred answer-providing chatbots. Notably, we did not observe any association between the EBAPS' total scores among students who preferred guided-inquiry and those who preferred answer-oriented chatbots. Furthermore, the observed differences did not remain statistically significant after applying a Bonferroni-adjusted significance level. Implications of these results for the design and instructional use of chatbots in physics education are discussed.
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Geophysics
On four representations of the law of aftershock evolution
A.V. Guglielmi and O.D. Zotov
The relaxation of the earthquake source following the main shock has been investigated both theoretically and experimentally, based on data regarding the
evolution of aftershocks. It is shown that Omori picture of aftershock
evolution is not holistic, whereas the Hirano-Utsu representation contradicts observations. Linear and discrete representations are proposed. They are based on original concepts regarding deactivation and the proper time of the source. The difference between the linear and discrete representations lies in the procedure for processing experimental data on aftershocks. In the linear representation, proper time is calculated based on the frequency of aftershocks. In a discrete representation, the source's proper time is measured by an imaginary underground clock, the rate of which differs radically from that of universal time. In the linear representation, the frequency of aftershocks is described by the simplest nonlinear differential equation. In the discrete representation, the aftershock frequency is described by a first-order linear differential equation. It has been found that aftershock activity decays exponentially with the source's proper time. Keywords: earthquake source, foreshocks, mainshock, aftershock theory, Omori law, Utsu's law, proper time, underground clock, deactivation coefficient, source relaxation.
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Optics
Near single-cycle pulse generation using a cascaded all-bulk multi-pass cell compression system
Saga Westerberg, Gaspard Beaufort, Sara Rushe Palacios et al. (+5 more)
We experimentally demonstrate the generation of sub-two-cycle optical pulses using a cascaded post-compression scheme based on two bulk multi-pass
cells. Starting from 220 fs, 100 ${\mu}$J pulses around 1030 nm, sequential spectral broadening and pulse compression reduce the pulse duration first to 50 fs and ultimately to 5.5 fs (1.6 optical cycles) at a central wavelength of 1058 nm. The ultra-broadband spectrum is enabled by a dispersion-controlled cavity. Comprehensive spectral, temporal, and spatial characterization confirms excellent pulse quality. Despite operating the second multi-pass
cell at peak powers several hundred times above the critical power for self-focusing in fused silica, no significant spatio-spectral or spatio-temporal distortions are observed, enabling direct use of the compressed 40 ${\mu}$J pulses in further experiments. Numerical simulations of the nonlinear spectral broadening show excellent agreement with the experimental results, supporting the underlying physical picture. These findings establish bulk multi-pass
cells as an efficient, compact, and robust platform for generating few-cycle pulses with excellent beam quality, offering considerable potential for strong-field and ultrafast applications, including extreme-ultraviolet generation and isolated attosecond pulse production.
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All authors Saga Westerberg, Gaspard Beaufort, Sara Rushe Palacios, Melvin Redon, Chen Guo, Miguel Miranda, Cord L. Arnold, Anne-Lise Viotti
Plasma Physics
A Neural Operator Closure for Landau Damping in Electrostatic Plasma
Samuel Burles, Enrico Camporeale and Oreste Pezzi
We present a data-driven
plasma fluid closure for both linear and nonlinear electrostatic Landau damping in one dimension. A
Fourier Neural Operator (FNO) is trained online within a differentiable fluid solver, with the loss computed on trajectories produced by the closed fluid simulation rather than on individual kinetic snapshots. The closure is non-Markovian, acting on a trailing window of the resolved moment history so as to represent the
memory of the unresolved dynamics. We demonstrate that a single FNO trained in this way reproduces both linear and nonlinear Landau damping, generalises to initial perturbation amplitudes outside the training set, and remains numerically stable when deployed in independent fluid simulations. In the nonlinear regime the learned heat flux reproduces the resolved-moment dynamics without matching the kinetic heat flux pointwise, behaving as an effective closure that compensates for the truncated higher moments, though the learned specific flux is expected to depend on the numerical scheme and training data. A sensitivity analysis of the trained model shows that it computes a genuine moment-to-flux relation whose reliance on the
memory window is physically structured.
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Plasma Physics
Nonlinear polarization effects on plasma screening for fusion reactions
Hanxiang Huang, Binbing Wu, Zhengfeng Fan et al. (+3 more)
Using a finite-temperature two-center Thomas-
Fermi-Dirac model, we investigate nonlinear
plasma screening effects on the fusion reactions D-T, $^{12}$C-$^{12}$C, and p-$^{11}$B. The effective interaction between a reacting ion pair is obtained self-consistently at the mean-field level. Combining this potential with a complex Woods-Saxon
nuclear potential, we solve the stationary Schrödinger equation to evaluate tunneling probabilities and reaction rates. Compared with Debye-Hückel theory, the two-center screening potential can be stronger or weaker, and the resulting fusion enhancement correspondingly amplified or suppressed, depending on the
plasma conditions and the internuclear separation. We identify the underlying mechanisms: relative to the single-center prediction, the nonlinear evacuation of background ions suppresses screening, whereas nonlinear electron accumulation enhances it. The two channels respond to different
plasma state parameters: the ionic suppression deepens with increasing coupling strength, whereas the electronic enhancement peaks at intermediate degeneracy. The two-center correction therefore follows a factorized scaling law in the
nuclear charges of the reacting pair and the
plasma state parameters. These findings highlight the importance of a self-consistent two-center treatment for determining effective interactions and evaluating static screening corrections to fusion reaction rates.
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All authors Hanxiang Huang, Binbing Wu, Zhengfeng Fan, Congzhang Gao, Jie Liu, Baisong Xie
Chemical Physics
Approaching Coupled Cluster Accuracy with Positive Semidefinite Vertex Corrected Self-Energies
Yaroslav Pavlyukh, Fabien Bruneval and Arno Förster
Hedin's formalism of functional derivatives is the best-known method for systematically constructing correlated electronic theories, largely due to the success of its lowest-order self-energy expansion, the $GW$ approximation. Beyond $GW$, diagrammatic resummation schemes attempt to mix correlations simultaneously across all particle-particle and particle-hole channels. Because such a comprehensive treatment is computationally prohibitive for realistic molecular systems, a highly effective alternative is to fully account for electronic correlations in one specific channel, typically the particle-hole channel. This idea was recently implemented for molecular systems [1], yielding a self-energy expressed in terms of excited-state energies and transition amplitudes from the solution of the Bethe-Salpeter equation, rather than the random phase approximation used in $GW$. While this approach is predictive and numerically efficient, it violates the fundamental positive-definiteness constraint of the electron spectral function in certain energy ranges. In this study, we resolve this physical flaw by deriving a positive semidefinite (PSD) extension of the theory using a rigorous framework based on the nonequilibrium Green's function formalism. The PSD constraint introduces new scattering channels and triplet intermediate states and restores the correct physical behavior. We demonstrate that it consistently improves quasiparticle energies across standard molecular
benchmarks, with an accuracy comparable to coupled-cluster reference calculations.
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Optics
A Group-Theoretical Framework for Local k-Space Topology and Berry Phase in 2D Photonic Systems
Xinyi Yuan and Grazia Salerno
Two-dimensional photonic
crystals (2D PhCs) enable fine-grained control over a broad set of Bloch modes without the constraints of band occupancy and natural
crystal structures, and, as intrinsically open systems, serve as versatile platforms for exploring diverse topological phenomena. Here, we develop a theoretical framework inspired by the irreducible-representation formalism in solid-state physics, while explicitly incorporating key characteristics of photonic Bloch systems, such as radiative coupling and transverse condition. Within this framework, we study the
symmetry origins of local k-space
topology, e.g., bound-states in the continuum and optical
vortex beams, and Berry phase in two representative systems. We further analyze, from a group-theory perspective, how tailored structural designs and targeted
symmetry perturbations can be exploited to manipulate these topological features. In particular, we showcase the application of the formalism to Bloch modes from distinct truncation approaches and specify the preferable regimes for each, both under a generic $n$-band configuration. The analysis can thereby be readily extended to a wide range of artificial wave
crystals beyond scalar Schrödinger-like operators and two-level treatment.
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Optics
Electronic Damage Suppression in X-ray Diffraction with Attosecond X-ray Pulses
Vladimir Lipp, Ichiro Inoue and Beata Ziaja
So far, the focus of state-of-the-art structure determination using x-ray free-electron
laser (XFEL) pulses has been on macromolecular crystallography. This approach has achieved remarkable success in solving the structure of microcrystals smaller than a few micrometres, which are difficult to investigate using conventional synchrotron sources. However, successful applications of XFELs to inorganic and small-molecule crystallography have been limited due to rapid electron excitation in these samples. This same issue has also prevented the use of XFELs in charge-density studies of solids. In this study, we propose using hard x-ray pulses with an attosecond duration for x-ray imaging of charge density in organic and inorganic systems. Simulations of irradiated diamond and silicon showed that attosecond x-ray pulses consistently reduce the electronic excitation for a fixed
photon energy and pulse fluence. Further reduction of transient electronic damage can be achieved by increasing the x-ray
photon energy under these conditions. These theoretical predictions demonstrate a powerful and well-founded strategy for visualizing valence-electron distribution, opening up new prospects for diffraction imaging studies with XFELs.
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Applied Physics
Mode-dependent photothermal responsivity mapping of tensile-stressed nanomechanical resonators
Thomas M. Tropper and Silvan Schmid
The photothermal responsivity of a tensioned nanomechanical resonator, the fractional frequency shift per absorbed optical power, depends on which vibrational mode is tracked and where the heat is deposited. We derive a closed-form model of this dependence for square membranes by treating the membrane as a grid of independent tensile fibers, each responding to its mean temperature. The responsivity map splits into a mode-independent conduction envelope and a mode term that peaks on the antinodal rows and columns of the mode, not at the antinodes, because fibers rather than points carry the modal strain energy. Scanning photothermal measurements of the $(1,1)$, $(1,2)$, $(2,1)$, and $(2,2)$ modes of a square silicon nitride membrane confirm the predicted maps with a correlation $r \geq 0.998$, with the envelope amplitude as the only fitted parameter. On trampoline resonators, the tether-limited thermal conductance flattens the envelope, making the mode term directly visible in raw scans. The measured mode-resolved maps provide the design input for dual-mode photothermal sensing with common-mode drift suppression, identifying pairs, such as a membrane's $(1,1)$/$(2,2)$ or a trampoline's torsional modes, as candidates that combine large differential responsivity with a shared thermal and mechanical environment.
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Optics · Cross-listed from astro-ph.IM
Information limits of photonic lantern wavefront sensing: a Fisher- and quantum-Fisher-information framework and its relation to Fourier-filtering sensitivity limits
Kalaga Madhav
The photonic lantern is an all-photonic wavefront sensor native to single-mode-fibre-fed instruments, but its performance is almost always quoted through a specific reconstruction
algorithm, obscuring how much wavefront information the device itself encodes. We develop, from first principles, the Fisher-information and Cramer-Rao theory of the photonic-lantern wavefront sensor,
benchmark it against the
quantum Cramer-Rao bound via an explicit multi-parameter
quantum-Fisher-information calculation, and relate it to two established frameworks: the
Fourier-filtering noise-propagation model of Chambouleyron et al (2023) and the classical/
quantum sensitivity limit of Haffert et al (2023). Treating the lantern as a deterministic map from aberration coefficients to N output intensities, we derive the Poisson and read-noise Fisher information
matrices (FIM), the per-mode CRLB, the per-
photon Fisher-Rao geometry on the intensity simplex, and a flux- and
estimator-independent sensitivity metric beta with
quantum ceiling beta = 2. The lantern CRLB scales as N_ph^(-1/2) and is bounded, mode by mode, by the
quantum limit of 1/2 rad rms per
photon. That multi-parameter bound is jointly saturable: the phase generators are real and commuting, so the mean Uhlmann
curvature vanishes and wavefront sensing carries no
quantum incompatibility between simultaneously estimated modes, extending Haffert et al's single-mode ceiling to all low-order modes at once. We further show that the
photon-noise sensitivity s_gamma of Chambouleyron et al is exactly the diagonal of our per-
photon FIM, whereas the CRLB uses the diagonal of its inverse; the two coincide only for a diagonal FIM, so s_gamma is optimistic for a mode-mixing lantern. The framework is device-agnostic: it returns
estimator-independent sensitivities comparable on a common beta <= 2 scale with pyramid, Zernike and PIAA-ZWFS sensors.
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Optics
Observation of Antichiral Hinge States in a Three-dimensional Gyromagnetic Photonic Crystal
Ziyao Wang, Tianzhi Xia, Han-Rong Xia et al. (+1 more)
Recent advances in topological physics have revealed a counterintuitive class of antichiral edge and surface states that propagate in the same direction along spatially separated parallel boundaries. To date, however, experimental realizations of antichiral states have been restricted to first-order topological phases, while their higher-order counterparts–antichiral hinge states–have remained experimentally elusive. Here, we report the first experimental observation of antichiral hinge states in a gyromagnetic photonic
crystal that realizes a three-dimensional (3D) modified Haldane model with dimerized interlayer coupling. Through microwave near-field mapping, we directly resolve their defining signatures: nonreciprocal, co-propagating transport along four parallel hinges and characteristically tilted hinge-state dispersions. These results extend antichiral
topology into the higher-order regime and provide a new platform for 3D nonreciprocal topological photonic devices.
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All authors Ziyao Wang, Tianzhi Xia, Han-Rong Xia, Zhen Gao
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Savi-Bhransha: Graph-Theoretic Dislocation-Loop Characterization in Crystals
Utkarsh Bhardwaj
Dislocation loops govern the properties of crystalline materials, but extracting their detailed characteristics from atomistic simulations is difficult when loops are fragmented or embedded in compact defect debris. We present Savi-Bhransha, a graph-theoretic method that reconstructs interstitial and vacancy loops directly from local defect-displacement motifs, without constructing a global interface mesh. The method identifies Burgers-vector family, habit plane, loop size, segment-wise edge/screw character, and boundary and bulk defect populations for BCC, FCC, and HCP
crystals. We apply it to single-cascade simulations over a range of energies in BCC W and HCP Zr, and to successive collision cascades in BCC W and FCC FeNiCr. We
benchmark the method against the Dislocation Extraction
Algorithm (DXA). Total dislocation lengths remain strongly correlated between the two methods, while Savi-Bhransha returns more stable loop-level objects in complex environments where DXA returns fragmented, overlapping open segments. Savi-Bhransha also better resolves mixed-morphology defects and dislocations near other defects, including vacancy clusters. Median runtime speedups are 6.34x for BCC W and 8.86x for HCP Zr, with peak-
memory reductions up to 7.77x. In successive W cascades, the resolved boundary-defect concentration brackets transient-grating-spectroscopy measurements and the predicted Burgers-vector fraction agrees with room-temperature TEM. In FCC FeNiCr, the method resolves Heidenreich-Shockley dissociation, with a Shockley-pair signature in about 91% of surviving <110>-family interstitial clusters. Savi-Bhransha therefore enables efficient,
topology-resolved analysis of large radiation-damage simulations and direct comparison with experimentally accessible observables.
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Plasma Physics
Comparative analysis of wavenumber response in phase contrast and spiral phase imaging systems for plasma diagnostics
Jigme Zangpo, Hirokazu Kobayashi, Haruki Kawaguchi et al. (+1 more)
Phase contrast imaging (PCI) has been used for decades to study
plasma density fluctuations, but its wavenumber response $k$ is constrained by the phase plate groove width and beam waist. Spiral phase contrast imaging (SPCI) with a spiral phase plate may offer broader sensitivity, even though its output signal is quadratic, because it has no constraint except at the central singularity, i.e., $k = 0$. In this work, we numerically compare the wavenumber response of both techniques using two distinct models: (i) static square phase objects with scale lengths $R$ ranging from 5 to 25 mm, and (ii) a time-evolving, anisotropic, multi-scale
turbulence field with a Kolmogorov-like spectrum. For static square objects, PCI exhibits a lower cutoff at $k_{\text{min}} \approx 0.1$ mm$^{-1}$, while SPCI produces measurable signals down to $k_{\text{min}} \approx 0.007$ mm$^{-1}$ via the autocorrelation of the gradient spectrum. For the
plasma-like
turbulence model, PCI retains its lower cutoff at $k \approx 0.1$ mm$^{-1}$. In contrast, SPCI produces measurable signals down to $k \approx 0.007$ mm$^{-1}$. These results suggest that SPCI provides low-wavenumber information below the PCI cutoff, offering complementary diagnostic information for multi-scale
plasma turbulence studies.
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All authors Jigme Zangpo, Hirokazu Kobayashi, Haruki Kawaguchi, Ryo Yasuhara
Fluid Dynamics · Cross-listed from math.AP
Local Well-Posedness for a Diffuse Interface Model for Two-Phase Flows from Mixture Theory
Helmut Abels, Harald Garcke and Julia Wittmann
Local-in-time well-posedness is established for a recently proposed diffuse interface model describing incompressible two-phase flows. The result constitutes the first analytical study of a model introduced by ten Eikelder et al. for the motion of a binary mixture of macroscopically immiscible, viscous, incompressible fluids with unmatched densities. In contrast to classic diffuse interface models based on a single mean velocity, this model is derived within the framework of mixture theory, assigning each phase its own momentum and mass balance, which results in a system of two coupled Navier–Stokes equations and two mass transport equations. The proof of the well-posedness result uses a fixed-point strategy, where the main difficulty lies in the analysis of the principal part of the associated linearized system.
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Optics · Cross-listed from cond-mat.mes-hall
Emergence of Propagating Exciton-Polaritons in Hybrid Waveguide-van der Waals Heterostructures
Alina Schubert, Karoline Becker, Andreas Thies et al. (+7 more)
Integrating few-layer materials into photonic
circuits is a promising concept for novel on-chip photonic applications. We incorporate transition metal dichalcogenides (TMDs) with femtosecond-
laser-written surface waveguides, which are embedded in fused silica chips. Our novel low-temperature optical spectroscopy setup enables coupling to the waveguide and simultaneous focus from the top to the TMD layer for a distinct excitation and collection of micro-photoluminescence ($\mu$PL) signals in several measurement geometries. Along these lines, we observe spectral changes of the A
exciton for encapsulated TMD monolayers when capturing the $\mu$PL signal propagating through the waveguide. Depending on the thickness of the encapsulation with hexagonal boron nitride (hBN), these changes manifest as energetic
redshifts of the A
exciton, or even a splitting of the A
exciton into two components. We attribute this behavior to strong coupling of the waveguide mode and the
exciton in the sample, giving rise to the formation of propagating
exciton-polaritons. Our interpretation is supported by calculations for a simplified model of a slab waveguide in the vicinity of an
exciton by using the transfer
matrix method. Having proven to be a highly adaptable framework for the study of propagating polaritons, our experimental platform likewise holds great promise for harnessing the unique properties of
exciton-polaristons in integrated photonic
circuits.
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All authors Alina Schubert, Karoline Becker, Andreas Thies, Rico Schwartz, Takashi Taniguchi, Kenji Watanabe, Henije Stolz, Alexander Szameit, Matthias Heinrich, Tobias Korn
Classical Physics
Revisiting Stress Analysis in a Three-Dimensional Elastic Hollow Sphere under Uniaxial Compression via the Inverse Laplace Transform Expressions within an Elastodynamic Framework
Satoshi Takada and Shintaro Hokada
The stress analysis of a three-dimensional elastic hollow sphere subjected to uniaxial compression is revisited, employing an elastodynamic framework. Through the application of the Laplace transform, the scalar and vector potentials of displacement are expanded, facilitating a detailed exploration of the system's mechanical behavior. The static solutions for displacement and stress distributions are derived in the long-time limit, which reveal key insights into the response of the elastic hollow sphere. Notably, on the inner surface, certain quantities exhibit a peak at the point where the angle between the compressive force and the point on the surface becomes perpendicular, indicating localized stress concentration. These findings provide a robust analytical approach for understanding and predicting the behavior of elastic hollow spheres under uniaxial loading, with implications for material science and structural engineering.
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Atmospheric and Oceanic Physics · Cross-listed from astro-ph.SR
Turbulent Convection: Modal Equations and Energy Pathways
S. Sridhar and Nishant K. Singh
We present a framework for studying high Rayleigh number turbulent convection to better understand
stellar and planetary convection zones. Utilizing the statistical
symmetries of the fully developed turbulent state of Boussinesq convection, we identify relevant mean and fluctuating quantities. After validating these
symmetry assumptions through numerical simulations, we formulate the governing equations. Vertical profiles of key physical quantities in the saturated turbulent state are explored in the simulations. To develop a modal theory, we use
Fourier expansions, review linear theory, and use the Craya-Herring velocity decomposition. The modal equations we derive describe high Rayleigh-number turbulent convection dynamics self-consistently in terms of nonlinear interactions between three mode types: growing
gravity modes, decaying
gravity modes, and horizontal modes. Energy extracted by the growing modes from the superadiabatic background subsequently follows multiple pathways toward dissipation, enabled by the mode couplings. Among these, the traditionally dominant pathway is the turbulent cascade of the growing modes themselves. Reduced modal equations capture this pathway, precisely describing (i) mutual interactions between growing modes, and (ii) the excitation of decaying and horizontal modes, which are subordinate to the growing modes. Determining the relative efficiency of the pathways requires investigating their modal spectra using numerical simulations and kinetic models.
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Space Physics · Cross-listed from astro-ph.IM
The CUSP CubeSat mission for space weather multi-physics analysis, design, and testing
Giovanni Lombardi, Riccardo Di Spirito, Sergio Fabiani et al. (+48 more)
The CUbesat
Solar Polarimeter (CUSP) mission aims to measure the linear polarization of
solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. We present the outcomes of the CUSP's Phase B study, which is ended on 2 July 2026. The design solutions adopted for the mission's most critical multi-physics design drivers will be discussed, these solutions have been formulated and applied to demonstrate compliance with system requirements at both the spacecraft and platform levels. Moreover, we will discuss the validation of the Payload model based on the environmental testing campaign (e.g., vibration) carried out on a demonstrator.
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All authors Giovanni Lombardi, Riccardo Di Spirito, Sergio Fabiani, Daniele Censi, Giovanni De Cesare, Ettore Del Monte, Riccardo Campana, Enrico Costa, Mauro Centrone, Nicolas De Angelis, Sergio Di Cosimo, Giuseppe Di Persio, Abhay Kumar, Pasqualino Loffredo, Gabriele Minervini, Fabio Muleri, Paolo Romano, Alda Rubini, Emanuele Scalise, Paolo Soffitta, Andrea Alimenti, Enrico Silva, Bruna Bertucci, Giovanni Ambrosi, Giovanni Cucinella, Vito Di Bari, Simone Di Filippo, Andrea Negri, Massimo Perelli, Dario Modenini, Andrea Curatolo, Nicolas Gagliardi, Daniele Pecorella, Alice Ponti, Paolo Tortora, Andrea Del Re, Davide Albanesi, Valerio Campamaggiore, Giulia De Iulis, Adam Ebrahim, Marco Schepis, Alessandro Zambardi, Ilaria Baffo, Pierluigi Fanelli, Costantino Zazza, Valerio Vagelli, Daniele Brienza, Immacolata Donnarumma, Matteo Mergè, Emanuele Zaccagnino, Alessandro Turchi
Fluid Dynamics · Cross-listed from cond-mat.soft
Phoretic flow in a three-dimensional wedge geometry
Abdallah Daddi-Moussa-Ider, Semyon Yakubovich and Maciej Lisicki
Understanding how chemically induced surface transport generates fluid motion in confined geometries is essential for the rational design of microscale pumping devices and active microfluidic systems. Here we develop a theoretical framework for chemically driven phoretic flows in a three-dimensional wedge geometry in the
diffusion-dominated regime. We formulate both the
diffusion and hydrodynamic problems using a
Fourier-Kontorovich-Lebedev spectral representation, exploiting the translational invariance and radial structure of the wedge. Green's functions for the concentration field are derived for reflecting and mixed reflecting-absorbing boundaries, reducing to finite image-like sums or closed-form expressions for commensurate wedge angles. The resulting slip velocity is then used to construct the three-dimensional Stokes flow through the Papkovich-Neuber representation, yielding explicit spectral solutions for the velocity field. These results establish a Green's-function framework for phoretic pumping in wedge-shaped confinement and provide analytical
benchmarks for numerical simulations of chemically driven transport in confined microfluidic systems.
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Fluid Dynamics
A note on the lower boundary condition for Ekman flows
Christian Puntini and Luigi Roberti
We show that the assumption of a stress-free boundary condition at a finite intermediate depth, namely, at the bottom of the Ekman layer, in the analysis of wind-driven ocean flows necessarily leads to an unphysical current profile. Indeed, if the $z$-derivative of the fluid velocity vanishes at a given depth, then this depth necessarily corresponds to a minimum of the velocity profile, with the velocity increasing beneath it. Using a WKB ansatz based on the small variations of the ocean's water density at great depths, we also argue that a no-slip condition at the bottom of the ocean, if sufficiently deep, still effectively implies (up to a very small error) the orthogonality of the Ekman transport and the wind-stress.
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Fluid Dynamics
Nonlinear asymptotic bubble growth in single-mode spherical Rayleigh-Taylor instability
De-Hua Zhang, Shi-Heng Wang, Ke-Jian Qian et al. (+3 more)
We present an analytical model for the nonlinear growth of a single-mode Rayleigh-Taylor instability (RTI) bubble in spherical geometry. The model captures the bubble growth along the polar axis, spanning the linear to nonlinear regimes, for arbitrary Atwood numbers and under both converging- and diverging-
gravity configurations. The model predicts that the bubble acceleration approaches an asymptotic value in the nonlinear stage. The spherical geometry is found to enhance the RTI bubble growth relative to planar and cylindrical configurations with the same effective perturbation wavenumber in the converging-
gravity cases, whereas it mitigates the bubble growth in the diverging-
gravity cases. The model predictions show favorable agreement with direct numerical simulations.
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All authors De-Hua Zhang, Shi-Heng Wang, Ke-Jian Qian, Zhu-Jun Li, Rui Yan, Hang Ding
Applied Physics
Integrated tunable magnonic devices for beyond 6 GHz signal processing
Maria Cocconcelli, Antonio Angotti, Federico Maspero et al. (+2 more)
In the search for novel technology platforms supporting the transition towards ”beyond 6G” telecommunications, magnonics is emerging as a viable route, primarily due to its intrinsic compatibility with the UWB-FR3 bands and its easy tunability. In this paper, we present a proof-of-concept device based on a CoFeB magnonic waveguide, fully integrated on silicon, which demonstrates all the key features of our integration approach, based on co-integrated hard
magnetic micromagnets, magnonic conduits, reconfigurable soft
magnetic elements and MEMS. The bias field enabling operation up to about 12 GHz is provided by SmCo micromagnets embedded in the silicon substrate. Real-time tunability is implemented in two ways. First, current-driven control is achieved via an integrated current line that generates an additional localized
magnetic field, enabling continuous tuning of Backward Volume
spin-wave propagation. Second, we achieve voltage-controlled tunability by integrating a NiFeMo soft
magnetic element onto a piezoelectric MEMS cantilever and flip-chipping it onto the magnonic device. Upon actuation, the cantilever brings the NiFeMo into proximity with the permanent micromagnets, where it captures the stray field. The resulting voltage-controlled displacement modulates the coupling between the hard and soft
magnetic components, effectively reducing the local bias field on the CoFeB waveguide and enabling fine control of Damon–Eshbach
spin waves.
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All authors Maria Cocconcelli, Antonio Angotti, Federico Maspero, Andrea Cattoni, Riccardo Bertacco