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Saturday 15 August

Data Analysis and Statistics

The geometry of uncertainty decomposition in profile-likelihood fits

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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Mesoscale and Nanoscale Physics

Field-Gated Programming of Nested Skyrmion Bags by Spatially Selective Skyrmion Writing

Nested skyrmion bags are composite magnetic solitons whose internal occupation numbers provide an expanded state space for multilevel information encoding. However, deterministic and region-selective writing of individual skyrmions into nested bags remains challenging. Here, using micromagnetic simulations, we propose a field-gated nanocontact protocol for generating and programming double-layer nested skyrmion bags S(m,S(n)). The protocol exploits the opposite field responses of bag regions with antiparallel magnetic backgrounds. Spatially segmented perpendicular magnetic fields selectively expand either the outer region or the inner bag until it overlaps with a nanocontact. A spin-polarized current pulse of the appropriate polarity then nucleates one skyrmion in the selected region, while subsequent field-driven contraction moves the written skyrmion away from the contact and restores the writing site for repeated operation. Starting from an empty nested bag S(0,S(0)), this procedure enables the controlled construction of S(m,S(0)), S(0,S(n)), and general S(m,S(n)) states. The simulated total topological charge changes in unit steps during sequential writing, confirming one-at-a-time and region-selective control. These results provide a possible route toward programmable nested topological states for multilevel spintronic information encoding.
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Biological Physics · Cross-listed from cs.LG

Earth Observation Foundation Models for Terrestrial Ecohydrology: From Representation Learning to Process Inference

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

General Relativity and Quantum Cosmology

Study of gravitational radiation at $\mathscr{J}$ for the general type-D Einstein-Maxwell solution with cosmological constant

We characterize the gravitational radiation present in the general Plebański-Demiański type~D solution with cosmological constant $\Lambda$ of any sign. We show that radiation escapes towards infinity if and only if the acceleration parameter is non-zero. We calculate the Cotton-York tensor and the boundary stress-energy tensor at infinity for negative $\Lambda$, and for positive $\Lambda$ the $D$ tensor that complements initial or final data at $\mathscr{J}$. In addition, we recast a recent parametrization of this family of metrics into a new form by a simple homothety, correctly identifying $\Lambda$, and study the existence and regularity of the possible axes of symmetry, searching for a relation between deficit angles and radiation. We also identify the branch of general non-radiating solutions with non-vanishing Cotton-York tensor at $ \mathscr{J} $.
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High Energy Physics (Phenomenology)

Dark Charge Conjugation and Complementary Constraints from $D^0$ Mixing and Rare Decays with Massless Dark Photons

We investigate how dark charge conjugation organizes rare $D^0$ decays involving a massless dark photon and how these decays complement neutral charm mixing in constraining a common flavor changing interaction. Within a simplified framework with a real pseudoscalar mediator, $D^0\to\gamma_{\mathrm D}\gamma_{\mathrm D}$ probes the portal that preserves $\mathcal{C}_{\mathrm D}$, whereas $D^0\to\gamma\gamma_{\mathrm D}$ probes the portal associated with $\mathcal{C}_{\mathrm D}$ breaking. Because the two decay channels and $D^0$ mixing share the same flavor normalization and mediator propagator, the flavor dependence can be eliminated analytically, converting the mixing constraint into a direct upper bound on the invisible decay rate. Combining current constraints from mixing, invisible decay, and the single dark photon channel, we identify a transition between regions dominated by mixing and regions dominated by invisible decay in mediator parameter space. The single dark photon search then yields conditional upper limits on the portal associated with $\mathcal{C}_{\mathrm D}$ breaking once the flavor normalization is fixed at its maximal value allowed by mixing and invisible decay. These results demonstrate a symmetry resolved complementarity between neutral meson mixing and rare charm decays in probing flavor changing interactions with a massless dark sector.
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Accelerator Physics

Relative and absolute dosimetric commissioning of the ELIMAIA–ELIMED laser-driven proton beamline at 23.4 MeV

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

High Energy Physics (Phenomenology)

Spin-dependent polarizabilities of heavy vector mesons

We investigate the spin-dependent electromagnetic polarizabilities of the heavy vector mesons \(D^*\) and \(B^*\) in heavy meson chiral perturbation theory up to \(\mathcal O(p^3)\). Using a twelve-element tensor basis for the real-photon Compton scattering on a spin-1 target, we determine two scalar, four vector and six tensor polarizabilities. We take the charm- and bottom-sector axial couplings from the measured \(D^*\) width and lattice-QCD calculations, respectively, and estimate the magnetic couplings in the nonrelativistic constituent-quark model. In the charm sector, the proximity of the charged \(D\pi\) thresholds generates strongly nonanalytic \(P\phi\)-loop contributions, producing large real contributions to several \(\bar D^{*0}\) polarizabilities and sizable imaginary parts for \(D^{*-}\), whose charged \(D\pi\) channel is open. The \(E1E1\)-type polarizabilities are enhanced much more strongly than their \(M1M1\)-type counterparts, consistent with the velocity suppression of the pion-cloud magnetic coupling. No analogous enhancement occurs for \(B^*\): the Born terms govern the magnetic polarizabilities, and the anomaly poles dominate the vector polarizabilities that receive no Born contribution. These results resolve the spin dependence of the \(D\pi\) threshold effect and provide benchmarks for future lattice-QCD studies.
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All authors Hao Dang, Liang-Zhen Wen, Yan-Ke Chen, Shi-Lin Zhu

Materials Science

Claude-SpinDynamics: a cross-platform, dual-precision CPU/GPU micromagnetic simulator with native mumax3 script compatibility

Quantitative spintronics increasingly depends on a handful of GPU micromagnetic codes, all of which require NVIDIA hardware and single precision throughout, leaving researchers without such hardware unable to run even the standard validation problems. We report Claude-SpinDynamics (Claude-SD), a new open source micromagnetic simulator with a cross platform C++20 core (Windows and Linux) and a Python interface that closes this gap: a complete CPU build, validated by the same test suite as the GPU path, runs every unit test and uMAG standard problem with no accelerator at all, alongside GPU builds offering both single and double precision, a choice of two demagnetization FFT backends, and natively implemented spin-orbit, spin-transfer, and Zhang-Li torques, Dzyaloshinskii-Moriya interaction, and percell materials.Claude-SD natively interprets mumax3's .mx3 scripting language, so existing community scripts run unmodified; under matched conditions the two codes agree cell-by cell to single-precision round-off, and, together with mumax+ and OOMMF, to within 2% on the uMAG dynamic-switching standard problem, with MuMax-CO agreeing to mumax3 to float32 round-off on the same problem. Benchmarked head-to-head against these three codes, Claude-SD's single-precision build is the fastest solver on small and two-dimensional problems and remains competitive at the largest grid sizes, while its double-precision and dual-FFT-backend paths are unmatched among GPU micromagnetic codes. A GPU replicabatching extension further advances an entire ensemble of finite-temperature trajectories in a single kernel launch per step, giving one to two orders of magnitude of throughput over a per-trial loop while reproducing single-trajectory results to numerical round-off. The complete source is openly licensed and distributed with runnable example notebooks and documentation for independent reproduction.
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Plasma Physics

AlgoPlasma: Open Algorithms for Plasma Modeling

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

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

Cosmology and Nongalactic Astrophysics

Prospects for Direct Detection of Ultralight Dark Matter candidates in deci-Hz Band with IndIGO-D

We investigate the sensitivity of IndIGO-D, a proposed space-based decihertz gravitational-wave interferometer, to different classes of ultralight dark matter. IndIGO-D will probe the $\sim0.01$–$10~\mathrm{Hz}$ frequency band between those accessible to current ground- and future space-based gravitational-wave interferometers, providing access to ultralight dark-matter masses beyond the reach of existing instruments. We consider two complementary signatures: interferometric displacements induced by coherently oscillating scalar (dilaton), vector (dark-photon, $U(1)_B$ and $U(1)_{B-L}$ gauge groups), and tensor fields with masses $m_{\rm DM}\sim10^{-17}$–$10^{-14}~\mathrm{eV}$; and changes in laser polarization induced by pseudoscalar axion dark matter at higher masses, around $m_a\sim10^{-12}~\mathrm{eV}$. For the dilatons, dark photons and tensors, we compute the expected sensitivities using two pipelines – cross-correlation and BSD excess-power – assuming L-shaped and triangular interferometer layouts and three representative noise power spectral densities (S1, S2, S3), each for two years of continuous observation. We find that the projected sensitivities agree to within a factor of order unity across the search pipelines and interferometer geometries. In particular, we show that IndIGO-D could open previously unconstrained coupling parameter space for vector and tensor dark matter across $m_{\rm DM}\sim10^{-16}$–$10^{-14}~\mathrm{eV}$, bridging the sensitivity of space- and ground-based experiments. For axion dark matter, we demonstrate that a complementary detection for laser light polarization shifts, limited primarily by photon shot noise, could probe the axion-photon coupling $g_{a\gamma}$ at masses around $m_a\sim10^{-12}~\mathrm{eV}$ at a level potentially better than that of other future experiments without degrading sensitivity to gravitational waves.
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Quantum Physics

On the zeros of the stellar representation in the discrete cylinder

The discrete cylinder phase space offers a natural setting for twisted photons, Josephson junctions, and certain bosonic codes. In that context, we build a number-of-zeros hierarchy for the stellar distribution of states on the discrete cylinder phase space, tied to usefulness for quantum computation. The orbital angular momentum (OAM) and phase eigenstate, having no zeros, sits at the bottom of the hierarchy and share mathematical properties with the coherent state on the plane phase space, both sharing zero rank and a positive Wigner distribution. This reveals a structural peculiarity of the cylinder: its coherent state—the wrapped coherent state—is instead the most quantum, carrying infinitely many zeros, so "coherent state" need not signal classicality across different phase-space geometries. We identify the operations that preserve or change the zero count, giving explicit access to every rank of the hierarchy. We then ask whether this hierarchy also governs localization. Using the $L^r$ norm, the inverse participation ratio, and the Wehrl entropy as complementary measures of spread in the Husimi density, we find that the two hierarchies need not track one another: the wrapped coherent state can be more localized than the OAM eigenstate even though it carries infinitely many zeros.
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Mesoscale and Nanoscale Physics

Temperature-Dependent Spin-Orbit Torque Generation in Perpendicularly Magnetized Topological Insulator-Magnetic Multilayer Heterostructures

We report a comprehensive temperature-dependent investigation of spin-orbit torque (SOT) generation in heterostructures comprising a perpendicularly magnetized metallic multilayer grown on top of a topological insulator (TI) epilayer. Temperature-dependent second-harmonic Hall measurements reveal distinct trends in the magnitude of the spin-orbit torque across the studied heterostructures. Samples incorporating Bi2Se3 exhibit torques reaching approximately 12 mT/(10^12 A m^-2) at 15 K, around 5 times larger than those in a multilayer without the topological layer. The structure with a thin 2-nm Ta buffer for the multilayer shows the strongest enhancement and a pronounced increase at low temperatures, highlighting efficient spin-current generation from the topological surface states. In contrast, the sample with a 10 nm-thick Ta spacer exhibits reduced torque efficiency, consistent with partial attenuation of spin transmission through the buffer. Systems lacking Bi2Se3 but containing two heavy metals (Ta and Pt) yield significantly smaller torques, around 2.5 mT/(10^12 A m^-2), despite the presence of conventional spin Hall sources. These observations underscore the dominant role of TI-derived spin-momentum-locked currents in driving large damping-like torques and their sensitivity to interfacial structure and buffer-layer thickness.
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All authors Soumyarup Hait, Benjamin A. Brereton, Ahmet Yagmur, Satoshi Sasaki, Gavin Burnell, Christopher H. Marrows

High Energy Physics (Experiment)

Deep Earth imaging through neutrino and seismic tomography

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

General Relativity and Quantum Cosmology

Fluid interpretation, Hawking–Ellis classification, and energy conditions of the proper kinetic gravity braiding stress tensor

We investigate the fluid interpretation, Hawking–Ellis classification, and energy conditions of the proper kinetic gravity braiding contribution to the stress tensor of minimally coupled scalar fields for timelike, spacelike, and open-region null scalar gradients. Using a $2+1+1$ decomposition adapted to the gradient, we derive the associated effective fluid variables. Unlike k-essence, braiding generates heat fluxes and pressure anisotropies: radial and tangential heat fluxes for timelike gradients, and a radial heat flux plus mixed radial–tangential anisotropies for spacelike gradients. These quantities depend only on the normal fundamental scalars and the two-dimensional accelerations, despite the larger set of variables appearing at intermediate stages. For open-region null gradients, the proper-braiding stress tensor has null-dust form. We obtain the complete Hawking–Ellis classification: the timelike sector is Type I for positive discriminant, Type II on the nontrivial discriminant hypersurface, and Type IV for negative discriminant; the spacelike sector has the same generic branches and additional Type II and Type III degeneracies when the squared radial heat flux equals the squared mixed anisotropy. The open-region null sector is Type II for nonzero null-dust density and vanishes in the zero-density case. Finally, the standard energy conditions further restrict the Type I and generic Type II sectors. The null energy condition excludes Types III and IV and, for spacelike gradients, every nonzero radial heat flux or mixed anisotropy. Thus admissible spacelike proper braiding is diagonal, whereas in the timelike sector the energy conditions bound the total heat flux.
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Materials Science

Linking Electronic Bonding and Short-range Order to Strength in $\alpha$-Titanium Alloys: A First-Principles Study

The development of accurate strength prediction models for titanium alloys is critical for advanced materials design. This study systematically examines how the mechanical properties of $\alpha$-Ti are affected by substitutional (X = Al, V, Mo) and interstitial (Y = H, C, N, O) alloying elements, with a focus on electronic bonding. Using density functional theory (DFT), we uncover the short-range ordering (SRO) of substitutional atoms and quantify their influence on the electronic bonding and mechanical behavior. The primary novelty of this work lies in developing a predictive model for tensile strength that goes beyond traditional empirical approaches. To quantify the contributions of individual solutes to strengthening, we use physically grounded quantum-chemical descriptors, such as the Integrated Crystal Orbital Hamilton Population (ICOHP), which is a direct measure of bond strength derived from first-principles calculations. The resulting formula quantitatively predicts the tensile strength of a wide range of $\alpha$-Ti alloys, demonstrating a significant advancement in the computational design of high-performance structural materials.
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Solar and Stellar Astrophysics

A self-consistent solar coronal heating model by Alfvenic waves

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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High Energy Physics (Theory)

Topological Field Theory and Stochastic Dynamics

In the late 1980s, Baulieu and Grossman demonstrated that the supersymmetric formulation of Langevin stochastic differential equations (SDEs), proposed earlier by Parisi and Sourlas, belongs to the family of Witten-type topological field theories (TFTs). From a certain angle, this finding may appear puzzling: TFTs have no local degrees of freedom, whereas SDEs do exhibit local fluctuations. In this paper, we address this apparent contradiction in the context of the supersymmetric theory of stochastic dynamics (STS), a generalization of the Parisi-Sourlas-Baulieu-Grossman approach to SDEs of arbitrary form. We further discuss how, within STS, dynamical chaos can be identified with the spontaneous breakdown of the corresponding topological supersymmetry, while 1/f noise can be understood as a consequence of the Goldstone theorem. The butterfly effect, in turn, calls for an effective field-theoretic description that may itself possess a hidden topological structure, as we speculate on the basis of the Ginzburg-Landau approach and insights from AdS/CFT duality.
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Physics and Society · Cross-listed from q-fin.RM

Is the medium the message? Social disclosure channels and firm risk

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

Quantum Physics

Anomalous Weak Pointer Shifts as Postselected Interference among Coarse-Grained Histories

Anomalous weak values and superoscillations allow a pointer to exhibit an effective shift outside the eigenvalue range of the measured observable. We reformulate this effect in a phase-space path-integral language. For each eigenvalue branch $a_j$ of the measured observable, {the interaction couples $a_j$ to the pointer position $\hat{x}_p$ and thereby translates the conjugate pointer momentum by $\gamma a_j$.} After postselection, {the branch-conditioned amplitudes are coherently superposed with coefficients chosen to produce a superoscillatory approximation. When this conditional amplitude acts on an initial pointer momentum wavepacket for which the finite superoscillatory-window condition is satisfied, the resulting momentum wavefunction behaves as if it had been translated by $\gamma A_w$, rather than by any of the eigenvalue-conditioned shifts $\gamma a_j$. This yields an effective path-integral representation of anomalous weak pointer shifts and motivates their interpretation in terms of interference among finite coarse-grained histories.} We discuss how this picture bears on conservation-law questions.
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Optics

Driven Time Crystal in Low-Symmetry ENZ Conductors

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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Instrumentation and Methods for Astrophysics

Design and Realization of the LST Main Structure for the Cherenkov Telescope Array

The 23 m diameter Large Size Cherenkov Telescope (LST) for CTA, located at 2250 m a.s.l. on the Canary Island of La Palma, is the next-generation Cherenkov telescope following MAGIC, H.E.S.S., and VERITAS. To enable rapid repositioning (180{\deg} in 18 s) for gamma-ray burst observations, the mechanical structure was designed to be ultra- lightweight (110 tons). The space-frame structure consists of slender struts made of carbon fibre, aluminium (dish and camera mast), and steel. The telescope is designed to withstand extreme environmental conditions at the ORM observatory on La Palma, including wind speeds up to 200 km/h, uplift forces, and ice loads of up to 30 tons. We present the structural design developed to meet these functional and environmental requirements. MPP Munich is responsible for the telescope's mechanical structure together with partner institutes in France (LAPP) and Spain (IFAE). The prototype, LST-1, has been operational since 2019, and three additional LSTs are curre1ntly under construction.
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All authors T. Schweizer, J. Eder, H. Wetteskind, C. Jablonski, R. Stadler, R. Mirzoyan, D. Paneque, T. Masahiro, A. Fiasson, N. Geffroy, G. Deleglise, O. Blanch, J. Mundet, R. Garcia, A. J. Penuela Lopez

Instrumentation and Methods for Astrophysics

Adapting the 23m LST-North mechanical structure design for the strong Chile seismic environment

The 23-meter-diameter Large-Sized Telescope (LST) is the largest size telescope of the next generation Cherenkov Telescope Array (CTA). The first telescope, LST-1, was installed at the Roque de los Muchachos Observatory (ORM) on La Palma at an altitude of 2,250 m in 2018 and has been in operation since 2019. Its ultra-lightweight structure (110 tons) enables extremely rapid repositioning (180{\deg} in 18 seconds) and has been designed to withstand extreme environmental conditions, including storms and winds exceeding speed up to 200 km/h. To deploy the same solid telescope design at the CTA Southern Observatory in Chile, the structure must be adapted to the significantly higher seismic demands of the site. To address this challenge, the Max Planck Institute for Physics (MPP) has proposed the integration of a seismic isolation system with the proven LST-1 structural design. This approach substantially reduces seismic loads and dynamic amplification, thereby avoiding extensive structural modifications and enabling the existing telescope design to be transferred to the Chilean site with only minor adaptations. In this contribution, we present the proposed seismic isolation concept and its feasibility studies. MPP is responsible for the mechanical structure of the LST and has validated the concept through detailed finite-element analyses and long-term structural lifetime assessments.
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All authors Thomas Schweizer, Josef Eder, Teshima Masahiro, Holger Wetteskind, Razmik Mirzoyan

Computational Physics · Cross-listed from stat.ML

Identifying parameter couplings and uncertainties of mixed-noise stochastic systems via full-covariance Gaussian mixture network

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

Quantum Physics

Equivalence of quantum resources under ergodic dynamics

Quantum resource theories characterize distinct forms of nonclassicality in many-body quantum states, raising the question of whether these resources evolve independently under generic ergodic dynamics. Considering diagnostics quadratic in the state, we show that the dynamics of different resource measures become mutually interdependent and are governed by a few common degrees of freedom. For Haar-random circuits, the purity together with a single resource witness suffices to reconstruct the remaining resource measures, as we demonstrate for coherence, various asymmetries, and number entropies. The same relations hold, to a good approximation, under chaotic Floquet and continuous-time Hamiltonian dynamics, establishing that this dynamical resource equivalence extends beyond random circuits. We further derive an exact coherence–imaginarity relation, remarkably accurate also beyond Haar-random circuits. Our results reveal an emergent simplification of many-body dynamics, in which sufficiently strong scrambling reduces seemingly distinct quantum resources to a few common dynamical degrees of freedom.
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Materials Science

Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe

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

General Relativity and Quantum Cosmology

Static Magnetic Brane Solutions in Quartic Quasi-Topological Gravity with Power-Law Maxwell Nonlinear Electrodynamics

In this paper, we investigate static magnetic brane solutions in (n+1)-dimensional quartic quasi-topological gravity coupled to power-law Maxwell nonlinear electrodynamics. We derive the corresponding solutions and analyze their geometric and physical properties. We observe that the solutions are horizonless and free of curvature singularities in the physically accessible region, while the spacetime generally exhibits a conical singularity with a nonzero angular deficit at the lower radial endpoint. We demonstrate that the endpoint is independent of the higher-curvature couplings lambda, mu, and c, whereas the near-endpoint geometry is mainly controlled by the magnetic parameter q and the nonlinear parameter s. At large radial distances, we find that the higher-curvature couplings govern the asymptotic behavior of the metric. We also establish that finite asymptotic solutions require 1/2 < s <= 2 and analyze the dependence of the angular deficit on q, s, and the endpoint parameter rho_+. Using the counterterm method, we calculate the conserved mass density and show that the static magnetic brane carries no net electric charge. Finally, we verify that the power-law Maxwell theory recovers linear Maxwell electrodynamics at s=1 and Einstein gravity when lambda=mu=c=0.
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All authors Alireza Alizadeh, Saheb Soroushfar, Mohammad Ghanaatian, Sayyed Mehrab Ramezani, Sudhaker Upadhyay, Kairat Myrzakulov

Quantum Physics

Time-Deterministic and Instruction-Dynamic Execution: A field-programmable gate array quantum-control processor

Long-running quantum computations, including error-corrected workloads, demand instruction availability, measurement-dependent control, and calibration updates. We present Time-Deterministic and Instruction-Dynamic Execution, an FPGA quantum-control processor supporting runtime revision at both instruction and parameter levels. Dynamic Instruction Parameter Update supplies one-shot, next-match patches before parameter capture, while Dynamic Instruction Stream Overwrite provides guarded replacement, logical deletion, and out-of-line insertion in eligible future regions of a resident program. A moving fetch-visibility guard coordinates instruction updates with execution, and event commitment isolates complete descriptors for independent hardware-timed dispatch. Revision applicability depends on update timing and execution progress; deterministic service applies to committed events under the stated scheduling conditions. The Xilinx ZCU102 implementation uses a 250-MHz control core and a 425-MHz timing/update domain. FPGA-resident measurements at the registered digital interfaces confirmed programmed-cycle dispatch for all tested descriptors committed at least one timing-domain cycle before their timestamps, with downstream ready and the stated FIFO ordering conditions. Separate tests confirmed post-commit timestamp and payload invariance. The minimum all-success mapped DIPU margin was four control-domain cycles, and a replacement of L instruction words completed in L+5 update-domain cycles under continuous payload delivery. Within the tested guard-distance range, rejected DISO requests reported an error and preserved the resident path, whereas all admitted revisions tested here executed complete revised sequences. These results provide a hardware execution basis for incorporating runtime-generated sequences and parameter corrections into precisely timed quantum computations with feedback.
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Cosmology and Nongalactic Astrophysics

Testing a Sign-Switch Cosmological Model with Curvature through Latest Planck 2018, DESI DR2 and PantheonPlus&SH0ES Observational Data

We investigate the spatial geometry of the Universe within the framework of a sign-switch dark energy scenario by extending the recently proposed $\Lambda_{\rm s}$CDM model to include a free curvature parameter $\Omega_k$.In this framework, the effective cosmological constant undergoes a transition from a negative to a positive value at a characteristic redshift $z_{\dagger}$. Using the latest Planck 2018 cosmic microwave background (CMB) data, DESI DR2 baryon acoustic oscillation (BAO) measurements, and the PantheonPlus&SH0ES Type Ia supernova sample, we derive joint constraints on the spatial curvature parameter $\Omega_k$ and other cosmological parameters. We find that Planck data itself slightly favors a closed universe within both the $\Lambda_{\rm s}$CDM$+\Omega_k$ and $\Lambda$CDM$+\Omega_k$ frameworks, although spatial flatness remains well within the allowed uncertainties. When low-redshift probes were included, the curvature constraints were significantly tightened. In particular, the full Pk18+DR2+PP&SH0ES dataset yields $\Omega_k = 0.0001 \pm 0.0014$ for the $\Lambda_{\rm s}$CDM model, indicating a universe that is remarkably consistent with spatial flatness. We further analyzed the correlations between $\Omega_k$, $H_0$, and $S_8$, finding that the inclusion of curvature and a sign-switch dark energy component helps stabilize cosmological parameter estimates while remaining compatible with current observational constraints. Model comparison using AIC and Bayesian evidence shows that the $\Lambda_{\rm s}$CDM model receives inconclusive/weak observational support relative to $\Lambda$CDM.
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All authors Archana Dixit, Manish Yadav, Anirudh Pradhan, M. S. Barak

Instrumentation and Methods for Astrophysics

Stress-Testing DANTE under Detector Domain Shift: a Representation-Coherent Reanalysis of LIGO O4a

This sixth version of the Domain-Adaptive Network for Transient Evaluation (DANTE) preprint stress-tests an unsupervised transient-noise pipeline under representation mismatch and observing-run adaptation. We reanalyse 10,429 detector-time strain candidates from 42 LIGO O4a sessions using frozen DINOv2 patch embeddings and a Top-k multiple-instance score. Candidate and native-background Q-transforms share Q in [4,64], and detector-specific thresholds are calibrated from 5,000 run-native windows by temporal-block bootstrap. The coherent analysis yields 6,365 ROBUST, 1,275 AMBIGUOUS, and 2,789 BACKGROUND statistical dispositions; 4,676 of 10,372 paired historical dispositions differ from the cross-representation v5 analysis. Direct controls resolve an O3b-O4a score shift and reduction after native adaptation for H1, but not L1, while known-glitch separation is detector- and morphology-dependent. Replicated studies quantify population-dependent sensitivity to background draw, clustering seed, dictionary size, and whitening, demonstrate native-index absorption, and identify conditional low-Q blindness. A conservative H1-L1 max-shift screen yields 13/8,806 values above threshold, but its on-source values and pooled per-event null maxima are not exchangeable. The primary two-null PEM endpoint shows no resolved ROBUST-BACKGROUND enrichment (p=1.000), and two catalogue overlaps are consistent with a circular-shift coverage proxy (p=0.651). Simulation-only compact-binary controls show detector- and distance-dependent disagreement between novelty, native disposition, and physical coincidence. We withdraw the v5 discovery, rate-limit, catalogue-recall, and survey-wide stability interpretations. The supported result is a measured set of failure modes and validity conditions for unsupervised detector characterization, not a new glitch class or an astrophysical search.
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2608.15166 · 15 Aug · 12 pages, 10 figures, 1 table. Sixth version: representation-coherent O4a reanalysis, detector-aware catalogue reconstruction, replicated robustness and failure-mode validation, physical and catalogue null controls, and withdrawal of unsupported v5 discovery, rate-limit, catalogue-recall, and survey-wide stability interpretations