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Tuesday 28 July

Quantum Physics

Engineering a Quantum Thermal Diode with Floquet Driving

Aqsa Rehman, M. Tahir Naseem and Adam Zaman Chaudhry

Controlling heat flow in small quantum systems is a central goal of quantum thermodynamics and nanoscale transport. A key challenge is to achieve strong thermal rectification without suppressing the transmitted heat current, a tradeoff that often arises in static diode configurations. We establish a Floquet-control mechanism in a minimal quantum thermal diode formed by two longitudinally modulated Ising-coupled qubits, each coupled to an independent thermal reservoir. From a microscopic system–bath model, we derive a Floquet–LGKS master equation that resolves the drive-assisted transition channels. The resonant undriven device with left–right symmetric bath couplings serves as the reciprocal benchmark, while static detuning provides a rectifying reference with reduced heat current. Single-side driving breaks this reciprocal structure by creating a Floquet-dressed contact opposite a purely thermal contact. For this configuration, we obtain a compact steady-state current formula and an exact blocking condition for suppressing one bias direction while retaining finite transport in the opposite direction. In the weak sinusoidal-drive regime, rectification begins quadratically in the modulation amplitude. Dual-side driving adds a Floquet pumping contribution to the interaction-mediated current, so complete blocking requires cancellation of both contributions. These results establish contact-selective Floquet dressing as a design principle for controllable heat-flow asymmetry in minimal quantum thermal devices.
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Physics and Society

Open-ended innovation arm-race in zero-sum games

Matteo Marsili and Leandro Chaves Rego

We discuss zero-sum games with open-ended innovation, whereby each player may introduce new strategies. The innovation process is modeled as a draw of new strategies form a distribution. It is argued that, when the cost of innovation is vanishingly small, this setting can lead to an everlasting innovation arm-race. In particular, the introduction of new technologies of the advanced player increases the marginal utility for technological innovation of the backward one, whereas innovation of the backward player discourages the more advanced one to innovate.
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Mesoscale and Nanoscale Physics

Relative hybridization textures as local coordinates for band geometry and topology

Caiyuan Ye, Zhong Fang, Hongming Weng et al. (+1 more)

Global diagnostics such as Berry curvature and quantum metrics characterize the geometry and topology of an occupied Bloch subspace, leaving the microscopic sectors that carry this structure implicit. We introduce the relative hybridization coordinate $Z$ as a projector-level diagnostic connecting these global quantities to local degrees of freedom. As the Grassmann graph coordinate relative to a chosen sector, $Z$ reconstructs the local projector and retains the phase and matrix orientation absent from ordinary weight or fat-band descriptions. On valid chart patches, its momentum-space texture encodes Berry curvature, quantum metric, Berry phases, and Wilson loops, while chart obstructions appear as rank-drop defects whose balanced-chart winding of $\det Z$ gives the first Chern number. In the QWZ model this defect inventory reproduces the Chern phase diagram. In the lattice BHZ model, matrix $Z$ diagnoses the orbital $E|H$ partition as a robust matched chart for the QSH geometry, while the spin partition remains essential to the block and $\mathbb Z_2$ interpretation and shows rank deficiency as a matched chart in the spin-conserving limit. The relative hybridization coordinate thus provides a sector-resolved framework for relating band geometry and topology to microscopic structure.
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All authors Caiyuan Ye, Zhong Fang, Hongming Weng, Quansheng Wu

Instrumentation and Methods for Astrophysics

AI's Capability in Assisting Scientific Research in Physics, Astrophysics, and Cosmology I: Literature Review

Anamaria Hell, Kateryna Vovk, Veena Krishnaraj et al. (+18 more)

We investigate how well large language models (LLMs) can assist with literature reviews for scientific research. We perform a controlled study of eight expert-conceived research projects across the areas of physics, astrophysics, and cosmology. Each project has a defined background and goal, and human experts and AI prompters are asked to perform identical literature review tasks in parallel. We compare the relevant literature selected by humans with that selected by mid-2025 LLMs (ChatGPT-4o, ChatGPT Deep Research, and Gemini). We find the overlap between human- and AI-selected references to be small ($<$6%), indicating that AI models do not yet reproduce a competent expert search on their own, though they have the potential to complement literature searches by humans. We then assess the reliability and completeness of AI-generated candidate references, distinguishing two types of hallucination: fabrications (references to nonexistent papers) and metadata mismatches (real papers with one or more incorrect fields). We find that while fabricated references make up 3% of the AI-generated references, 64% are real papers with at least one incorrect field (title, author, year, journal, DOI, or link), indicating that the mid-2025 models require systematic verification. However, the performance is significantly improved for the 2026 model ChatGPT Pro 5.5, with a single-project test showing zero fabrication or metadata mismatches.
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All authors Anamaria Hell, Kateryna Vovk, Veena Krishnaraj, Jia Liu, Kosuke Aizawa, Adrian E. Bayer, Linda Blot, Jessica Cowell, Suyog Garg, Jonathan Grée, Ben Horowitz, Masaya Ichikawa, Kanyuni Iemoto, Keigo Kondo, Zacharie Lorsin, Kevin McCarthy, Jamie Robinson, Miguel Ruiz-Granda, Leander Thiele, Ievgen Vovk, Mingshen Zhou

High Energy Physics (Phenomenology)

The 95 GeV Excess in Models with Two Higgs Doublets plus One Singlet: Model Distinction via Four-top Final States and Triple Higgs Couplings

S. Heinemeyer, C. Li, G. Moortgat-Pick et al. (+1 more)

We investigate the prospects for experimentally distinguishing the Next-to-Two-Higgs-Doublet Model (N2HDM) and the Two-Higgs-Doublet Model with a Complex Singlet (2HDMS) in the Yukawa type II realization. Both models can successfully accommodate the reported Higgs-boson excesses around 95 GeV while satisfying current theoretical and experimental constraints, leading to very similar predictions for the observed Higgs spectrum and signal strengths. We analyze how they can nevertheless be discriminated through observables sensitive to the scalar potential and the CP-odd sector. Analytical expressions for the trilinear Higgs couplings are derived, exhibiting characteristic contributions induced by the additional cubic interactions of the 2HDMS. We study the corresponding phenomenology in two complementary collider environments: four-top production at the High-Luminosity LHC, probing the different pseudoscalar sectors. In a second step we analyze Higgs pair production at a future high-energy $e^+e^-$ collider, providing direct sensitivity to the trilinear Higgs couplings. We quantify the potential to distinguish the two models by introducing the minimum deviation from the N2HDM limit required for a $2\sigma$ difference between the two models. Although our numerical analysis focuses on benchmark scenarios describing the 95 GeV excesses, the proposed approach provides a general framework for discriminating between singlet-extended Higgs sectors at future colliders.
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All authors S. Heinemeyer, C. Li, G. Moortgat-Pick, D. Schieber

Computational Physics · Cross-listed from cs.LG

A Physics-Informed Neural Operator for Thermal Ranking of Low-Cost Wall Materials in Hot-Dry Climates

Muhammad Akbar Khan, Fahim Raees and Ubaida Fatima

Identifying cost-effective indigenous building materials that minimise heat penetration through walls is critical for indoor thermal comfort in low-income rural housing in hot-dry climates, where summer temperatures routinely exceed 45 C. We present a two-stage computational framework for thermal ranking of five low-cost indigenous wall materials: mud brick, clay-straw adobe, lime-stabilised bamboo panel, fired clay brick, and lime-mud composite. First, a validated Crank-Nicolson finite difference method (FDM) solves the one-dimensional transient heat equation with Robin boundary conditions under diurnal solar and outdoor air-temperature forcing, generating 1500 periodic-day solutions across a nine-dimensional parameter space by Latin Hypercube sampling. Second, a Physics-Informed Neural Operator (PINO) with a Fourier Neural Operator (FNO) backbone learns the parameter-to-solution operator mu -> T(x,t), enforcing both data fidelity and PDE consistency. The trained PINO attains a relative L2 field error of 5.14e-4 and a 0.201 K mean absolute error on the peak inner surface temperature, preserving the FDM material ranking exactly; PINO trained on 150 FDM samples matches a data-only FNO trained on twice as many, so the physics loss is most valuable when data are scarce. The periodic-day formulation also yields the ISO 13786 time lag and decrement factor, reproduced to within 0.99 h and 0.010. At nominal hot-dry summer conditions, clay-straw adobe achieves the best cost-performance index among widely available materials. A climate sweep, confirmed by FDM spot checks, reveals a regime boundary: under sub-ambient outdoor conditions the ranking inverts to conductive fired clay brick, delineating heat-exclusion and heat-rejection regimes. The framework supports evidence-based material selection for post-flood reconstruction in hot-dry regions.
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High Energy Physics (Theory)

Toward the Structure Constants of $\mathcal{N}=2$ Liouville Theory

Beatrix Mühlmann and Themistocles Zikopoulos

We discuss the structure constants of spacelike $\mathcal{N}=2$ Liouville theory on the two-sphere. Due to the absence of a particular $b \leftrightarrow b^{-1}$ self-dual symmetry, where $b$ is the theory's coupling, the standard analytic bootstrap toolkit that was used to solve the bosonic and $\mathcal{N}=1$ theories cannot be implemented in a straightforward way. Our approach, instead, relies on the fact that $\mathcal{N}=2$ Liouville theory is dual by mirror symmetry to the $\mathrm{SL}(2)_k/\mathrm{U}(1)$ supercoset, whose target space is the $2$d fermionic black hole. Leveraging this duality, we obtain explicit expressions for the winding number preserving and violating structure constants on the supercoset side, and test them on the Liouville side through a semiclassical analysis finding agreement up to one-loop order. We also discuss the chiral rings of the theory and evaluate correlators of $\frac 12$-BPS operators.
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Quantum Physics

Discrete power-law decay of subsystem distance after a quantum quench

Bin Sui and Jiaju Zhang

We present a numerical study of subsystem distance decay following a global quantum quench in the infinite one-dimensional transverse-field Ising chain, using the mathematically rigorous Bures distance $B_A(t)$ to quantify the deviation of the time-evolved reduced density matrix from its stationary generalized Gibbs ensemble state. We show that the late-time decay follows a discrete power law $B_A(t) \sim t^{-\lambda}$, with the exponent $\lambda$ confined to discrete values: $1$, $5/4$, $3/2$, $7/4$, $2$, $5/2$, and potentially further values. The specific exponent is jointly determined by the pre- and post-quench transverse fields, as well as by properties of the symmetric excitation-fraction function $m_S(\varphi)$, defined on $\varphi\in[0,\pi]$ to characterize the pre-quench Hamiltonian eigenstates, including continuity, boundary values, and first-derivative boundary values, among others. The previously established $t^{-3/2}$ decay for the initial ground state of the pre-quench Hamiltonian is naturally recovered as a special case of this general classification. Our results reveal a universal discrete structure governing local equilibration dynamics in integrable quantum systems.
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Strongly Correlated Electrons

Aharonov-Casher phase in twisted bilayer graphene

Igor Kuzmenko, Y. B. Band and Yshai Avishai

The Aharonov-Casher (AC) effect is a quantum mechanical phenomenon in which the wave function of a particle with a magnetic moment moving in a region subject to an electric field develops a phase shift due to spin-orbit interaction, even if no classical force acts on it. This phase also depends on the medium through which the particle moves. Here we focus on the AC phase of an electron moving in twisted bilayer graphene (TBG) lying in the $x$-$y$ plane, subject to a uniform electric field perpendicular to the plane of the graphene, ${\bf E}=E{\hat{\bf z}}$. The AC phase is determined by an $SU(2)$ vector potential ${\bf A}$ from which a phase factor is generated, and used to perform a gauge transformation of the Hamiltonian. We find that the AC phase for a straight line path between two points in the TBG plane is linear with $E$ and exhibits sharp peaks at the magic angles. To help demonstrate an experimental method for determining the AC phase, we examine the probability of polarized electron propagation from a source tip to a drain tip in a double-tip scanning tunneling spectroscopy configuration.
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Physics and Society · Cross-listed from cs.AI

Engine-Equal, Human-Unequal: A Reproducible Outcome Skew in Engine-Assessed Equal Chess Positions

Jesung Park

Among chess opening positions that a strong engine judges essentially equal (Stockfish 18 evaluation within 10 centipawns of zero, depth-stable) and that humans actually reach on Lichess (October 2025; 1,661 positions, 16.1M occurrences), human results are not balanced. Positions carry outcome skews, each the gap between its games' actual results and what the players' ratings predict, whose directions are stable properties of the naturally-reached position: some positions favour White, others Black. These skews reproduce across three re-partitions – disjoint player-account sets (primary), time, and disjoint rating bands – and on an out-of-sample month eight months later. On the primary split, each position's skew is measured once in each account group, and the replication slope asks how well one measurement predicts the other after removing rating and opening-family effects: one means undiminished carry-over; zero, no linear relation. We find 0.69 (family-clustered 95% CI [0.65, 0.74]), rising to 0.94 on the most-popular, best-measured positions. The slope's value depends on the position mix. Existence is the invariant claim: it survives every tighter evaluation band, search depth, calibration, and popularity cutoff we test, and replicates within blitz and rapid separately. The typical skew is small (median $|\delta| \approx 0.018$, about two percentage points of White score), yet it reproduces, position by position, across disjoint accounts. At these positions the disfavoured side also thinks longer. Even where the evaluation is most confident, it is not a sufficient statistic for human outcomes. The result is observational, and the causal question is left to a pre-registered randomised companion study.
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General Relativity and Quantum Cosmology

Taub-NUT as gravitational dyon with torsion

Dmitri Gal'tsov and Rostom Karsanov

We show that the Levi-Civita connection for the Taub-NUT metric is singular on Misner strings and generates an Einstein tensor containing the squares of the delta function. This can be improved by introducing torsion, in which case the Einstein tensor may be interpreted as that of a cosmic string with negative variable tension. Komar flows in Misner strings are generated by torsion, which is therefore responsible for the asymptotic Komar charges. The Taub-NUT metric then appears as a soliton supported by two spin-fluid beams.
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High Energy Physics (Experiment)

Measurement of the fragmentation properties of jets containing $\Upsilon$(nS) mesons in proton-proton collisions at $\sqrt{s}$ = 13 TeV

CMS Collaboration

A measurement of the fragmentation properties of jets containing $\Upsilon$(nS) mesons using proton-proton collision data at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$, is presented. The $\Upsilon$(nS) mesons associated with jets are reconstructed via their decays producing pairs of oppositely charged muons. The longitudinal and transverse projections of the momenta of the $\Upsilon$(nS) mesons along the momenta of the corresponding jets are studied. The results are compared with Monte Carlo predictions, including recent developments in the modelling of quarkonia production in parton showers. The description of the data by these Monte Carlo predictions is found to be unsatisfactory, leaving room for improvements in the modelling of such processes.
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Materials Science

Transformer Atomic Cluster Expansion: TRACE

Paramvir Ahlawat

Designing machine-learning interatomic potentials involves achieving the precise representation of complex many-body interactions alongside the efficiency required for scalable molecular dynamics. We introduce Transformer Atomic Cluster Expansion (TRACE), an energy-conserving architecture that combines atomic cluster expansion density correlations with local multihead cross-attention. The correlations form an O(3)-equivariant state for each center, which queries tensorial neighbor features that remain fixed functions of species and geometry. No learned state is passed between atoms. On a laptop MacBook-M1, we train and test TRACE for polymorphic cesium lead iodide, liquid water, and intramolecular methyl migration against experiments. For cesium lead iodide, TRACE reproduces the r$^2$SCAN+rVV10 ordering of four polymorphs and gives a classical edge-sharing hexagonal non-perovskite($\delta$) to corner-sharing cubic perovskite($\alpha$) Gibbs-free-energy crossing $\simeq$580K near the experimental observations of $\simeq$600K. By employing enhanced sampling to cross high energy barriers, the same TRACE potential successfully captures the $\delta$-to-$\alpha$ perovskite transformation without any reinforcement learning. A water potential trained on a reduced set of CCSD(T) configurations places the first oxygen–oxygen maximum at 2.85~Å, compared to the experimental value of 2.80~Å. For the gas-phase methyl migration in 2,2-dimethylisoindene, umbrella sampling yields an activation free energy of $27.92\pm0.03$~kcal~mol$^{-1}$, in close agreement with the experimental measurement of $29.2\pm1.1$~kcal~mol$^{-1}$. Across these diverse benchmarks, a single unified architecture successfully captures multi-species crystallization, liquid structures, phase diagrams, and chemical reactivity.
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Quantum Physics · Cross-listed from cs.SE

KQFuzz: Knowledge-Guided Fuzzing for Quantum Libraries via Large Language Models

Fuyuan Xia, Qixin Zhang, Chenhao Ying et al. (+5 more)

As quantum computing continually improves, ensuring the reliability and correctness of quantum libraries has become increasingly critical. To this end, many LLM-based fuzzing approaches towards quantum libraries have been proposed to uncover potential bugs. However, these methods still suffer from limitations such as insufficient flexibility and low efficiency, which hinder the progress of the quantum computing field. To address these challenges, we propose KQFuzz, a novel knowledge-guided fuzzer for quantum libraries. It leverages comprehensive codebase knowledge to ground LLM-based test generation, synergizing this with fitness-guided evaluation and two-level mutations to explore complex execution paths and trigger potential bugs. Firstly, KQFuzz introduces a novel prompting scheme tailored to quantum programs, which strategically incorporates knowledge of the codebase to efficiently generate high-quality quantum seed programs. Moreover, we develop evaluation and mutation strategies to handle the generated seed programs, facilitating efficient fuzzing execution while further enriching the diversity of the resulting test cases. We implement KQFuzz and conduct fuzzing on three popular quantum libraries, including Qiskit, PennyLane, and Cirq. Experimental results demonstrate that our approach significantly outperforms other state-of-the-art methods, with coverage improved by up to 18.44%. During the development of KQFuzz, we discovered 13 bugs, all of which have been confirmed and 12 have already been fixed by the developers.
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All authors Fuyuan Xia, Qixin Zhang, Chenhao Ying, Haojin Zhu, Shuai Wang, Yuan Luo, Pingchuan Ma, Yuxuan Du

General Relativity and Quantum Cosmology

Conserved Gravitational Charges as Curvature Fluxes

Emel Altas and Bayram Tekin

Conserved gravitational charges are commonly expressed as surface integrals of the metric perturbation and its first derivatives. We show that, in the usual asymptotically AdS and asymptotically flat settings, the standard charges admit equivalent representatives as fluxes of linearized curvature. The construction uses a divergence-free rank-four tensor whose trace is proportional to the cosmological Einstein tensor. On a maximally symmetric AdS background, it reproduces the known curvature representation of the Abbott-Deser charges. The asymptotically flat construction is not obtained by taking a naive $\Lambda \rightarrow 0$ limit, since the Killing two-form vanishes for translations. We instead introduce an antisymmetric Poincaré Killing potential. A representative Killing potential adapted to the algebraic Bianchi identity converts the linearized Einstein current into a total divergence and yields a single curvature-flux formula. Its translation sector reproduces the ADM energy–momentum, while in four dimensions its Lorentz sector reproduces the angular momentum and boost/center-of-mass charges under the standard Regge-Teitelboim falloff and parity conditions. The normalization is checked explicitly for Schwarzschild, boosted Schwarzschild, and Kerr data. On non-maximally symmetric Einstein backgrounds, background Weyl curvature generates additional terms, so the maximally symmetric construction does not directly extend to a pure codimension-two curvature-flux formula.
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Quantum Physics

Nonlocal Magnonic Cat States in Hybrid Magnon-Qubit Architectures

Urmimala Dewan, Roson Nongthombam, Sampreet Kalita et al. (+1 more)

The quantum superpositions of coherent states offer an alternative to the conventional qubit-based encodings by harnessing the large Hilbert space available in bosonic modes, including those realised in microwave and optical cavities, magnons, and mechanical resonators. Beyond their advantages for local information processing, establishing long-distance quantum networks for such bosonic states is crucial for scalable quantum communication and distributed quantum computation. In this work, we propose an entanglement-swapping-based protocol to generate a bipartite magnonic cat state shared between spatially separated subsystems. Each subsystem comprises a hybrid architecture consisting of a superconducting transmon qubit coupled to a yttrium iron garnet (YIG) sphere that supports magnon modes. By performing a projective Bell-state measurement on the qubits, the initially established magnon-qubit entanglement is coherently transferred to the remote magnon modes, resulting in a nonlocal magnonic cat state. For experimental characterisation of the gener- ated states, we perform quantum state tomography through reconstruction of the Wigner function using joint displaced parity measurements of the magnon modes. Our scheme provides a feasible route towards realising long-distance magnonic entanglement and contributes to the advancement of hybrid quantum network architectures.
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All authors Urmimala Dewan, Roson Nongthombam, Sampreet Kalita, Amarendra K. Sarma

Chemical Physics

On transition path times for condensed-phase non-adiabatic electron transfer reactions under a two-parabola model

Ryo Nihei, Hiroki Uratani and Hirofumi Sato

Condensed-phase non-adiabatic electron transfer (ET) reactions play an important role in various areas of science. The characteristics of the microscopic transition processes involved in these reactions and their dynamic behavior remain poorly understood. In this study, we performed non-adiabatic simulations based on the Zhu-Nakamura theory, combining the two-parabola model with Kramers-like Langevin dynamics. We numerically analyzed the dependence of the macroscopic reaction time and the timescale of the microscopic transition process on the diabatic coupling between the diabatic states and on the friction parameter in Langevin dynamics. Although the microscopic transfer process is generally regarded as instantaneous in the non-adiabatic regime, we found that the timescale of the microscopic transition process can still be a non-negligible fraction of the macroscopic reaction time.
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Quantum Physics

Coherent control of subradiant excitations in atomic rings

Milena Djatchkova, Igor Lesanovsky and Beatriz Olmos

Subradiant excitations in ordered subwavelength atomic arrays are protected against radiative decay, making them a promising platform for storing and manipulating photonic excitations. The external geometry of the array, combined with dynamical control of the atomic dipole orientation, enables localized trapping and coherent transport of these subradiant excitations. Here, we theoretically demonstrate these capabilities in ring-shaped atomic arrays. Specifically, we show adiabatic transport of a localized excitation around a single ring, coherent transfer of a single excitation between two neighboring rings with geometry-controlled selectivity, and interaction-induced conditional phase shifts between two simultaneously trapped excitations in neighboring rings. Depending on the ring geometry, these realize either an entangling iSWAP-type exchange or a controlled-phase operation with tunable conditional phase. Together, these results demonstrate the potential of ordered atomic arrays as a platform for coherent photonic quantum information processing with dissipation-protected collective excitations.
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Applied Physics · Cross-listed from cs.LG

Using Data-Derived Priors to Guide CNN Architecture Design for NIR Chemometrics

Dário Passos

Convolutional neural networks (CNN) for near-infrared (NIR) chemometrics are often designed using generic architectural rules, although spectral datasets differ in sampling, smoothness, redundancy, and sample size. We tested whether these properties can provide empirical priors for CNN design. Across 25 NIR regression tasks, we computed descriptors of dataset size, spectral length and spacing, entropy, intrinsic rank, autocorrelation, and wavelet-scale structure. Two interpretable 1D-CNN scaffolds (a minimal single-convolution model and an extended shallow model with optional branching, dilation, etc) were optimized using five-fold cross-validated Bayesian hyperparameter optimization (HPO). Relationships extracted from near-optimal trials were converted into warm-start heuristics and evaluated directly and through leave-one-dataset-out (LODO) validation. The clearest relationships involved convolutional receptive fields. In the minimal CNN, the preferred kernel fraction decreased with spectral entropy and intrinsic rank, increased with the wavelet energy-support fraction, and the learning rate tended to decrease with training-set size. Direct and LODO heuristics were competitive with HPO, with median test-RMSE ratios of 0.953 and 1.017, respectively. The extended CNN showed similar but less transferable structure across branch usage, dilation, dropout, filter counts, and receptive-field choices. Ten stochastic refits showed seed sensitivity comparable to that of HPO-selected configurations. In a separate experiment, joint preprocessing and CNN HPO outperformed standardized-spectra HPO in 19 of 25 tasks, although gains were dataset-dependent. These results show that spectral descriptors can provide practical CNN design priors, guiding shallow NIR models toward plausible hyperparameter regions before target-specific tuning
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High Energy Physics (Phenomenology)

Constraining axion quadratic couplings with the Hulse-Taylor binary system

Ziwen Yin, Shyam Balaji, Malcolm Fairbairn et al. (+1 more)

The orbital evolution of the Hulse-Taylor binary neutron star system is described to high precision by general relativity, in which gravity is the only long-range force and gravitational waves provide the dominant energy-loss channel. We use this precision test of relativistic binary dynamics to derive new constraints on axion couplings to stable neutron star constituents: neutrons, electrons, and muons. Quadratic shift symmetry breaking axion-fermion couplings allow binary systems to lose energy through dipole and quadrupole emission of axion waves. These couplings also mediate long range, spin independent forces in two different regimes: in an ambient dark matter background, and when a tachyonic phase transition is triggered inside the neutron stars. For light QCD axions our constraints can be recast as limits on the axion decay constant, which are complementary to other probes for $m_a\lesssim 10^{-12}\text{ eV}$ and $f_a\lesssim M_\textrm{pl}$. For $m_a\lesssim10^{-12}\,{\rm eV}$, we place, to our knowledge, the strongest available constraint on the quadratic axion–muon coupling scale, providing a complementary probe to supernova cooling.
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All authors Ziwen Yin, Shyam Balaji, Malcolm Fairbairn, David J. E. Marsh

Quantum Physics

The Natural Formulation of Cubic-Phase Dynamics in the Linear Potential

Maximilian L. D. D. Pellner and Georgi Gary Rozenman

A quantum wave packet in a linear potential, i.e. a constant force such as gravity, accumulates a cubic-in-time phase, universal across Schrödinger-type platforms. The natural formulation of the cubic phase dynamics follows from their canonical realization, the Airy eigenstates. The eigenforce, the potential gradient for which the Airy profile is stationary and hence the intrinsic force behind its known self-acceleration absent any applied force, derives from the eigenvalue problem and characterizes the state uniquely up to a rigid translation. Alongside the applied force, it underlies the analytically closed form of these dynamics, comprising three known contributions, intrinsic, force-induced, and a cross term. The force-induced one alone is shape-independent, whereas the Airy eigenstate renders the other two non-dispersing. The cubic coefficient factorizes into two Newtonian force balances, vanishing at the stationary eigenstate and at a non-trivial zero where the phase cancels while the packet keeps accelerating. This exposes the eigenforce as an effective antagonist to the applied force, not only in the caustic's self-acceleration but here also within the phase, while leaving the centroid untouched by Ehrenfest's theorem. Spatially uniform within each packet, it escapes direct measurement, accessible only as the relative phase of two colliding packets, each in its own potential. The relative cubic coefficient is symmetry-forbidden for identical packets and activated by preparation asymmetry. Simulated interference of two truncated Airy packets demonstrates the extraction. Spanning ultracold atoms, paraxial optics, and surface-gravity water waves, it provides a platform-independent probe of the cubic phase and, through its force dependence, of the constant force itself.
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Statistical Mechanics

Entanglement asymmetry in the gapped XYZ spin-$\frac12$ chain

Felipe Taha Sant'Ana

The entanglement asymmetry measures how strongly a symmetry is broken inside a subsystem. Analytic results at equilibrium have so far covered free theories and, perturbatively, the critical XXZ chain. We compute the Rényi entanglement asymmetries of a large interval in the gapped, $U(1)$-breaking phase of the interacting XYZ chain. The calculation combines three ingredients. A charged-moment identity, which we prove for fermionic Gaussian and for injective matrix-product ground states, ties the asymmetry to the static susceptibility of the broken charge. A non-conservation sum rule then evaluates the susceptibility from sine-Gordon form factors, its two-kink and one-breather channels providing a lower bound on the universal amplitude. The Baxter–Johnson–Krinsky–McCoy solution supplies the kink mass for different couplings. Infinite-system density-matrix renormalization group simulations built on these masses reproduce the master formula.
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General Relativity and Quantum Cosmology

Spin precession in the strong deflection limit

Jiafei Geng, Yunchuan Xiang, Qingquan Jiang et al. (+1 more)

The strong deflection limit (SDL) of the deflection angle is well established for general spherically symmetric spacetimes, but a systematic SDL treatment of spin precession has been lacking. We derive the SDL expansion for the spin precession angle of particles propagating along geodesics in static, spherically symmetric, and asymptotically flat spacetimes. The SDL coefficients are obtained, and a simple relation linking the precession angle to the deflection one is established. Applying the formalism to Schwarzschild and Reissner-Nordström (RN) spacetimes, we obtain fully analytic SDL coefficients for the former and perturbative charge corrections to $\mathcal{O}(Q^2)$ for the latter. These results explicitly verify the universal spin-flip of massless particles in backward scattering, which is the underlying mechanism governing the absence of the glory spot. While the spin precession of massless particles is charge-independent, massive particles acquire a non-trivial charge dependence that distinguishes the RN case from Schwarzschild.
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All authors Jiafei Geng, Yunchuan Xiang, Qingquan Jiang, Xiankai Pang

Solar and Stellar Astrophysics

From simulations to observations of cool plasma: What we can learn from synthetic spectra

V. Jerčić, T. A. Kucera, A. G. M. Pietrow et al. (+2 more)

Cool plasma of coronal rain or prominences and filaments is ubiquitous in the solar corona. We explored the synthetic spectra of MgII h&k lines in detail and analyse how well a non-adiabatic magnetohydrodynamic (MHD) simulation of condensations in the corona matches observations when comparing the synthetic with the observed spectra. We applied, a Python implemented, non-local thermodynamic equilibrium (non-LTE) radiative-transfer framework, Promweaver to create synthetic spectra from a 2.5D MHD simulation created with MPI-AMRVAC. The simulation shows a dynamic system of numerous cold, dense thread-like structures that we compare to observations of the $\textit{Interface Region Imaging Spectrograph}$ (IRIS), with a focus on flare-driven coronal rain. We give a detailed description of the simulation from the aspect of the synthetic spectra. We show how and why the particular spectra form. A single thread already demonstrates great complexity. We further used the quartile analysis to systematically explore the evolution of observables in the observed and the synthetic spectra. This gives an overview of how the parameters change in time and that the changes seen in the simulation fit with the changes seen in observations. The results show that the simulation, in some aspects, matches particularly well to the observations of flare-driven coronal rain. Furthermore, we explored relations of parameters of the simulation and the observables. We find significant correlation between intensity and density, but not with temperature (in the studied temperature range of 5 to 20 kK). As a result, there is also a correlation of intensity and pressure. This relation allows us to further relate intensity and the vertical component of the Lorentz force. This brings us a step closer to a better understanding of the connection between the observed spectra and the atmosphere from which it originates.
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All authors V. Jerčić, T. A. Kucera, A. G. M. Pietrow, P. Antolin, J. M. Jenkins

High Energy Physics (Experiment)

Search for the $\boldsymbol{B^0 \to K^0_{\rm S} \tau^+ \tau^-}$ decay

Belle, Belle II Collaborations: M. Abumusabh, I. Adachi et al. (+430 more)

We present the first search for $B^0 \to K^0_{\rm S} \tau^+\tau^-$ decays. We look for signal decays in $B^0\bar B^0$ events produced in asymmetric-energy electron-positron collisions. This work uses samples from the Belle and Belle~II detectors, comprising 1.16 billion $\Upsilon(4S)$ events. In $\Upsilon(4S)\to B^0\bar{B}^0$ decays, the non-signal $\bar{B}^0$ meson is fully reconstructed in a hadronic channel. For the signal $B^0$ meson, $\tau$-lepton decays into final states with a single charged particle are selected. We observe no evidence for the signal and set an upper limit on the branching fraction $\mathcal{B}(B^0\to K^0_{\rm S} \tau^+\tau^-) < 8.3 \times 10^{-4}$ at the 90% confidence level. Combining this with the recent measurement of the isospin-partner decay $B^+\to K^+\tau^+\tau^-$, we determine an upper limit $\mathcal{B}(B\to K\tau^+\tau^-) < 5.4\times10^{-4}$ at the 90% confidence level.
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All authors Belle, Belle II Collaborations: M. Abumusabh, I. Adachi, A. Aggarwal, Y. Ahn, H. Aihara, M. Akdag, N. Akopov, S. Alghamdi, M. Alhakami, A. Aloisio, N. Althubiti, K. Amos, M. Angelsmark, N. Anh Ky, C. Antonioli, D. M. Asner, H. Atmacan, T. Aushev, V. Aushev, R. Ayad, V. Babu, H. Bae, N. K. Baghel, S. Bahinipati, P. Bambade, Sw. Banerjee, M. Bartl, J. Baudot, A. Beaubien, F. Becherer, J. Becker, J. V. Bennett, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, V. Bhardwaj, B. Bhuyan, F. Bianchi, T. Bilka, D. Biswas, A. Bobrov, D. Bodrov, A. Bondar, G. Bonvicini, J. Borah, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, F. Callet, Q. Campagna, M. Campajola, M. Carminati, G. Casarosa, C. Cecchi, M.-C. Chang, P. Cheema, L. Chen, B. G. Cheon, C. Cheshta, H. Chetri, K. Chilikin, K. Chirapatpimol, H.-E. Cho, K. Cho, S.-J. Cho, S.-K. Choi, S. Choudhury, S. Chutia, J. Cochran, J. A. Colorado-Caicedo, I. Consigny, L. Corona, H. Crotte Ledesma, S. Cuccuini, J. X. Cui, S. Das, E. De La Cruz-Burelo, S. A. De La Motte, G. de Marino, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, R. Dhayal, A. Di Canto, J. Dingfelder, Z. Doležal, X. Dong, M. Dorigo, K. Dugic, G. Dujany, P. Ecker, J. Eppelt, R. Farkas, P. Feichtinger, T. Ferber, T. Fillinger, C. Finck, G. Finocchiaro, F. Forti, A. Frey, B. G. Fulsom, A. Gabrielli, P. Gagneja, A. Gale, E. Ganiev, M. Garcia-Hernandez, R. Garg, G. Gaudino, V. Gaur, V. Gautam, A. Gaz, A. Gellrich, G. Ghevondyan, D. Ghosh, H. Ghumaryan, R. Giordano, A. Giri, P. Gironella Gironell, A. Glazov, B. Gobbo, R. Godang, O. Gogota, W. Gradl, E. Graziani, D. Greenwald, Y. Guan, K. Gudkova, I. Haide, H. Haigh, Y. Han, K. Hayasaka, H. Hayashii, S. Hazra, C. Hearty, M. T. Hedges, G. Heine, I. Heredia de la Cruz, T. Higuchi, M. Hoek, M. Hohmann, R. Hoppe, P. Horak, C.-L. Hsu, T. Humair, T. Iijima, K. Inami, G. Inguglia, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, P. Jackson, D. Jacobi, W. W. Jacobs, E.-J. Jang, S. Jia, Y. Jin, A. Johnson, K. K. Joo, K. H. Kang, G. Karyan, F. Keil, C. Ketter, C. Kiesling, C. Kim, D. Y. Kim, H. Kim, J.-Y. Kim, K.-H. Kim, H. Kindo, K. Kinoshita, P. Kodyš, T. Koga, S. Kohani, A. Korobov, S. Korpar, E. Kovalenko, R. Kowalewski, P. Križan, P. Krokovny, T. Kuhr, Y. Kulii, J. Kumar, R. Kumar, K. Kumara, T. Kunigo, S. Kurokawa, A. Kuzmin, Y.-J. Kwon, S. Lacaprara, T. Lam, J. S. Lange, T. S. Lau, R. Leboucher, F. R. Le Diberder, H. Lee, M. J. Lee, C. Lemettais, P. Leo, C. Li, H.-J. Li, L. K. Li, Q. M. Li, S. X. Li, W. Z. Li, Y. Li, Y. B. Li, Y. P. Liao, J. Libby, J. Lin, S. Lin, Z. Liptak, V. Lisovskyi, C. Liu, M. H. Liu, Q. Y. Liu, Z. Q. Liu, D. Liventsev, S. Longo, A. Lozar, T. Lueck, C. Lyu, J. L. Ma, Y. Ma, M. Maggiora, S. P. Maharana, R. Maiti, G. Mancinelli, R. Manfredi, E. Manoni, M. Mantovano, D. Marcantonio, S. Marcello, M. Marfoli, C. Marinas, C. Martellini, A. Martens, T. Martinov, L. Massaccesi, M. Masuda, T. Matsuda, D. Matvienko, S. K. Maurya, M. Maushart, J. A. McKenna, Z. Mediankin Gruberová, R. Mehta, F. Meier, D. Meleshko, M. Merola, C. Miller, M. Mirra, K. Miyabayashi, H. Miyake, R. Mizuk, G. B. Mohanty, S. Moneta, A. L. Moreira de Carvalho, H.-G. Moser, N. Mudgal, Th. Muller, H. Murakami, R. Mussa, I. Nakamura, K. R. Nakamura, M. Nakao, H. Nakazawa, Y. Nakazawa, M. Naruki, Z. Natkaniec, A. Natochii, M. Nayak, M. Neu, S. Nishida, R. Nomaru, A. Novosel, S. Ogawa, R. Okubo, H. Ono, Y. Onuki, G. Pakhlova, S. Pardi, J. Park, K. Park, S.-H. Park, A. Passeri, S. Patra, T. K. Pedlar, R. Pestotnik, M. Piccolo, L. E. Piilonen, P. L. M. Podesta-Lerma, T. Podobnik, A. Prakash, C. Praz, S. Prell, E. Prencipe, M. T. Prim, S. Privalov, I. Prudiiev, H. Purwar, P. Rados, S. Raiz, K. Ravindran, J. U. Rehman, M. Reif, S. Reiter, M. Remnev, L. Reuter, D. Ricalde Herrmann, I. Ripp-Baudot, G. Rizzo, S. H. Robertson, J. M. Roney, A. Rostomyan, N. Rout, S. Saha, L. Salutari, D. A. Sanders, S. Sandilya, L. Santelj, C. Santos, V. Savinov, B. Scavino, S. Schneider, G. Schnell, M. Schnepf, K. Schoenning, C. Schwanda, Y. Seino, K. Senyo, J. Serrano, M. E. Sevior, C. Sfienti, C. P. Shen, X. D. Shi, T. Shillington, T. Shimasaki, J.-G. Shiu, D. Shtol, B. Shwartz, A. Sibidanov, F. Simon, J. B. Singh, J. Skorupa, R. J. Sobie, A. Soffer, A. Sokolov, E. Solovieva, W. Song, S. Spataro, K. Špenko, B. Spruck, M. Starič, P. Stavroulakis, S. Stefkova, R. Stroili, M. Sumihama, K. Sumisawa, M. Takahashi, M. Takizawa, U. Tamponi, K. Tanida, F. Testa, A. Thaller, D. V. Thanh, T. Tien Manh, O. Tittel, R. Tiwary, D. Tonelli, E. Torassa, K. Trabelsi, F. F. Trantou, I. Tsaklidis, M. Uchida, I. Ueda, T. Uglov, K. Unger, Y. Unno, K. Uno, S. Uno, P. Urquijo, Y. Ushiroda, S. E. Vahsen, R. van Tonder, K. E. Varvell, M. Veronesi, A. Vinokurova, V. S. Vismaya, L. Vitale, V. Vobbilisetti, R. Volpe, M. Wakai, S. Wallner, M.-Z. Wang, X. L. Wang, A. Warburton, S. Watanuki, C. Wessel, X. P. Xu, B. D. Yabsley, S. Yamada, W. Yan, W. P. Yan, J. Yelton, K. Yi, J. H. Yin, K. Yoshihara, C. Z. Yuan, J. Yuan, L. Yuan, Y. Yusa, L. Zani, F. Zeng, M. Zeyrek, B. Zhang, X. Zhao, V. Zhilich, J. S. Zhou, Q. D. Zhou, X. Y. Zhou, L. Zhu, R. Žlebčík

High Energy Physics (Phenomenology)

Virtual state and two-pole structure: $\Xi(1690)$ and $\Xi(1820)$ from BESIII data on $\psi(3686)\to K^-\Lambda\bar{\Xi}^+$

Jun He

We investigate the nature of the $\Xi(1690)$ and $\Xi(1820)$ resonances by analyzing the recent BESIII data on $\psi(3686) \to K^-\Lambda\bar{\Xi}^+$ within a coupled-channel rescattering framework. The calculation includes the channels $\bar{K}\Lambda$, $\bar{K}\Sigma^{(*)}$, $\pi\Xi^{(*)}$, $\eta\Xi^{(*)}$, and $K\Omega$. A direct fit to the data reveals that the $\Xi(1690)$ is best described as a virtual state located right below the $\bar{K}\Sigma$ threshold, a feature that naturally explains its very sharp peak observed in the $K^-\Lambda$ invariant mass spectrum. In contrast, the $\Xi(1820)$ exhibits a two-pole structure originating mainly from the coupled contributions of the $K\Sigma^*$ and $\pi\Xi^*$ channels, showing a two-pole pattern similar to that of the well-known $\Lambda(1405)$ and accounting for the unexpectedly broad width measured by BESIII. These findings provide new insights into the dynamical generation of hyperon resonances and highlight the importance of high-precision data from charmonium decays.
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Mathematical Physics · Cross-listed from math.AP

Well-posed homogenized strain-gradient models for linear elastodynamics and elastostatics in arbitrary periodic media

Rémi Cornaggia, Marc Bonnet, Giuseppe Rosi et al. (+2 more)

This work develops well-posed homogenized strain-gradient models for linear elastostatics and elastodynamics in periodic media, with a primary focus on elastic wave propagation. Using the classical two-scale asymptotic expansion method, we carry out second-order periodic homogenization for media in $\mathbb{R}^d$ ($d = 2, 3$), with no restriction on the periodicity cell geometry or material distribution. Reciprocity identities applied to suitably chosen pairs of cell solutions provide alternative expressions for the effective stiffness and inertia tensors arising at the leading, first and second orders, substantially reducing the number of cell problems that must actually be solved. Since direct two-scale homogenization beyond leading order generically yields ill-posed effective operators, a Boussinesq-trick procedure is introduced, involving a tunable scalar weight, to recast the resulting fourth-order partial differential equation as a valid strain-gradient elasticity (SGE) model possessing the requisite symmetry, sign-definiteness and coercivity properties. These properties are then used, via the Hille-Yosida theorem, to establish the well-posedness of the corresponding transient initial-value and forced-response problems. Several practically relevant special cases are examined, including centrosymmetric cells, homogeneous mass density and homogeneous elasticity, each yielding simplified model structures. Numerical illustrations on three two-dimensional periodicity cells (square, hexagonal and a non-centrosymmetric chiral lattice) compare the resulting dispersion relations against reference Floquet-Bloch computations and assess transient wave propagation, demonstrating the model's capacity to capture anisotropic and dispersive effects beyond classical elasticity while preserving mathematical well-posedness.
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All authors Rémi Cornaggia, Marc Bonnet, Giuseppe Rosi, Saad El Ouafa, Nicolas Auffray

Exactly Solvable and Integrable Systems

Tau functions of the constrained matrix KP hierarchy

Xiaohan Fan, Jipeng Cheng and Jinbiao Wang

The constrained matrix KP hierarchy $(L^{k})_{<0}=\sum_{i=1}^{m}Q_{i}\partial^{-1}R_{i}^{\intercal}$ is investigated from the aspects of tau functions. Firstly, the matrix KP hierarchy is viewed as one special reduction of the multi-component KP hierarchy. Then bilinear equations of the constrained matrix KP hierarchy as the multi-component KP hierarchy are given in terms of tau functions. Finally based upon these results, the tau functions for the constrained matrix KP hierarchy are constructed by using the multi-component boson-fermion correspondence. Notice that the solutions of the constrained matrix KP hierarchy are derived without using quasi-determinants.
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Mathematical Physics · Cross-listed from math.QA

Graph integrals, Feynman periods, and single-valued multiple zeta values

Jean-Luc Portner

The Borel classes generating the stable cohomology of the general linear group can be represented by invariant differential forms. It is known that pulling these forms back along a tropical Torelli map yields canonical convergent integrals associated to graphs, which are closely connected to the cohomology of $\mathrm{GL}_n$ and of graph complexes. A natural question is what numbers these graph integrals are. We answer this for primitive canonical integrals by showing that they coincide with a family of complex position-space integrals arising in deformation quantisation. As a consequence, canonical integrals of graphs evaluate to single-valued multiple zeta values. We further deduce that every single-valued multiple zeta value occurs as a rational linear combination of Feynman periods of graphs with massless propagators. Finally, in the commutative graph complex, our result implies that the two associated cocycles agree.
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Materials Science

Ferroelectricity and antiferroelectricity in the BaS-PbS system with the rocksalt structure

Alexander I. Lebedev

The ferroelectric instability in superstructures, superlattices, quantum wires, and disordered solid solutions in the BaS–PbS system with the NaCl structure has been discovered and investigated using first-principles calculations within the density functional theory. The emergence of ferroelectricity in these structures is associated with the instability of TO phonons in linear –Pb–S–Pb–S– chains, which arises as a result of stretching of the structures upon the introduction of large barium atoms. Additionally, it has been discovered that, alongside ferroelectric phases, the structures also exhibit stable, competing antiferroelectric phases and those with a mixed ferroelectric–antiferroelectric ordering (ferroelectrically polarized one-dimensional Pb–S chains arranged in an ordered or disordered manner in the perpendicular direction). These phases often become the ground state of the studied systems. The closeness of the energies of the ferroelectric, antiferroelectric, and mixed states indicates the emergence of a multi-minimum potential with an infinite number of wells separated by potential barriers in the configuration space. This suggests a possible emergence of nonergodicity in the structures at low temperatures.
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