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Physics

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Materials Science

Surface Functionalization Enables Two-Dimensional Altermagnetism and Giant Tunnel Magnetoresistance

Zhou Cui, Ziye Zhu, Bowen Hao et al. (+7 more)

Two-dimensional (2D) altermagnets (AMs) are highly desirable for ultrafast, stray-field-free spintronics because they combine compensated magnetic order and momentum-dependent spin splitting with the scalability, tunability, and interface compatibility of atomically thin materials. However, practical 2D AMs remain scarce. Rather than relying solely on the search for intrinsic 2D AMs, an appealing route is to transform known 2D antiferromagnets (AFMs) into AMs through symmetry engineering. Here, we propose surface functionalization as a symmetry-guided, nonvolatile chemical switch for realizing this AFM-to-AM transformation. By breaking inversion and out-of-plane mirror symmetries while preserving the rotation symmetry connecting opposite-spin sublattices, single-sided functionalization lifts spin degeneracy and induces altermagnetic spin splitting. Using monolayer FeSe as a representative platform, first-principles calculations show that hydrogenation, oxidation, and fluorination convert spin-degenerate antiferromagnetic FeSe into a d-wave AM with pronounced momentum-dependent spin splitting. At the device level, our transport simulations reveal that the functionalized FeSe monolayer magnetic tunnel junctions exhibit giant tunnel magnetoresistance (TMR) up to $1.87\times10^3\%$, originating from momentum-selective spin filtering between parallel and antiparallel Néel-vector configurations. The strong dependence of TMR on functionalization geometry further demonstrates that surface chemistry provides an effective control knob for altermagnetic transport. Our work establishes a symmetry-to-chemistry-to-device strategy for engineering 2D AMs and developing high-performance altermagnetic spintronic devices.
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All authors Zhou Cui, Ziye Zhu, Bowen Hao, Xunkai Duan, Xuan Zhou, Yali Xie, Huali Yang, Baisheng Sa, Runwei Li, Tong Zhou

Quantum Physics

On estimating operator norm distance, with optimal trace distance estimation when one state is pure

Yupan Liu, Qisheng Wang and Zhan Yu

We investigate the computational complexity of estimating the operator norm distance ${\rm T}_{\infty}(\rho_0,\rho_1)$, defined via the operator norm $\|A\|_{\infty} = \sigma_{\max}(A)$, given ${\rm poly}(n)$-size state-preparation circuits of $n$-qubit quantum states $\rho_0$ and $\rho_1$. We provide efficient quantum estimators for the operator norm distance whose complexity is independent of the rank (and thus the dimension) of the states: 1. When one state is pure, we establish an optimal quantum estimator using $\Theta(1/\epsilon)$ queries to the state-preparation circuits. Consequently, for constant additive error, say $\epsilon=1/5$, our estimator runs in ${\rm poly}(n)$ time. Since the operator norm distance ${\rm T}_{\infty}(|\psi\rangle\!\langle\psi|,\rho)$ is exactly half of the trace distance ${\rm T}(|\psi\rangle\!\langle\psi|,\rho)$, our result also gives rank-independent query complexity for estimating both quantities, whereas the approaches due to van Apeldoorn, Cornelissen, Gilyén, and Nannicini (SODA 2023) and Wang and Zhang (TIT 2024) have query complexity scaling at least linearly with ${\rm rank}(\rho)$, which can be $\exp(n)$ in general. 2. For general quantum states, we also provide a quantum estimator using $\widetilde{O}(1/\epsilon^{3/2})$ queries to the state-preparation circuits, which shows that the corresponding promise problem is ${\sf BQP}$-complete and improves the ${\sf QMA}$ upper bound sketched by Liu and Wang (ESA 2025). Together with an $\Omega(1/\epsilon)$ quantum query complexity lower bound, this leaves only square-root room for improvement. The key intuition behind our estimators is that, when one state is pure, the pure state $|\psi\rangle$ has overlap at least $1/2$ with the top unit eigenvector of $|\psi\rangle\!\langle\psi|-\rho$, reflecting a structural feature specific to the operator norm distance.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG

Transformers with Physics-Informed Encodings and Simulation-Based Inference for Robust Detection of Eccentric Binary Black Holes in Pulsar Timing Array Data

Subhajit Dandapat and Alvin J. K. Chua

Pulsar timing arrays (PTAs) provide a unique window into nanohertz gravitational waves (GWs), but extracting astrophysical parameters from noisy, long-baseline timing residuals remains computationally challenging with traditional Bayesian techniques due to the high dimensionality of the parameter space, complex and correlated noise models, and the cost of repeated likelihood evaluations. We introduce a Transformer with a physics-informed positional-encoding framework for the efficient inference of eccentric binary black holes in relativistic orbits from PTA data. Our approach embeds analytical GW phase evolution directly into the model through structured positional encodings, enabling the network to learn physically meaningful representations from raw PTA timing residuals. We then use generative models, including discrete and continuous conditional normalizing flows, to infer posterior distributions within a simulation-based inference framework. Across a range of signal-to-noise ratios, the proposed method achieves improved accuracy, sharper posteriors, and faster inference compared to physics-agnostic baselines. While presented for deterministic white-noise signals, the modular framework readily generalizes to realistic PTA analyses incorporating red noise and additional components. This work highlights the potential of physics-aware deep learning models as scalable alternatives to conventional inference pipelines for next-generation PTA datasets.
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Quantum Gases

Experimental signatures of bosonic pairing in a two-component Bose gas

Omar Almonajed, M. Iskin and M. Ö. Oktel

Two-component bosonic droplets are commonly described within Bogoliubov theory, where beyond-mean-field quantum fluctuations stabilize the system against mean-field collapse. In the interaction regime where droplets form, however, the Bogoliubov excitation spectrum contains an imaginary branch associated with the underlying instability, which is typically omitted when evaluating the beyond-mean-field energy. Bosonic pairing theory provides an alternative description with a fully real excitation spectrum. In this work, we reformulate bosonic pairing theory within an operator formalism, making its underlying approximations transparent, and compare its predictions with those of Bogoliubov theory for a homonuclear binary Bose mixture across the crossover from a weakly interacting gas to the droplet regime. Working at fixed particle density, we determine the variational parameters of bosonic pairing theory self-consistently and focus on the regime in which both theories possess real excitation spectra, allowing a direct comparison. We find that bosonic pairing theory yields a lower grand potential than Bogoliubov theory and predicts qualitatively distinct correlation signatures, including enhanced long-wavelength interspecies momentum-space correlations and a finite density static structure factor at experimentally accessible low momenta. These differences persist over a broad range of interaction strengths and suggest that correlation and structure-factor measurements can provide direct experimental tests of bosonic pairing across the gas-to-droplet crossover.
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Quantum Physics

Algebra of quantum mechanics via classical phonons. I: The Schrodinger equation as the Newtonian equation of motion and quantum observables as classical averages

Emmanuel Giner

The Schrodinger equation for a single spinless particle is formally obtained via a classical phonon model, namely the Frenkel-Kontorova model. Starting from a one-dimensional lattice of coupled harmonic oscillators, we show that the continuous limit of the corresponding Newtonian equation of motion yields the Klein-Gordon equation for a real-valued field. By introducing a complex-valued change of variables mixing the real-valued displacement and velocity fields, and by separating fast and slow time scales, the Klein-Gordon equation is written as the Schrodinger equation within the non-relativistic limit. This complex change of variable also allows to rewrite classical global observables of the phonon field, such as the total energy or momentum, as the corresponding quantum observables. Additionally, we show that when a friction force is incorporated into the classical model, the corresponding Klein-Gordon equation can be rewritten as a Schrodinger equation with a non-Hermitian Hamiltonian. While the global approach is limited here to the non-relativistic regime and does not address the measurement problem, quantization or relativistic effects, it nonetheless illustrates how quantum algebra and complex-valued wave functions can be exactly reproduced using classical dynamics. The relativistic regime for a spinless particle and the link between commutators and Poisson brackets is addressed in the second part of this series.
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Accelerator Physics

Beam-Level Nonlinear Compton Spectra via a Neural Network Surrogate Model

Antonina Timoshenko, Maxim Malakhov, Alexander Fedotov et al. (+1 more)

Nonlinear Compton scattering enables sources of intense high-energy radiation. However, predicting source-level spectra for realistic electron beams typically requires computationally expensive trajectory-based calculations, whereas existing analytical models for spectral envelopes are limited to a restricted range of laser pulse parameters. Here, we demonstrate that, for electron beams with sufficiently broad phase-space distributions, beam-level nonlinear Compton spectra can be predicted without lengthy numerical calculations. Our approach combines a fast neural-network surrogate for single-electron spectral envelopes with particle-wise Lorentz transformations. Benchmarked against trajectory-based numerical calculations with thousands of macroparticles, the surrogate reproduces the macroscopic spectral-angular structure while reducing the computational cost by orders of magnitude.
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All authors Antonina Timoshenko, Maxim Malakhov, Alexander Fedotov, Sergey Rykovanov

Materials Science

Morphology-Property Interplay in Chemo-Mechanics of Ion-Intercalation Active Particles

Rongyue Lin, Royal C. Ihuaenyi, Juner Zhu et al. (+1 more)

Morphology, material property, and mechanical constraint jointly govern the chemo-mechanical behavior of ion-intercalation particles, yet their coupled effects remain insufficiently understood. Here we establish a thermodynamically consistent single-particle framework and combine analytical solutions with multiphysics simulations to determine how these factors regulate lithiation and stress generation. We study hollow spherical, cylindrical, and ellipsoidal particles with isotropic or transversely isotropic material properties under fully constrained, inner-free, or unconstrained boundary conditions. We show that the transient lithiation pathway and the associated stress and strain fields are governed not by morphology, property, or constraint alone, but by their coupled interaction: isotropic particles are sensitive to the mechanical constraint, whereas transversely isotropic particles exhibit persistent heterogeneous lithiation dominated by anisotropic diffusivity. Flux decomposition analysis reveals that the mechanical contribution to Li flux is negligible in spheres but dominant in ellipsoids. Correlation analysis further shows that Li concentration and volumetric strain exhibit strong anti-correlation in unconstrained particles but weak correlation under full constraints. Bayesian optimization of hollow ellipsoids identifies Pareto-optimal morphologies that balance lithiation capacity against peak tensile stress. These results provide a unified framework for the morphology-property interplay in intercalation particles and offer morphology design principles for chemo-mechanical stability.
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All authors Rongyue Lin, Royal C. Ihuaenyi, Juner Zhu, Ruobing Bai

Nuclear Experiment

Measurement of isolated prompt photon production in $p$+$p$ collisions at $\sqrt{s} = 200$ GeV with the sPHENIX detector

sPHENIX Collaboration: M. I. Abdulhamid, U. Acharya, G. Adawi et al. (+217 more)

The differential cross section of isolated prompt photon production is measured as a function of photon transverse energy ($E_{\mathrm{T}}^{\gamma}$) in proton–proton ($p$+$p$) collisions at $\sqrt{s} = 200$ GeV. The data were recorded in $2024$ with the sPHENIX detector at the Relativistic Heavy Ion Collider. Photons are reconstructed in $|\eta^{\gamma}| < 0.7$ and $12 < E_{\mathrm{T}}^{\gamma} < 32$ GeV using the electromagnetic calorimeter, and an isolation requirement is imposed using both the electromagnetic and hadronic calorimeters. The measured cross section is compared with the PYTHIA Monte Carlo event generator and perturbative quantum chromodynamics (pQCD) calculations at next-to-leading and next-to-next-to-leading order. The pQCD calculations are consistent with the result within the quoted uncertainties. This measurement provides a test of pQCD calculations for a process with sensitivity to the gluon parton distribution function of the proton and establishes the $p$+$p$ baseline for forthcoming sPHENIX measurements of isolated prompt photons in heavy-ion collisions.
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All authors sPHENIX Collaboration: M. I. Abdulhamid, U. Acharya, G. Adawi, I. Ahmed, C. A. Aidala, Y. Akiba, M. Alfred, A. Alsayegh, D. M. Anderson, V. V. Andrieux, A. Angerami, N. Applegate, M. U. Ashraf, B. Azmoun, V. R. Bailey, S. Bathe, A. Bazilevsky, R. Belmont, J. Bennett, J. C. Bernauer, J. Bertaux, H. Bossi, A. Brahma, J. W. Bryan, M. Chamizo-Llatas, S. B. Chauhan, D. Chen, J. Chen, C.-Y. Chi, M. Chiu, J. Clement, E. W. Cline, M. Connors, R. Corliss, Y. Corrales Morales, E. Croft, N. d'Hose, M. Daradkeh, S. J. Das, A. P. Dash, G. David, C. T. Dean, X. Dong, A. Drees, J. Driebeek, J. M. Durham, A. Enokizono, H. Enyo, R. Esha, B. Fadem, K. Finnelli, D. Firak, D. S. Fitzgerald, L. V. Flores-Sanchez, A. Francisco, J. Frantz, A. Frawley, M. Fujiwara, G. Garmire, Y. Go, I. Goel, Y. Goto, N. Grau, S. V. Greene, S. K. Grossberndt, T. Hachiya, J. S. Haggerty, D. A. Hangal, T. Harada, S. Hasegawa, M. Hata, W. He, X. He, T. Hemmick, A. Hodges, A. Holt, B. Hong, S. Howell, H. Z. Huang, J. Huang, C. Hughes, J. Hwang, M. Ikemoto, Y. Ishigaki, J. James, H.-R. Jheng, H. Jiang, M. Kano, L. Kasper, T. Kato, A. M. Khan, M. S. Khan, T. Kikuchi, B. Kimelman, A. G. Knospe, N. Kumar, R. Kunnawalkam Elayavalli, C. M. Kuo, J. Kvapil, J. Lajoie, A. Lebedev, S. Lee, L. Legnosky, S. Li, X. Li, S. Liechty, S. Lim, D. Lis, M. X. Liu, W. J. Llope, D. A. Loomis, R.-S. Lu, C. Ma, L. Ma, W. Ma, V. Mahaut, E. Mannel, T. R. Marshall, C. Martin, G. Mattson, C. McGinn, E. McLaughlin, T. Mengel, A. S. Menon, M. Meskowitz, A. Milov, I. Mitrankov, M. Mitrankova, N. Morimoto, D. Morrison, L. W. Mwibanda, C.-J. Naïm, J. L. Nagle, I. Nakagawa, A. Narde, C. E. Nattrass, D. Neff, S. Nelson, P. A. Nieto-Marín, R. Nouicer, G. Nukazuka, E. O'Brien, G. Odyniec, V. A. Okorokov, A. C. Oliveira da Silva, I. Omae, J. D. Osborn, G. J. Ottino, J. Park, A. Patton, H. Pereira Da Costa, D. V. Perepelitsa, M. Peters, S. Ping, C. Pinkenburg, R. Pisani, C. Platte, T. Protzman, M. L. Purschke, J. Putschke, R. J. Reed, S. Regmi, B. Rehman, E. Renner, D. Richford, C. Riedl, C. Roland, G. Roland, M. Rosati, A. Saed, T. Sakaguchi, H. Sako, S. Salur, J. Sandhu, M. Sarsour, S. Sato, B. Sayki, C. Scarlett, J. Schambach, M. Schernau, R. Seidl, B. D. Seidlitz, Y. Sekiguchi, M. Shahid, D. M. Shangase, Z. Shi, C. W. Shih, M. Shimomura, R. Shishikura, E. Shulga, A. Sickles, J. Singh, R. A. Soltz, W. Sondheim, P. Steinberg, D. Stewart, M. Stojanovic, S. Stoll, Y. Sugiyama, W.-C. Tang, S. Tarafdar, H. Tsujibata, E. Tuttle, E. N. Umaka, M. Vandenbroucke, J. Velkovska, V. Verkest, A. Vijayakumar, M. Watanabe, V. Wolfe, C. Woody, W. Xie, Z. Ye, K. Yip, Z. You, C.-J. Yu, X. Yu, X. Yu, W. A. Zajc, J. Zhang

General Relativity and Quantum Cosmology

Identifying lensed gravitational waves with physics-informed posterior learning

Tian-Yang Sun, Xiao Guo, Jing-Fei Zhang et al. (+1 more)

Gravitational lensing of gravitational waves can probe compact lenses, dark matter substructure, and cosmological distances, but identifying lensed events is difficult when unrelated binary mergers overlap in the same analysis window. We develop physics-informed posterior learning for ranking lensed multi-image signals against unrelated multiple-merger events. The method exploits the geometric-optics consistency that lensing can change amplitudes, arrival times, and Morse phase offsets while preserving the intrinsic phase evolution of the source. We infer a simulation-trained approximate posterior for the common detector-frame chirp mass and symmetric mass ratio, and fuse posterior samples with direct waveform features. Training uses generic multi-image simulations, while point-mass, singular-isothermal-sphere, singular-isothermal-ellipsoid, and shear-perturbed lenses are reserved for held-out lens-family evaluation. For the observationally motivated binary-black-hole population, the fusion ranking raises the detection efficiency from $20.8\%$ to $35.2\%$ at a $1\%$ reference false-positive-rate threshold calibrated on the corresponding unrelated multiple-merger sample. It lowers the network signal-to-noise ratio needed for $50\%$ detection efficiency from 45.3 to 33.5, which corresponds to a 1.35 times larger signal-to-noise-ratio-equivalent distance scale. The gain is limited by loud unrelated multiple-merger events that are partly source consistent, and by the need to calibrate the unrelated multiple-merger population. These results suggest that physical consistency can become a guiding principle for machine learning searches in dense gravitational-wave catalogs.
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All authors Tian-Yang Sun, Xiao Guo, Jing-Fei Zhang, Xin Zhang

General Relativity and Quantum Cosmology

Radiated Energy Spectrum, Radiated Angular Distribution and Non-linear Memory from the One-loop Gravitational Bremsstrahlung Waveform

Donato Bini, Thibault Damour, Stefano De Angelis et al. (+1 more)

The frequency-domain gravitational waveform emitted by the scattering of two non-spinning massive particles has recently been derived at next-to-leading, i.e. one-loop, post-Minkowskian order, $h(\omega, \theta,\phi) \sim G^2 + G^3$. Building on this one-loop-accurate frequency-domain gravitational waveform, we successively derive the spectral gravitational-wave (GW) radiance, $dE^{\rm gw}/(d\omega d\Omega)$, the radiated GW energy spectrum, $dE^{\rm gw}/d\omega$, and the radiated GW angular distribution, $dE^{\rm gw}/d\Omega$, up to order $G^4$ included. We deduce from the radiated angular distribution the multipole expansion of the non-linear memory up to order $G^5$ included, thereby extending previous results. We work in the center-of-mass frame, and our results reach the fractional 7.5PN accuracy. For completeness, we include the tree-level information (considered in the center-of-mass frame).
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All authors Donato Bini, Thibault Damour, Stefano De Angelis, Andrea Geralico

Fluid Dynamics

Mechanisms of lift generation and drag invariance by asymmetric surface roughness on a sphere

Putu Brahmanda Sudarsana, Jagmohan Singh and Anchal Sareen

The mechanisms governing transverse force generation on a sphere with asymmetric dimpled roughness are investigated using wall-resolved large eddy simulation at $Re=U_\infty d/\nu=100{,}000$ for $k/d=0.004$, $0.006$, and $0.008$. Previous experiments by Sudarsana et al. (2024) showed that asymmetric roughness can generate lift comparable to the peak Magnus force on a rotating sphere while leaving the mean drag nearly unchanged. The present simulations reproduce this behavior and reveal the coupled mechanisms responsible for lift generation and drag invariance. Pressure-force decomposition shows that asymmetric dimples redistribute the streamwise pressure contribution between the upstream and downstream hemispheres with little change in net drag, while producing a finite transverse pressure imbalance that generates lift. A Fourier decomposition further shows that pressure drag is governed primarily by the axisymmetric pressure component, whereas lift is governed by the non-axisymmetric component. The dimples also produce distinct transition pathways on the two hemispheres: the dimpled side undergoes near-wall transition before separation, delaying separation non-uniformly to $\phi_s\sim105^\circ - 125^\circ$, while the smooth side separates in a laminar state at $\phi_s\sim80^\circ$. The resulting pressure asymmetry drives sidewash from the smooth to the dimpled side, which rolls up into a counter-rotating streamwise vortex pair that amplifies wake deflection beyond that expected from separation-angle differences alone. These results show that lift generation arises from the coupled interaction of asymmetric transition, non-uniform separation, pressure-driven sidewash, and coherent wake reorganization.
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High Energy Astrophysical Phenomena

Cross-validation of six dispersion measure estimation methods for FRB 20240114A

Tonglun Wang, Songbo Zhang, Yuanchuan Zou et al. (+11 more)

Fast Radio Bursts (FRBs) are important cosmological probes, but their applications depend critically on accurate dispersion measure (DM) determinations. We present a systematic comparison of six DM estimation methods using 2,874 bursts from FRB20240114A, the most active repeating FRB currently known, observed by FAST during a single 4.4-hr session on 2024 March 12. This large, homogeneous sample over a short timescale, during which the propagation environment is expected to be nearly static, provides an ideal benchmark for isolating algorithmic effects on DM determination. We investigate the dependence of inter-method consistency on signal-to-noise ratio (S/N), burst morphology, and radio frequency interference (RFI). Low-S/N bursts exhibit significantly larger inter-method deviations, while single-component bursts produce highly consistent DM values across methods. In contrast, complex double- and multiple-component bursts with drifting substructures lead to substantial inter-method scattering, indicating that DM discrepancies are primarily driven by algorithmic responses to burst morphology. RFI does not significantly alter the global statistical behavior of DM deviations, but it affects density-filtering methods through morphology distortion caused by frequency-channel masking. Even after imposing strict inter-method consistency constraints, FRB20240114A still exhibits notable apparent DM fluctuations spanning $\sim$528-534~pc~cm$^{-3}$ over 15,780s. For morphologically simple bursts these variations far exceed the measurement uncertainty and, on second-to-minute timescales, cannot arise from any plausible change in the line-of-sight electron column, pointing instead to a frequency-dependent emission-time structure intrinsic to the bursts that mimics dispersion.
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All authors Tonglun Wang, Songbo Zhang, Yuanchuan Zou, Xuan Yang, Pei Wang, Di Xiao, Xianghan Cui, Ye Li, Hao Qiu, Yingze Shan, Junyi Shen, Ya Zeng, Longxuan Zhang, Wenlong Zhang

Solar and Stellar Astrophysics

Star Planet Interactions

Arghyadeep Paul, Kristina Kislyakova, Manuel Güdel et al. (+13 more)

Star-planet interactions (SPIs) describe the continuous exchange of energy, momentum, and mass between exoplanets and their host stars through radiative, tidal, magnetic, and particle-driven processes. Together, these interactions shape the structure, evolution, and observable properties of exoplanetary systems. In this review, we bring together current theoretical and observational understanding of SPIs, highlighting how stellar radiation, winds, and magnetic activity influence planetary atmospheres, interiors, and orbital evolution, while using the Solar System as a valuable reference for interpreting these processes. High-energy stellar radiation, particularly in the far- and extreme-ultraviolet and X-ray bands, drives atmospheric heating, photochemistry, ionisation, and escape. These effects are further influenced by stellar winds and magnetic interactions, which can either protect planetary atmospheres or accelerate their loss over time. Tidal interactions redistribute energy and angular momentum, producing internal heating and driving orbital migration and circularisation. Magnetic star-planet coupling provides additional pathways for energy transfer through reconnection and current systems, potentially enhancing atmospheric escape, heating planetary ionospheres and interiors, and generating observable signatures such as radio emission and enhanced stellar activity. We discuss how these processes work together, emphasising that their long-term impact depends on stellar evolution, planetary properties, atmospheric structure, and magnetic field strength. By presenting radiative, tidal, and magnetic interactions within a unified framework, this review highlights the physical mechanisms that shape planetary environments and identifies the key observational signatures that will complement future studies of exoplanet evolution and habitability.
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All authors Arghyadeep Paul, Kristina Kislyakova, Manuel Güdel, Rim Fares, Judy Chebly, Sergio Joya, Miljenko Čemeljić, Katja Poppenhäger, Julian Alvarado-Gomez, Silva Järvinen, Cesar Bertucci, Dibyendu Nandy, Antonio García Muñoz, Antoine Strugarek, Mayank Narang, Shyama Narendranath

Optics

Quench, Glow, or Stay Silent: Distance-Controlled Up-Conversion Emission near Metallic Nanowires

Maciej Cwierzona, Michal Zebrowski, Pavel Dziarhai et al. (+5 more)

We demonstrate controlled transitions between competing radiative and nonradiative decay channels in the up-conversion luminescence of NaYF4:Er3+/Yb3+ nanocrystals placed in proximity to metallic nanowires. The nanocrystal-nanowire separation is used as a key control parameter governing the optical response. An essential aspect of our approach is the removal of inhomogeneous residual polymer layers from the nanowires, eliminating any compromise on distance control and reproducibility in emitter-metal hybrid nanostructures. Replacing them with a well-defined polymer spacer yields controlled access to three qualitatively distinct interaction regimes: luminescence quenching, plasmonic enhancement, and effective decoupling. Transitions between these regimes are shown to reflect changes in the dominant energy relaxation pathways: from nonradiative losses in direct contact with the metal, through modification of the local photonic density of states and coupling to plasmon-mediated modes, to behavior characteristic of quasi-isolated emitters. The plasmonic origin of the emission enhancement in the intermediate regime is evidenced by an increase in luminescence intensity accompanied by shortened decay times, as revealed by fluorescence lifetime imaging microscopy of up-conversion nanocrystals. All experiments were performed on single nanostructures, thereby excluding artefacts arising from aggregation effects and strengthening the interpretation of the observed phenomena. The presented approach provides controlled access to plasmon-modified decay channels and offers a basis for the rational design of functional nanophotonic and sensing structures with tailored optical properties.
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All authors Maciej Cwierzona, Michal Zebrowski, Pavel Dziarhai, Joanna Niedziolka-Jonsson, Martin Jonsson-Niedziolka, Marcin Nyk, Sebastian Mackowski, Dawid Piatkowski

Physics and Society

Tax Migration as Social Contagion: A Tipping-Point Model with Application to the Scandinavian Wealth Tax Debate

Anders G Frøseth

Blandhol (2025) estimates that wealth-tax-induced emigration from Norway reduces long-run GDP by 1.3%. Dansk Industri scaled this figure to argue that a Danish wealth tax would cost billions - a claim central to the 2026 Danish election campaign. We develop a social contagion model in which the emigration rate depends on a visibility-weighted fraction of prior emigrants, producing tipping-point dynamics. Embedding the model in the Fokker-Planck framework of Froseth (2026, arXiv:2603.05283), we show that the micro-to-macro extrapolation underlying the 1.3% figure requires five identification conditions to hold simultaneously - each of which is violated. Using a panel of the 400 wealthiest Norwegians (2011-2025), we estimate the Pareto tail exponent (approximately 1.3, stable across years), identify the emigrants within Blandhol's 2016-2020 sample window, and document a hidden channel of heir-emigration - 36 recent cases carrying approximately 127 bn NOK - invisible in panel data because controlling owners retain their A-shares while heirs emigrate with economic exposure only. The event-study sample is dominated by passive wealth-holders with near-zero productivity haircuts, and the wealth-weighted integral that determines the GDP effect is controlled by individuals entirely absent from the sample. The Norwegian emigration wave is a non-scalable, path-dependent tipping event, not a smooth elasticity.
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Statistical Mechanics

The Reweighting Principle in Statistical Mechanics

Salvatore Romano

Reweighting of probability measures provides a unifying perspective on ensemble transformations in statistical mechanics. We distinguish two complementary classes of reweighting: soft constraints, which redistribute probability while preserving the support of the reference measure, and hard constraints, which impose support restrictions through conditioning. We show that exponential tilting and conditioning on an exact observable value arise as the minimum relative entropy updates associated with soft expectation constraints and hard exact-value constraints, respectively. Their relative entropies naturally inherit complementary thermodynamic structures: exponential tilting gives rise to the Legendre structure of the canonical ensemble and reduces, for a uniform reference measure, to Gibbs entropy, whereas conditioning reduces to Boltzmann entropy through the surprisal of the constrained macrostate. By introducing an enlarged probability space in which observables are treated as explicit random variables, we further show that canonical and microcanonical ensembles arise as marginal and conditional distributions of a common joint reference measure. In the thermodynamic limit, large-deviation concentration makes soft and hard constraints macroscopically equivalent, providing a probabilistic interpretation of canonical–microcanonical ensemble equivalence. Finally, we outline how the same information-theoretic framework naturally extends to path space, suggesting a unified probabilistic description of equilibrium statistical mechanics and conditioned stochastic dynamics.
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Earth and Planetary Astrophysics

Interpreting ALMA Multiwavelength Continuum Observations of PDS 70 c: An Optically Thick Dust Ring in the Circumplanetary Disk

Yuhito Shibaike, Satoshi Okuzumi, Takahiro Ueda et al. (+2 more)

Giant planets form small gas disks, called circumplanetary disks (CPDs), during gas accretion. The CPD of PDS 70 c has been detected by the Atacama Large Millimeter/submillimeter Array (ALMA) in (sub)millimeter continuum emission, which is interpreted as thermal emission from dust in the CPD. The resulting spectral index suggests that the disk is optically thick over a wide range of wavelengths. However, this is inconsistent with previous CPD dust models, which predict that the disk is optically thin because of radial dust drift. Here, we present a new interpretation of the multiwavelength observations: the CPD hosts an optically thick dust ring, whose existence has been discussed in the context of satellite formation. We demonstrate that a dust-ring model that incorporates gas accretion, dust evolution, and dust thermal emission, is consistent with the observations under reasonable conditions, whereas a conventional ring-less model requires more stringent conditions. We also show that the dust ring inferred from the observations potentially satisfies the conditions for exomoon formation via streaming instability and subsequent gravitational instability.
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All authors Yuhito Shibaike, Satoshi Okuzumi, Takahiro Ueda, Kiyoaki Doi, Misato Fukagawa

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

A Spectral Generalisation of the Variance Ratio: Eigenstructure of Long-Horizon Portfolio Covariance and a Multi-Memory Factor Model of U.S. Equity Returns

Anders G Frøseth

We propose a multivariate generalisation of the Lo-MacKinlay (1988) variance ratio that decomposes long-horizon equity-return dynamics into separate return-channel and volatility-channel memory components across the cross-section of asset returns. The framework identifies a parsimonious five-factor model - capturing persistent, antipersistent, and multi-scale memory in returns and volatility - that fits four U.S. portfolio panels (the Fama-French 49-industry universe, its pre/post-1998 halves, and the Fama-French 100 size x book-to-market sort) and a European replication (Fama-French Europe 25), recovering seven stylised facts of long-horizon equity dynamics simultaneously across all five panels. Three findings carry economic content. (i) The same five-factor decomposition fits all five panels, indicating a cross-sectional structure robust to industry vs. size-and-value sorts, to sub-periods, and to U.S. vs. developed-European markets. (ii) U.S. equity volatility memory underwent a regime transition in the late 1980s - not at the static 1998 split-half boundary - with the slowest component of the volatility cascade lengthening from approximately two to four years; a 1000-replicate rolling-window bootstrap localises the transition with strictly non-overlapping 90% confidence bands separating pre- and post-transition windows. (iii) The cross-sectional loadings driving return-channel long memory are economically distinct from those driving volatility-channel cascade memory: a cross-channel beta-inversion test finds no panel with the positive alignment a single shared loading predicts, rejecting the shared-loading hypothesis toward anti-alignment on the two largest panels at Bonferroni p = 0.0004. Characteristics that predict return-momentum patterns therefore need not predict volatility-persistence patterns.
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High Energy Astrophysical Phenomena

Long-period radio transient PSR J0901-4046 is not an Isolated White Dwarf Pulsar

Maxim Lyutikov, Mukremin Kilic, Alexander Wolszczan et al. (+1 more)

We report the Chandra non-detection of PSR J0901$-$4046, a $P=75.89 $ seconds long-period radio transient (LPT). For a distance of 467 pc, the upper limit on X-ray luminosity is $L_X \leq$ few $\times 10^{28}$ erg s$^{-1}$. For the measured $P$ and $\dot{P}$, this upper limit, approximately 50 times lower than the previous Swift observations, is comparable to the spin-down luminosity of a neutron star, but would be approximately four orders of magnitude smaller than the spindown power of a white dwarf. Our results disfavor isolated WDs as the central star in PSR J0901$-$4046. We suggest that the isolated LPTs are powered by magnetic dissipation (not rotation), in a way similar to magnetars' radio emission.
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All authors Maxim Lyutikov, Mukremin Kilic, Alexander Wolszczan, Craig Heinke

Statistical Mechanics

Quantum tunneling Mpemba effect

Hisao Hayakawa and Satoshi Takada

We investigate a quantum tunneling Mpemba effect for a particle in a continuous one-dimensional symmetric double-well potential subject to irreversible boundary loss. The dissipation is described by a complex absorbing potential (CAP) and the corresponding conditional no-jump evolution. Using a biorthogonal spectral representation, we derive the exact non-Hermitian decomposition of the subnormalized density matrix and analyze the corresponding relaxation dynamics. We show that the off-diagonal coefficients exhibit a parity selection rule, leaving same-parity interference terms in general. To isolate the interplay between thermal spectral preparation and mode-dependent decay rates, we introduce a diagonal spectral relaxation measure $S(t,T_i)$. For a quartic double well, numerical calculations reveal finite-time crossings of $S(t,T_i)$ prepared at different initial temperatures, as well as a non-monotonic temperature dependence of selected diagonal spectral weights. These features are explained by the enhanced thermal population of spatially extended, rapidly leaking excited states. In contrast, the trace distance of the normalized conditional state to the asymptotic quasi-stationary state exhibits no crossing, demonstrating that the anomalous ordering is specifically a spectral Mpemba effect rather than a universal acceleration of the complete conditional state. Our continuous-space formulation provides a real-space perspective on anomalous quantum relaxation without invoking universal nodal or topological theorems.
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Materials Science

Atomistic study of finite temperature properties in ferroelectric BiAlO$_3$

Indranil Mal, Chandan Kumar Vishwakarma, Mohd Zeeshan et al. (+2 more)

The lead-free perovskite ferroelectrics captivate researchers with their unique functional properties leading to important technological applications. In the search for a new lead-free perovskite of technological importance, we develop a first-principles based atomistic model to accurately predict the properties of BiAlO$_3$ in experimentally relevant conditions. Consistent with the experimental observations, our simulations predict a rhombohedral ferroelectric ($R3c$) ground state for BiAlO$_3$ facilitated by a structural phase transition from paraelectric (cubic, $Pm\Bar{3}m$) phase. The room-temperature spontaneous polarization and Curie temperature are obtained to be 81 $\mu$C/cm$^2$ (along [111] direction) and 1160 K, respectively. Our simulations reveal strong coupling between ferroelectric and antiferrodistortive modes for a broad spectrum of temperature and electric field. We find that hydrostatic pressure suppresses both spontaneous polarization and Curie temperature, while both uniaxial and biaxial stresses induce multiple phase transitions in BiAlO$_3$.
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All authors Indranil Mal, Chandan Kumar Vishwakarma, Mohd Zeeshan, I. Ponomareva, B. K. Mani

Materials Science

Structural, electronic, and optical properties of 2D $\alpha$-graphdiyne from first-principles

Ashkan Shekaari, Mahmoud Jafari, Sana Afshar et al. (+1 more)

The structural, electronic, and optical properties of monolayer $\alpha$-graphdiyne ($\alpha$-GDY) are systematically investigated using density-functional theory within the plane-wave pseudopotential formalism. The electronic band structure reveals a gapless Dirac crossing at the K point, indicating Dirac-semimetallic behavior within the PBE/GGA framework. The calculated total and orbital-projected density of states show that the electronic states near the Fermi level are dominated by the carbon $2p$ orbitals, while the contribution of the $2s$ orbitals is comparatively weak. The optical response exhibits pronounced polarization dependence. The in-plane dielectric function displays a strong low-energy electronic response and negative values of its real part, whereas the out-of-plane component remains positive throughout the investigated energy range. Consistently, the absorption coefficient, extinction coefficient, reflectivity, and electron energy-loss spectra reveal pronounced optical anisotropy. The calculated plasma frequencies are approximately $3.21$~eV for in-plane polarization and $1.06$~eV for out-of-plane polarization, highlighting the strongly anisotropic electronic response of the monolayer. These findings demonstrate that $\alpha$-GDY combines Dirac-like electronic behavior with highly anisotropic optical properties, indicating its potential relevance to polarization-sensitive optoelectronic, plasmonic, and nanoelectronic applications.
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All authors Ashkan Shekaari, Mahmoud Jafari, Sana Afshar, Rahil Mansouri

2607.03841 · 4 Jul · VERY IMPORTANT NOTE: This version has been peer-reviewed and revised accordingly. I uploaded it two days ago, but the system only updated the author list and abstract instead of replacing the entire manuscript. Therefore, I am submitting the full replacement again. I would appreciate it if you could kindly ensure that the entire manuscript is replaced this time

Abstract PDF $FERMI ×1$PLSM ×1

High Energy Astrophysical Phenomena

Neutron stars with an agnostic Dark sector: Core and Halo configurations from a two-fluid approach

Asit karan, Tuhin Malik, Asim Kumar Saha et al. (+2 more)

The study of dark matter admixed neutron stars has the potential to advance our understanding of dark matter particle candidates. However, the large parameter space of dark matter particle masses restricts a systematic, model-independent study. In this analysis, we employ agnostic hadronic and dark-matter equations of state to construct dark-matter-admixed neutron stars within a two-fluid formalism. Dark matter is characterized solely by its low-density equation of state and mass and is modeled as a Fermi gas, while hadronic matter is anchored at low and high densities by chiral effective field theory and perturbative quantum chromodynamics calculations. A speed-of-sound parametrization describes the intermediate- and high-density regimes of both hadronic and dark matter, enabling an agnostic treatment of the dark matter equation of state that is constrained only by thermodynamic consistency and does not favor softer or stiffer behavior. Within this agnostic framework, we find that dark matter does not generically compactify the star: light dark matter forms extended halos that raise the tidal deformability, while heavy dark matter forms compact cores that lower it. Consequently, the dominant observational constraint shifts from gravitational-wave tidal deformability for light, halo-dominated models to NICER mass-radius data for heavy, core-dominated models. Using current data at $1\sigma$, we constrain the dark matter fraction to $f_{\mathrm{DM}} \lesssim 0.11$ for light dark matter. By treating the medium- and high-density dark matter equation of state agnostically within a fermionic framework, our approach yields conservative and broadly applicable bounds on the dark matter content of neutron stars. Neutron stars with similar masses but very different tidal deformabilities could be a smoking-gun signature of dark matter in neutron stars.
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All authors Asit karan, Tuhin Malik, Asim Kumar Saha, Constança Providência, Ritam Mallick

Pattern Formation and Solitons

On the Nonlinear Sensitivity of Phononic Frequency Combs to Physical Perturbations

Madhurendra Mishra, Zhen Qi and Adarsh Ganesan

Phononic frequency combs offer a rich platform for nonlinear sensing, yet how their observable properties respond to changes in physical parameters remains poorly understood. Using a reduced two-mode autoparametric resonance model, we investigate how primary and secondary detuning, drive amplitude, and relative damping jointly shape amplitude and frequency sensitivity across the nonlinear parameter space. We find that sensitivity is far from uniform: primary detuning shifts the comb response smoothly, secondary detuning produces sharply localized transitions near resonance manifolds, and drive amplitude concentrates peak sensitivity close to the activation threshold rather than deep within the comb state. The relative damping redistributes energy continuously between modes without introducing discontinuities. The nonlinear sensitivity of amplitude and frequency observables across all parameters points to a common physical origin in autoparametric resonance, nonlinear saturation, and coupling-induced synchronization, offering a coherent basis for designing nonlinear sensing platforms with deliberate, parameter-aware sensitivity engineering.
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Materials Science

Janus MgAlB_2 MBene: a dipole-engineered anode for ultrafast Li-ion transport and exceptional lithium storage

Pritam Samanta, Sashank Kumar Pandey, Amit Kumar Jana et al. (+1 more)

In this work, we propose a group II/IIIA-based Janus MBene, MgAlB_2, and investigate its electrochemical properties using first-principles calculations. The substitution of one Mg layer in Mg_2B_2 MBene by an Al layer breaks the structural symmetry and generates a permanent out-of-plane polarization, giving rise to a distinct electronic environment compared with the parent Mg_2B_2 and Al_2B_2 monolayers. Electronic-structure analysis reveals enhanced orbital hybridization among B, Mg, and Al states near the Fermi level, resulting in improved electronic delocalization across the monolayer. The Janus MgAlB_2 monolayer is found to possess excellent dynamical, mechanical, and thermal stability. Owing to its polarization-modified energy landscape, Li ions migrate with an exceptionally low diffusion barrier of 17.1 meV, corresponding to a room-temperature diffusion coefficient of 3.43x10^-10 cm^2/s. Unlike the pristine Mg_2B_2 and Al_2B_2 monolayers, which support only a single stable adsorption layer, MgAlB_2 accommodates two complete Li layers. Detailed analysis shows that the residual polarization retained after first-layer lithiation continues to promote Li adsorption, whereas increasing Li-Li electrostatic interactions eventually limit further storage. As a result, the Janus monolayer delivers a high theoretical specific capacity of 1470.24 mAh/g together with a small volume expansion of only 3.7% during maximum lithiation. The present study demonstrates that intrinsic polarization can be utilized to regulate both the thermodynamics and kinetics of Li storage, providing a design strategy for high-rate and high-capacity two-dimensional electrode materials.
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All authors Pritam Samanta, Sashank Kumar Pandey, Amit Kumar Jana, Prakash Parida

Quantum Physics

Matter-wave Induced Transparency

Tongkang wang, Yuqi Liu, Wenlan Chen et al. (+2 more)

Electromagnetically induced transparency suppresses optical absorption through destructive interference, playing a central role in light-matter interaction and quantum information science. We report matter-wave induced transparency, where atomic collisional interactions induce transmission through a lossy molecular potential for the incident atomic scattering waves. Using cesium Bose-Einstein condensates and modulation-induced Feshbach resonances, we realize a three-level atom-molecule coupled system with unprecedented flexibility. Under the dark state condition, a narrow and tunable transparency window appears within a broad dissipative collisional resonance. The transparency window linewidth is controlled by modulation-induced coupling. And scattering pathways are selectable via multifrequency Floquet modulation. These results establish an interference-based route for exploring programmable nonequilibrium and non-Hermitian physics, steering quantum chemistry and precision measurements.
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All authors Tongkang wang, Yuqi Liu, Wenlan Chen, Zhendong Zhang, Jiazhong Hu

Astrophysics of Galaxies

Excitation of warm HD and H$_2$ and implications for the interstellar deuterium abundance

David A. Neufeld

Rotational emission from HD provides a direct probe of deuterium in warm molecular gas, but the conversion of HD line fluxes to total column densities is sensitive to non-LTE excitation. I present calculations of the non-LTE rotational excitation of HD and H$_2$ and a method for fitting their rotational diagrams simultaneously. Because HD remains subthermally excited to higher densities than H$_2$, the combined analysis constrains the thermal pressure as well as the HD/H$_2$ abundance ratio. I apply this method to JWST/MIRI observations of 26 positions in 10 protostellar outflows from the JOYS survey, published previously by Francis et al. (2025), including 17 positions with secure detections of at least three HD lines. Two-temperature, isobaric models generally provide good fits to the measured H$_2$ and HD level populations. For 11 positions with HD detections, the inferred pressures span $p/k_B=8.4\times10^7$ - $5.1\times10^9\ {\rm K\,cm^{-3}}$; for the remaining six, the HD populations approach LTE and provide only lower limits on the gas pressure. Excluding two positions toward IRAS 4B with comparatively poor fits, the median and mean inferred HD/H$_2$ abundance ratios are $1.42\times10^{-5}$ and $1.47\times10^{-5}$, respectively, only 28$\%$ and 29$\%$ of the value expected if all primordial deuterium were present as HD. These results confirm that HD/H$_2$ is generally low in shocked molecular gas while demonstrating that pressure-dependent non-LTE excitation must be modeled explicitly. Translating the measured HD/H$_2$ ratios into elemental D/H requires additional modeling of shock chemistry.
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Chemical Physics

Application of SAP-X2C to Spectroscopy and Comparison to Screened Nuclear Spin-Orbit Approximations

Yannick J. Franzke and Christof Holzer

Recently, Surjuse and Valeev [J. Chem. Theory Comput. 22, 3443-3452 (2026).] suggested to use a simple superposition of atomic potentials to account for the two-electron picture-change error in one-electron exact two-component (SAP-X2C) theory. Herein, we generalize this ansatz to analytical derivative theory and apply SAP-X2C to molecular spectroscopy. The accuracy is assessed for NMR, EPR, Mössbauer, UV/vis, as well as X-ray absorption spectroscopy. A thorough comparison with four-component results and the even simpler screened nuclear spin-orbit (SNSO) approximation reveals that both SNSO-X2C and SAP-X2C perform excellently for spectroscopic properties, with SAP-X2C yielding slightly lower errors. Another major advantage is its well defined thermodynamic limit and less empirical nature. Therefore, SAP-X2C may be expected to become the default choice to mitigate the two-electron picture-change error in density functional theory approaches for spectroscopy thanks to its accuracy, simplicity, and efficiency. More complicated approaches to account for this error based on atomic mean-field ansätze may still be relevant for high-level correlated methods and highly accurate thermochemistry.
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Fluid Dynamics

A comprehensive Darcy-type law for viscoplastic fluids: II. Rheology & topology

Emad Chaparian

We extend our recently proposed framework (Chaparian, Phys. Rev. Fluids 10(9) 093301, 2025) for deriving a Darcy-type law governing viscoplastic flows through porous media to incorporate more applied aspects. In particular, the present work considers a more realistic rheological model (i.e. Herschel-Bulkley, describing the shear-thinning nature of practical yield-stress fluids) along with a wider range of porous media topologies. In our earlier work, the problem was addressed by decomposing the full Bingham number spectrum (representing the ratio of the yield stress of the fluid to the characteristic viscous stress) into three main regions: (i) low Bingham numbers (weak yield stress limit) corresponding to Newtonian flow, (ii) high Bingham numbers (strong yield stress limit) representing yield limit/plastic flow, and (iii) intermediate Bingham numbers (transition regime). By deriving theoretical models for the two asymptotic limits of the spectrum and combining them, we obtained a Darcy-type law applicable across the entire range of Bingham numbers. In contrast to our original work, where the weak yield stress limit reduces to a Newtonian flow, here, this limit instead follows a power-law asymptote that captures the shear-thinning dominated behaviour of Herschel-Bulkley fluids. In the present study, we derive a scaling to address this limit. The framework is further generalised to incorporate a broader spectrum of porous media topologies, enabling a systematic assessment of how pore geometry influences the resulting macroscopic flow law. The proposed framework provides a unified theoretical basis for predicting yield-stress fluid transport through complex porous media and establishes a pathway towards finding macroscopic models applicable to a wide range of natural systems and industrial processes.
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Quantum Physics

A regularization method for quantum neural networks using data symmetry

Hiroshi Ohno

Leveraging data symmetries has recently become a key strategy in quantum neural networks (QNNs) to improve training efficiency. In this study, we propose a symmetry-informed regularization method for QNNs based on an input density matrix. By introducing a penalty term that encourages the model to align with data symmetry, our method enables improved training speed. This symmetry-based regularization is simple to implement and does not require an explicitly specified symmetry group, although it requires access to training samples or to the input distribution from which an empirical or theoretical input density matrix can be constructed. We evaluate the method through numerical experiments on both classification tasks and quantum generative adversarial networks. In the small-scale classification experiments, the regularizer produced modest improvements in early-stage convergence and test loss. Our findings highlight the potential of symmetry-aware regularization in enhancing the performance of QML models.
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