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Physics

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Monday 13 July

High Energy Astrophysical Phenomena

Discovering Millisecond Pulsars in Globular Clusters with the GMRT (GCGPS)

Jyotirmoy Das, Jayanta Roy, Paulo C. C. Freire et al. (+6 more)

The Globular Clusters GMRT Pulsar Search (GCGPS) project, launched in mid-May 2023, has emerged as one of the most successful pulsar surveys conducted with the upgraded Giant Metrewave Radio Telescope (uGMRT), leading to the discovery of several new millisecond pulsars (MSPs). The recently concluded Phase I of the survey resulted in the discovery of seven MSPs across four globular clusters (GCs), all of which previously had no known pulsars. These discoveries have enabled the precise determination of the dispersion measures (DMs) for the respective clusters for the first time. Consistent timing follow-up revealed that out of the seven MSPs, three are confirmed binaries, while two are isolated. This paper summarises the design and the implementation of Phase I of the GCGPS project, presents the key scientific results obtained so far, and outlines the strategy and progress of the recently initiated Phase II observations.
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All authors Jyotirmoy Das, Jayanta Roy, Paulo C. C. Freire, Scott M Ransom, Bhaswati Bhattacharyya, Karel Adámek, Wes Armour, Sanjay Kudale, Mekhala V. Muley

Optics

Heterogeneous-Gradient Phase–Polarization Alignment and Maximal-Ratio Weight Allocation for Multi-Aperture Coherent FSO Reception

Cheng Chen, Tong Luo, Jiayin Xue et al. (+5 more)

Multi-aperture coherent reception can improve freespace optical (FSO) links by converting spatial diversity into coherent combining gain. In turbulent links, the aperture branches are simultaneously affected by relative phase errors, polarization mismatch, and unequal signal-to-noise ratios (SNRs). Existing methods treat phase/polarization alignment and branch-weight allocation as separate operations, or absorb all impairments into a high-dimensional MIMO equalizer that obscures the physical meaning of each aperture's contribution. This paper proposes a structured blind combining method based on heterogeneous gradient sources: phase and per-aperture polarization parameters are updated by closed-form analytical gradients that maximize the combined output power, while aperture weights and an optional global polarization angle are updated by gradients derived from the constellation-radius error. An exponential parameterization pn = eqn/N ensures positivity without clipping. The internal variable qn is adapted by radius-error gradients, thereby allocating maximal-ratio-combining-like weights according to the quality of the already aligned branches.
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All authors Cheng Chen, Tong Luo, Jiayin Xue, Siyu Gong, Qun Zhang, Linsheng Fan, Qi Wu, Yanfu Yang

Atmospheric and Oceanic Physics

HourGlass: A probabilistic data-driven temporal downscaler for global and regional weather forecasting

Magnus Sikora Ingstad, Mariana C. A. Clare, Olav Ersland et al. (+16 more)

Many forecast applications require high frequency temporal resolution, yet most state-of-the-art data-driven weather forecasting systems operate at 6-hourly resolution. Although direct hourly forecasting is possible, it suffers from error accumulation and temporal inconsistency. We introduce HourGlass, a probabilistic data-driven temporal downscaling method that reconstructs the evolution between forecast states. HourGlass is trained using variants of the continuous ranked probability score (CRPS) preserving small-scale spatial variability while encouraging temporal consistency. Unlike existing deterministic temporal downscaling approaches, which tend to produce overly smooth fields, HourGlass generates realistic probabilistic forecasts. Training on forecast trajectories rather than reanalysis or analysis data also avoids the temporal inconsistencies present in datasets used by previous methods. We evaluate HourGlass in two settings: AIFS-HourGlass, applied globally to ECMWF's AIFS-Single and AIFS-ENS forecast systems, and Bris-HourGlass, applied regionally to MET Norway's high-resolution stretched-grid ensemble model, Bris. Verification against observations shows that both models retain the skill of their underlying forecasting systems while producing temporally coherent hourly forecasts with realistic small-scale variability. Case studies demonstrate physically consistent evolution during rapidly developing weather events, including extratropical cyclones and organised convection. Hourly precipitation remains challenging: HourGlass improves the spatial realism of precipitation fields but still underestimates the most intense extremes, a common limitation of data-driven weather forecasting models. These results demonstrate that HourGlass effectively bridges the gap between 6-hourly data-driven forecasts and the hourly products required for operational regional and global forecasting.
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All authors Magnus Sikora Ingstad, Mariana C. A. Clare, Olav Ersland, Vera Gahlen, Håvard Homleid Haugen, Ophélia Miralles, Even M. Nordhagen, Thomas N. Nipen, Ivar A. Seierstad, John Bjørnar Bremnes, Michael Maier-Gerber, Zied Ben Bouallègue, Harrison Cook, Christian Lessig, Gert Mertes, Cathal O'Brien, Florian Pinault, Ana Prieto Nemesio, Matthew Chantry

Quantum Physics

Tunable non-Hermitian skin effect and topological phases in ladders with staggered nonreciprocal interleg hopping

Pu-Xuan Li and Qi-Bo Zeng

We investigate the non-Hermitian skin effect (NHSE) and topological phases in a ladder model with staggered nonreciprocal interleg hopping, consisting of a Su-Schrieffer-Heeger chain coupled to a normal tight-binding chain. By tuning the system parameters, we show that the direction of the NHSE under open boundary conditions can be reversed and can even become energy dependent. The NHSE is further characterized by the spectral winding number under periodic boundary conditions. We also demonstrate that the interleg coupling significantly enlarges the topologically nontrivial parameter regime. Remarkably, there are two topological phases characterized by winding numbers $W=\pm1$, with the zero-energy topological edge modes residing on different sites in the two legs. Furthermore, increasing the nonreciprocity of the interleg hopping modifies the topological phase boundaries and eventually drives the system into a topologically trivial phase. Our results establish staggered nonreciprocal interleg hopping as an effective mechanism for engineering both the non-Hermitian skin effect and topological phases in ladder systems.
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Nuclear Theory

Search for the Double Poles of the Scattering Matrix in Light Nuclei

David Cardona Ochoa, Marek Płoszajczak and Nicolas Michel

Exceptional points (EPs) are non-Hermitian degeneracies at which two eigenvalues and their eigenvectors coalesce, producing a defective Hamiltonian and a double pole of the $S$-matrix. Using the coupled-channel Gamow Shell Model with the $\ell=1$ spin-orbit strengths as control parameters, we locate and characterize EPs in $^6\text{Li}$, $^7\text{Li}$, $^7\text{Be}$, and $^8\text{Be}$, and analyze their imprint on energies, widths, phase rigidity, spectroscopic factors, elastic cross sections, survival probabilities, and spectral functions. The signatures of the EP in scattering and time-domain observables are found to be strongly channel-dependent, and threshold effects play a decisive role in determining the accessibility of the EP in parameter space.
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Nuclear Theory

Ab initio study of $\beta$-decay and pairing in $N=Z$ nuclei

Subhrajit Sahoo and Praveen C. Srivastava

We investigate the $\beta$-decay properties of $rp$-process waiting-point nuclei $^{72}$Kr, $^{68}$Se, and $^{64}$Ge from realistic nuclear forces based on chiral effective field theory. The ab initio valence-space in-medium similarity renormalization group method is employed for this purpose to consistently derive Hamiltonians and Gamow-Teller operators from chiral two- and three-nucleon interactions. The calculated half-lives and branching ratios indicate that nearly the entire decay intensity is confined within 1 MeV of excitation energy in the daughter nuclei. We address the isoscalar and isovector pairing and their impact on ground state properties of these waiting-point nuclei, along with several other $N=Z$ systems in the $fp$-shell. Our results do not provide evidence for an isoscalar condensate or any dominant isovector pairing condensate-like phase in these $N=Z$ nuclei. We present the full $B(\mathrm{GT})$ strength distributions and discuss the influence of pairing correlations on them. The present work provides a microscopic picture of $\beta$-decay strengths and pairing in $N=Z$ nuclei far from the stability line.
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Astrophysics of Galaxies

Mass–size evolution and the emerging passive–density relation revealed by JWST/NIRCam in the Spiderweb protocluster

J. Nadolny, J. M. Pérez-Martínez, H. Dannerbauer et al. (+8 more)

We investigate how the environment affects galaxy structure in the Spiderweb protocluster at $z=2.16$ using JWST/NIRCam F115W, F182M, and F410M imaging (rest-frame $\sim 3500$Å to $1.4\,\mu$m). We perform homogeneous multi-wavelength parametric modelling of the single-Sérsic and bulge–disc decomposition for the Spiderweb member sample of 103 galaxies within the JWST field of view (up to $\sim 2\times R_{200}$). Star-forming galaxies follow a mass–size relation broadly consistent with the field, with a mildly steeper trend at the high-mass end within uncertainties. Passive galaxies exhibit a flatter mass–size relation, and their typical size (intercept at fixed stellar mass) lies between that of the coeval field and cluster passive populations, indicating an intermediate evolutionary stage. In both star-forming and passive systems, bulges are systematically more compact than discs. Galaxy sizes decrease slightly with increasing wavelength, whereas ALMA-detected dusty star-forming galaxies exhibit a much steeper wavelength dependence, consistent with centrally concentrated, obscured star formation. The passive fraction depends primarily on local density: it resembles the field at $\Sigma \lesssim 100$–$200\,{\rm gal\,Mpc^{-2}}$ and rises to $\sim60\%$ at $\Sigma \gtrsim 1000\,{\rm gal\,Mpc^{-2}}$, although with relatively large uncertainties due to the small number of galaxies in the highest-density bins, with no significant additional dependence on clustercentric distance. We also find a weak but significant correlation between local density and Sérsic index (strongest in F410M), but no clear correlation with effective radius or the star-formation rate surface density $\Sigma_{\rm SFR}$. These results support a picture in which quenching and structural transformation are already advanced, while the size growth is still ongoing.
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All authors J. Nadolny, J. M. Pérez-Martínez, H. Dannerbauer, B. Haussler, M. Huertas-Company, K. Daikuhara, T. Kodama, Y. Koyama, A. Naufal, P. G. Pérez-González, Y. H. Zhang

Solar and Stellar Astrophysics

Pre-flare and active region plasma flows and structure seen by the short wavelength camera on SOLAR-C/EUVST

James McKevitt, Sarah Matthews, David H. Brooks et al. (+20 more)

The mechanisms triggering solar flares and driving coronal heating occur across wide temperature ranges on small spatial scales and short timescales, making them difficult to observe with current instrumentation. The upcoming SOLAR-C mission, launching in the late 2020s, will provide unprecedented plasma diagnostic capability with its high-throughput extreme-ultraviolet (EUV) spectroscopic telescope (EUVST), capable of ~0.2 arcsec/pix spatial sampling (~0.4 arcsec resolution), continuous temperature coverage from 0.02-15 MK, and exposure times down to 0.5 seconds. We present forward modelling of the spectrograph's short wavelength camera (170-210 Å; SOLAR-C/EUVST-SW) and its response to log T~6.2 coronal plasma in a three-dimensional MHD-simulated pre-flare active region. We compare this performance to that of the previous-generation EUV Imaging Spectrometer (EIS) on Hinode (SOLAR-B). Our results demonstrate that SOLAR-C/EUVST can distinguish individual flux tubes in simulated active region loops which Hinode/EIS cannot resolve. In simulated pre-flare plasma, SOLAR-C/EUVST captures sharp velocity gradients between adjacent upflowing and downflowing plasma which Hinode/EIS is unable to resolve. Doppler velocity measurement accuracy will reach better than 1 km/s in active regions. We show that this next-generation spectrograph can be expected to directly observe processes potentially related to flare triggering, such as plasma flows from low-altitude reconnection linked to emerging flux, and determine whether active region loops consist of a small number of strands or the hundreds predicted by magnetic reconnection-induced nanoflare heating models.
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All authors James McKevitt, Sarah Matthews, David H. Brooks, Toshifumi Shimizu, Akiko Tei, Ignacio Ugarte-Urra, Shinsuke Imada, Shin Toriumi, Charles M. Brown, Ryohko Ishikawa, Yukio Katsukawa, Hirohisa Hara, Duncan Rust, David Walton, Berend Winter, Deborah Baker, Hamish Reid, Peter Young, Tiago M. D. Pereira, Louisa Bradley, Alexey Shitvov, Louise Harra, International SOLAR-C team

Physics and Society

Charting the life of Billboard hits through memory, turnover, and predictability

Arthur A. B. Pessa, Angelo A. Flores, Matjaz Perc et al. (+1 more)

Rankings shape the visibility and success of cultural products, yet their temporal dynamics remain underexplored when comparing distinct ranked objects within the same domain. Here, we use nearly seven decades of Billboard Hot 100 songs and six decades of Billboard 200 albums to investigate how success emerges, persists, and differs between songs and albums. We find that albums exhibit a heavier-tailed permanence distribution and reenter the charts more often than songs, whereas songs typically have longer uninterrupted runs. Similarity between successive charts decays much faster for songs than for albums, suggesting that individual hits reflect shorter-lived collective attention, while albums retain longer cultural memory. Rank-turbulence divergence shows that consecutive charts are similar, but that top positions are dominated more by rank reshuffling than by turnover. Entropy-based analyses reveal high uncertainty in rank movements, with distinct historical patterns for songs and albums and a strong dependence on trajectory length. Clustering of trajectories shows that chart success is organized into a small number of typical pathways, including canonical rise-and-fall trajectories, high-end persistence, and monotonic decline. Together, these results show that musical charts are not merely records of popularity, but dynamic memory systems in which attention, turnover, and predictability interact differently for songs and albums.
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All authors Arthur A. B. Pessa, Angelo A. Flores, Matjaz Perc, Haroldo V. Ribeiro

Mathematical Physics · Cross-listed from math.AP

Absence of non-compactly supported minimisers for the Lieb-Oxford bound

Simone Di Marino and Rodrigue Lelotte

We prove the minimisers of the Lieb-Oxford bound (if any) for a fixed (and finite) number of particles $N \geq 1$ are necessarily compactly supported, extending a result proved by E. H. Lieb and S. Oxford in the one-particle case.

High Energy Astrophysical Phenomena

Probing radiation micro-physics in M 87 I. Total intensity and broad-band spectra

Christian M. Fromm, Yosuke Mizuno, Ziri Younsi et al. (+6 more)

Next generation Very Long Baseline Interferometers (VLBI) will provide dense sampling of the Fourier space together with high signal to noise ratios allowing to reliably observe and image faint jet structure in M 87 at mm-wavelength. The proposed next generation Event Horizon Telescope (ngEHT) and next generation Very Large Array (ngVLA) offers the unique capability to simultaneously resolve and image the accretion flow around the supermassive black hole in M 87 together with the jet launching and acceleration zone. In order to explore these capabilities and to provide theoretical expectations we perform general relativistic magnetohydrodynamic simulations of accretion on to black holes and jet launching. M 87 has been the target for multiple observations across the entire electromagnetic spectrum. Among these VLBI observations provide unique capability to resolve the jet structure down to several gravitational radii. In this work we provide possible observable signatures which will allow us to distinguish between different electron heating models and particle distributions. We use general relativistic magnetohydrodynamics and simulate the accretion of the magnetised plasma onto Kerr-black holes in 3D. The multi-frequency radiative signatures of these simulations are computed taking different electron heating and distribution functions into account. The results of our simulations show that with a dynamical range of $1\times 10^4$ and a frequency range from 86 GHz to 345 GHz observations with future VLBI arrays have the potential to tell turbulent and magnetic reconnection electron heating and the electron distribution function apart.
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All authors Christian M. Fromm, Yosuke Mizuno, Ziri Younsi, Ainara Saiz-Perez, Hector Olivares, Antonios Nathanail, Alejandro Cruz-Osorio, Matthias Kadler, Karl Mannheim

Cosmology and Nongalactic Astrophysics

Direct Primary Beam Correction: Untangling Mutual Coupling in 21-cm Cosmological Experiments with the SKA-Low Radio Telescope

Oscar S.D. O'Hara, Quentin Gueuning, Eloy de Lera Acedo et al. (+7 more)

Mutual coupling between antennas has emerged as the dominant direction-dependent corruption in dense aperture arrays, imprinting pronounced sub-MHz spatial and spectral structure that compromises the time-gating and foreground-separation strategies used to isolate the faint 21-cm signal. In this work, we introduce Direct Primary Beam Correction, a domain-agnostic framework for reconstructing the far-field radiation pattern relative to an arbitrary reference via a regularised, direction-weighted linear inversion of stacked Jones matrices, thereby enabling the removal of direction-dependent distortions such as mutual coupling. Using full-wave electromagnetic simulations of SKA-Low, we demonstrate that this framework reconstructs the radiation pattern down to the numerical noise floor within a suitably conditioned field of view, with the reconstruction accuracy governed by the regularised inversion and the fidelity of the underlying beam model. Applying the framework to a simulated 4-hour observation of the EoR0 field in the $122$–$134$~MHz band, we identify two principal implications for 21-cm power-spectrum analysis. First, restricting the correction to the main lobe and near sidelobes is inadequate: chromatic grating lobe contributions, whether left insufficiently or entirely uncorrected, continue to contaminate the EoR window. Second, mutual-coupling-induced contamination is temporally coherent and, being anchored to the fixed array geometry, does not average down across snapshots as the EoR field is tracked. Direct primary beam correction, therefore, provides a computationally efficient means of mitigating mutual coupling; however, robust recovery of the EoR window necessitates either full-sky correction or explicit separation of main-beam and sidelobe contributions prior to power-spectrum estimation.
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All authors Oscar S.D. O'Hara, Quentin Gueuning, Eloy de Lera Acedo, John Cumner, Dominic Anstey, Anthony Brown, Fred Dulwich, Andrew Faulkner, Ashish Mhaske, Oskar Zetterstrom

Solar and Stellar Astrophysics

Potential Solar Precursors to Magnetic Switchbacks

Durgesh Tripathi, Maria S. Madjarska, Judy Karpen et al. (+9 more)

The origin of magnetic switchbacks-large-amplitude, spherically polarized magnetic-field fluctuations with local polarity inversions shown to be nearly ubiquitous in the inner heliosphere by Parker Solar Probe-is presently one of the most outstanding open questions in solar and heliospheric science. The occurrence of these structures in the young solar wind is a topic of active research, focusing not only on their characteristics and evolution but also on unraveling the puzzle of their origin. We first discuss the potential influence on switchback (SB) formation of large-scale coronal dynamics and restructuring processes that shape and regulate the extended solar corona. Following that, we review the dynamics, physical properties, occurrence rate, and energetics of numerous possible precursor small-scale dynamic events that occur throughout the solar atmosphere, emphasizing their possible roles in creating SBs. Finally, we discuss some recent studies attempting to connect in situ observations of SBs and SB patches with remote-sensing observations, and the related challenges in identifying solar wind source regions precisely and linking in situ observations to transient solar phenomena. We also clarify the terminology used by the solar community to describe small-scale solar phenomena.
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All authors Durgesh Tripathi, Maria S. Madjarska, Judy Karpen, Marco Velli, Clara Froment, Etienne Pariat, Spiros Patsourakos, Nour E. Raouafi, Alexis P. Rouillard, Alphonse C. Sterling, Kostas Tziotziou, Peter F. Wyper

Astrophysics of Galaxies

An HI+radio continuum study of local cluster galaxies: Intercepting the early stages of environmental processing with MeerKAT

Alessandro Ignesti, Paolo Serra, Alessandro Bianchetti et al. (+14 more)

The evolution of galaxies in clusters is driven by their interaction with the environment, which deeply affects and alters the properties of the multi-phase interstellar medium. Here we make use of MeerKAT observations to study the properties of the neutral and nonthermal interstellar medium, traced respectively by the HI 21 cm line and by the radio continuum emission at 1.4 GHz, out to about twice the virial radius of three local ($z\simeq0.04$) galaxy clusters, namely IIZW108, A4059 and A3558, with $M_{200}\simeq2-9\times10^{14}~M_\odot$. We assemble a sample of 61 galaxies, including the so-called jellyfish and unwinding galaxies, detected in both HI and radio continuum, and derive their optical properties from IR-to-UV photometry using ancillary data. We find that cluster galaxies in our sample are on average $\sim2.7$ times more star-forming than galaxies with the same stellar and HI mass in the field, indicating that the HI + radio-continuum selection has intercepted galaxies at the very early stages of their environmental processing when the external pressure has not yet removed the gas, but the resulting fast compression has enhanced both the star formation and the radio continuum luminosity. The study also reveals that galaxies at the initial stage can features a radio luminosity excess due to the old relativistic electrons permeating the interstellar medium. We show that unwinding galaxies are characterized by high stellar and HI masses, arguing that their peculiar morphology may results from their large baryonic mass. Finally, via the stacking analysis of 677 optically-selected cluster members we quantitatively show that cluster galaxies are more HI-poor than in the field, and the deficiency steadily grows approaching the cluster center where galaxies have, on average, a factor $\sim3\times$ less HI mass than those in the field.
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All authors Alessandro Ignesti, Paolo Serra, Alessandro Bianchetti, Antonino Marasco, Alessia Moretti, Francesca Loi, Bianca M. Poggianti, Benedetta Vulcani, Laura Bisigello, Myriam Gitti, Marco Gullieuszik, Augusto E. Lassen, Rosita Paladino, Christoph Pfrommer, Mpati Ramatsoku, Francesco Sinigaglia, Neven Tomičić

Superconductivity

Interference-Enhanced Large Electron-Phonon Coupling from Raman-active Breathing Modes in Moiré Semiconductors

Ning Mao, Shaozheng Wang, Cheng Xu et al. (+6 more)

Superconductivity was recently observed in twisted WSe2 and MoTe2, raising a central question: is the pairing driven by electronic correlations, by phonons, or by both? Answering it requires determining the electron-phonon coupling (EPC) in these moiré semiconductors, whose calculation in realistic supercells of thousands of atoms lies beyond the reach of direct first-principles methods. Here we combine filling-dependent Raman spectroscopy with machine-learning first-principles calculations to obtain the EPC mode by mode in supercells of up to tens of thousands of atoms. Raman reveals only a few moiré phonons whose frequencies shift strongly with filling; we trace this to an interference selection rule: a phonon couples strongly only when its displacement texture matches the static lattice-reconstruction pattern, and is otherwise suppressed by destructive interference. The rule selects the low- and high-frequency breathing modes seen in Raman and makes the coupling peak at large twist angles, near those at which superconductivity appears. Lattice-reconstruction interference thus emerges as an organizing principle for moiré EPC, pointing to a substantial, potentially dominant, phonon contribution to large-angle pairing.
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All authors Ning Mao, Shaozheng Wang, Cheng Xu, Xumin Chang, Kenji Watanabe, Takashi Taniguchi, Claudia Felser, Shengwei Jiang, Yang Zhang

Mesoscale and Nanoscale Physics

Extended Landau–Lifshitz equation for nanomagnets: a path-integral derivation of surface-induced magnetization nutation

H. Kachkachi and P. Thibaudeau

An effective dynamical equation for the magnetization of a nanomagnet with surface anisotropy is derived from an atomistic spin Hamiltonian using the spin coherent-state path integral formalism. The derivation proceeds in two steps. First, the continuum Euclidean action for the many-spin nanomagnet is obtained, including the Wess–Zumino–Witten (Berry phase) term, as well as exchange, Zeeman, and core/surface anisotropy contributions. Second, the local magnetization density is decomposed into a slowly varying macrospin component and transverse spin-misalignment fluctuations driven by surface effects. A systematic expansion of the action is then performed up to quadratic order in the transverse-fluctuation variables. Under the adiabatic approximation, in which transverse modes relax much faster than the macrospin, these modes are eliminated by using their static Green's function solution. This results in a closed, extended Landau–Lifshitz equation for the macrospin, featuring an effective field with nontrivial corrections from spin misalignment. These corrections renormalize both the Zeeman and anisotropy fields and introduce additional terms that act as nutation- and damping-like contributions. ... Together, these results establish a microscopic foundation for surface-induced magnetization nutation in nanomagnets and provide a framework to estimate corrections to the precession frequency and effective damping. The corresponding shift in the ferromagnetic-resonance frequency and linewidth is measurable with standard GHz spectrometers, and the underlying adiabatic-elimination mechanism is expected to generalize to any slow magnetic variable coupled to a bath of fast-fluctuating modes.
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Chemical Physics

Efficient, direct calculation of reaction rate coefficients based on a partially rearranged rovibrational Hamiltonian. A full-dimensional case study of the H$_2$ + D $\rightarrow$ HD + H reaction

Gábor A. Ecseri, Attila G. Császár and Csaba Fábri

It is shown that an efficient, direct, and fully quantum mechanical calculation of thermal reaction rate coefficients requires a new, partially rearranged form of the numerically-constructed exact kinetic energy part of the rovibrational Hamiltonian expressed in internal coordinates. Using this Hamiltonian and an accurate, full-dimensional potential energy surface characterizing the H$_2$ + H exchange reaction, developed by Mielke, Garrett, and Peterson (J. Chem. Phys. 2002, 116, 4142), reaction rate coefficients in the temperature range of $75-800$ K have been computed for the H$_2$ + D $\rightarrow$ HD + H reaction. The paper puts particular emphasis on the exact treatment of overall molecular rotation and on nuclear spin symmetry.
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Physics Education

Generative AI in Higher Education Laboratory Learning: A Qualitative Case Study of Epistemic Scaffolding and Assessment Boundaries

Matteo Tuveri and Alessandro Riggio

Advanced physics laboratories require students to integrate disciplinary knowledge, experimental practice and scientific argumentation across complex observational and analytical tasks. The increasing availability of generative artificial intelligence (GenAI) adds complexity to this coordination, since AI systems may function as conceptual explainers, operational assistants, artefact reviewers or apparently authoritative evaluators. This exploratory qualitative case study examines AstroTutor, a constrained GenAI tutor introduced as an optional support resource in a Master's-level advanced astrophysics laboratory. The study investigates how students framed the tutor within a broader GenAI-mediated learning ecology that included the instructor, peers, course materials, observations, measurements, data analysis and final assessed reports. Seven students attended the course, five used the tutor, and three groups produced a final report. The analysis combined content analysis, thematic analysis and frame analysis. Drawing on chat logs, final reports and limited post-use reflective responses, the results identify five principal GenAI functions: interface interpreter, warrant organiser, report scaffold, unstable authority and resource whose traces may appear in downstream reports. These findings extend previous research on GenAI in education to the context of advanced physics laboratories, showing that its use requires explicit design boundaries, guidance on legitimate and prohibited practices, verification routines, and assessment requirements that preserve students' epistemic responsibility. The educational implications of a GenAI-mediated learning ecology in advanced physics laboratories are also discussed.
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High Energy Physics (Experiment)

Observation of $\eta_{c} \to p\bar{p}\eta$ via $\psi(3686) \to \gamma p\bar{p}\eta$

BESIII Collaboration: M. Ablikim, M. N. Achasov, P. Adlarson et al. (+766 more)

The decay $\eta_c\to p\bar{p}\eta$ is observed for the first time with a significance of exceeding $10\sigma$. It is found by analyzing $(2712.4 \pm 14.3)\times10^{6}$ $\psi(3686)$ events accumulated at the BESIII detector. The measured branching fraction of $\eta_c\to p\bar{p}\eta$ via $\psi(3686) \to \gamma p \bar{p} \eta$ is significantly influenced by the interference between the resonant $\eta_c$ decay and the non-resonant process $\psi(3686) \to \gamma p \bar{p} \eta$ and is measured in both constructive- and destructive-interference scenarios. The joint branching fraction of $\psi(3686)\to \gamma\eta_c$, $\eta_c\to p\bar{p}\eta$ is measured to be $(3.2 \pm 0.1 \pm 0.9)\times10^{-6}$ or $(8.7 \pm 0.3 \pm 2.1)\times10^{-6}$ for constructive- or destructive-interference solutions, respectively, where the first uncertainties are statistical and the second systematic. The branching fraction of $\eta_c\to p\bar{p}\eta$ is determined to be $\mathcal{B}(\eta_c\to p\bar{p}\eta)=(0.90 \pm 0.04 \pm 0.21 \pm 0.13)\times10^{-3}$ or $(2.42 \pm 0.07 \pm 0.48 \pm 0.34)\times10^{-3}$ for the two solutions, respectively, where the third uncertainties are due to the uncertainty in the branching fraction of $\psi(3686)\to \gamma \eta_c$.
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All authors BESIII Collaboration: M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, C. S. Akondi, R. Aliberti, A. Amoroso, Q. An, Y. H. An, M. S. Anderson, Y. Bai, O. Bakina, H. R. Bao, X. L. Bao, M. Barbagiovanni, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. B. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, D. Cabiati, H. Cai, M. H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, X. Y. Chai, J. F. Chang, T. T. Chang, G. R. Che, Y. Z. Che, C. H. Chen, Chao Chen, G. Chen, H. S. Chen, H. Y. Chen, M. L. Chen, S. J. Chen, S. M. Chen, T. Chen, W. Chen, X. R. Chen, X. T. Chen, X. Y. Chen, Y. B. Chen, Y. Q. Chen, Z. K. Chen, J. Cheng, L. N. Cheng, S. K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. Cottee-Meldrum, H. L. Dai, J. P. Dai, X. C. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, Z. Y. Deng, A. Denig, I. Denisenko, M. Destefanis, F. De Mori, E. Di Fiore, X. X. Ding, Y. Ding, Y. X. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, Z. J. Dong, M. C. Du, S. X. Du, Shaoxu Du, X. L. Du, Y. Q. Du, Y. Y. Duan, Z. H. Duan, P. Egorov, G. F. Fan, J. J. Fan, Y. H. Fan, J. Fang, Jin Fang, S. S. Fang, W. X. Fang, Y. Q. Fang, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, Q. X. Feng, Y. T. Feng, M. Fritsch, C. D. Fu, J. L. Fu, Y. W. Fu, H. Gao, Xu Gao, Y. Gao, Y. N. Gao, Y. Y. Gao, Yunong Gao, Z. Gao, S. Garbolino, I. Garzia, L. Ge, P. T. Ge, Z. W. Ge, C. Geng, A. Gilman, K. Goetzen, J. Gollub, J. B. Gong, J. D. Gong, L. Gong, W. X. Gong, W. Gradl, M. Greco, M. D. Gu, M. H. Gu, C. Y. Guan, A. Q. Guo, H. Guo, J. N. Guo, L. B. Guo, M. J. Guo, R. P. Guo, X. Guo, Y. P. Guo, Z. Guo, A. Guskov, J. Gutierrez, J. Y. Han, T. T. Han, X. Han, F. Hanisch, K. D. Hao, X. Q. Hao, F. A. Harris, C. Z. He, K. K. He, K. L. He, F. H. Heinsius, C. H. Heinz, Y. K. Heng, C. Herold, P. C. Hong, G. Y. Hou, X. T. Hou, Y. R. Hou, Z. L. Hou, H. M. Hu, J. F. Hu, Q. P. Hu, S. L. Hu, T. Hu, Y. Hu, Y. X. Hu, Z. M. Hu, G. S. Huang, K. X. Huang, L. Q. Huang, P. Huang, X. T. Huang, Y. P. Huang, Y. S. Huang, T. Hussain, N. Hüsken, N. in der Wiesche, J. Jackson, Q. Ji, Q. P. Ji, W. Ji, X. B. Ji, X. L. Ji, Y. Y. Ji, L. K. Jia, X. Q. Jia, D. Jiang, S. J. Jiang, X. S. Jiang, Y. Jiang, J. B. Jiao, J. K. Jiao, Z. Jiao, L. C. L. Jin, S. Jin, Y. Jin, M. Q. Jing, X. M. Jing, T. Johansson, S. Kabana, X. L. Kang, X. S. Kang, B. C. Ke, V. Khachatryan, A. Khoukaz, O. B. Kolcu, B. Kopf, L. Kröger, L. Krümmel, Y. Y. Kuang, X. Kui, N. Kumar, A. Kupsc, W. Kühn, Q. Lan, W. N. Lan, T. T. Lei, M. Lellmann, T. Lenz, C. Li, C. H. Li, C. K. Li, Chunkai Li, Cong Li, D. M. Li, F. Li, G. Li, H. B. Li, H. J. Li, H. L. Li, H. N. Li, H. P. Li, Hui Li, J. N. Li, J. S. Li, J. W. Li, K. Li, K. L. Li, L. J. Li, L. K. Li, Lei Li, M. H. Li, M. R. Li, M. T. Li, P. L. Li, P. R. Li, Q. M. Li, Q. X. Li, R. Li, S. Li, S. X. Li, S. Y. Li, Shanshan Li, T. Li, T. Y. Li, W. D. Li, W. G. Li, X. Li, X. H. Li, X. K. Li, X. L. Li, X. Y. Li, X. Z. Li, Y. Li, Y. H. Li, Y. B. Li, Y. C. Li, Y. G. Li, Y. P. Li, Z. H. Li, Z. J. Li, Z. L. Li, Z. X. Li, Z. Y. Li, C. Liang, H. Liang, Y. F. Liang, Y. T. Liang, Z. Z. Liang, G. R. Liao, L. B. Liao, M. H. Liao, Y. P. Liao, J. Libby, A. Limphirat, C. C. Lin, C. X. Lin, D. X. Lin, T. Lin, B. J. Liu, B. X. Liu, C. Liu, C. X. Liu, F. Liu, F. H. Liu, Feng Liu, G. M. Liu, H. Liu, H. B. Liu, H. M. Liu, Huihui Liu, J. B. Liu, J. J. Liu, K. Liu, K. Y. Liu, Ke Liu, Kun Liu, L. Liu, L. C. Liu, Lu Liu, M. H. Liu, P. L. Liu, Q. Liu, S. B. Liu, T. Liu, W. M. Liu, W. T. Liu, X. Liu, X. K. Liu, X. L. Liu, X. P. Liu, X. T. Liu, X. Y. Liu, Y. Liu, Y. B. Liu, Yi Liu, Z. A. Liu, Z. D. Liu, Z. L. Liu, Z. Q. Liu, Z. X. Liu, Z. Y. Liu, X. C. Lou, H. J. Lu, J. G. Lu, X. L. Lu, Y. Lu, Y. H. Lu, Y. P. Lu, Z. H. Lu, C. L. Luo, J. R. Luo, J. S. Luo, M. X. Luo, T. Luo, X. L. Luo, Z. Y. Lv, X. R. Lyu, Y. F. Lyu, Y. H. Lyu, F. C. Ma, H. L. Ma, Heng Ma, J. L. Ma, L. L. Ma, L. R. Ma, Q. M. Ma, R. Q. Ma, R. Y. Ma, T. Ma, X. T. Ma, X. Y. Ma, F. E. Maas, I. MacKay, M. Maggiora, S. Maity, S. Malde, L. M. Mansur, Y. J. Mao, Z. P. Mao, S. Marcello, A. Marshall, F. M. Melendi, Y. H. Meng, Z. X. Meng, G. Mezzadri, H. Miao, T. J. Min, R. E. Mitchell, X. H. Mo, B. Moses, N. Yu. Muchnoi, J. Muskalla, Y. Nefedov, F. Nerling, H. Neuwirth, Z. Ning, S. Nisar, Q. L. Niu, W. D. Niu, Y. Niu, C. Normand, S. L. Olsen, Q. Ouyang, I. V. Ovtin, S. Pacetti, Y. Pan, A. Pathak, Y. P. Pei, M. Pelizaeus, G. L. Peng, H. P. Peng, X. J. Peng, Y. Y. Peng, K. Peters, K. Petridis, J. L. Ping, R. G. Ping, S. Plura, V. Prasad, L. Pöpping, F. Z. Qi, H. R. Qi, S. Qian, W. B. Qian, C. F. Qiao, J. H. Qiao, J. J. Qin, J. L. Qin, L. Q. Qin, L. Y. Qin, P. B. Qin, X. P. Qin, X. S. Qin, Z. H. Qin, J. F. Qiu, Z. H. Qu, J. Rademacker, K. Ravindran, C. F. Redmer, A. Rivetti, M. Rolo, G. Rong, S. S. Rong, F. Rosini, Ch. Rosner, M. Q. Ruan, W. R. Ruangyoo, N. Salone, A. Sarantsev, Y. Schelhaas, M. Schernau, K. Schoenning, M. Scodeggio, W. Shan, X. Y. Shan, Z. J. Shang, J. F. Shangguan, L. G. Shao, M. Shao, C. P. Shen, H. F. Shen, W. H. Shen, X. Y. Shen, B. A. Shi, Ch. Y. Shi, H. Shi, J. L. Shi, J. Y. Shi, M. H. Shi, S. Y. Shi, X. Shi, H. L. Song, J. J. Song, M. H. Song, T. Z. Song, W. M. Song, Y. X. Song, Zirong Song, S. Sosio, S. Spataro, S. Stansilaus, F. Stieler, M. Stolte, S. S Su, G. B. Sun, G. X. Sun, H. Sun, H. K. Sun, J. F. Sun, K. Sun, L. Sun, R. Sun, S. S. Sun, T. Sun, W. Y. Sun, Y. C. Sun, Y. H. Sun, Y. J. Sun, Y. Z. Sun, Z. Q. Sun, Z. T. Sun, H. Tabaharizato, N. T. Tagsinsit, C. J. Tang, G. Y. Tang, J. Tang, J. J. Tang, L. F. Tang, Y. A. Tang, Z. H. Tang, L. Y. Tao, M. Tat, J. X. Teng, J. Y. Tian, W. H. Tian, Y. Tian, Z. F. Tian, K. Yu. Todyshev, I. Uman, E. van der Smagt, B. Wang, Bin Wang, Bo Wang, C. Wang, Chao Wang, Cong Wang, D. Y. Wang, F. K. Wang, H. J. Wang, H. R. Wang, J. Wang, J. J. Wang, J. P. Wang, K. Wang, L. L. Wang, L. W. Wang, M. Wang, Mi Wang, N. Y. Wang, P. Wang, S. Wang, Shun Wang, T. Wang, W. Wang, W. P. Wang, X. F. Wang, X. L. Wang, X. N. Wang, Xin Wang, Y. Wang, Y. D. Wang, Y. F. Wang, Y. H. Wang, Y. J. Wang, Y. L. Wang, Y. N. Wang, Yanning Wang, Yaqian Wang, Yi Wang, Yuan Wang, Z. Wang, Z. L. Wang, Z. Q. Wang, Z. Y. Wang, Zhi Wang, Ziyi Wang, D. Wei, D. H. Wei, D. J. Wei, H. R. Wei, F. Weidner, H. R. Wen, S. P. Wen, U. Wiedner, G. Wilkinson, M. Wolke, J. F. Wu, L. H. Wu, L. J. Wu, Lianjie Wu, S. G. Wu, S. M. Wu, X. W. Wu, Z. Wu, H. L. Xia, L. Xia, B. H. Xiang, D. Xiao, G. Y. Xiao, H. Xiao, Y. L. Xiao, Z. J. Xiao, C. Xie, K. J. Xie, Y. Xie, Y. G. Xie, Y. H. Xie, Z. P. Xie, T. Y. Xing, D. B. Xiong, G. F. Xu, H. Y. Xu, Q. J. Xu, Q. N. Xu, T. D. Xu, X. P. Xu, Y. Xu, Y. C. Xu, Z. S. Xu, F. Yan, L. Yan, W. B. Yan, W. C. Yan, W. H. Yan, W. P. Yan, X. Q. Yan, Y. Y. Yan, H. J. Yang, H. L. Yang, H. X. Yang, J. H. Yang, R. J. Yang, X. Y. Yang, Y. Yang, Y. G. Yang, Y. H. Yang, Y. M. Yang, Y. Q. Yang, Y. Z. Yang, Youhua Yang, Z. Y. Yang, W. J. Yao, Z. P. Yao, M. Ye, M. H. Ye, Z. J. Ye, K. Yi, Junhao Yin, Z. Y. You, B. X. Yu, C. X. Yu, G. Yu, J. S. Yu, L. W. Yu, T. Yu, X. D. Yu, Y. C. Yu, Yongchao Yu, C. Z. Yuan, H. Yuan, J. Yuan, Jie Yuan, L. Yuan, M. K. Yuan, S. H. Yuan, Y. Yuan, C. X. Yue, Ying Yue, A. A. Zafar, F. R. Zeng, S. H. Zeng, X. Zeng, Y. J. Zeng, Yujie Zeng, Y. C. Zhai, Y. H. Zhan, B. L. Zhang, B. X. Zhang, D. H. Zhang, G. Y. Zhang, Gengyuan Zhang, H. Zhang, H. C. Zhang, H. H. Zhang, H. Q. Zhang, H. R. Zhang, H. Y. Zhang, Han Zhang, J. Zhang, J. J. Zhang, J. L. Zhang, J. Q. Zhang, J. S. Zhang, J. W. Zhang, J. X. Zhang, J. Y. Zhang, J. Z. Zhang, Jianyu Zhang, Jin Zhang, Jiyuan Zhang, L. M. Zhang, Lei Zhang, N. Zhang, P. Zhang, Q. Zhang, Q. Y. Zhang, Q. Z. Zhang, R. Y. Zhang, S. H. Zhang, S. N. Zhang, Shulei Zhang, X. M. Zhang, X. Y. Zhang, Y. T. Zhang, Y. H. Zhang, Y. P. Zhang, Yao Zhang, Yu Zhang, Yu Zhang, Z. Zhang, Z. D. Zhang, Z. H. Zhang, Z. L. Zhang, Z. X. Zhang, Z. Y. Zhang, Zh. Zh. Zhang, Zhilong Zhang, Ziyang Zhang, Ziyu Zhang, G. Zhao, J.-P. Zhao, J. Y. Zhao, J. Z. Zhao, L. Zhao, Lei Zhao, M. G. Zhao, R. P. Zhao, S. J. Zhao, Y. B. Zhao, Y. L. Zhao, Y. P. Zhao, Y. X. Zhao, Z. G. Zhao, A. Zhemchugov, B. Zheng, B. M. Zheng, J. P. Zheng, W. J. Zheng, W. Q. Zheng, X. R. Zheng, Y. H. Zheng, B. Zhong, C. Zhong, X. Zhong, H. Zhou, J. Q. Zhou, S. Zhou, X. Zhou, X. K. Zhou, X. R. Zhou, X. Y. Zhou, Y. X. Zhou, Y. Z. Zhou, A. N. Zhu, J. Zhu, K. Zhu, K. J. Zhu, K. S. Zhu, L. X. Zhu, Lin Zhu, S. H. Zhu, T. J. Zhu, W. D. Zhu, W. J. Zhu, W. Z. Zhu, Y. C. Zhu, Z. A. Zhu, X. Y. Zhuang, M. Zhuge, J. H. Zou, J. Zu

Quantum Physics

Quantum algorithms for second-order boundary value problems

Lauri Kettunen and Tejas Shinde

Second-order boundary value problems are central to computational science, yet standard matrix-based numerical formulations can obscure the local geometric structure that quantum circuits may exploit. Here we introduce a framework for explicitly constructing finite-dimensional counterparts of continuous differential operators in a form compatible with quantum computation. Starting from the exterior derivative, its adjoint, and the Hodge operator, we derive discrete realizations of second-order operators on primal–dual cell complexes and reformulate them as star-local update rules expressed through explicit functions that return the relevant bounding chains rather than through matrix representations. This yields simple, uniform, and scalable quantum circuits. We demonstrate the construction for div–grad and curl–curl operators, showing that the same star-local compilation principle extends across different operators, cell complexes, and manifold dimensions within a common framework. More generally, the framework provides a systematic route to quantum algorithms for partial differential equations.
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Nuclear Experiment

Structure of even-even Zr isotopes with 52$\leq$N$\leq$58 neutrons

W. Urban, A. Abramuk, T. Rza̧ca-Urban et al. (+5 more)

Excited levels in $^{92}$Zr have been studied in cold-neutron capture reaction using the EXILL Ge array at ILL Grenoble. Excited levels in $^{94}$Zr and $^{98}$Zr nuclei have been studied using high-statistics $\gamma$-coincidence data from neutron-induced fission of $^{235}$U measured with EXILL. The goal of was to search for new levels in $^{92,94,98}$Zr and to improve spin-parity assignments to excited levels. Total of 54 new levels, 180 new $\gamma$ transitions and 70 new or improved spin-parity assignments have been determined in the three isotopes in the present work. A precise neutron binding energy of 8634.81(2) keV has been determined in $^{92}$Zr. In $^{94}$Zr a Gamow-Teller transition is proposed. The (9$^-$), 3894.1-keV level in $^{98}$Zr is likely a few ns isomer. A new technique of estimating half-lives in a picosecond range, developed in this work, provided 61 half-lives and 60 B($\pi ,\lambda$) rates for transitions in $^{96,98}$Zr and $^{94,96}$Sr. New-type systematics, backed by Large Scale Shell Model calculations have been used to classify 2$^+$ excitations in Zn-Zr even-even nuclei of the 50$\le$N$\le$60 range. This information and new systematics of 0$^+$ excitations in Sr and Zr isotopes explain the evolution of collectivity in zirconium isotopes, showing the role of various single particle excitations in the phase transition and coexistence of the region. The role of the $\nu$9/2$^+$[404] extruder orbital as a catalyst in creating 0$^+$ excitations and the deformation change in the region has been discussed.
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All authors W. Urban, A. Abramuk, T. Rza̧ca-Urban, M. Jentschel, P. Mutti, U. Köster, G. de France, C.A. Ur

Accelerator Physics

Beam based undulator trajectory alignment at European XFEL

Winfried Decking, Frank Brinker, Lars Froehlich et al. (+2 more)

Precise alignment of the undulator trajectory onto a straight line is a per-requisite for high fidelity SASE operation, which in turn also enables non-standard operation modes like self-seeding or two-color operation. At European XFEL electron and photon beam-based method are combined with a step-by-step performance-based optimization to ensure that the trajectory is on a straight line over most of the length of the about 250 m long undulator system.
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All authors Winfried Decking, Frank Brinker, Lars Froehlich, Matthias Scholz, Wolfgang Freund

Quantum Gases

Ab initio path integral Monte Carlo study of the 2D uniform electron liquid at finite temperatures

Tobias Dornheim, Fotios Kalkavouras, Paul Hamann et al. (+3 more)

We present extensive ab initio path integral Monte Carlo (PIMC) simulations of the two-dimensional uniform electron gas (2DEG), covering a broad range of density parameters $r_s=0.1,\dots,50$ and temperatures $\Theta=k_\textnormal{B}T/E_\textnormal{Fermi}=0.5,\dots,16$. This allows us to analyze various structural, linear density response and spectral properties. We find clear evidence of a roton-type feature in the dynamic structure factor at strong coupling and intermediate wavenumbers. We also benchmark novel dielectric theory implementations for the 2DEG~[Kalkavouras et al.~arXiv:2601.14989] for structural and spectral properties across the liquid phase diagram. The PIMC results can be used to benchmark existing theories and approximations, and guide the development of new methodologies.
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All authors Tobias Dornheim, Fotios Kalkavouras, Paul Hamann, Zhandos A. Moldabekov, Jan Vorberger, Panagiotis Tolias

High Energy Astrophysical Phenomena

Cosmic-ray anisotropy: sensitivity of methods and implications for KASCADE data

M. Yu. Kuznetsov, N. A. Petrov and E. M. Shinkevich

We study the problem of measuring the anisotropy of high-energy cosmic rays across all angular scales. The limited field of view and non-uniform exposure of ground-based cosmic-ray experiments reduce their sensitivity to real anisotropy of cosmic-ray arrival directions. A widely used signature of anisotropy – a dipole of the flux expansion over the right ascension – provides very limited understanding of the underlying physics of cosmic-ray origin and propagation. In this study we test two other methods: the angular power spectrum and the autocorrelation function for sensitivity to possible medium- and small-scale anisotropies of cosmic-ray flux. We find that the autocorrelation function is the most sensitive estimator for an underlying physical anisotropy in most of the models tested, while the angular power spectrum can provide additional knowledge about cosmic-ray flux properties, when the anisotropy is strong enough. As a test of our findings, we apply these methods to $10\%$ sample of the KASCADE experiment public data. Namely, we consider all-particle set of events and sets of individual mass groups classified by a convolutional neural network. We find an indication of anisotropy at $> 2.5 \sigma$ level at $\sim 10^\circ$ angular scale for the iron nuclei mass group at $E \gtrsim 20$ PeV with both the angular power spectrum and the autocorrelation methods.
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Mathematical Physics · Cross-listed from math.DS

Computable Ergodic Optimisation

Léopoldine Gayral and Mathieu Hoyrup

Links between physicals systems and computability properties have been an active field of investigation in recent years. Inspired by a previous work in the context of positive temperature Gibbs measures, we prove here that in the context of zero-temperature ergodic optimisation, for a computable potential and provided with several reasonable assumptions, the maximum ergodic average is a computable real number, and the set of maximising measures is a $\Pi_1$-computable compact set. Then, in the more specific context of symbolic dynamics, with finite-range interactions on subshifts of finite type, we provide an explicit algorithm to compute both the maximum ergodic average and the set of maximising measures in finite time, with a matching code repository.
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High Energy Astrophysical Phenomena

Synchrotron radiation in nonuniform magnetic field

V.S. Beskin, A.Yu. Istomin, F.A. Kniazev et al. (+1 more)

The distortion of the spectrum of synchrotron radiation received by a distant observer due to magnetic field inhomogeneity is discussed. It is shown that for single-particle radiation, a noticeable difference in the integrated spectrum from the case of a uniform magnetic field occurs only for observation times significantly exceeding the observer's departure from the beam pattern, and only for subrelativistic particles, when the radiation arrives from regions with significantly different magnetic fields during the observation time. For shorter observation times, field inhomogeneity leads only to small-scale distortions (smaller or comparable in frequency to the gyrofrequency) and does not manifest itself in the averaged spectrum. For the case of a particle ensemble, which is of interest for astrophysical applications, the difference in the integrated spectrum becomes negligible.
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All authors V.S. Beskin, A.Yu. Istomin, F.A. Kniazev, T.I. Khalilov

Quantum Physics

From Leaves to Clusters: Depth-Efficient SAT-Oracle Synthesis Based on the FORM Model

Zhihang Li, Wei Zi, Shuai Yang et al. (+7 more)

Quantum oracles play a fundamental role in many quantum algorithms, such as Grover's search and quantum counting. In oracle synthesis, reducing the circuit depth under a limited number of ancilla qubits is essential, given the constraints of current quantum devices. However, for satisfiability oracles (SAT-oracles) under a limited ancilla budget, existing synthesis methods fail to fully exploit clause-level parallelism, leading to deep circuits. In practice, evaluating clauses in parallel can quickly exhaust the ancilla budget. To address this issue, we introduce the Clustered Synthesis Tree (CST), a depth-oriented SAT-oracle synthesis framework that exploits clause-level parallelism while respecting the ancilla budget. CST leverages a recursive synthesis tree as the backbone for scheduling clause evaluations and groups its clause leaves into clusters, whose clauses are evaluated in parallel by a reversible oracle called ClausePack. To form the clusters, CST introduces a polynomial-time heuristic called SeedGrow for the NP-hard clause-grouping problem, and the resulting tree is compiled into an executable circuit by CST-Map. Compared with the depth-oriented pAND baseline, CST can reduce the circuit depth by an average of 10.2x and 8.8x-11.0x on SATLIB and random 4-CNF benchmarks, respectively, under the same ancilla budgets, while also outperforming the width-oriented pAND, clause-storing, and qSAT baselines.
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All authors Zhihang Li, Wei Zi, Shuai Yang, Bei Zhou, Zongjiang Yi, Woji He, Yingjie Lin, Kaixiang Ji, Heru Du, Jinchen Xu

General Relativity and Quantum Cosmology

Sonic black holes with thick horizons in BECs

Daniel Peñalver, Marco De Vito, Roberto Balbinot et al. (+1 more)

We consider simple one dimensional models of acoustic black holes formed by Bose-Einstein condensates where the flow is stepwise homogeneous. We shall concentrate on the case in which an extended sonic region is present, i.e. a region where the flow velocity equals exactly the speed of sound. These models can be thought of as acoustic black holes with a thick horizon. Particular attention will be devoted to the number of created particles and to the density-density correlation functions, these latter being at present time the experimental tool to identify Hawking like radiation in acoustic black holes.
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All authors Daniel Peñalver, Marco De Vito, Roberto Balbinot, Alessandro Fabbri

Soft Condensed Matter

A method for measuring the dispersion of elastic waves in disordered computer-solids

Edan Lerner

The dispersion of elastic waves in disordered solids plays a key role in determining the vibrational density of states and harmonic wave attenuation rates. As such, the availability of robust computational approaches to the precise extraction of the dispersion is of key importance. Here we present a simple method – the imposed wave method (IWM) – , which provides direct access to the dispersion of elastic waves in computer models of solids, without any fitting involved. We directly benchmark the method against the `ground-truth' obtained from direct diagonalization of solids' hessian matrices, to find good agreement. We discuss limitations of and finite-size effects in the method, and show that exploiting the method's finite-size scaling provides access to a fundamental quantifier of mechanical disorder that determines wave attenuation rates and spectral widths.
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High Energy Physics (Theory)

Brouwer Degree of Thermodynamic Multicritical Points in Black Holes

Bidyut Hazarika and Prabwal Phukon

In this manuscript, we propose a novel topological framework based on the heat capacity of black holes to investigate the topology of thermodynamic multicritical points. We construct a two-dimensional thermodynamic vector field whose isolated zeros correspond to the critical points of the system. The local topology of each critical point is characterized by its Brouwer degree, which serves as a locally conserved topological quantity. Applying this formalism to several AdS black hole solutions, we demonstrate that each system possesses a globally conserved topological charge. Although the number of thermodynamic critical points changes as the thermodynamic parameters are varied, the total topological charge remains invariant throughout the evolution. We show that these topological transitions are governed by the creation or annihilation of topologically neutral defect pairs carrying opposite Brouwer degrees. Our results provide a unified topological framework for understanding the emergence, evolution, and classification of thermodynamic multicritical points in black hole systems.
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