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Thursday 30 July

Mesoscale and Nanoscale Physics

Significant ordinary Nernst effect contribution to spin-orbit torque harmonic Hall measurements in metallic structures

Igor Lyalin, C. C. Chiang and C. L. Chien

The harmonic Hall measurements are commonly used to quantify the spin-orbit torque in ferromagnet/normal metal bilayers. The contribution from ordinary Nernst effect to the second harmonic voltages is usually assumed to be negligible and omitted in the data analysis. We show that in Cr/Co bilayers the ordinary Nernst effect cannot be neglected and can lead to largely exaggerated values of spin-orbit torque efficiency. Conducting additional experiments, we estimate the Nernst coefficient of Cr and find it comparable to the values reported for other metals. Consequently, the ordinary Nernst effect should be carefully considered when employing the harmonic Hall technique to quantify spin-orbit torque in metals, while the results of some previous works might need to be re-examined.
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Mathematical Physics · Cross-listed from math.PR

Perturbed Beta Corners Process

Leonid Petrov and Jiaming Xu

We introduce and study the perturbed $\beta$-corners process, a deformation of the classical $\beta$-corners process. The latter is a probability measure on interlacing arrays of real numbers that, for the classical values $\beta=1,2,4$, describes the joint distribution of eigenvalues of principal submatrices of a Gaussian random matrix with the corresponding GOE/GUE/GSE symmetry. For classical $\beta$, the perturbed process arises from adding a deterministic diagonal matrix $A=diag(a_1,...,a_N)$ to a GOE/GUE/GSE matrix. The eigenvalues of the resulting random matrix depend symmetrically on $a_1,...,a_N$, but this symmetry does not extend to the whole corners process. We extend the construction to all $\beta>0$ via multivariate Bessel functions, and analyze the crystallization ($\beta\to\infty$) of the resulting interlacing array, proving a law of large numbers and a central limit theorem in two regimes. For fixed perturbation, the eigenvalue repulsion dominates, and the array crystallizes on the same lattice of polynomial-derivative roots, with the same discrete Gaussian free field fluctuations, as in the unperturbed case treated by Gorin and Marcus (arXiv:1706.07393). New phenomena appear in the second regime, where the $a_i$'s grow linearly in $\beta$. Then the external source competes with the repulsion at leading order. Here the array freezes on a deformed lattice characterized by a coupled system of optimality equations. The fluctuations are governed by the same discrete Gaussian free field, now attached to the deformed lattice. The deformed lattice equations decouple in the special case of a single spike in the last coordinate. Then the deformed lattice is obtained explicitly by applying one shifted derivative $D_c f = f' + cf$ followed by iterated ordinary derivatives.
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Chaotic Dynamics

Chaos in reason: How chain-of-thought LLMs can look for an answer

Gregorio Jaca, Kristóf Benedek and János Török

Large Language Models (LLMs) have achieved remarkable performance across a wide range of tasks, yet their internal dynamics remain poorly understood. In this work, we apply the tools of nonlinear dynamics and chaos theory to LLMs. By analyzing both text and hidden state trajectories, we demonstrate that LLMs exhibit hallmark signatures of chaos, including strong sensitivity to initial conditions, manifested as intermittent, jump-like divergence of nearby trajectories combined with bounded evolution, with consistent results across different distance metrics. An exact Jacobian analysis of the Transformer's sub-blocks shows that self-attention and the feed-forward network expand and propagate perturbations, while normalization and residual connections counteract this expansion and promote stability. Recurrence plots show structural similarities between LLMs and canonical chaotic systems such as the Lorenz attractor, while dimension analysis reveals fractal structures in the hidden state space, particularly pronounced in the last layers. We propose that the nonlinear coupling induced by attention mechanisms plays a key role in driving this chaotic behavior.
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High Energy Astrophysical Phenomena

Thermal or Non-thermal? Diffuse emission in the infall region of stacked galaxy groups

E. Bulbul, X. Zhang, Z. Ding et al. (+16 more)

The faint infall regions surrounding the virial radius of galaxy groups remain largely unexplored due to their low X-ray surface brightness. Using the large statistical power of SRG/eROSITA survey observations, we present the first spectroscopic measurement of the intragroup medium (IGrM) in the infall regions of a large sample of low-mass galaxy groups ($M_{\rm tot}<1\times10^{14}\,M_{sun}$), extending to $\sim2\,R_{200m}$ (2.2 Mpc). Through spectral stacking of 827 nearby groups from the first eROSITA All-Sky Survey catalog, we detect diffuse emission and measure the thermodynamic properties of gas at densities previously inaccessible to X-ray observations. The stacked spectra are well described by a Gaussian differential emission measure model, yielding a temperature distribution with a mean temperature of $0.96_{-0.04}^{+0.05}$ keV and width of $0.28_{-0.10}^{+0.10}$ keV, and a metal abundance of $0.21_{-0.04}^{+0.06}$ A$_{sun}$, consistent with expectations for group outskirts. The inferred electron densities decrease from $(4.8\pm1.3)\times10^{-5}$cm$^{-3}$ at $(0.7-2)\,R_{500c}$ to $(5.5\pm2.0)\times10^{-6}$ cm$^{-3}$ at $(2-4)\,R_{500c}$, demonstrating eROSITA's ability to probe the low-density outskirts of galaxy groups. Residual emission in the spectra suggests the presence of an additional spectral component. While a secondary thermal interpretation requires an unexpectedly hot, metal-poor plasma, a non-thermal inverse Compton model provides an equally plausible explanation, contributing $\sim30\%$ of the thermal flux. Assuming that the additional component is produced by inverse Compton emission from a common population of relativistic electrons, the inferred magnetic field strength would be in the sub-$\mu$G regime.
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All authors E. Bulbul, X. Zhang, Z. Ding, T. Mistele, M. Kluge, E. Artis, Y. E. Bahar, K. Dennerl, D. Eckert, L. Fiorino, P. F. Hopkins, N. Malavasi, A. Merloni, K. Nandra, E. Quataert, M. E. Ramos-Ceja, J. S. Sanders, J. Strunk, S. Zelmer

Materials Science

Finite-temperature bulk moduli from an EOS-based Grüneisen function

Çetin K{\i}l{\i}ç

An equation-of-state (EOS)-based construction of the Grüneisen function is developed and assessed through predictions of finite-temperature bulk moduli. In this approach, the volume dependence of the Grüneisen function is expressed analytically in terms of static EOS information, anchored by Debye temperatures obtained from elastic data sampled near equilibrium, and constrained by the infinite-compression limit. The resulting form requires as material-specific input only static energy-volume data and near-equilibrium elastic properties, with no parameters adjusted to thermal data. Within a Mie–Grüneisen–Debye framework, the approach is examined for diamond, magnesium oxide, silicon, and sodium chloride, chosen to span a broad range of stiffness, using machine-learning interatomic potentials from the Universal Models for Atoms (UMA) and Universal Point Edge Transformer (UPET) families, together with a dispersion-corrected variant of UMA. The calculated bulk moduli reproduce the expected experimental softening trends and capture the overall scale of the bulk-modulus temperature derivatives, although the level of quantitative agreement depends on the material, the underlying interatomic potential, and the selected analytic EOS form. These results show that an EOS-based construction of the Grüneisen function can capture the leading thermal-softening behavior of bulk moduli without fitting to thermal data. The observed sensitivity to the underlying static description further suggests that the framework may help identify deficiencies relevant to thermoelastic transferability and thereby inform future training and validation strategies for universal machine-learning interatomic potentials.
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General Relativity and Quantum Cosmology

Degenerate Limits of Scalar-Tensor Gravity

Bekir Baytaş and Xiao-Kan Guo

We study the degenerate limits of the scalar-tensor theory of gravity in its Hamiltonian connection dynamics formulation. The degenerate limit of the spatial triad is effectuated by a local scaling transformation of the triad, which leads to the degenerate limits of all other geometric quantities and relations in the connection dynamics. We derive the constraints for the degenerate scalar-tensor theory of gravity and discuss their physical implications.
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Mathematical Physics · Cross-listed from math.NA

A Unified Discrete Gradient-SAV Framework for Structure-Preserving Integration

Elena Celledoni, David Martín de Diego, Brynjulf Owren et al. (+1 more)

We present a framework combining discrete gradient (DG) methods with the Scalar Auxiliary Variable (SAV) approach to construct structure-preserving integrators for dissipative and conservative systems. The key observation is that SAV quadratization lifts the dynamics to an extended state space on which the modified energy has an exact discrete-gradient identity. This viewpoint yields three integrators with different accuracy and cost profiles: a first-order semi-implicit Forward Euler scheme, a second-order self-adjoint Midpoint scheme, and a second-order Predictive scheme with reduced implicitness. The construction extends to almost-Poisson systems and preserves selected Casimir invariants under an enforceable discrete condition. Numerical experiments cover the Allen–Cahn equation, an Ohta–Kawasaki-type nonlocal gradient flow, a double-well Hamiltonian oscillator, and a Poisson system with a nonlinear cubic Casimir.
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All authors Elena Celledoni, David Martín de Diego, Brynjulf Owren, Miguel Vaquero

History and Philosophy of Physics

Can AI Follow In Einstein's Footsteps?

Michael Shalyt, Nathan Regev, Marin Soljačić et al. (+1 more)

AI is accelerating physics discovery, but perhaps away from Einstein-level theory building. To understand this gap, we must recognize a striking trend: while being very successful, the most visible AI contributions to physics discovery appear to mirror the historical development of physics, but in reverse. Human discovery in physics progressed, in broad strokes, from ancient pattern prediction, through phenomenological laws such as Kepler's, to principle-based universal theories such as relativity and the Standard Model. On the AI side, prominent contributions to physics discovery point in the opposite direction: early milestones emphasized explicit equation-discovery methods, such as symbolic regression, whereas more recent frontier contributions are powerful predictors such as AlphaFold and GraphCast, which can be remarkably accurate yet do not provide clear theoretical understanding. If this trend continues, AI would become extraordinarily good at prediction but may struggle to ever propose its first serious contender to quantum gravity or other paradigm-level theories. We review the current landscape of AI for physics discovery and highlight a critical missing skill: the ability to pose the right questions or invent the right principles to guide the development of new theories and the tests to falsify them. This mode of discovery has driven many of the deepest advances since the 17th century, where symmetry, simplicity, and new mathematical frameworks guided theory construction before experimental tests. Equipping AI systems with such skills could move them from predicting within known frameworks to proposing the next paradigm-level discovery in physics.
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All authors Michael Shalyt, Nathan Regev, Marin Soljačić, Ido Kaminer

Pattern Formation and Solitons

Wave patterns in two-dimensional networks of non-locally coupled oscillators with phase delay

Phillip Nimphius and Nariya Uchida

We studied the wave patterns in non-locally, repulsively coupled oscillators on a 2D lattice. The repulsive coupling is tuned by the phase delay $\alpha \pi$ and the wave patterns are found in the regime $\alpha \in \left[0.5, 1\right]$. We focused on the growth of orientationally correlated domains and found that the average total boundary size $\overline{|B|}$ obeys an approximate power law $\overline{|B|}\propto t^{-b}$ for $\alpha = 0.8$ and $\alpha =0.9$. In contrast, at $\alpha = 0.7$, the dynamics is disrupted by defect-mediated domain formation and domain splitting. The fitting-window dependence of the apparent exponent $b$, as well as the mean and standard deviation of the wave speed $c$, decreases with increasing $\alpha$, which is consistent with the linear stability analysis of the wave solution.
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Instrumentation and Detectors

Bounded-Latency Spherical-Histogram Reconstruction for Compton Cameras

Francisco J. Albiol, Luis Caballero, José Escalante et al. (+4 more)

Gamma-ray imaging with Compton cameras is computationally demanding because conventional reconstruction retains the list-mode acquisition inside the inversion loop: event-dependent cone/voxel interactions must be recomputed as the event count grows. We present a spherical-histogram framework in which each Compton event is encoded online into detector-centred angular histograms. Volumetric reconstruction is then performed from coherent histogram snapshots using a precomputed sparse projection operator. This turns the event stream into a bounded reconstruction state, decoupling event accumulation from iterative inversion. The method supports multi-view and multi-resolution operation, non-blocking acquisition, and iterative forward/backward reconstruction whose dominant cost depends.
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All authors Francisco J. Albiol, Luis Caballero, José Escalante, Alberto Albiol, Salvador Tortajada, Elena Larrea Estrelles, José Luis Leganés-Nieto

Quantum Physics

Resource-efficient quantum-selected configuration interaction for molecular properties

Suprava Sahoo, Abdul Kalam, Kenji Sugisaki et al. (+2 more)

The quantum-selected configuration interaction identifies important determinantal basis functions through real-time evolution of a reference wavefunction and diagonalizing the Hamiltonian matrix in the resulting selected subspace. However, implementing the full electronic Hamiltonian on noisy quantum devices leads to rapidly increasing circuit complexity, limiting its scalability. To address this issue, we identify the dominant fermionic excitation operators and perform reference-state fidelity loss analysis to construct a compact Hamiltonian, reducing computational overhead while retaining high precision. Applied to Group IIIA monofluorides (BF, AlF, GaF, InF, and TlF), the proposed framework achieves a near-quadratic improvement in Hamiltonian-term scaling, enabling resource-efficient simulations. We employ this framework to compute the relativistic ground-state energies and permanent electric dipole moments (PDMs) of the systems under consideration. After validating the framework via simulations, we demonstrate hardware execution for AlF and TlF on the IBM Marrakesh processor using active spaces of up to 20 qubits. For a 20-qubit TlF system, the reduced Hamiltonian yields a reduction of higher than $ 98\%$ in both circuit depth and two-qubit gate counts, with the resulting PDMs from quantum hardware matching complete active space configuration interaction values within $99.99\%$. These results demonstrate the scalability of this approach on noisy intermediate-scale quantum devices.
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All authors Suprava Sahoo, Abdul Kalam, Kenji Sugisaki, V. S. Prasannaa, B.P. Das

High Energy Astrophysical Phenomena

The SRG/eROSITA All-Sky Survey DR2: Cumulative X-ray catalogues from the first three surveys and multi-wavelength counterparts in the western Galactic hemisphere

M. E. Ramos-Ceja, G. Lamer, M. Salvato et al. (+111 more)

The eROSITA telescope array on board the Spektrum-Roentgen-Gamma (SRG) mission began its all-sky survey program in December 2019, scanning the sky at an approximately six-month cadence. Here, we present new catalogues of point-like and extended X-ray sources derived from the first three completed eROSITA all-sky surveys (eRASS:3), covering the western Galactic hemisphere, which Germany's eROSITA consortium holds proprietary rights for. We describe the observational strategy, data processing, and analysis pipelines. We also characterise the resulting X-ray source populations. The eRASS:3 main catalogue contains nearly two million sources, including 1,911,744 point-like and 63,796 extended sources, detected in the 0.2-2.3 keV energy band, eROSITA's most sensitive energy window. This volume has doubled the X-ray source content of eRASS1 and provides a comprehensive census of X-ray-emitting objects across diverse astrophysical classes. We also released a secondary hard catalogue of nearly 15,000 sources detected in the harder 2.3-5.0 keV energy band. In addition, we released six catalogues, three for the main sample and three for the hard sample, in which we identify and classify the optical and infrared counterparts of eRASS:3 point-like sources. This approach delivers a homogeneous, high-quality identification of mostly extragalactic X-ray emitters; for example, we estimate that approximately 88% of the 1.4 million counterparts identified within the footprints of the Legacy Survey Imaging for DESI are extragalactic sources. This work has enabled the generation of samples optimised for completeness and purity, while expanding the discovery space for rare populations. The second data release (DR2) of the SRG/eROSITA all-sky survey is a catalogue-only release, comprising the catalogues presented in this work together with an updated version of the eROSITA upper flux limit server.
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All authors M. E. Ramos-Ceja, G. Lamer, M. Salvato, A. Merloni, J. S. Sanders, A. Georgakakis, T. Liu, E. Bulbul, J. Buchner, K. Dennerl, M. J. Freyberg, S. Friedrich, I. Kreykenbohm, C. Maitra, K. Nandra, P. Predehl, T. H. Reiprich, J. Robrade, A. Schwope, R. Shirley, B. Stelzer, I. Stewart, R. Seppi, H. Starck, D. Tubin-Arenas, I. Traulsen, E. Artis, C. Aydar, P. Baldini, F. Balzer, W. Becker, M. M. Bennedik, W. Bornemann, M. Brueggen, J. Brink, M. Brusa, V. Burwitz, M. Canal i Saguer, N. Clerc, J. Comparat, M. Coriat, J. V. Correa-Rodrigues, S. Czesla, L. Dauner, J. Dietl, Z. Ding, L. Ducci, T. Dwelly, L. Fiorino, S. Freund, P. Friedrich, R. Gaida, E. Gatuzz, S. T. Guida, S. Haemmerich, F. Haberl, G. Hartner, S. Hernandez-Diaz, Z. Igo, N. Ilic, D. M. Kaltenbrunner, A. Khokhriakova, W. Kink, C. Kirsch, M. Kluge, S. Krippendorf, M. Krumpe, S. Kulkarni, J. Kurpas, E. Kyritsis, R. Laktionov, A. Liu, M. Lorenz, N. Malavasi, M. G. F. Mayer, N. Meidinger, T. Mistele, S. Mueller, D. Muñoz-Giraldo, N. T. Nguyen-Dang, Q. Ni, S. Ok, N. Ota, G. Puehlhofer, F. Pacaud, A. Pandya, E. Perinati, C. Pommranz, G. Ponti, K. Poppenhaeger, K. G. Pradeep, A. Rau, W. Roster, S. Rukdee, S. Saeedi, A. Santangelo, M. Sasaki, S. Sheth, S. Shreeram, M. Sommer, A. Srivastava, V. Suleimanov, J. Truemper, N. Vasilas, A. Veronica, N. Webb, P. Weber, J. Wilms, M. C. H. Yeung, F. Zangrandi, S. Zelmer, X. Zhang, Y. Zhang, X. Zheng

Quantum Physics

Quantum Magnonics: Quantum States Generation and Applications

Zi-Xu Lu, Xuan Zuo, Xin-Lei Hei et al. (+5 more)

Hybrid systems based on magnons in ferromagnetic materials, such as yttrium iron garnet, have achieved remarkable development in the last decade. These include the coupling of magnons to microwave and optical photons, superconducting qubits, phonons, spins, the center-of-mass motion of a ferromagnet, etc. Here, we review both the experimental and theoretical progress in this field, focusing on the generation of magnonic quantum states and their applications in a broad range of fields. Since the strong coupling is a prerequisite for achieving coherent quantum control of magnons and preparing magnonic quantum states, we start by introducing representative strong-coupling experiments in cavity magnonics, then review a series of protocols for creating various magnonic quantum states, such as Fock, cat, squeezed, and entangled states, and discuss their potential applications in macroscopic quantum studies, quantum information science, quantum sensing, magnonic quantum devices, dark matter detection, and so on. Finally, we summarize the review and give an outlook for the future study of quantum magnonics.
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All authors Zi-Xu Lu, Xuan Zuo, Xin-Lei Hei, Gang Liu, Zeng-Xing Liu, Qi Guo, Peng-Bo Li, Jie Li

Superconductivity

Cavity Tuning of the CDW–Superconductivity Interplay in a Kagome Metal

Lan-Ting Shi, I-Te Lu, Xin Wang et al. (+3 more)

Kagome metals host competing electronic orders, including charge-density-wave (CDW) order and superconductivity, shaped by intertwined lattice, electronic-correlation, and kagome-geometric effects. Here, using quantum electrodynamical density functional theory, we identify an equilibrium cavity route for reshaping this balance in the kagome metal CsV$_3$Sb$_5$. An out-of-plane polarized single-mode cavity selectively softens CDW-related phonons, counteracting pressure-induced hardening and extending the CDW instability toward higher pressures. In the high-pressure regime where the CDW instability is otherwise suppressed, cavity coupling redistributes Eliashberg spectral weight toward lower frequencies, enhances the total electron–phonon coupling (EPC), and increases the EPC-based Allen–Dynes estimate of $T_c$. This response originates from a charge-density redistribution induced by the out-of-plane photon mode, which modifies lattice restoring forces and drives the phonon and EPC renormalization. These results establish cavity quantum electrodynamics as a viable equilibrium route for tuning intertwined charge order, lattice dynamics, and superconductivity in kagome materials.
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All authors Lan-Ting Shi, I-Te Lu, Xin Wang, Dongbin Shin, Lede Xian, Angel Rubio

Physics and Society · Cross-listed from cs.LG

Train Small, Deploy Large: Zero-Shot GNN Transfer Through Geometric Renormalization

Robert Jankowski, Pedro Almagro-Blanco, Marián Boguñá et al. (+2 more)

Graph neural networks (GNNs) can operate on large graphs but become infrastructure-sensitive at the scale of millions of nodes and typically require scalable training techniques for even larger graphs. This raises a central question: when can a model trained on a smaller, scaled-down replica of a graph be deployed on the full-resolution graph without retraining? We introduce a zero-shot transfer protocol in which a GNN is trained on a graph coarse-grained by geometric renormalization (GR), and the resulting weights are transferred directly to the original network. Across synthetic and real-world networks, training on GR scaled-down replicas preserves much of the original-scale predictive performance while significantly reducing training cost. We further find that learned representations and predictive trajectories remain aligned across scales. These findings suggest that structural similarity may be more important than network size in determining GNN transferability, opening a path toward scale-equivariant graph architectures.
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All authors Robert Jankowski, Pedro Almagro-Blanco, Marián Boguñá, Melanie Weber, M. Ángeles Serrano

Earth and Planetary Astrophysics

Accretion Burst Crystallizes Silicates in a Planet-Forming Disk

Jeong-Eun Lee, Chul-Hwan Kim, Jaeyeong Kim et al. (+13 more)

Crystalline silicates form at high temperatures (> 900 K; Fabian et al. 2000; Hallenbeck et al. 1998). Their presence in comets (Hanner et al. 1994; Hayward et al. 2000; Wooden et al. 2002; Shinnaka et al. 2018) suggests that high-temperature dust processing occurred in the early Solar System and was subsequently transported outward to comet-forming regions. However, direct evidence for this crystallization and redistribution in Sun-like protostars has remained elusive. By comparing James Webb Space Telescope (JWST) mid-infrared spectra of the periodically bursting protostar EC 53 (Lee et al. 2020), we detect crystalline silicate (forsterite and enstatite) emission features that appear only during the burst. The emergence of these features indicates active crystal formation via thermal annealing in the hot inner disk during the accretion burst. We also detect a nested outflow-a collimated atomic jet enclosed by slower molecular outflows, consistent with magnetohydrodynamic (MHD) wind models (Pascucci et al. 2025). This configuration provides a mechanism for outward transport of freshly crystallized silicates (Giacalone et al. 2019). Our results provide the first direct observational evidence of in-situ silicate crystallization during episodic accretion bursts in a very young star still embedded in its dense envelope. Although we do not directly detect grains transported to the outer disk, the observed trends are consistent with outward redistribution, indicating that both dust processing and transport occur during the earliest and most dynamic stages of star formation.
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All authors Jeong-Eun Lee, Chul-Hwan Kim, Jaeyeong Kim, Seokho Lee, Young-Jun Kim, Seonjae Lee, Giseon Baek, Joel D. Green, Gregory J. Herczeg, Doug Johnstone, Klaus M. Pontoppidan, Yuri Aikawa, Yao-Lun Yang, Logan Francis, Mihwa Jin, Hyerin Jang

Earth and Planetary Astrophysics

The International Lunar Reference System

Agnès Fienga

As the exploration of the Moon accelerates in the coming years, there is already an urgent need to standardise the Position, Navigation and Timing of spacecraft, and consequently for the definition of the lunar reference system and frame. This document gathers the most recent recommendations of the the International Association of Geodesy (IAG) / International Astronomical Union (IAU) Joint Working Group (WG) 1.1.3 "Lunar Reference frames" on the topic. Despite the challenges for producing a Lunar Reference System and Frame due to the limited number of control points and a single data type, the WG proposes applying an approach developed for Global Navigation Satellite Systems (GNSS). This supports an accurate and reliable reference system, consistent with International Earth Rotation and Reference Systems Service (IERS) standards and, based on redundant sources, ensures resilience for the lunar Position, Navigation and Timing (PNT) framework. The first realization of the International Lunar Reference Frame 2026 (ILuRF2026), ILuRF2026, is delivered on the temporay website https://ilurs-6e772d.gitlab.io/ and on the future http://ilurf.gssc.esa.int together with associated software.
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Solar and Stellar Astrophysics

Long-term high-resolution spectroscopic monitoring of the evolved metal-poor binary PS Gem

V.G. Klochkova, V.E. Panchuk, J.K. Zhao et al. (+3 more)

We present results of long-term high-resolution spectroscopic monitoring of the extremely low-metallicity star PS Gem (=HD 52961), associated with IRAS 07008+1050. The spectra were obtained with the 6-meter BTA telescope at a resolving power of R=60000 during 1997–2025, providing a homogeneous dataset spanning nearly three decades. Quantitative measurements of the H$\alpha$ two-peaked profile reveal repeatable phase-dependent variations of the peak-intensity ratio $I_{\rm V}/I_{\rm R}$ and the absorption-core velocity over multiple orbital cycles, whereas the peak separation remains nearly constant at $\Delta V_r = 78\pm 4$ km s$^{-1}$. The heliocentric radial velocity measurements yield a systemic velocity of $\gamma=7.46\pm 0.64$ km s$^{-1}$ and an orbital semi-amplitude of $K=2.49$ km s$^{-1}$. No significant long-term secular drift is observed over the monitoring interval. The stellar luminosity, estimated from the equivalent width of the OI 7773 Ȧ triplet ($W_{\lambda}=1.16\pm$ 0.02 Ȧ), corresponds to $\log(L/L_{\odot})\approx$3.5. The average radial velocity of diffuse interstellar bands is consistent with the location of PS Gem in the Local Arm. These observations provide rare multi-decade time-domain constraints on the dynamical behavior of this evolved metal-poor star.
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All authors V.G. Klochkova, V.E. Panchuk, J.K. Zhao, Y.Q. Wu, N.S. Tavolzhanskaya, G. Zhao

Materials Science

A Combined Microbeam and Phase-Field Approach to Identify the Toughness and Ultimate Strength of Amorphous Silica

Gustavo Alberto Rosales-Sosa, Gergely Molnar, Yoshinari Kato et al. (+7 more)

This work presents a new approach to evaluating the toughness, described by the critical energy release rate ($G_c$), and ultimate tensile strength ($\sigma_c$) of amorphous silica (SiO$_2$ glass), combining microbeam tests and phase-field calculations. The latter provides a numerical route to brittle fracture without prescribing explicit fracture surfaces a priori, enabling crack initiation and propagation to be tracked. Single-notched microbeams and newly designed bone-shaped microbeams with a notch-free gauge section were fabricated by Focused Ion Beam (FIB) milling nd tested under bending in air, probing the brittle-fracture and strength-controlled regimes, respectively. Both geometries were modeled by Finite Element Analysis (FEA) coupled with a phase-field formulation. We found $G_c = 5.1$~J/m$^2$ (critical stress intensity factor $K_{IC} = 0.61$~MPa$\cdot$m$^{1/2}$), an intrinsic material length scale $\ell_c = 9.1$~nm, and $\sigma_c = 6.8$~GPa, consistent with previously reported brittle properties of silica glass. Through a parametric study, we show the effect of notch geometry on the fracture response of the microbeams and the impact of dimensional measurement error on the determined toughness. Unlike conventional micromechanical methods that yield only $K_{IC}$, our combined microbeam geometries and phase-field approach simultaneously deliver $G_c$ and $\sigma_c$, bridging brittle-fracture characterization and the strength-controlled regime inaccessible to toughness-only techniques.
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All authors Gustavo Alberto Rosales-Sosa, Gergely Molnar, Yoshinari Kato, Taichi Nakashima, Takahito Ohmura, Etienne Barthel, Guillaume Kermouche, Sergio Sao Joao, Shingo Nakane, Hiroki Yamazaki

Quantum Physics

Exact Incompatibility-Breaking Criterion for Unital Qubit Channels

Yujie Zhang

We study when a noisy qubit channel renders all positive-operator-valued measures (POVMs) jointly measurable. For every unital qubit channel, we derive the exact incompatibility-breaking criterion and prove that projective measurements already determine the boundary for arbitrary POVMs. Through the steering–joint-measurability correspondence, this result gives the exact POVM-steering boundary for all two-qubit states with maximally mixed marginals, with the Werner states recovered as a special case. For nonunital qubit channels, we construct a generally asymmetric parent POVM and obtain an explicit sufficient incompatibility-breaking condition, which in turn yields a sufficient unsteerability criterion for arbitrary two-qubit states.
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High Energy Astrophysical Phenomena

Comprehensive X-ray Study of Giant Radio Galaxies with XMM-Newton and Chandra

Niraj Maurya, Satish S. Sonkamble, Suraj Dhiwar et al. (+3 more)

We present a systematic X-ray spectral analysis of 27 giant radio galaxies (GRGs) using archival XMM-Newton and Chandra data. Roughly 44% of the sample show intrinsic absorption ($N_{\mathrm{H,int}} \gtrsim 10^{21}\,\mathrm{cm}^{-2}$), while several exhibit narrow Fe K$\alpha$ emission lines with equivalent widths up to $\sim$570 eV. Soft X-ray features are also common, including thermal plasma emission (kT$\sim 0.2$–0.8 keV) and ionized absorbers, in some cases consistent with high-velocity outflows. The photon indices are typically hard (median $ \Gamma \sim 1.6$), in line with radio-loud AGN. A comparison between nuclear X-ray luminosity and extended radio power shows that many sources host relatively strong X-ray cores compared to their lobes, pointing toward possible restarted nuclear activity. For 10 GRGs with published black hole masses, we explore preliminary relations with X-ray luminosity, Eddington ratio, and photon index. We find a positive trend between $M_{\rm BH}$ and $L_{2-10\,{\rm keV}}$, while Eddington ratios show no clear dependence on mass. A tentative negative relation between $\lambda_{\rm Edd}$ and $\Gamma$ hints at inefficient accretion, although confirmation will require larger samples. Overall, GRGs display diverse nuclear conditions and accretion states, supporting scenarios where obscuration, episodic or restarted activity, and low-efficiency accretion shape their long-term evolution.
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All authors Niraj Maurya, Satish S. Sonkamble, Suraj Dhiwar, M. B. Pandge, S. Ilani Loubser, Avinash Kale

Materials Science

Tilt-driven ferrielectricity in PbZrO$_3$

Huazhang Zhang, Ying Liu, Carson Carroll et al. (+6 more)

We reveal a tilt-driven mechanism for ferrielectricity in prototypical antiferroelectric PbZrO$_3$. Specifically, introducing an additional octahedral tilt into the antiferroelectric $Pbam$ phase breaks the symmetry constraint that enforces equal antiparallel dipoles, converting the compensated “$\uparrow \uparrow \downarrow \downarrow$” nonpolar configuration into an uncompensated “$\uparrow \uparrow \downarrow \downarrow$” polar $Pmc2_1$ phase. First-principles calculations show that the $Pmc2_1$ phase becomes stabilized under lattice contraction and gains increasing free-energy advantage over competing phases at finite temperatures. Atomic-scale imaging directly confirms the presence of $Pmc2_1$-like structures in thin films and single crystals. This work identifies a symmetry-governed, kinetically easily accessible pathway to ferrielectricity and establishes a form of “competitive” improper ferroelectricity, with broad implications for antiferroelectrics.
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All authors Huazhang Zhang, Ying Liu, Carson Carroll, Saptam Ganguly, Bin Xu, Xiaozhou Liao, Gustau Catalan, Philippe Ghosez, Nicholas C. Bristowe

Instrumentation and Methods for Astrophysics

PhySR: Physics-Informed Neural Network for Super-Resolution Reconstruction in Radio Synthesis Imaging

Hongkun Yang, Li Zhang, Ming Zhang et al. (+1 more)

Radio telescope arrays are constrained by the number of antennas and baseline distribution, resulting in incomplete spatial-frequency sampling, limited image resolution, and blurring, distortion, and loss of small-scale structures caused by coupling between the primary and synthesized beams. Existing general-purpose model-driven methods remove observational effects sequentially and may accumulate errors, but cannot directly address limited imaging resolution, while data-driven methods lack explicit physical constraints. We propose PhySR, an end-to-end physics-informed neural network that combines a U-Net backbone, dynamic cascaded upsampling, a multiscale feature residual module, and a differentiable physical forward model incorporating the primary beam response, PSF convolution, and scale mapping. PhySR directly reconstructs high-resolution images from low-resolution dirty images without high-resolution labels while maintaining observation-domain consistency. Experiments on simulated SKA-Mid data show that, for 4x super-resolution, PhySR achieves a PSNR of 44.65 dB, an SSIM of 0.9940, and an RMSE of 0.0065. Compared with existing general-purpose methods, PSNR and SSIM improve by approximately 13.23 dB and 0.3760, respectively. Compared with mainstream deep learning models, PSNR and SSIM improve by 6.50 dB and 0.0682, while RMSE decreases by 0.0069. PhySR also remains stable for 2x and 8x super-resolution and achieves low observation-domain consistency errors, demonstrating advantages in coupling-effect removal, small-scale structure recovery, and physical consistency.
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All authors Hongkun Yang, Li Zhang, Ming Zhang, Yong-Feng Huang

Strongly Correlated Electrons

Trion Excitations in Twisted Bilayer Graphene: A Quantum Monte Carlo Study

Shibo Shan, Cheng Huang, Patrick Ledwith et al. (+1 more)

Determining the nature of charge carriers is a fundamental goal in the study of strongly correlated electron systems. Here, we employ the continuous-field momentum-space quantum Monte Carlo method to reveal exotic "Dirac trion" excitations in the finite-temperature normal state of twisted bilayer graphene. While the ground state is a symmetry-breaking insulator with gapped ($\sim$ 20 meV) electron-like excitations, we show that a small temperature ($\sim$ 3 meV), well below the interaction scale, drives the system into a strongly fluctuating symmetric normal state. We demonstrate that this normal state hosts gapless excitations consisting of three-particle bound states, two electrons and one hole, that are exactly orthogonal to the higher-energy electrons at the zero-momentum gapless point. These Dirac trions have the remarkable property of being arbitrarily light despite being composed of heavy constituents, and their spectra can be easily tuned by varying the twist angle and interlayer hopping strength. Our unbiased quantum many-body computation sheds light on the Dirac trions in a projected correlated flat-band setting and opens the door for further investigation of many-body excitations in strongly correlated topological bands beyond Landau levels.
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All authors Shibo Shan, Cheng Huang, Patrick Ledwith, Zi Yang Meng

Medical Physics

Three-Photon Bayesian Imaging of Ortho-Positronium

L. Raczynski, W. Krzemien, A. Coussat et al. (+5 more)

PET provides functional images relying on two-photon coincidences from positron-electron annihilation. In human tissue, about 40% of annihilations are preceded by Ps formation, of which o-Ps component partially decays into three photons, with the remainder annihilating via pick-off or spin-exchange into two photons. This three-photon channel carries additional information about the surrounding micro-environment, including the three-to-two-photon yield ratio as a potential diagnostic marker. We propose the TRIO algorithm, a novel three-photon event-by-event image reconstruction algorithm formulated as a Bayesian maximum a posteriori inference problem. TRIO unifies time-based trilateration, energy-based reconstruction and, for the first time, a physics-informed prior derived from the QED description of Ps decay within a single probabilistic framework. In contrast to positronium lifetime imaging, which requires a prompt photon and is therefore restricted to specific radionuclides, TRIO relies solely on the three photons and is fully compatible with standard radionuclides such as 18F. Monte Carlo simulation modelled after the Siemens Biograph Quadra scanner demonstrates a mean position error of 1.62~cm, improving by approximately a factor of two over the time-based trilateration (3.05 cm) and by about an order of magnitude over energy-based reconstruction alone (18 cm). More importantly, the proposed Bayesian approach is compatible with existing TOF-PET scanners that can register three-photon annihilation coincidences.
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All authors L. Raczynski, W. Krzemien, A. Coussat, M. Bala, B.C. Hiesmayr, K. Klimaszewski, M. Obara, R. Y. Shopa

Statistical Mechanics

Non-reciprocity drives a Brownian dimer out of equilibrium

Suman Pramanik, Soham Dutta and Arnab Saha

We consider the minimal model of a two dimensional Brownian dimer consisting of two overdamped monomers, trapped in an isotropic harmonic potential and mutually coupled by a non-reciprocal harmonic spring that violates Newton's action-reaction principle. We have shown that the non-reciprocal interaction alone can drive the system far from equilibrium, in the absence of any external time dependent drive and being in contact with a single thermal bath. The exact steady state probability distribution and current are explicitly calculated for the zero-rest-length limit of the spring, which eventually maps our model to another non-equilibrium phenomenon, called Brownian gyration. For a spring with finite rest length, these quantities are calculated numerically.
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Pattern Formation and Solitons

Nonlinear Fourier spectral signatures of rogue waves observed in Bose-Einstein condensates

Zhihao Zhang, Yankai Huang, Tiantian Li et al. (+2 more)

Modulation instability provides an important framework for understanding rogue wave (RW) formation on continuous backgrounds. However, the formation mechanism and nonlinear spectral structures of RWs in Bose-Einstein condensate (BEC) matter-wave systems with vanishing boundary conditions remain largely unexplored. Here, we employ the nonlinear Fourier transform (NFT), based on the integrable structure of the focusing nonlinear Schrödinger equation and the Zakharov-Shabat scattering problem, to investigate two representative classes of first-order RWs in BEC systems. Through nonlinear spectral analysis and Darboux reconstruction, we demonstrate that both Gaussian-wave-packet-induced extreme localization events and experimentally observed Peregrine solitons are governed by the coherent dynamics of discrete soliton modes encoded in the nonlinear spectrum. For Gaussian initial states, increasing the initial width leads to an increasing number of discrete eigenvalues, resulting in a transition from fundamental solitons and bound states to Christmas-tree-like RW structures. For experimentally observed Peregrine solitons, localized perturbations reshape the discrete spectral configuration and phase evolution, enabling coherent focusing of multiple bound soliton modes. Furthermore, we reveal the spectral mechanism of higher-order RWs and propose an inverse spectral-engineering approach based on discrete-spectrum phase matching. Our results provide a nonlinear spectral perspective for understanding and controlling RW formation in matter-wave systems with vanishing boundary conditions.
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All authors Zhihao Zhang, Yankai Huang, Tiantian Li, Denglong Wang, Jie Peng

High Energy Physics (Theory)

A comparison of two constructions for dynamical corrections to Wald entropy

Sayantani Bhattacharyya, Parthajit Biswas and Nilay Kundu

In this work, we analyze the differences and similarities between two recent constructions, which are distinct in their methodologies for extending the Wald entropy of stationary black holes to non-stationary situations in general higher-derivative gravity. One of them, denoted by $S_\text{Wall}$, is constructed by exploiting the boost symmetry of the near-horizon geometry, whereas the other, denoted by $S_\text{dyn}$, is obtained from a covariant phase-space analysis based on the Wald-Iyer Noether charge formalism. While $S_\text{dyn}$ is, by construction, defined only for linearized fluctuations around a stationary black hole solution, $S_\text{Wall}$ does not require such a linearization for its construction. Although the linearization is necessary to interpret $S_\text{Wall}$ as a well-defined notion of entropy, the construction itself naturally contains terms that are higher order in the dynamical fluctuations. By comparing the technical structures underlying the two constructions, we clarify the fundamental differences between the methods on which they are based. We demonstrate that while the construction of $S_\text{dyn}$ given the $S_\text{Wall}$ is straightforward, the converse is more subtle. We develop an algorithm to obtain a local expression for $S_\text{Wall}$ from a known expression for $S_\text{dyn}$ in a generic diffeomorphism-invariant theory of gravity, provided certain technical conditions are satisfied. We justify our analytical findings with explicit demonstrations in a particular case: the Riemann-squared example of the higher-derivative theory of gravity.
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High Energy Astrophysical Phenomena

eRASSU J043115.8-711730 :the first pulsating symbiotic super-soft X-ray source in the Magellanic Bridge

Tathagata Saha, Chandreyee Maitra, Philip Charles et al. (+9 more)

The Magellanic Bridge stellar population is a relic of the tidal interaction between the Large and Small Magellanic Clouds. A comprehensive view of the evolution of the Bridge stellar population requires probing the compact remnants of stellar evolution, otherwise hidden at optical wavelengths. The all-sky survey conducted by the eROSITA instrument on-board the Spectrum Roentgen Gamma observatory has discovered a significant population of compact-object-powered systems in the Bridge using X-ray. The candidate super-soft source eRASSU J043115.8-711730 (hereafter J0431-71) was discovered as a part of this campaign, and we present here a deeper study of this source using XMM-Newton and SALT spectroscopy, long-term optical-infrared photometry using OGLE, ATLAS, ASAS-SN, WISE, and GAIA data. J0431-71 is a highly variable super-soft X-ray source, classified as a red giant with the GAIA color-magnitude diagram. The source exhibits: (a) a thermal X-ray spectrum with a temperature of kT$\sim$30 eV and a bright state luminosity of $3.2\times10^{37}$~erg~s$^{-1}$ in the 0.15-1 keV band, (b) Balmer emission lines, [Fe X] coronal line, HeII emission, and the Bowen fluorescence blend, (c) an optical and infrared periodicity of $\sim$500-560 days in phase with the X-ray-UV emission, (d) a 'redder-when-brighter' trend in the stellar emission with a $\sim$520 day period indicating a pulsating donor star. We argue that the observed spectral and temporal properties in J0431-71 are consistent with a high-accretion rate onto a white-dwarf via Roche-lobe overflow, making J0431-71 the first symbiotic source discovered in the Bridge.
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All authors Tathagata Saha, Chandreyee Maitra, Philip Charles, Frank Haberl, David Kaltenbrunner, Andrzej Udalski, David Buckley, Itumeleng Monageng, Lee Townsend, Manami Sasaki, Sara Saeedi, Mara Salvato

High Energy Physics (Theory)

Vacuum fluctuations in Rainbow space-time: Study of Casimir effect

Bhagya. R and Suman Kumar Panja

We investigate the Casimir effect in rainbow space-time, focusing on leading-order corrections to the Casimir energy and force. Starting with the scalar field Lagrangian in rainbow space-time, with parallel plates introduced through delta-function potentials, we find the corresponding energy-momentum tensor. We obtain the vacuum expectation value of this energy-momentum tensor by expressing it as a quadratic operator acting on the Green's function. By solving the Euler-Lagrange equation of a scalar field in rainbow space-time, we obtain the Green's function solutions. Employing these Green's function solutions in the vacuum expectation value of the energy-momentum tensor, we obtain the modified Casimir energy and Casimir force expressions in rainbow space-time. We study the variation of the deformed Casimir force and energy with the distance between the plates for different choices of rainbow functions. Our results show that for two choices of rainbow functions, the absolute value of the Casimir energy and force is decreasing or increasing, whereas for one specific choice of rainbow functions, it remains the same as the standard result in Minkowski space-time. Comparing our result with experimentally measured value of Casimir force, we obtain the bound on the rainbow parameter dependent terms to be of the order of 10^-24.
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