High Energy Astrophysical Phenomena
Cheng-Jun Xia, Toshiki Maruyama, Nobutoshi Yasutake et al. (+1 more)
We investigate the properties of magnetized Coulomb
crystals in
neutron star crusts using a fully three-dimensional geometry with periodic boundary conditions. The electron density profiles are fixed via the Thomas-
Fermi approximation, and the nonuniform
magnetic fields are treated with the equivalent
magnetic charge method. The study focuses on Coulomb
crystals composed of $^{12}$C at an ion number density $n_d = 10^{-9}\ \text{fm}^{-3}$, subjected to various external
magnetic fields.
Nuclei are described by a Gaussian wave function, where the width $b$ encapsulates the effects of zero-point ion vibrations and finite temperature. Our findings show that the
crystal softens as $b$ increases. The Madelung constant $K_M$ fluctuates with the external
magnetic field $B_{z0}$ at $B_{z0}\leq 3\times 10^{14}$ G. At higher field strengths, $K_M$ increases until $B_{z0} \approx 3\times 10^{15}$ G and then decreases. The body-centered cubic (BCC)
lattice is slightly more stable than the face-centered cubic (FCC)
lattice when $B_{z0} < 3\times 10^{15}$ G, whereas the FCC
lattice may become more stable at larger $B_{z0}$. The elastic constants $c_{11}-c_{12}$ and $c_{44}$ are computed and tabulated, which grow with $B_{z0}$ for $3\times 10^{14}\ \mathrm{G}\lesssim B_{z0}\lesssim 2\times 10^{15}$ G and then decline toward zero as the field strength increases further. For $B_{z0}\gtrsim 10^{16}$ G, it becomes difficult to identify a stable
lattice structure. These results provide valuable insights into the role of strong
magnetic fields in shaping the properties of Coulomb
crystals in compact
stars.
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All authors Cheng-Jun Xia, Toshiki Maruyama, Nobutoshi Yasutake, Toshitaka Tatsumi
Instrumentation and Methods for Astrophysics
White paper on the relevance of the European Solar Telescope (EST) for the French heliophysics
E. Pariat, Q. Noraz, B. Perri et al. (+61 more)
The project of the European
Solar Telescope aims to provide a state-of-the art infrastructure to study the Sun and its interactions with Earth and the heliosphere. This 4.2m aperture
telescope will be equipped with multi conjugate adaptive optics, light-polarisation analyser, imaging spectrograph and integral field unit spectrographs. It will provide unprecedented observations of the
solar photosphere and chromosphere and of the dynamical events and features that pertains to the low
solar atmosphere. The EST project is presently in a phase of crystallisation, aiming at the creation of an European Research Infrastructure Consortium. While the French community has continuously been associated with the development of the EST project, some specific scientific aspects are more particularly relevant for the French astrophysics and heliophysics communities. The present review highlights the scientific research axes of high interest from the French community that shall strongly benefit from EST. The later will not only advance numerous topics of
solar physics, as well as
solar adaptive optics developments, but will also provide unrivaled
datasets of high interest in the framework of space weather. This review also aims to highlight the space weather use that can be done with future EST observations, that will be particularly relevant for French heliophysicists.
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All authors E. Pariat, Q. Noraz, B. Perri, N. Poirier, C. Froment, L. Bigot, G. Aulanier, B. Gelly, J. Aboudarham, S. Aizawa, O. Alexandrova, S. Alqeeq, T. Amari, F. Auchère, G. Bernoux, M. Berthomier, V. Bommier, X. Bonnin, P. Boumier, A. S. Brun, I. Bualé, E. Buchlin, A. Canou P. Canu, T. Corbard, F. Cornu, C. Coustillet, G. Cozzani, L. D'herbomez, S. Diaz Castillo, T. Dudok de Wit, M. Faurobert, A. Finley, D. Fontaine, R. A. Garcia, R. Grappin, L. Hadid, K. H. Henadhira Arachchige, M. Janvier, L. Jouve, R. Kieokaew, H. Kirkwood, B. Lavraud, J.-P. Le Breton, O. Le Contel, N. Le Nestour, F. Leblanc, S. Masson, N. Meyer-Vernet, S. Parenti, F. Pitout, M. Rieutord, J. Romero Castañeda, A. Rouillard, C. Ruiz de Galarreta, F. Sahraoui, B. Schmieder, P. Simon, A. Strugarek, M. Tallon, P. Thepthong, J. Touresse, J.-C. Vial, N. Vilmer, A. Zaslavsky
Mathematical Physics
Typical geometry of self-repelling polymers in a constant force field
Kamil Khettabi and Yvan Velenik
We study a general class of self-repelling
polymers on $\mathbb Z^2$, including the simple random walk, the self-avoiding walk and the repulsive Domb-Joyce model, in the presence of a constant force field acting on each monomer. Conditioning the
polymer to have fixed length and fixed endpoints, we identify the limiting free energy and prove that typical trajectories concentrate exponentially near a deterministic macroscopic shape. This shape is characterized as the unique minimizer of a variational problem and can be interpreted as a geodesic of a height-dependent Finsler metric. We also analyze two limiting regimes with universal features: for small field strength, in the symmetric case, the geodesic is close to a classical catenary, while for large field strength it converges to a universal polygonal shape governed by the nearest-neighbor
lattice constraint.
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Data Analysis and Statistics · Cross-listed from q-bio.NC
Graph-based analysis of inflammatory profiles in New Onset Refractory Status Epilepticus (NORSE)
Linon Denis, Martin Guillemaud, Vincent Navarro et al. (+2 more)
Background and Objectives: Cryptogenic new-onset refractory status epilepticus (cNORSE) represents one of the most severe forms of status epilepticus, occurring in patients without prior neurological disease, and remaining of unknown aetiology despite extensive diagnostic evaluation. Emerging evidence supports a role for immune dysregulation in cNORSE; however, marked heterogeneity in inflammatory signatures has been reported, complicating the selection of targeted immunotherapies. Therefore, a critical need for tools facilitating the interpretation of cytokine panels exists. Methods: Building on the identification of distinct inflammatory groups of cNORSE patients using a graph clustering approach applied to a cohort of 62 patients with serum profiling of 96 cytokines, we tailored new models to quantify attribution probability to biologically validated clusters. Statistical assessment of the most informative model involved Monte-Carlo simulations and custom-developed parametric tests. Ultimately, we applied our framework to the implementation of a clinician-friendly interface for inflammatory profiling. Results: Our approach enables quick processing of several cytokine profiles, providing the most likely inflammatory cluster, associated attribution probability, and statistical confidence. For longitudinal assessments, the proposed method may also allow tracking the
evolution of inflammatory trajectories over time. Conclusion: Systematic statistical characterization of the inflammatory heterogeneity in cNORSE requires the development of clinically actionable support tools. Our study offers a framework that may support personalized immunomodulatory strategies in cNORSE patients through clustering-based cytokine profiling.
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All authors Linon Denis, Martin Guillemaud, Vincent Navarro, Aurélie Hanin, Mario Chavez
High Energy Astrophysical Phenomena
Asteroseismology of neutron stars with both hyperons and $\Delta$ resonances
Hao Sun, Jia-Xing Niu, Yong Gao et al. (+2 more)
Employing various relativistic energy density functionals for nucleon-nucleon interactions, we investigate the impact of hyperons and $\Delta$ resonances on the frequencies of non-radial oscillations in
neutron stars, where the universal coupling scheme is adopted for the $\Delta$-
meson couplings. It is found that the inclusion of $\Delta$ resonances is essential for
neutron stars to accommodate the recent mass and radius measurements of PSR J0030+0451, PSR J0740+6620, PSR J0437-4715, PSR J0614-3329, and HESS J1731-347. As $\Delta$ resonances start to emerge in
neutron stars' inner core, the $g$-mode oscillation energy becomes concentrated within the $\Delta$-admixed region, leading to a sharp increase in the $g$-mode frequency. We also examine the $f$-mode and $p$-mode oscillations and find that the impact of $\Delta$ resonances on these modes is less pronounced than the $g$-modes. The oscillation frequencies calculated in the Cowling approximation are then compared with those from full general relativity, confirming that the Cowling approximation introduces an error of approximately 20% for the $f$-modes and within 10% for the $g$-modes. The notable effect of $\Delta$ resonances on
neutron stars' $g$-mode frequencies holds important implications for probing the internal composition of
neutron stars.
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All authors Hao Sun, Jia-Xing Niu, Yong Gao, Hong-Bo Li, Cheng-Jun Xia
Mathematical Physics · Cross-listed from math.SP
A reverse Faber–Krahn inequality for the Robin Laplacian with negative boundary parameter: small coupling in all dimensions
Nunzia Gavitone, David Krejcirik and Gloria Paoli
We establish Bareket's
conjecture from 1977 for convex domains in all dimensions in the regime of weak boundary coupling. In other words, we consider the Laplace operator, subject to negative boundary conditions, and show that the ball maximises the first
eigenvalue among all bounded convex domains of fixed volume, provided that the boundary parameter is sufficiently close to zero. The smallness depends on the volume and dimension only. The proof relies on a comparison with spherical shells with combined Neumann–Robin boundary conditions obtained via the method of parallel coordinates, which we manage to extend to all dimensions, and on a careful analysis of the corresponding radial problem.
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Quantum Physics
Wigner's Phase Space Current for Variable Beam Splitters – Phase Space Rotations and Newtonian Trajectories
Ole Steuernagel, Hsien-Yi Hsieh, Hua-Li Chen et al. (+1 more)
Beam splitters allow us to superpose two continuous single mode
quantum systems. To study the behaviour of beam splitters' strongly mode mixing dynamics we consider variable beam splitters acting on Wigner's phase space distribution, W , the
evolution of which is governed by the continuity-equation {\partial \tau} W = - {\nabla} J. We derive the form of the corresponding Wigner current, J. J's form allows us to use a classical trajectories-approach to analyze the influence of the two modes on each other. We show that the dynamics for variable beam splitters amounts to a rotation confined within the plane of the two positions together with the same simultaneous rotation confined within the plane of the two momenta. In this way explicit and very transparent expressions for the rotated Wigner distributions and Wigner currents can be given in terms of classical trajectories. This helps us to gain deeper insights and perform geometrical analyses of the mixing of modes at beam splitters.
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All authors Ole Steuernagel, Hsien-Yi Hsieh, Hua-Li Chen, Ray-Kuang Lee
Chemical Physics
Enhancing quantum-classical configuration interaction methods using a neural-network classifier
Severino Zeni, Giovanni Varutti, Jacopo Nespolo et al. (+1 more)
Selected configuration interaction methods achieve near-exact electronic structure calculations by iteratively constructing compact variational spaces, but their efficiency depends critically on the heuristics used to identify important determinants. Here, we introduce a data-driven selection framework that recasts determinant importance as a binary classification task and integrates a neural-network classifier into the iterative CI workflow through an active-learning loop. At each iteration, a random subset of candidate determinants is labelled via temporary diagonalisation, and the trained classifier guides selection of the remaining configurations. We demonstrate the utility of this framework for both classical and
quantum CI methods by calculating the ground-state energy of a diatomic molecule. Our method achieves result parity with traditional configuration interaction methods at substantially lower computational cost: roughly a $\times 5$ reduction in
memory and per-iteration cost for the classical cHCI variant, and convergence in markedly fewer iterations for the
quantum-classical cSQD variant. These results establish classifier-assisted determinant selection as a lightweight, method-agnostic tool for compressing variational spaces and accelerating both classical and hybrid
quantum-classical configuration interaction
algorithms.
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All authors Severino Zeni, Giovanni Varutti, Jacopo Nespolo, Dimitrios Trypogeorgos
High Energy Astrophysical Phenomena
EP251023a: A fast X-ray transient featuring a magnetar-powered optical internal plateau followed by a steep decay
Shuai-Qing Jiang, Dong Xu, Wei-Hua Lei et al. (+33 more)
EP251023a is an extragalactic fast X-ray transient (eFXT) detected solely by EP without a gamma-ray counterpart. The
prompt emission consists of a main emission with a duration $T_{90}=292\pm19$ s, followed by a long-lasting tail emission that persists until the observation ends at $T_0+1571$ s. With the upper limit of Konus–Wind, we derived a conservative upper limit on the isotropic gamma-ray energy $E_{\gamma,\rm{iso}}$ of $5.7 \times 10^{52}$ erg for the main emission phase. A
redshift of $z = 2.232\pm0.001$ is identified from strong absorption features in the Keck spectrum, which also indicate a relatively low host-
galaxy HI column density. Based on the broadband spectral energy distribution, the late-time light curves show an achromatic plateau, followed by an extremely steep decay with a slope of 3.99 after a break at about 49 ks, which is consistent with a rapidly spinning millisecond magnetar engine. Under the isotropic wind scenario, we obtain the initial period $P_0<2.27$~ms and the
magnetic field strength $B_p<8.33\times10^{14}$~G for the magnetar; whereas considering a jet collimation with a typical opening angle of 0.1 rad relaxes these constraints to $P_0<32.15$~ms and $B_p<1.18\times10^{16}$~G. Together with GRB\,070707, EP251023a may represent a rare class of optical magnetar-powered internal plateaus with little external-shock contamination, unlike previous examples detected primarily in X-rays. Future discoveries of similar events will help clarify the relationship between magnetar-powered internal emission observed in the optical band and that detected only in X-rays.
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All authors Shuai-Qing Jiang, Dong Xu, Wei-Hua Lei, Jie An, Yuan-Chuan Zou, Zi-Pei Zhu, Ryan Chornock, Dmitry Svinkin, Wen-Xiong Li, E. Fernández-García, Yue Wu, Wen-Da Zhang, Shao-Yu Fu, Xing Liu, Lin-Bo He, Moira Andrews, A. J. Castro-Tirado, Joseph R. Farah, Dmitry Frederiks, M. Gritsevich, D. Andrew Howell, Ding-Fang Hu, Alexandra L. Lysenko, A. Maury, Curtis McCully, S. B. Pandey, I. Pérez-García, Anna Ridnaia, Anastasia Tsvetkova, Mikhail Ulanov, S.-Y. Wu, Kathryn Wynn, D.-R. Xiong, Hao-Nan Yang, B.-B. Zhang, Tong Zhao
High Energy Physics (Theory)
Holography for an AdS$_5$ to Hyperscaling-Violating Flow via Dimensional Reduction from 8d Einstein-Matter Gravity
Ji-Seong Chae
We construct a classical eight-dimensional Einstein–matter model whose reduction on a three-
torus admits an AdS$_5$ ultraviolet
vacuum and a hyperscaling-violating infrared solution. Neutral scalar winding maintains the ultraviolet
vacuum, while its disappearance allows the infrared geometry to become locally AdS$_8$. The same reduction fixes the running gauge coupling, charged scalar mass and interactions. We derive the
vacuum conditions, the radial
evolution equations and the infrared spectrum. Scalar and vector superfluid orders are then compared using exact ultraviolet zero modes and analytic infrared
eigenvalue identities. The scalar and vector instabilities in the infrared coincide at a unique scalar mass above the Breitenlohner–Freedman bound. Their nonlinear competition is governed by a quartic free energy that includes electric response and the change between fixed chemical potential and fixed density. For the interpolating geometry, we identify the conditions under which the two orders can appear together and form a locally stable phase.
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Plasma Physics
OpenMP GPU Acceleration and Portability of TRIMEG-C1 for Electromagnetic Gyrokinetic Simulations in Tokamak Plasmas
Giorgio Daneri, Zhixin Lu, Matthias Hoelzl et al. (+2 more)
The Triangular mesh-based gyrokinetic code TRIMEG-C1 solves the gyrokinetic equations using the particle-in-
cell scheme to simulate electromagnetic instabilities in tokamak
plasmas. TRIMEG-C1 utilizes a high-order C1 finite element method, which captures the accurate physics with lower grid resolution than the C0 method. In this work, we focus on achieving a portable implementation on multiple graphics processing unit (GPU) architectures to accelerate the TRIMEG-C1 code for future physics studies. The OpenMP framework is chosen as the acceleration framework for GPU offloading on different hardware platforms, specifically, NVIDIA and AMD GPUs. The particle pushing procedure, as well as particle-to-grid operations have been adapted for GPU execution. A speedup of $\approx9$ for the particle pusher kernel is achieved on 2 AMD MI300A APUs (Accelerated Processing Unit) compared with 2 AMD 9754 CPUs. In addition, the efficiency of hybrid MPI-OpenMP offloading parallelization was assessed by oversubscribing GPU resources. The Ion Temperature Gradient (ITG) mode was simulated using the GPU implementation, and its correctness was verified by comparing the physics results in terms of the energy growth rate and the two-dimensional mode structures.
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All authors Giorgio Daneri, Zhixin Lu, Matthias Hoelzl, Luca Venerando Greco, Edoardo Carrà
Solar and Stellar Astrophysics
Chinese Sunspot Drawings and Their Digitization-(VIII) Release of a Machine Readable Parameters Catalog
G.H. Lin and S. Liu
We present a systematically revised and manually verified digital catalog of historical sunspot drawing observations from Chinese observatories, encompassing sunspot number, sunspot group number, and sunspot area measurements. This represents an updated release of China's early sunspot drawings that have been utilized in numerous published studies over the years, with ongoing refinements and corrections progressively incorporated during the course of those studies and now consolidated through a systematic round of data revision aimed at improving internal consistency and usability for the broader research community. To facilitate scientific utilization, selected comparisons with international reference sunspot data are presented, focusing on relative sunspot numbers (RSN) and sunspot group numbers (GN) from Yunnan Observatory (YNO) and Purple Mountain Observatory (PMO), while sunspot area measurements are also included in this release but are not compared with international
datasets in the present work. For RSN, both raw and k-corrected values are analyzed; for GN, only raw counts are used as no dedicated correction factor exists in the Chinese records. The results demonstrate strong positive correlations, with correlation coefficients consistently exceeding 0.95 for all comparisons, confirming the reliability and scientific value of these historical records. Systematic differences are observed: raw YNO RSN values are systematically higher than SIDC by about 17.6%, while raw PMO RSN values are about 6.0% lower. After k-correction, YNO shifts to a 20.9% deficit, suggesting over-correction, while PMO remains lower with a 15.5% deficit. Notably, GN exhibits smaller systematic offsets (16.5% for YNO and 8.5% for PMO) and serves as a more robust index for long-term
solar cycle studies.
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Medical Physics
Unpaired Deep Learning Synthesis of Photon-Counting CT Material Basis Maps from Non-contrast Energy-Integrating Abdominal CT Images
Ruihan Huang, Staffan Holmin and Mats Persson
Photon-counting Computed
Tomography (PCCT) is the most advanced Computed
Tomography (CT) technology, offering significant improvements in image quality and diagnostic capabilities. However, since PCCT has only recently been adopted in the clinc, there are no publicly available PCCT image
datasets for study. We therefore aim to synthesize PCCT spectral material-basis images from publicly available EID CT images. We propose a two-step deep learning model designed to synthesize
photon-counting spectral material basis images from public Energy-Integrating Detector (EID) CT images. In the first step, we use a Denoising
Diffusion Implicit Model (DDIM) to generate EID CT images from PCCT images. In the second step we use a U-Net with a Domain-
Adversarial Neural Network to predict water and iodine maps from generated EID CT images. We also reconstruct basis images and virtual monoenergetic images (VMIs) from the predicted material-basis maps for evaluation. We evaluated the generated water and iodine maps as well as the 40 and 70 keV PCCT images in terms of Hounsfield Unit accuracy, modulation transfer function and noise power spectrum as well as qualitative image appearance. The reconstructed 40 and 70 keV PCCT images exhibit higher spatial resolution while preserving the anatomical structures and textures of the original EID CT images, thereby demonstrating the feasibility of the proposed approach. The proposed framework provides a feasible approach for synthesizing PCCT spectral material-basis images from conventional EID CT without requiring paired images. This method has the potential to provide large sets of synthetic training and evaluation data for PCCT
algorithm development in data-limited environments.
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General Relativity and Quantum Cosmology
Thin accretion disks around a Schwarzschild acoustic black hole
R. M. Yusupova, R. N. Izmailov and R. Kh. Karimov
We investigate the properties of a thin
accretion disk in the Novikov-Thorne framework around a Schwarzschild acoustic black hole characterized by a nonzero background fluid four-velocity $v_{r} = \sqrt{2M\xi/r}$, where $\xi$ is a tuning parameter. The Novikov-Thorne formalism is used here phenomenologically, with the Schwarzschild acoustic black hole treated as an effective background geometry for comparing disk observables with those of the Schwarzschild black hole. We show that the acoustic black hole exhibits two regimes depending on $\xi$. For $0 < \xi \leq 2.8$, the disk is in a strengthening regime, in which the radiative characteristics are enhanced relative to the Schwarzschild case. For $\xi > 2.8$, the disk is in a weakening regime, in which the radiative characteristics are reduced relative to the Schwarzschild case. The most pronounced change in the radiative characteristics is associated with the behaviour of the marginally stable orbit radius $r_{ms}$, whose branch change near $\xi\approx 2.8$ produces a sharp modification of the flux, temperature, and luminosity profiles. For the numerical illustrations, we adopt a toy model with black hole mass $M = 15M_{\odot}$ and compare the corresponding flux, temperature, spectral luminosity, efficiency, and Eddington luminosity with those of the Schwarzschild black hole. These differences may provide phenomenological diagnostics for comparing effective compact object geometries.
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Fluid Dynamics
Aquatic locomotion by an elastically mounted flexible foil actuated by an oscillating force
Ramon Fernandez-Feria
An analytical formulation of the fluid-structure interaction of a flexible foil driven by an oscillating force actuating on its elastically mounted leading edge, so that it can heave, pitch and deform passively with the hydrodynamic forces, is used to investigate the aquatic locomotion of a body, responsible for the whole drag and thrusted by the oscillating flexible foil. The small-amplitude theoretical model is validated with previous theoretical and experimental results for a body propelled by a rigid plate oscillating with a prescribed heaving motion and passive pitch. The inclusion of passive heave and deformation allows to expand the parametric ranges for optimal self-propulsion conditions in terms of length travelled by flapping cycle (stride length) and locomotion efficiency. In addition to the known optimal locomotion condition localized near the resonance of the torsional spring on which the foil is elastically mounted, which here is modulated by its coupling with the resonances of the translational spring and of the structural deformation of the foil, another even better local optimal locomotion condition is found near the translational spring branch of the elastic support resonance that occurs at lower stiffnesses of both springs. Unlike the local maximum of efficiency close to the natural frequency associated with the torsional spring branch, which increases with the stiffness of the foil, being the highest for a rigid foil, the larger local maximum associated with the translational spring branch increases as the stiffness of the foil decreases.
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Statistical Mechanics
Universal Extraction of Quantum Critical Exponents and Phase Transitions via Tailored Hilbert Space
Ye Xiong
Finite-size scaling and the renormalization group form the central toolkit for analyzing
quantum phase transitions (QPTs). In this Letter, we introduce a novel
Hilbert-space tailoring scheme to probe
quantum critical phenomena. Applied to the second-order QPT of the one-dimensional (1D) XY model, our method yields precise critical points and exponents on
lattices containing merely 50 unit
cells. We further establish the universal applicability of this framework via investigations of the Berezinskii-Kosterlitz-Thouless transition in the 1D XXZ chain: critical parameters are recovered with as few as 12
lattice sites. This technique may open an alternative, efficient route to universally characterize QPT across many-body
lattice systems.
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Quantum Physics
Non-adiabatic transitions in the density matrix formalism
Pasquale Di Bari, Shreya Pandit and Ye-Ling Zhou
We show that a density
matrix formalism provides a useful description of non-adiabatic transitions in two-state
quantum systems. Compared to a traditional
Hamiltonian formalism, even in the absence of decoherence when there is full equivalence between the two, the density
matrix formalism provides a convenient change of variables that yields a powerful general analytical solution. This solution nicely describes a transition regime between the well known Landau-Zener-Stuckelberg-Majorana (LZSM) approximation and the extremely non-adiabatic limit. Our results have very general applications, within a large variety of problems in
quantum physics,
neutrino physics, cosmology.
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Other Condensed Matter
The effect of pressure on the splitting in $^3$He in nematic aerogel
V.V. Dmitriev, D.V. Petrova, A.A. Soldatov et al. (+1 more)
Here, we present the results of an investigation of how the pressure affects the splitting of the superfluid transition temperature in $^3$He in anisotropic aerogel. It is well known that boundary conditions significantly influence the properties of superfluid phases in aerogel. When aerogel strands are coated with a $^4$He layer in
magnetic field, new phases, such as the polar, polar-distorted A (DA), polar-distorted B (DB), and $\beta$ phases, become energetically favorable. In contrast, without this coating, the system tends to favor phases resembling the bulk A, B, and A$_1$ phases. Our earlier results showed a nonlinear dependence of the superfluid transition temperature splitting in pure $^3$He, but the range of nonlinearity did not match the theoretical predictions based on
magnetic scattering effects. To further investigate this discrepancy, we performed measurements of the splitting under varying pressures for both pure $^3$He and with $^4$He coverage of the aerogel strands.
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All authors V.V. Dmitriev, D.V. Petrova, A.A. Soldatov, A.N. Yudin
Materials Science
Proximity-Induced Spin Reorientation in Monolayer CrI$_3$ on Hexagonal WTe$_2$
Dániel Tibor Pozsár, Marcell Balázs Sípos, Amador García-Fuente et al. (+7 more)
Magnetic anisotropy controls the orientation and thermal stability of two-dimensional
magnetic order. Predicting proximity-induced changes in anisotropy requires linking the electronic structure to microscopic
magnetic interactions and finite-temperature behavior. Here we study monolayer CrI$_3$ on hexagonal WTe$_2$ using a first-principles-to-finite-temperature workflow centered on relativistic
spin-
Hamiltonian mapping. We find that WTe$_2$ reorients the CrI$_3$ magnetization from out-of-plane to in-plane and substantially enhances the
magnetic ordering scale within the extracted
spin models. Analysis of the extracted
spin Hamiltonians shows that the reorientation is driven by a substrate-induced change in the balance between symmetric anisotropic exchange and onsite anisotropy. We establish a transferable workflow for proximity-controlled magnetism in two-dimensional van der Waals
heterostructures.
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All authors Dániel Tibor Pozsár, Marcell Balázs Sípos, Amador García-Fuente, Péter Nemes-Incze, Viktor Ivády, Efrén Navarro-Moratalla, Jaime Ferrer, László Szunyogh, László Oroszlány, Zoltán Tajkov
Chaotic Dynamics
Slow-spectrum preshaping for reservoir computing: Attractor reconstruction in attracting submanifolds under partial observation
Satoshi Oishi, Hiroshi Yamashita, Hideyuki Suzuki et al. (+1 more)
Data-driven reproduction of chaotic dynamics under partial observation remains a challenge despite its practical importance. Reservoir computing (RC) and other data-driven approaches often succeed in short-term prediction but are sensitive to hyperparameters and frequently fail to reproduce the long-term statistical properties of the system. As recently shown, a major cause of this failure is spurious slow modes induced by training, which render the reconstructed invariant set transversally unstable in the representation space. To address this, a design principle called Attractor Reconstruction in Attracting Submanifolds (ARAS) was proposed, which requires the reconstruction to lie in a low-dimensional, transversally attracting submanifold. Under full observation, ARAS was realized by an input-layer design that limits the number of slow modes perturbed during training and anchors the remaining modes to stay fast, thereby suppressing spurious slow modes. However, under partial observation, this design alone fails because the submanifold designed to be attracting cannot retain the observation history needed to unfold the observed data into a faithful reconstruction. In this study, we propose slow-spectrum preshaping, which introduces a slow spectrum into the reservoir prior to feeding input data. The induced slow modes then retain a
memory of past observations within the submanifold, while the input-layer design makes the submanifold transversally attracting, so that ARAS is realized under partial observation. Through numerical experiments on various chaotic systems, we show that our approach enables reliable short-term prediction and long-term reproduction of chaos over a wide range of hyperparameters without a posteriori tuning.
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All authors Satoshi Oishi, Hiroshi Yamashita, Hideyuki Suzuki, Sho Shirasaka
Geophysics
Suppressing Spontaneous Droplet Shrinkage in Cahn-Hilliard-Stokes Microflows
A. M. Gurin
This paper addresses non-physical artifact, specifically spontaneous droplet shrinkage, in Cahn-Hilliard-based simulations of immiscible two-phase microflows. That artifact arise from the energy functional's preference for reduced interfacial area, leading to shifts in
equilibrium phase fractions away from the physical bounds of 0 and 1. A
curvature-dependent correction is proposed that shifts the double-well potential to counteract this drift. This method is validated on the following test cases: an isolated droplet in a cubic cavity, drainage in a synthetic porous medium, and flow through a T-shaped junction. Results demonstrate significant suppression of phase fraction overshoot/undershoot and improved droplet volume conservation.
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Soft Condensed Matter
Broadband molecular dynamics simulation of confined Brownian motion
Quentin Thomas, Clara Mefo Sop, Maxime Lavaud et al. (+3 more)
Molecular dynamics with an explicit solvent resolves the hydrodynamic response of a Brownian colloid in bulk and near a rigid wall over acoustic, inertial, and diffusive time scales. Bulk spectra establish a continuum reference and reveal departures associated with discrete-solvent dynamics. Under confinement, thermal spectra provide a measurement of the space-dependent added mass, while velocity autocorrelations determine space-dependent, anisotropic hydrodynamic
memory and
diffusion. All together, these measurements connect the enhanced added mass and reduced mobility near a wall, and probe the discrete-continuum crossover.
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All authors Quentin Thomas, Clara Mefo Sop, Maxime Lavaud, Yacine Amarouchene, Thomas Salez, Pascal Damman
Chaotic Dynamics · Cross-listed from math.DS
When Entropy flows: drifting along the route to Chaos
Eran Igra, Valerii Sopin and Yanghong Yu
Consider a smooth one-parameter family of vector fields defined over some smooth
manifold transitions from order into chaos. Inspired by the Second law of Thermodynamics, one is led to ask: can we find a flow whose dynamics realize this transition? To answer this question, motivated by the Mallet-Yorke Orbit Index theory, the Arnold-Khesin scheme for hydrodynamics and a heuristic argument by Rene Thom, we introduce a construction that transforms any one-parameter family of vector fields into a new object: the "
Entropy flow". The
Entropy flow is a flow defined on the product of the phase space with the parameter space and is best thought of as a flow generated by the original one-parameter family together with a drift in the parameter space, that pushes the trajectory of a given initial condition into a disordered, more complex state. To exemplify, for the Period Doubling, the Ruelle-Takens-Newhouse and the Intermittency routes to chaos the
Entropy flow behaves exactly as expected - that is, it truly pushes trajectories into more complex states. In addition, in the spirit of Forcing Theory, in the paper we use the Conley index to discuss how one can use the
Entropy flow to study the connection between
topology and bifurcations. Moreover, drawing on the numerical and analytic evidence, we will analyze how the
Entropy flow behaves in several examples of famous flows, including the Lorenz system, the Rössler attractor, and the breakup of the Shilnikov homoclinic scenario.
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Cosmology and Nongalactic Astrophysics
The large scale structure probes of dark energy
Pengjie Zhang and Shang Li
We present a brief review on the large scale structure (LSS) probes of dark energy. We cover probes that directly constrain dark energy such as
baryon acoustic oscillation,
redshift space distortion, weak
lensing and cluster number count. We also review auxiliary probes that mitigate systematics in dark energy constraints, such as the SZ effect to constrain baryonic effect and broadband
galaxy clustering to calibrate photometric
redshift. We demonstrate the synergy between these probes in delivering dark energy constraint of both high precision and high accuracy.
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High Energy Physics (Theory)
Topics in Celestial holography: A bottom-up perspective
Bin Zhu
We review some selected topics in celestial holography on the search for a celestial dual to
quantum gravity in flat spacetimes. We focus on the bottom-up approach, emphasizing
symmetries, key elements in celestial CFT, interplay with twistor theory, and connection to AdS/CFT.
Chemical Physics
Investigating causality between principal components in protein dynamics
Debarshi Banerjee, Ali Hassanali and Alessandro Laio
Principal component analysis (PCA) is widely used to characterize collective
protein motions from molecular dynamics (MD) simulations. While PCA identifies the dominant modes of structural fluctuation, it does not reveal whether different principal components (PCs) causally influence each other. Here, we investigate this question using a recently introduced causal-discovery framework [Del Tatto et al, PNAS 2024], which allows to infer putative causal asymmetries between high-dimensional time series. We apply this approach to long-timescale MD trajectories of two
proteins. By analyzing relationships among PCs, we construct directed networks describing how PCs influence one another across time scales. These directional relationships, whose existence is a necessary condition for the presence of a causal link, are not captured by conventional covariance-based analyses and provide information that is complementary to PCA and Time-lagged Independent Component Analysis (TICA). Our results suggest that our causal inference approach can uncover previously hidden aspects of the dynamical organization of
protein motions and offer a new perspective on this very popular class of collective variables.
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Chaotic Dynamics
Recursive behavior in a diatomic FPUT lattice
Guo Deng, Andrea Pezzi, Genghong Lin et al. (+1 more)
We study the diatomic FPUT
lattice with cubic anharmonic potential, and analyze the recurrent behaviour of its solutions. We find that two distinct types of recurrence occur. One type is the classic FPUT recurrence; for such recurrence, we find that the relation between recurrence period and nonlinear strength is similar to that in the monatomic case. The other type, which cannot exist in the monatomic
lattice, is the recurrence due to the interactions between modes in the two branches of the dispersion relation. Indeed, we prove the existence of the optical-acoustical-acoustical resonant interaction between three
Fourier modes for which a recurrent behavior in the distribution of the energy is observed. In addition, we develop a reduced
Fourier-space dynamical model that reproduces the same recurrent behavior. We assess the robustness of our results through numerical simulations of the diatomic Toda
lattice and the diatomic granular chain; in both cases, the same recursive behavior is observed. Finally, in the continuous limit, we derive from the diatomic model a system of three coupled PDEs which are known to be integrable.
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All authors Guo Deng, Andrea Pezzi, Genghong Lin, Miguel Onorato
Cosmology and Nongalactic Astrophysics
Extragalactic test of General Relativity with time-delay gravitational lenses
Wuzheng Guo, Shuo Cao, Qiumin Wang et al. (+4 more)
Strong gravitational
lensing, a key prediction of General Relativity (GR), offers a unique environment for examining alternative modified
gravity theories. In this Letter, we employ a model-independent approach to estimate the parameterized post-Newtonian parameter $\gamma_{\rm PPN}$ using the time-delay measurements from H0LiCOW strong
lensing systems. To minimize potential biases from cosmological models in testing GR, we use Gaussian Process regression (GPR) to reconstruct angular diameter distances ($D_{\rm A}$) from the newest
baryon acoustic oscillation (BAO) measurements, provided by the Dark Energy Spectroscopic Instrument (DESI) DR2 data. Based on the reconstructed angular diameter distances and four H0LiCOW lenses, we directly estimate the post-Newtonian parameter $\gamma_{\rm PPN}=0.93^{+0.16}_{-0.17}$ and the sound horizon scale $r_{\rm d}=136.36^{+5.14}_{-3.20}~{\rm Mpc}$. This is the first simultaneous measurement of $\gamma_{\rm PPN}$ and $r_{\rm d}$ without any assumptions about the contents of the universe or the theory of
gravity. In the new framework of distance ratio $D_{\Delta t}/D_{\rm l}$ which avoids the bias introduced by $r_{\rm d}$, the $\gamma_{\rm PPN}$ constraint can be further improved to $\gamma_{\rm PPN}=0.89^{+0.19}_{-0.15}$. Our results provide a direct test of GR at the extragalactic scale, which is well consistent with the prediction of GR within $1\sigma$.
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All authors Wuzheng Guo, Shuo Cao, Qiumin Wang, Yun Chen, Marek Biesiada, Tonghua Liu, Yujie Lian
High Energy Physics (Phenomenology)
Non-holomorphic $S^{\prime}_{4}$ modular symmetry for leptons and leptogenesis
Cai-Chang Li, Jun-Nan Lu, Xiang-Yan Gao et al. (+2 more)
We perform a comprehensive and systematic investigation of
lepton models based on the non-holomorphic $S^{\prime}_{4}$ modular
symmetry, by using level 4 polyharmonic Maaß forms spanning integer weights from $-4$ to $6$. The light
neutrino masses are generated by the type-I seesaw mechanism with two right-handed
neutrinos, no flavon fields other than the modulus $\tau$ is introduced, and the generalized CP
symmetry is not imposed. An exhaustive numerical analysis yields 36 viable models with only four real couplings besides the modulus $\tau$ when
neutrino masses are normal ordering. They are classified into three categories, each containing twelve models which yield quite similar predictions for
lepton observables and are distinguished by the assignment of $E^c_1$. Furthermore, we perform a detailed numerical analysis for one representative model from each category. These representative models are found to yield very sharp predictions for
neutrino masses and mixing parameters, and they are distinguished by the predictions for the atmospheric mixing angle $\theta_{23}$, the Dirac CP phase $\delta_{CP}$ and the Majorana CP phase $\alpha_{21}$. Furthermore, we find that only two of these three representative models accommodate successful thermal leptogenesis in the unflavored regime, reproducing the observed
baryon asymmetry with the identical parameter values that satisfy
neutrino oscillation data. In these models, the real part of the modulus $\tau$ is the unique source of CP violation in both
lepton mixing and leptogenesis.
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All authors Cai-Chang Li, Jun-Nan Lu, Xiang-Yan Gao, Ming-Hua Weng, Gui-Jun Ding
Fluid Dynamics
Numerical comparison of energy- versus circulation-preserving stochastic vortex dynamics
Sagy Ephrati and Darryl D. Holm
We compare two
geometric stochastic frameworks for the two-dimensional Euler equations, being the circulation-preserving
stochastic advection by Lie transport (SALT) and the energy-preserving
stochastic forcing by Lie transport (SFLT) approaches. While preserving both circulation and energy is ideal, their simultaneous conservation restricts perturbations to a
stochastic reparametrization of time. Consequently, a fundamental choice must be made between preserving structure or the kinetic energy. Analysis reveals that SALT is significantly more sensitive to high-frequency flow components, with noise effects scaling by $| \bk |^2$ relative to SFLT. This suggests that SALT acts as a localized perturbation sensitive to sharp gradients, while SFLT behaves as a more regularized global forcing. Numerical experiments on a traveling dipole,
vortex merger, and forced-damped
turbulence confirm that SALT introduces uncertainty localized near dynamically active vorticity gradients, whereas SFLT produces a more diffuse variance field spread across the domain. These results illustrate how the choice of
geometric invariant fundamentally determines scale-sensitivity and spatial distribution of modeled uncertainty in
vortex dynamics.
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