High Energy Astrophysical Phenomena
Prospect for Detection of Strongly Lensed Multi-messenger Signals of Binary Neutron Star Mergers
Zhiwei Chen, Youjun Lu and Changwen Zeng
The gravitational
lensing of multi-messenger signals from binary
neutron star mergers (BNSs), including gravitational waves (GWs), short Gamma-Ray bursts (sGRBs), kilonovae, and afterglows, can serve as a unique probe to constrain the mass of the graviton and cosmological parameters. In this paper, we estimate the detection rates of lensed electromagnetic counterparts associated with lensed BNS GW events detected by
Cosmic Explorer and Einstein
Telescope. For kilonovae and afterglows, we further consider a complementary pointed follow-up strategy targeting pre-identified
galaxy-scale lens candidates within the GW localization region. By utilizing both numerical and observational constraints on BNS mergers, we find that: (1) Future $\gamma$-ray
telescopes, even with a sensitivity more than ten times better than that of
Fermi-GBM, may only detect lensed sGRB
prompt emission at a rate $\sim 0.1$ yr$^{-1}$, corresponding to $\sim 2\times 10^{-3}$ of detectable lensed BNS GW events. (2) For the known-lens pointed strategy, the identifiable lensed-host fraction is approximately $0.15-0.30$ for the fiducial deep lens-catalog case considered, suggesting a possible gain in per-lens sensitivity for faint kilonovae and afterglows. (3) An RST-like near-infrared facility could detect lensed kilonovae at rates of approximately $\sim 0.45^{+0.81}_{-0.34}$, $0.55^{+0.98}_{-0.41}$, and $0.078^{+0.139}_{-0.059}$ yr$^{-1}$ in the F106, F158, and F213 bands, respectively. (4) Lensed afterglows remain difficult to detect in the optical and
radio bands, while ATHENA-like X-ray observations may detect $0.5-5$ events over ten years.
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Mathematical Physics · Cross-listed from math.AP
On the Gross-Pitaevskii model with a moving impurity: Cauchy problem and superfluidity criterion
Paolo Antonelli and Martino Caliaro
We study the one-dimensional Gross-Pitaevskii equation with a traveling delta potential and non-zero conditions at infinity. This model describes the effect of a moving
impurity in a
quantum fluid. Firstly, we show that the associated Cauchy problem is globally well-posed in the energy space. This requires the definition of a conserved energy, which involves the notion of renormalized momentum. Secondly, we study the existence and stability of stationary states in a co-moving reference frame. It is known that there exists an
impurity-dependent critical velocity above which no stationary state exists. For velocities below the critical one, two different stationary states appear. We show the orbital stability of the one with higher minimal density.
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Soft Condensed Matter
Density-Induced Reentrant Coarsening in a Two-Temperature System
Partha Sarathi Mondal, Anish Kumar, Nayana Venkatareddy et al. (+2 more)
Understanding how nonequilibrium driving modifies phase-separation kinetics remains a fundamental challenge. Here we show that phase separation in a two-temperature system exhibits a striking density-induced reentrant coarsening behavior. Using Brownian dynamics simulations and a coarse-grained field-theoretic model, we find that the characteristic domain size grows as $L(t)\sim t^{1/z}$, displaying a reentrant sequence $(t^{1/3} \rightarrow t^{1/4}\rightarrow t^{1/3})$ with increasing density. While the low- and high-density regimes are governed by classical
curvature-driven bulk
diffusion, the intermediate-density regime exhibits anomalously slow growth. We show that this slowdown originates from a transport bottleneck arising from the interplay of particle diffusivity, particle availability, and attachment kinetics, which suppresses the effective mass flux between domains. Unlike
equilibrium phase separation, where density primarily affects morphology and crossover scales, the two-temperature drive renders density a key control parameter for coarsening pathways. Our results uncover a nonequilibrium mechanism for anomalous domain growth in two-temperature systems.
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All authors Partha Sarathi Mondal, Anish Kumar, Nayana Venkatareddy, Prabal K. Maiti, Shradha Mishra
Chemical Physics
Probing Extended Recognition Sites in Zn-Metalloproteins via Quantum Chemistry and Polarizable Molecular Dynamics
Nohad Gresh and Jean-Philip Piquemal
Zn-metalloproteins play vital roles in numerous metabolic processes, making them high-value targets for structure-based drug design. To advance these efforts, it is useful to unravel the individual components of the intermolecular interaction energies (DE) that stabilize the Znbinding cavity, both in the absence and presence of bound
protein ligands. Here, we utilize
quantum chemistry (QC) to decompose DE into distinct physical contributions. The relative magnitudes of these components vary significantly depending on the coordination number (four to six) and the chemical nature ('hard' vs. 'soft') of the Zn-coordinating ligands. These high-level QC analyses serve to calibrate and validate polarizable molecular mechanics potentials, effectively extending the accurate description of electronic effects beyond the immediate Zn-binding cavity to enlarged recognition sites and, ultimately, entire
protein systems over long molecular dynamics (MD) simulation timescales. Following a concise overview of our QC methodology, we present validation studies on complexes containing up to 300 atoms and discuss the prospects of applying this framework to large-scale simulations of Zn-metalloprotein-ligand complexes. Finally, the structural and energetic role of discrete, highly polarizable water molecules is highlighted.
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Plasma Physics
Counter-streaming heat-flux closure for electron-only collisionless magnetic reconnection
Madox C. McGrae-Menge, Jacob R. Pierce, Maria Almanza et al. (+6 more)
In electron-only collisionless
magnetic reconnection (MR), a regime of growing importance in turbulent space
plasmas, electrons develop strongly non-Maxwellian distributions that invalidate conventional fluid closures based on assumptions of near local thermodynamic
equilibrium. Using particle-in-
cell (PIC) simulations, we identify the physical origin of the electron heat-flux: counter-streaming between electron sub-populations originating from opposite sides of the current sheet, with each sub-population remaining approximately adiabatic. This insight yields a novel fluid closure, which we implement in fluid simulations using two adiabatic electron fluids initialized on opposite sides of the current sheet. The fluid simulations capture the heat-flux, reconnecting current density, thermal pressure, and bulk flows as observed in PIC, within a reduced fluid description that conventional single-electron-fluid models fundamentally cannot reproduce. The closure is most accurate at low $\beta_{\text{Reconn.}}$ and $B_{\text{Guide}}/B_{\text{Reconn.}}$, regimes relevant to Earth's magnetotail, where it establishes counter-streaming as the physical origin of heat-flux in electron-only collisionless MR and enables its computationally efficient fluid modeling.
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All authors Madox C. McGrae-Menge, Jacob R. Pierce, Maria Almanza, Alexander Velberg, Nathaniel Barbour, William D. Dorland, Nuno F. Loureiro, Frederico Fiuza, E. Paulo Alves
Biological Physics
Spontaneous patterning of cell size on curved surfaces
Yuan He and Shi-Lei Xue
Tissue surfaces exhibit complex
curvature during embryogenesis and oncogenesis. Evidence shows that
cells can actively sense
curvature to regulate behavior and fate, yet the underlying mechanism remains unclear. Here, we develop a vertex model for arbitrary curved surfaces and uncover spontaneous
cell size patterning on ellipsoidal surfaces:
cells in high-
curvature regions are consistently larger than those in low-
curvature regions. This non-uniformity arises from a mechanical competition encoded in Riemannian geometry: positive Gaussian
curvature reduces the perimeter-to-area ratio of polygonal
cells, relaxing
cell-edge tension in high-
curvature regions, which is compensated by area expansion to maintain global force balance. This area pattern is robust against variations in model parameters and matches observations in biological systems. The perimeter pattern, in contrast, is governed by competition between the intrinsic
geometric tendency and the deformation required by force balance, and undergoes reversal beyond a critical shape index. Together, these findings establish self-organized spatial variations in
cell size as a potential physical mechanism for
curvature sensing.
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High Energy Astrophysical Phenomena
Microquasar Cygnus X-3 as the PeVatron powering the Cygnus Bubble
Zhaodong Shi, Guangwei Wang, Ruizhi Yang et al. (+1 more)
The recent discovery by the LHAASO collaboration of a variable ultra-high-energy (UHE; $E_\gamma \ge$ 100 TeV) $\gamma$-ray source associated with the microquasar Cygnus X-3, with a spectrum extending to several PeV, provides compelling evidence for a hadronic super-PeVatron operating within the binary system. Inside the binary, the accelerated
protons lose only a small fraction of their energy; upon escaping into the interstellar medium, they propagate diffusively to form a vast gamma-ray “
halo" structure extended to hundreds of parsecs. We argue that this
halo has already been detected and corresponds to the Cygnus Bubble, an extended UHE $\gamma$-ray source reported by the LHAASO collaboration – which possesses an angular extension of $\approx 6^{\circ}$ and an energy spectrum reaching 1 PeV. While the Cygnus Bubble is generally attributed to the
star-forming region Cygnus X (specifically the Cygnus OB2 association at 1.4 kpc), we demonstrate that an association with Cygnus X-3 is physically more natural at energies above 400 TeV. This is supported by the
cosmic-ray radial distribution, derived from the $\gamma$-ray and gas distributions, which points to continuous injection from a point-like source. The energetic requirements of the central accelerator are reasonably affordable and feasible. This reassignment identifies the Cygnus Bubble as a member of the recently discovered population of microquasar UHE $\gamma$-ray
halos.
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All authors Zhaodong Shi, Guangwei Wang, Ruizhi Yang, Felix Aharonian
Quantum Physics
Phase-Selected Efficient Single-Photon Frequency Conversion via Local Fano Resonance in a Two-Giant-Atom Waveguide-QED System
Qing-Ao Xiang, Yan Liu, Xin-Yuan Yang et al. (+1 more)
Efficient single-
photon frequency conversion is investigated in a two-
giant-atom waveguide-QED system, where a two-level
giant atom and a $\Lambda$-type three-level
giant atom couple to a common one-dimensional waveguide. While the $\Lambda$-type atom provides the inelastic channel, the two-level atom induces secondary coherent coupling, creating multi-path interference for the converted
photon. Using the real-space approach and within the Markovian approximation, we derive analytical four-channel scattering amplitudes and reveal that the inelastic transmission spectrum, governed by three complex resonance poles, exhibits a multi-peak interference pattern. By introducing a local single-pole approximation, we reduce this complex spectrum to a local Fano lineshape, decomposing it into a coherent superposition of a local background term and a single-pole resonant term. The interplay between these two terms-controlled by the
photon propagation phase between the
giant atoms' coupling points-determines the conversion efficiency, with the background suppression condition leading to a Lorentzian reduction. Based on the single-pole resonance weight, we formulate a phase-selection criterion for highly efficient conversion. Compared with both the small-atom and single $\Lambda$-type
giant-atom models, the two-
giant-atom scheme achieves substantially enhanced inelastic transmission over a broader frequency-conversion range. This work reveals how phase-controlled local Fano resonance enables high-efficiency frequency conversion, establishing a general paradigm for engineering resonant light-matter interactions in structured
quantum systems.
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All authors Qing-Ao Xiang, Yan Liu, Xin-Yuan Yang, Ya-Ju Song
Materials Science
Unveiling Nanoscale Surface Damage Dynamics in Swift Heavy Ion Irradiated Gallium Nitride
Jiayu Liang, Shaowei He, Wenlong Liao et al. (+9 more)
This work systematically unveils the nanoscale surface damage dynamics in gallium nitride by investigating the atomistic mechanisms of hillock formation. The results identify two distinct hillock morphologies dependent on electronic energy loss (Se) values. Bell-shaped hillocks form under 18.2 keV/nm Kr irradiation, whereas crater-rim hillocks with central holes emerge under 40.2 keV/nm Ta irradiation. Microstructural analysis reveals that Ga-rich hillocks are accompanied by the generation of metastable zincblende nanodomains. These nanodomains preferentially aggregate around the periphery or sidewalls of the hillocks and exhibit a high spatial correlation with screw dislocations. Further temperature-dependent studies indicate that elevated temperatures significantly enlarge the overall dimensions of the hillock structures without altering their fundamental morphologies. Notably, under Ta irradiation above 1200 K, the high temperatures drastically reduce the viscosity and surface tension of
liquid gallium. This enhanced fluidity of the transient molten phase promotes the formation of penetrating nanochannels.
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All authors Jiayu Liang, Shaowei He, Wenlong Liao, Tan Shi, Hang Zang, Yonghong Li, Wenbo Liu, Xiaojun Fu, Chuanjian Yao, Huan He, Jianan Wei, Chaohui He
Materials Science
Ethaline deep eutectic solvent under nanoconfinement: Unveiling structural and dynamical changes
Kamar Mohammad Nadim, Mozhdehei Armin, Lefort Ronan et al. (+5 more)
Hybrid nanomaterials incorporating deep eutectic solvents (DES) in porous hosts or at solid interfaces are gaining increasing
attention for their potential interest across a wide range of applications. Under these conditions, the performances of DESs may be influenced by interfacial effects and spatial restrictions. In this study, we examined the effects of nanoconfinement on both the structure and molecular dynamics of the prototypical DES ethaline (a mixture of choline chloride and ethylene glycol) when confined within the cylindrical mesopores of SBA-15 (Dp $\approx$ 8.1 nm) and MCM-41 (Dp $\approx$ 3.5 nm) silicas, using
neutron diffraction and quasielastic
neutron scattering. It demonstrates that ethaline remains structurally homogeneous under confinement, showing no evidence of core-shell segregation within the pore cross-section. The molecular dynamics of the confined ethaline preserve the key characteristics observed in its bulk state. Translational
diffusion follows a jump-
diffusion mechanism, with
diffusion coefficients that remain remarkably close to the bulk values, showing only a modest reduction in MCM-41. A more pronounced increase in the residence time t0 between translational molecular jumps is observed. It corresponds to roughly a factor of 3-8 under confinement in SBA-15, and reaches up to a tenfold enhancement in MCM-41 relative to bulk. Similarly, the characteristic relaxation time, tL, associated with the localized in-cage motion of ethaline, increases by approximately 20% in SBA-15 and up to 50% in MCM-41. However, the molecular trajectories, modeled from the elastic incoherent structure factor, remain largely preserved under confinement, showing only a marginal reduction in intra-basin motional amplitudes.
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All authors Kamar Mohammad Nadim, Mozhdehei Armin, Lefort Ronan, Moréac Alain, Ollivier Jacques, Appel Markus, Viviana Cristiglio, Denis Morineau
Materials Science
Phonon scattering mechanisms in WTe$_2$ observed by ultrafast coherent phonon spectroscopy
Mizuki Akei, Yu Mizukoshi and Muneaki Hase
Revealing the mechanisms of
phonon scattering is crucial for understanding material properties such as transport characteristics and optical responses. It can be discussed by measuring the temperature dependence of the
phonon energy and lifetime. To gain insight into these mechanisms in Weyl semimetal T$_d$-WTe$_2$, we investigated coherent
phonons using time-resolved pump-probe spectroscopy in a wide temperature range from 4.6 to 300 K. The temperature dependence of the frequency and decay rate of the two high-frequency optical modes was described by the conventional anharmonic
phonon-
phonon scattering model. In contrast, the low-frequency mode at 2.4 THz exhibited anomalous behavior, which can be interpreted as the contribution of
phonon-electron scattering.
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Materials Science
A modified Moss rule highlights underexplored classes of high refractive index materials
Eugène Bertin, Finja Tadge and Andrea Crovetto
High refractive index dielectrics are central to photonic applications, yet the empirical Moss rule imposes a fundamental trade-off between refractive index and optical transparency. We introduce a modified Moss rule anchored to the optical absorption edge rather than the fundamental bandgap, capturing materials where various physical mechanisms suppress absorption well above the electronic gap. Screening the Materials Project database with this metric reveals recurring chemical compositions and structural prototypes in the materials with the most promising refractive index/transparency trade-offs. These materials include chalcopyrites, Zintl pnictides, and early transition metal multi-anion chalconitrides and oxichalcogenide compounds. Hybrid density functional theory calculations reveal that the chalconitride (Hf,Zr)2(S,Se)N2 family can achieve a combination of ultra-high refractive indices, low effective masses and transparency windows extending into the UV, potentially surpassing state-of-the-art TiO2. Our results establish (Hf,Zr)2(S,Se)N2 compounds as a unique and largely unexplored material family for next-generation photonic applications.
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Computational Physics
Inverse Low-Dimensional Manifold Reconstruction Framework for Spatiotemporal Reconstruction of Compressible Physical Fields
Qiang Liu, Feng Ma, Wei Zhu et al. (+4 more)
Compressible physical fields are widely present in the real physical world, but current artificial intelligence lacks an understanding mechanism for the non-differentiable features in compressible physical fields. Addressing the limitations of existing deep learning architectures in handling global non-differentiable features, we propose the Inverse Low-Dimensional
Manifold reconstruction framework (ILDM). This framework couples the Non-differentiable Approximation Function (NAF) for capturing non-differentiable features in compressible flows with the Smooth Fluid Reconstruction (SFR) module tailored for smooth fluid regions. Extensive evaluations across 1D and 2D
benchmarks, including Riemann problems and double Mach reflection, demonstrate that ILDM significantly outperforms cPINN and R-adaptive DeepONet. Specifically, ILDM achieves superior localization of non-differentiable interfaces and maintains robust super-resolution performance even with low-resolution inputs, establishing a physically consistent and scalable paradigm for data-driven fluid dynamics.
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All authors Qiang Liu, Feng Ma, Wei Zhu, Xiyu Jia, Jianmin Xue, Jun Wen, Gaojun Fu
Quantum Physics
Selective Quantum Mpemba Dynamics in Chaotic Spin Chains
Ri-Hua Zheng, Yang Xiao, Yu Wang et al. (+2 more)
In a
symmetry-restoration
quantum Mpemba effect, an initial state with stronger local
symmetry breaking can lose that
memory faster than a state that starts closer to the symmetric
manifold. We study how this local ordering reversal depends on the spatial profile of a longitudinal field in a clean U(1)-conserving
spin chain, comparing spectral level statistics with crossings of the
entanglement asymmetry for the same
Hamiltonians. We find that Gaussian orthogonal ensemble (GOE)-like level statistics alone do not determine whether Mpemba crossings occur. Across field textures, GOE-like spectra can occur with or without
entanglement-asymmetry crossings at the same field strength. In a near-staggered detuned field, the total charge-sector coherence reverses its ordering while the
entanglement asymmetry retains its initial order. This contrast links the crossing response to the distribution of local charge-sector coherence and its entropic weighting in the reduced density
matrix.
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All authors Ri-Hua Zheng, Yang Xiao, Yu Wang, Ye-Hong Chen, Yan Xia
High Energy Physics (Experiment)
The Dark Photon in the PHELEX Experiment
A.V.Kopylov, I.V.Orekhov, V.V.Petukhov et al. (+1 more)
This paper presents diurnal measurements of the single-electron count rate in the PHELEX experiment using multi-cathode counters over the period from 2023 to 2026. The results obtained are interpreted as an indication of a possible effect from dark
photons with masses ranging from 10 to 40 eV. The correlation of the measured rates in counters with Fe and Al cathodes suggests that the effect does not depend on the
magnetic properties of the cathode material. This can be interpreted as an argument against many dark matter models related to
magnetic moments. The result, if confirmed in an independent experiment, could narrow the range of possible candidates to those that interact primarily through an electric (or longitudinal) field, insensitive to
spin. A dark
photon with kinetic mixing fits this description ideally.
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All authors A.V.Kopylov, I.V.Orekhov, V.V.Petukhov, A.E.Solomatin
General Relativity and Quantum Cosmology
Testing General Relativity with GWTC-4.0 through mixture models
Koustav Chandra and Juan Calderón Bustillo
Gravitational-wave observations of compact binary mergers have enabled precision tests of
gravity in the strong-field dynamical regime. Current approaches combine single-event results that assume deviations from General Relativity (GR) are uniformly distributed across events, limiting their flexibility and potentially biasing the inferred evidence. We introduce a simple mixture-model framework in which a fraction $\zeta$ of events is consistent with GR, while a fraction $1 - \zeta$ deviates from it, without imposing constraints on the population distribution of the deviation parameters. We apply this method to publicly available results from the LIGO-Virgo-KAGRA (LVK) collaboration on O1-O4a compact binary mergers obtained through FTI, pSEOBNR, and KerrPostMerger tests. We find that the data are consistent with all events satisfying GR. However, we obtain respective Bayes factors $B^{\zeta=1}_{\zeta \neq 1} \simeq 20 $, $10$ and $15$, which are much smaller than those inferred from existing LVK analyses, indicating that the data require greater flexibility in modelling possible deviations than standard approaches permit. In light of our results, we recommend using flexible mixture models to test GR across compact-merger catalogues, unless there are obvious physical motivations to impose more restrictive models, as in the case of graviton-mass estimates.
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Astrophysics of Galaxies
Unveiling the Milky Way with a Gaia DR3 census of OB-type stars within 2 kpc. I. Tracing local Galactic structure, massive star-forming regions and core-collapse supernova progenitors
Alexis L. Quintana, Kiril Maltsev, Eloisa Poggio et al. (+10 more)
O- and B-type
stars are young and hot, thereby serving as vital tracers of the
star formation and spiral arm structure of the Milky Way. At the dusk of the
Gaia DR3 era, a high-confidence and accurate catalogue appears timely. We have characterized 105,971 OB-type
stars (T$_{\rm eff} >$ 10,000 K) within 2 kpc from the Sun, using an astro-photometric
Bayesian inference tool. Our map unveils a complex view of the young
stellar populations across the thin disk, with prominent large-scale features such as the Cepheus Spur, the
Giant Oval Cavity, and a segment the Sagittarius-Carina arm all visible. Their inhomogeneous spatial distribution implies that massive
star formation has taken place clustered across a few highly concentrated regions. We find a correlation between the overdensities of OB-type
stars and young open clusters, and attribute departure from it to extinction effects. We identify 4200
stars as model-dependent core-collapse
supernova (ccSN) or direct-collapse black hole (BH) progenitor candidates, including 6 ccSN progenitor candidates within 125 pc – the maximum radius within which a ccSN explosion could be harmful to Earth's biosphere – but our analysis suggests none of them exploding within the next 5 Myrs. Finally, we anticipate more evolved OB-type
stars to collapse to form BHs within the next 1 Myr than ccSN progenitors will explode, despite the former's much scarcer number. A possible interpretation is a recent
star formation burst in the local Milky Way, consistent with overdensities of ccSN progenitor candidates in Cyg OB2 and the Sagittarius-Carina arm.
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All authors Alexis L. Quintana, Kiril Maltsev, Eloisa Poggio, Emily L. Hunt, Nicholas J. Wright, Sara R. Berlanas, Laia Casamiquela, Abel de Burgos, Hanna Parul, Misha Haywood, Paola Di Matteo, Chervin Laporte, Juan Martínez García
Strongly Correlated Electrons
Ab initio thermodynamic statistical modeling of the miscibility gap and the metal-insulator phase transition in SrTi$_{1-x}$V$_x$O$_{3}$
Luka Wibmer, Chiara Ostendorf, Dominik Spath et al. (+3 more)
The substitutional
alloy SrTi$_{1-x}$V$_x$O$_3$ interpolates between the band
insulator SrTiO$_3$ and the correlated metal SrVO$_3$, exhibiting a composition-driven metal–
insulator transition whose origin combines Mott physics with local chemical disorder. Previous first-principles studies relied on individual supercells, which cannot capture the thermally disordered solid solution, since configurations of identical composition can display very different electronic properties. Here we treat the
alloy within a generalized quasi-chemical approximation, a thermodynamically consistent statistical framework in which every property is obtained as an ensemble average over all
symmetry-inequivalent clusters, weighted by occurrence probabilities that minimize the Gibbs mixing free energy. This provides a well-defined procedure to average over different supercells, and places the structural and electronic descriptions on an equal footing. From the mixing thermodynamics we obtain a miscibility gap with a critical temperature of 1443 K, consistent with experimental evidence. Combining the cluster ensemble with dynamical mean-field theory, we track the density of states at the
Fermi level across the full composition range: whereas density-functional theory alone predicts a metal for all $x>0$, the correlated spectral function reproduces the transition, evolving from insulating below $x\approx0.3$ to metallic near $x=1$. Finally, classifying clusters as metallic or insulating and performing site percolation on a simple cubic
lattice yields a sharp onset of system-spanning conduction near $x\approx0.4$. These results establish a thermodynamically consistent, configuration–averaged framework applicable to the broader class of correlated materials.
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All authors Luka Wibmer, Chiara Ostendorf, Dominik Spath, Christoph Heil, Pedro N. Ferreira, Markus Aichhorn
General Relativity and Quantum Cosmology
The twin paradox in the vicinity of rotating black holes
Shuiquan Bai and Geraint F. Lewis
The twin paradox is a foundational thought experiment in the special theory of relativity where a returning twin ages less than the one who remains stationary. However, the intricacies of the twin paradox remain relatively underexplored in the curved spacetimes of general relativity. Here we explore the twin paradox in the vicinity of a rotating black hole, where the existence of multiple paths between two events creates significant complexity. We develop a numerical framework based on residual maps and optimisation to identify possible trajectories. We find a strong negative correlation between a traveller's experienced proper time and both the azimuthal distance travelled and the magnitude of acceleration. We apply numerical Jacobi field analysis to examine conjugate points along geodesics within the Kerr geometry, finding that only the geodesic with the minimal azimuthal distance contains no conjugate points. This provides beginner students of general relativity with a visual tool to understand general relativistic concepts, helping to correct flat-spacetime intuitions.
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Mathematical Physics
Hamiltonian reduction from particular integrals
R. Azuaje, A. M. Escobar-Ruiz and I. Gutierrez-Sagredo
We develop a
geometric reduction mechanism generated by systems of particular integrals, namely, families of functions whose time derivatives close linearly on the family. Their common zero set is dynamically invariant. In the
Hamiltonian case, under a weak involution condition, the restricted dynamics is presymplectic, and its characteristic quotient carries a reduced
Hamiltonian flow. This yields a direct bridge between particular integrals, presymplectic reduction, and lower-dimensional
Hamiltonian dynamics, and leads to a Liouville-type notion of particular integrability. We illustrate the framework through mechanical examples and lift constructions, including variants of the Eisenhart lift.
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Quantum Physics
Quantum Recurrence Plot Algorithm Based on Quantum Principal Component Analysis
Hanhuai Zhu, Jingjing Huang, Zhi-Xi Wang et al. (+1 more)
Recurrence Plot (RP) is a method employed to analyze the periodicity, chaoticity, and nonlinear characteristics of complex systems.
Quantum Principal Component Analysis (QPCA), on the other hand, achieves dimensionality reduction of sample data using density
matrices based on
quantum circuits. We improve the distance threshold function of the recurrence plot
algorithm using a density operator conceptually equivalent to the covariance
matrix, integrate it with
quantum circuits, and thereby develop a
Quantum Recurrence Plot (QRP)
algorithm. This
algorithm achieves ultra-high efficiency in parallel computing, reduces computational costs, and simultaneously upgrades the traditional grayscale recurrence plot to colored heatmaps, enabling a better revelation of the system's dynamical characteristics.
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All authors Hanhuai Zhu, Jingjing Huang, Zhi-Xi Wang, Shao-Ming Fei
Other Condensed Matter
Dzyaloshinskii-Moriya Gradients Unlock Topological Dimensional Reduction in Magnetic Hopfions
Kui Yuan, Hailong Shen, Jiawei Dong et al. (+12 more)
Three-dimensional
magnetic solitons retain topological protection only while their
spin field remains continuous. Here we show that chemical inhomogeneity can break this protection in a controlled way, converting a hopfion-like toroidal texture into an effectively two-dimensional skyrmion string. Tilt-dependent Lorentz transmission electron microscopy, electron energy-loss spectroscopy, and micromagnetic simulations of pristine, uniformly Y-doped, and nonuniformly Y-doped disordered TiO2 nanoparticles embedded in a FeCrNiMn host reveal two regimes. Uniform Y doping enriches Ti3+/oxygen-vacancy localization centers and stabilizes closed rings with
Hopf invariant QH approximately 1. Nonuniform Y doping forms a Ti4+-rich, vacancy-depleted boundary that creates a sharp q=D/(2A) gradient and a weak-moment leakage channel. This coupled mismatch torque and continuity leakage split the ring, leaving a skyrmion-string remnant and a field-sensitive helicity texture.
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All authors Kui Yuan, Hailong Shen, Jiawei Dong, Xin Zhang, Longqing Chen, Yihan Wang, Bo Liu, Qing Zhang, Zhengshang Wang, Wenbin Qiu, Xiaoyi Wang, Bing Han, Yang Qiu, Kun Zhang, Xudong Cui
Atomic Physics
Absolute frequency measurement of a $^{176}$Lu$^+\,(^{3}\mathrm{D}_1)$ standard against the NRC-FCs2 fountain with $2.6\times10^{-16}$ uncertainty
K. J. Arnold, Bin Jian, Zhao Zhang et al. (+6 more)
We report an improved absolute frequency measurement of the $^{176}$Lu$^+\,(^{3}\mathrm{D}_1)$ optical frequency standard, evaluated via a remote link to the NRC-FCs2 caesium fountain primary frequency standard. Operating a single ion clock with 94.2% uptime over 10 days, and using an ambiguity-resolved precise point positioning (PPP-AR) link over the Global Positioning System, we determine an absolute frequency of $353\,638\,794\,073\,800.332(91)\,$Hz at a fractional uncertainty of $2.6 \times 10^{-16}$. This agrees with our previous result, which underpins the Comité international des poids et mesures recommended frequency value, and reduces the uncertainty by a factor of 3.6.
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All authors K. J. Arnold, Bin Jian, Zhao Zhang, Qi Zhao, Qin Qichen, N. Jayjong, M. D. K. Lee, Scott Beattie, M. D. Barrett
Quantum Gases
A low-energy effective Hamiltonian for Landau quasiparticles: II. Application to the contact Fermi gas
Pierre-Louis Taillat and Hadrien Kurkjian
This article follows up on arxiv:2511.15938, in which we developed an
Hamiltonian renormalization scheme to construct a quantized theory of
Fermi liquids. Here, we apply this formalism to a low-temperature atomic
Fermi gas where the short-range interactions are fully parametrized by the s-wave scattering length $a$. We
benchmark our renormalized theory by recovering known perturbative results on the static properties of the
Fermi gas, such as the Lee-Huang-Yang expansion of the equation of state, the Galitskii expansion of the momentum distribution, and the Gor'kov-Melik Barkhudarov preexponential correction to the critical temperature. We then turn to the transport dynamics and demonstrate the presence of a preexponential correction to the speed of zero sound when including corrections of second order in $a$. Finally, we develop an efficient numerical method to solve the transport equation exactly, and we apply it to study the crossover from the collisionless to the hydrodynamic regime in the density and polarisation response functions.
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Medical Physics · Cross-listed from eess.IV
From Data Completeness to Data Sufficiency: A Task-Driven Imaging Framework for Intraoperative CBCT under Quality-Time-Dose Trade-offs
Yi Jia, Rongjun Ge, Yang Chen et al. (+2 more)
Mobile C-arm cone-beam computed
tomography (CBCT) has been widely used for real-time intraoperative 3D imaging. However, current practice often mechanically applies the fan-beam CT criterion of "180{\deg} plus fan angle" in pursuit of "data completeness" in reconstruction. This review argues that, under the single circular trajectory of three-dimensional cone-beam geometry, complete data are mathematically unattainable; moreover, blindly increasing sampling may exacerbate the trade-off among intraoperative image quality (Q), imaging time (T), and radiation dose (D). Against this background, this review reframes the evaluation of intraoperative CBCT around "data sufficiency" rather than "data completeness." This perspective moves beyond the excessive pursuit of absolute mathematical and analytic accuracy, and instead emphasizes task-specific minimum image-quality thresholds required for clinical decision-making. By synthesizing evidence from multiple clinical scenarios, this review suggests that approximation errors can be acceptable when clinical decision-making requirements are satisfied, thereby achieving a Q-T-D balance.
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All authors Yi Jia, Rongjun Ge, Yang Chen, Yan Xi, Wenjun Xia
Materials Science
Minimizing propagated density errors of atomic core-electron for simultaneously accurate bandgaps and lattice constants in closed-shell Copper semiconductors
Kuiyu Ye, Haitao Liu, Yuanchang Li et al. (+1 more)
Density functional theory struggles to accurately determine electron density of atoms, whose error is inevitably encoded into the pseudopotential and propagated into solid-state calculations. However, little is known about how this affects accuracy nor how to remedy it. In this work, through a systematic study of the effect of Cu atomic density on bandgap and
lattice constants of over 50 Cu-containing simple closed-shell
semiconductors, we find that core-electron density can drastically affect
nuclear attraction to valence electrons and subsequent charge distribution and energy position of Cu 3$d$ electrons. The error can be eliminated at its source by employing modified Hartree-Fock pseudopotentials for Cu core while retaining (semi-)local functionals for valence electrons. This real-space partitioning approach leads to simultaneous high-accuracy in bandgap and
lattice constants across the entire material class.
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All authors Kuiyu Ye, Haitao Liu, Yuanchang Li, Shengbai Zhang
Quantum Physics
Bayesian Gill-Massar Bound: An Attainable Lower Bound for Qubit Parameter Estimation
Ke-Han Zhao, Koichi Yamagata and Jun Suzuki
We study lower bounds for
Bayesian quantum parameter estimation, with a particular focus on
qubit models. While several lower bounds on the Bayes risk have been proposed, including the
Bayesian symmetric logarithmic derivative (B-SLD) type bound and the
Bayesian Nagaoka-Hayashi (B-NH) bound, there is no definite proof available to show they are attainable except for special cases. Thus, identifying attainable bounds together with their corresponding optimal measurement strategies remains a central open problem in
Bayesian quantum estimation. In this work, we introduce a new
Bayesian lower bound, referred to as the
Bayesian Gill-Massar (B-GM) bound, inspired by the logic of Gill-Massar bound in point estimation. We derive an analytical closed-form expression of the bound and show that it is attainable for any
qubit model. In particular, we prove that the optimal
Bayesian strategy can be realized by a projection-valued measure associated with a single effective direction determined by the weight
matrix and the B-SLD-type Fisher information
matrix. We provide numerical comparisons between the B-GM, B-NH, and B-SLD-type bounds in higher-dimensional models. Our results show that the B-GM bound has a limitation in high-dimensional models with few parameters, since it can be negative.
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Fluid Dynamics
Learning Turbulence Closures with Physics-Informed Neural Networks for the Rayleigh-Taylor Transition to Turbulence
Paul Creusy, Benoît-Joseph Gréa, Antoine Briard et al. (+1 more)
Reynolds-averaged Navier-Stokes (RANS)
turbulence models are known to perform poorly in predicting the dynamics of Rayleigh-Taylor mixing when
turbulence is not fully developed, particularly during the transition from an initially perturbed interface. In this work, we investigate the use of data-driven strategies to enhance a simple $k$-$\varepsilon$-$b$ model for this transitional regime. The
turbulence model is first embedded within a surrogate physics-informed neural network (PINN), enabling the calibration of coefficients that account for parametric errors and the identification of corrective terms representing structural errors associated with missing physical processes. The learned corrections are then re-expressed onto the model state variables and relevant flow indicators, leading to explicit analytical modifications of the closure. The resulting fully interpretable corrected model is assessed against an extensive database of direct numerical simulations (DNS) of Rayleigh-Taylor flows. This framework enables improved predictions of the mixing-layer growth during the transition to
turbulence.
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All authors Paul Creusy, Benoît-Joseph Gréa, Antoine Briard, Téo Granger
Fluid Dynamics
Route survival and spectral modification of finite-depth salt-finger plume forests under imposed mean shear
Sriram P. Kalathoor
Salt-finger plume forests in a finite layer can differ in strength and in the route by which interfacial activity becomes vertically connected. We use direct three-dimensional simulations to test whether such a route is a short-lived realization-specific transient or a persistent route family under an added mean-shear perturbation. The baseline route atlas holds density ratio, diffusivity ratio, Prandtl number, interface thickness, roughness amplitude, domain, and resolution fixed while varying the imposed interfacial roughness spectrum. Low-mode roughness forms a broad connecting endpoint, high-annulus roughness forms a localized route-
memory endpoint, and mixed roughness forms a delayed scale-transfer route. A second mixed realization preserves continuous active-width, spectral, and transport measures after \(t=45\), with mean absolute differences of \(3.1\%\) in \(w\)-active width, \(1.6\%\) in salinity-active width, \(2.8\%\) in broad spectral fraction, and \(3.6\%\) in salt flux, while shifting the binary scalar-contact label. We then impose an initial tanh mean shear on the mixed route. The full-resolution shear case reaches \(t=60\) and preserves finite-depth reach: first velocity contact occurs at \(t=57.75\), first salinity contact occurs at \(t=59.5\), and both times match the unsheared mixed reference. The spectral branch is redistributed. At \(t=60\), the broad fraction is \(1.116\) times the mixed value, the intermediate fraction is \(0.530\) times the mixed value, and the short-wave fraction is \(1.278\) times the mixed value. In this finite-depth configuration, route survival means preserved reach and contact timing with a changed spectral pathway.
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General Relativity and Quantum Cosmology
Primordial black hole in Lorentz-violating theories: Insights from Bumblebee gravity
Mohsen Khodadi and Javad T. Firouzjaee
The Bumblebee
gravity (BG) model, featuring spontaneous Lorentz
symmetry breaking via a vector field non-minimally coupled to
curvature, has been widely used to explore Lorentz-violating effects in cosmology. We investigate
primordial black hole (PBH) formation within this framework, deriving the complete set of modified perturbation equations. We demonstrate that BG, sourced by a timelike vector field, introduces three distinct enhancements to PBH abundance–modified expansion history, suppressed collapse threshold, and amplified power spectrum–which together render PBHs viable dark matter candidates across the asteroid-mass window for modest Lorentz-violating couplings. However, a systematic analysis of the quadratic action reveals that these phenomenological consequences emerge from a theoretically pathological foundation. The vector sector exhibits an intrinsic ghost instability, while the requirement of a stable
symmetry-breaking minimum simultaneously induces a tachyonic instability on timescales far below cosmological scales. The model thus suffers from a fundamental inconsistency: the conditions for cosmological viability and spontaneous
symmetry breaking are mutually exclusive within the minimal Bumblebee framework. Our results illustrate both the notable power of Lorentz violation to influence early Universe observables and the necessity of a consistent theoretical foundation for such predictions.
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