Astrophysics of Galaxies
Multi-band Structural Analysis of KiDS-selected Low Surface Brightness Galaxies with Hyper Suprime-Cam Imaging
Dipanjan Mitra and Kanak Saha
We present a homogeneous multi-band structural analysis of 205 KiDS-selected low surface brightness
galaxy (LSBG) candidates using deep Hyper Suprime-Cam (HSC) $G$, $R$, and $I$-band imaging. Structural parameters were derived using single-component Sérsic modeling with GALFIT. The sample is dominated by diffuse systems with low Sérsic indices, with the distributions consistently peaking near $n\approx0.7$ across all bands. The estimated $B$-band central surface brightness distribution has a median value of $\tilde{\mu}_{0,B}=24.55$ mag arcsec$^{-2}$, indicating that the
galaxies lie firmly within the low surface brightness regime. The catalog is strongly dominated by red systems, comprising 178 red LSBGs (87.3$\%$) and 27 blue LSBGs (12.7$\%$). Despite this color bimodality, the red and blue subsamples show similar structural properties, with no statistically significant differences in Sérsic index, effective radius, axis ratio, or surface brightness distributions. The absence of a correlation between color and axis ratio further suggests that
dust reddening is unlikely to be the primary driver of the red colors. Overall, the sample provides a well-characterized structural reference set of LSBGs in the HSC footprint and confirms that the KiDS selected candidates are predominantly genuine low surface brightness
galaxies.
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Computational Physics
The Heat Kernel Expansion: Curvature for Shock Detection in Higher-Order Financial Networks
Mohammad Elsayed and Sara Najem
This work follows the
evolution of financial networks in Norway over a period of nine years at a monthly rate. The data consist of board directors and their affiliations to companies, which we model as simplicial complexes. In this framework, directors are represented as nodes and companies as faces of the complex. To characterize the latter, we focus on three topological measures: the Euler characteristic, computed through the Betti numbers, torsion computed through the reduced determinant of the higher-order
Laplacians, and higher-order clustering coefficients. The first two fail to capture the effect of imposed law on representation, unlike our notion of
curvature which is a geometrical measure computed from the coefficients of the series expansion of the heat kernel in powers of time, which is our major contribution in this work. In particular, the Euler characteristic integrates
curvature, and thus local information is lost. Subsequently, not every topological measure can reliably capture shocks in networks. Further, the number of spanning trees may undergo significant changes at the lowest order, yet these changes need not be reflected in the torsion. Conversely, the change in the
curvature revealed variation in the board interlock due to legislation, and serves as a sensitive measure for detecting shocks in networks. Inflection points in
curvature are associated with external forcing, and minima with shock arrival times. Sharp transitions are also observed in the components of torsion, while smooth changes are observed in higher-order clustering.
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High Energy Astrophysical Phenomena
On the braking index evolution of PSR B0540-69: wind braking of pulsars
H. Tong
The
pulsar PSR B0540-69 has both a braking index measurement and
spin-down state change. After its
spin-down state change, it shows an increasing braking index with time. Previously, it is pointed out that the
spin-down state change may be caused by an enhanced particle wind. The prediction is that its braking index will be smaller in the high
spin-down state. The current measured braking index is approaching the previous prediction. The transient variation of braking index may be due to a small varying part of the particle density. The braking index
evolution of PSR B0540-69 is found to be in an exponential form. Its braking index is expected to approach some steady value. Future braking index measurement may make clear the physics for the braking index
evolution. It may also help to make test the particle acceleration mechanism in the
pulsar magnetosphere. Finally, a phenomenological treatment of the wind braking model is presented in the appendix. It can simplify the applications of wind braking model to
pulsar braking index, intermittent
pulsars and PSR B0540-69.
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Solar and Stellar Astrophysics
The Curious Case of Dark Faculae on M Dwarf Stars
Alexander~I.~Shapiro, Sara~Seager, Sami~K.~Solanki et al. (+6 more)
The study of
exoplanet atmospheres has brought a renewed interest in
stellar astrophysics. Specifically,
stellar magnetic activity from the host
star contaminates
exoplanet atmosphere transmission spectra, as evidenced by observations from the James Webb Space
Telescope. The
stellar surface
magnetic features in the form of dark spots caused by large concentrations of surface
magnetic fields and more diffuse and extended faculae caused by small-scale
magnetic field concentrations change the apparent size of the
star in a wavelength-dependent way. This spot and faculae contribution to the change in transit depth contaminates the planetary signal. Here we study the transition from bright faculae on G- and K-
dwarfs to dark faculae on M-
dwarfs. This dark appearance of faculae is in significant contrast to the conventional picture that faculae are brighter than the quiet
star region as they are on the Sun. We use the 3D radiative magnetohydrodynamics code MURaM to simulate faculae, and calculate the faculae spectra with the MPS-ATLAS radiative transfer code. We present a qualitative explanation for the transition from dark to bright faculae attributing it to shallower flux tubes and reduced vertical temperature gradients at the surfaces of M
dwarfs relative to the Sun.
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All authors Alexander~I.~Shapiro, Sara~Seager, Sami~K.~Solanki, Nadiia~Kostogryz, Veronika~Witzke, Krishnamurthy~Sowmya, Tanayveer~Bhatia, Yvonne~C.~Unruh, Robert~Cameron
Computational Physics · Cross-listed from cs.LG
Physics-Informed Neural Network with Squeeze-Excitation-like Attention
Yun-Fei Song, Long-Gang Pang, Fu-Peng Li et al. (+1 more)
We introduce SEA-PINN, a novel architecture that incorporates a Squeeze-Excitation-like
attention mechanism into physics-informed neural networks to dynamically recalibrate the importance of
neurons across layers. A key feature of SEA-PINN is its highly stable initialization. On 17 out of 20
benchmark problems, SEA-PINN exhibit nearly negligible variance and significantly reduced initial loss, establishing a quasi-deterministic and favorable starting point for optimization. Notably, without employing
Fourier feature
embeddings or periodic activation functions, SEA-PINN attained competitive accuracy (83% vs. 90% improvement relative to FNN-PINN on the high-frequency case 7) as compared with TSA-PINN-a model specifically engineered for high-frequency problems via learnable frequencies in sinusoidal activations. Furthermore, integrating SEA-PINN into TSA-PINN boosted performance by 42.49%. These results underscore SEA-PINN as a lightweight plug-in module that enhances nonlinear representation power, promotes more robust and efficient convergence, and strengthens the overall reliability of physics-informed learning.
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All authors Yun-Fei Song, Long-Gang Pang, Fu-Peng Li, Jun-Jie Zhang
Quantum Physics
QMCtwin: Master-Equation Simulation of Syndrome Statistics Beyond Pauli Noise
Tong Shen, Huo Chen, Benchen Huang et al. (+4 more)
As
quantum error correction moves toward large-scale experimental implementations, decoder performance increasingly depends on how faithfully hardware noise is translated into syndrome statistics. Standard stabilizer workflows achieve scalability by replacing device dynamics with
stochastic Pauli or detector-error models, but this compression can discard coherent phase information, nonunital drift, continuous-time effects of always-on couplings, and correlations generated by simultaneous
Hamiltonian and dissipative
evolution. Here we present QMCtwin, a sign-problem-suppressed
quantum Monte Carlo framework for master-equation simulation of QEC
circuits, and apply it to a full syndrome-extraction round of a distance-$7$ rotated surface code with $97$ physical
qubits. The open-system model includes realistic superconducting-device noise mechanisms such as relaxation, pure dephasing, coherent gate miscalibration, residual $ZZ$ crosstalk, and drive-
qubit detuning. By directly estimating syndrome observables from the QMC-generated
stochastic density
matrix estimator, we compare the master-equation dynamics with their Pauli-twirled Clifford simulation counterparts. QMCtwin predicts syndrome-extraction biases and correlations between syndromes and proxies of logical-string-parity that are absent or strongly suppressed in the
stochastic Pauli description. We introduce information-theoretic diagnostics that further quantify how information concerning syndromes versus string-parity proxies differs between the realistic master-equation simulation and the corresponding Pauli-twirled model. These results show that QMC-based master-equation digital twins can expose noise features hidden by conventional Pauli/Clifford noise models and provide a practical path toward more accurate decoder-facing syndrome models.
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All authors Tong Shen, Huo Chen, Benchen Huang, Tyler Takeshita, Arian Vezvaee, Izhar Medalsy, Daniel A. Lidar
Mathematical Physics
Universal Properties of Nonlinearly Perturbed Maxwell Theory
Tengyang Liu and Yisong Yang
We show that a general nonlinearly perturbed Maxwell theory of electromagnetism possesses three universal fundamental properties: (i) A finite-energy electric point charge. (ii) Exclusion of finite-energy
magnetic monopoles and dually charged dyons. (iii) Arbitrary smallness of the effective radius of a point electric charge and the associated local undetectedness of the electric charge and energy. In particular, this last property offers a classical explanation for the invisibility of the electron, as a point electric charge, in accordance with the smallness of its effective radius. This nonlinear theory of electromagnetism has the feature that it minimally perturbs the Maxwell theory with a nonlinearity profile that is as general as possible such that the three universal properties stated above are all maintained.
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Soft Condensed Matter
Epithelia Realize Nematopolar Topological Defect Structures
Tianxiang Ma, Niels de Graaf Sousa, Valeriia Grudtsyna et al. (+2 more)
We introduce a shape-based polar order parameter that captures the structural asymmetry of
cells within epithelial monolayers. By combining bright-field imaging and traction force microscopy, we demonstrate that shape polarity serves as a unifying biomechanical metric, integrating the physical information encoded by nematic directors, principal stresses, and cellular motion. Furthermore, we show that the tissue organizes into a mixed polar-nematic phase, characterized by the coexistence of integer ($\pm 1$) and half-integer ($\pm 1/2$) defects. Through mechanical perturbations, we demonstrate that both substrate stiffness and
cell-
cell adhesion modulate the density of these excitations and the length of domain walls binding like-signed positive half-integer defects. Using a minimal continuum model of polar-nematic active matter, we establish that this mixed phase is fundamentally driven by the interplay of active stresses and polar-nematic elasticity. These findings provide a direct experimental evidence that epithelial monolayers behave as nematopolar matter, in which coupled polar and nematic elastic interactions jointly shape the active state
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All authors Tianxiang Ma, Niels de Graaf Sousa, Valeriia Grudtsyna, Farzan Vafa, Amin Doostmohammadi
Optics
Mid-infrared photothermal imaging flow cytometry
Yusei Sugawara, Keiichiro Toda, Genki Ishigane et al. (+2 more)
Imaging flow cytometry (IFC) enables high-throughput single-
cell analysis but largely relies on fluorescence labeling to obtain molecular specificity. Label-free vibrational imaging can provide intrinsic chemical contrast, yet coherent Raman-based methods interrogate only a limited axial volume, which restricts quantitative whole-
cell analysis under flow. Mid-infrared photothermal (MIP) microscopy offers a promising route to overcome this limitation by combining linear mid-infrared (MIR) absorption-based chemical contrast with visible-light detection, allowing chemical imaging of a broader axial volume of each
cell in a wide-field configuration. However, applying MIP microscopy to rapidly flowing
cells has been difficult because conventional frame-sequential acquisition of MIR-ON and MIR-OFF images is highly susceptible to motion-induced subtraction artifacts. Here we demonstrate MIP-IFC, a label-free imaging flow cytometry platform based on single-shot nanosecond-dual-pulse MIP (SNAP-MIP) microscopy. SNAP-MIP encodes the MIR-ON and MIR-OFF states into separate
holographic channels within a single camera exposure, reducing their temporal separation to 20 ns. This single-shot acquisition suppresses motion artifacts and increases the allowable sample velocity for artifact-free MIP imaging by five orders of magnitude compared with conventional frame-sequential MIP imaging. Leveraging this capability, MIP-IFC acquired chemical images at 500 frames per second and achieved a cellular event rate up to ~70 events s^-1. We demonstrate quantitative chemical discrimination of flowing microbeads and apply MIP-IFC to single-
cell profiling of oleic-acid-induced lipid accumulation, adipocyte differentiation, and confluence-dependent cellular heterogeneity. These results establish MIP-IFC as a high-throughput, quantitative, label-free chemical imaging platform for single-
cell phenotyping under flow.
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All authors Yusei Sugawara, Keiichiro Toda, Genki Ishigane, Masato Fukushima, Takuro Ideguchi
Lattice Field Theory
Scalar diquark mass and quark–diquark potential from lattice QCD using the potential method with a static quark
Kai-Wen Kelvin-Lee and Noriyoshi Ishii
We study the scalar diquark mass and the
quark–diquark potential by applying a HAL QCD-inspired potential method to a baryonic system composed of a scalar diquark and a static
quark. The diquark mass is determined self-consistently by requiring that the p-wave baryonic spectrum obtained from two-point correlators be reproduced within the potential framework. Numerical calculations are performed using $2+1$
flavor QCD gauge configurations generated by the PACS-CS Collaboration on a $L^{3} \times T = 32^{3} \times 64$
lattice with $a^{-1} \approx 2.176$ GeV and the pion mass, $m_{\pi} \approx 702$ MeV. From the analysis, we obtain a scalar diquark mass which is close to the naïve constituent
quark estimate $ (2/3)m_{N}$, together with a
quark–diquark potential of the Cornell type (Coulomb + linear). The string tension extracted from the
quark–diquark potential agrees within approximately 5% with that obtained from the static
quark–antiquark potential (Wilson Loop).
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High Energy Physics (Phenomenology)
Constraining ADD black holes at the LHC with $\sqrt{s} = 14$ TeV
Ashfaque Ahmad, Sudhir Kumar Gupta and Abbas Ali
We explore the possibility of the microscopic black hole formation at the Large
Hadron Collider (LHC) in the context of the ADD model, for the centre-of-mass energy $\sqrt{s} = 14~\mathrm{TeV}$ with an integrated luminosity of $349.4~\mathrm{fb}^{-1}$ and provide constraints on the black hole mass, $M_{\mathrm{B}}$ by taking into account the effects of loss during the formation process of black holes through the parameter $\zeta$. Our analysis reveals that for $\zeta = 0$, black holes with $M_{\mathrm{B}} \leq 11.83~\mathrm{TeV}$ are disfavored in the case of three extra dimensions ($\mathcal{D}$), for the reduced Planck scale $\Lambda_{\mathcal{D}}$) of about a few TeV. The corresponding values for $\Lambda_{\mathcal{D}} = 9~\mathrm{TeV}$ turn out to be about $10.33~\mathrm{TeV}$. A significant reduction in the aforementioned limits is bserved while the loss gets higher, e.g. for $\zeta = 0.35$, $M_{\mathrm{B}}$ reduces to $7.65~(6.82)~\mathrm{TeV}$ at $\Lambda_{\mathcal{D}} = 1~(9)~\mathrm{TeV}$. These limits change to $12.03~(10.88)~\mathrm{TeV}$ and $7.80~ (7.03)~\mathrm{TeV}$ respectively for $\zeta = 0~(0.35)$ and $\Lambda_{\mathcal{D}} = 1~ (9)~\mathrm{TeV}$ at 95% CL in case $\mathcal{D}$ is raised to seven.
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Cosmology and Nongalactic Astrophysics
Is dark matter decaying ?
Jeremy Mould
An enduring signature of the decay of unstable dark matter constituents into other particles would manifest as a measurable discrepancy in the matter density parameter (Omega_m) between the recombination era (z ~ 1000) and the local Universe (z = 0). While precision measurements of the
Cosmic Microwave Background tightly constrain the initial matter budget, evaluating this decay hypothesis requires an equally precise audit of the current epoch. We find that current local inventories of baryonic and dark matter are subject to systematic uncertainties - particularly in accounting for the warm-hot intergalactic medium, diffuse intra-cluster media, and the exact profiles of low-mass dark matter
halos - rendering a definitive verdict on late-time dark matter decay currently hard to pin down. Furthermore, existing astrophysical bounds on
cosmic rays, the diffuse gamma-ray background, and reionization history already heavily constrain potential decay channels during this epoch. However, next-generation observational technology is poised to resolve these local accounting gaps. Upcoming high-resolution spectroscopic surveys, next-decade X-ray missions, and advanced weak
lensing campaigns will drastically reduce
baryon and mass-mapping uncertainties, transforming the late-time matter audit into a cleaner, more definitive test.
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Nuclear Theory
Parameter-free deformation variables of the proxy-SU(3) symmetry in even-even actinide, superheavy and hyperheavy nuclei with Z=82-126, N=82-258
Dennis Bonatsos, V. K. B. Kota, Andriana Martinou et al. (+5 more)
Superheavy and hyperheavy
nuclei are one of the frontiers of
nuclear structure nowadays, while also for many actinides rather limited experimental information exists. Therefore, theoretical methods providing parameter-independent predictions for these
nuclei are of particular interest. Such a method is the proxy-SU(3) approximation to the shell model, which has been adequately tested against experimental data in medium-mass and heavy
nuclei up to the rare earth region, and has been found to provide reliable, parameter-independent predictions for the collective deformation variables beta and gamma. Within the proxy-SU(3) approach, the SU(3)
symmetry of the 3-dimensional harmonic oscillator, which is destroyed beyond the sd shell by the strong
spin-orbit interaction, is restored through a
unitary transformation. For each
nucleus, the most symmetric irreducible representation (irrep) allowed by the Pauli principle and the short-range nature of the nucleon-nucleon interaction, called the highest-weight (hw ) irrep in mathematical
language, is found to suffice, except in cases in which the hw irrep turns out to be completely symmetric, so that the next highest weight (nhw) irrep has also to be included. In this article we provide a full collection of the hw and nhw irreps, as well as of the corresponding parameter-free predictions for the deformation variables beta and gamma, for all atomic
nuclei ranging from Z=82, N=82 to Z=126, N=258. Several cases exemplifying the use of the collected results for studying the prolate to oblate shape transition, mirror
symmetries, as well as the
evolution of the collective variables along the valley of stability are also considered.
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All authors Dennis Bonatsos, V. K. B. Kota, Andriana Martinou, S. K. Peroulis, D. Petrellis, P. Vasileiou, T. J. Mertzimekis, N. Minkov
Mathematical Physics · Cross-listed from math.NA
Second order explicit splitting scheme for fluid-poroelastic structure interaction problems
Yifan Wang, Jeonghun Lee and Suncica Canic
Efficient and provably accurate partitioned methods for fluid-poroelastic structure interaction remain challenging because explicit treatment of the Stokes-Biot interface coupling condition can compromise stability. In this work, we develop and analyze a fully discrete, second-order, explicit splitting scheme for the time-dependent Stokes-Biot problem on fixed domains. The method combines BDF2 time stepping with second-order Adams-Bashforth extrapolation of interface data through a Robin reformulation, yielding a partitioned
algorithm in which the Stokes and Biot subproblems are solved independently and in parallel at each time step. The main analytical contribution is a rigorous stability and error analysis for this second-order explicit coupling strategy. Using BDF2 energy identities, a sharp decomposition of the extrapolated interface terms, and discrete trace estimates, we prove a closed stability bound under a
parabolic CFL condition. We then derive an a priori error estimate through a projection-based framework using a Fortin projection for the fluid variables and Ritz-type projections for the poroelastic variables. The analysis identifies consistency defects from BDF2 time discretization, Adams-Bashforth interface extrapolation, and the projected kinematic relation. It shows that the total errors in fluid velocity, structure velocity, pore pressure, and elastic displacement are bounded by C times the sum of the kth power of the mesh size and the square of the time step, for k from 1 to 3, in bulk energy norms. Numerical experiments with manufactured solutions confirm second-order temporal convergence and optimal-order spatial convergence. We also include a moving-domain example with Navier-Stokes fluid flow, demonstrating applicability beyond the fixed-domain Stokes-Biot setting analyzed.
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General Relativity and Quantum Cosmology
Photon surface extensions in general spherical dust collapse
Roberto Giambò and Camilla Lucamarini
We extend the analysis of
photon surfaces in spherical
dust collapse to the general, non-marginally bound case, i.e.\ allowing the energy function $k(x)$ of the Lemaître–Tolman–Bondi (LTB) model to be non-zero. Starting from the dynamical-systems formulation developed in our previous work for the marginally bound case (arXiv:2509.01368 [gr-qc]), we derive the
photon surface equations for the LTB metric with $k(x)\neq 0$, and we recast the
geometric condition for a timelike hypersurface to be a
photon surface as a non-autonomous first-order dynamical system. Even though the LTB
evolution equation does not integrate inclosed form when $k(x)\neq 0$, the implicit solutions available in the literature, together with comparison
theorems for ordinary differential equations, are sufficient to reduce the problem to a single scalar equation, governed by one quantity which vanishes identically for homogeneous data. Using this reduction we show that the extension of the exterior
photon sphere $r=3M$ into the collapsing cloud is unique, and null, if and only if the central singularity is covered. When the singularity is naked, uniqueness fails: besides the null hypersurface there exists a one-parameter family of genuinely timelike
photon surfaces matching $r=3M$, all of them reaching the central singularity. The threshold separating the two behaviours coincides with the one separating black hole and naked singularity end states. We also show that the null
photon surface reaches the central singularity if and only if the singularity is naked. The structural dichotomy between the naked and covered end states is discussed in connection with possible observational signatures in the early-time
evolution of black-hole shadows.
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Materials Science
MinSurf: resolving the atomic-scale stability landscape of mineral surfaces
Fengzijun Pan, Zhoulin Liu, Pingyang Zhang et al. (+4 more)
Mineral surfaces govern interfacial reactivity in carbon mineralization, geo-energy storage, contaminant immobilization, heterogeneous catalysis and electrochemical interface engineering. Yet atomistic simulations often rely on commonly used facets or facet-level stability criteria, while distinct atomic terminations of the same crystallographic orientation are rarely resolved systematically because experimental characterization and density functional theory (DFT) calculations remain costly across large surface spaces. Here we present MinSurf, a high-throughput framework that resolves mineral surface selection as a surface-energy and morphology problem. MinSurf integrates surface enumeration, DFT labelling, machine-learning interatomic potentials and Wulff construction to predict stable terminations, surface-energy landscapes and
equilibrium crystal morphologies. Applied to ten representative minerals, MinSurfSet comprises 764 surface slabs, with 90 corresponding oriented unit
cells constructed as bulk references for surface-energy evaluation. The resulting MinNEP model predicts DFT surface energies with a mean absolute error of 0.0119 eV per Angstrom squared and achieves an overall acceleration of 1.14 x 10^4 relative to DFT. MinNEP preserves the DFT-derived morphology-determining surface-energy hierarchy and reproduces the dominant Wulff-exposed facets, while X-ray diffraction provides an independent crystallographic consistency check for alpha-quartz
benchmark. By linking atomic terminations, surface energies and
equilibrium morphologies, MinSurf provides reproducible and physically representative surface models for high-throughput simulations of mineral interfaces across energy, environmental and advanced inorganic materials.
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All authors Fengzijun Pan, Zhoulin Liu, Pingyang Zhang, Jiaqiu Xu, Zepeng Fan, Dawei Wang, Jianzhong Pei
Quantum Physics
Robust Generation of Topological Biphoton Mode via Adiabatic Passage
Jaesung Lim, Jihwan Kim, Dong-Gil Im et al. (+4 more)
Topological waveguide arrays support robust mode propagation in the presence of fabrication imperfections, providing a significant advantage for on-chip
quantum information processing. However, this robustness does not fully extend to nonlinear biphoton generation. Structural disorder can enhance the excitation of non-topological biphoton modes during nonlinear interactions, which degrades the
quantum properties of the generated state. To overcome this limitation, we propose an adiabatic passage that connects an isolated site to a topological defect array. By initiating the nonlinear process in a strongly isolated regime, nonlinear coupling to unwanted modes is effectively suppressed, thereby preserving the Schmidt number of the generated state. The subsequent adiabatic connection facilitates the high fidelity transfer of the generated biphoton into the topological biphoton mode. Our numerical simulations demonstrate that, unlike conventional topological structures, the adiabatic scheme maintains both high biphoton fidelity and a unit Schmidt number in the presence of waveguide gap disorder. Furthermore, we show that this robustness extends to path entangled NOON states, achieving a near-unity
quantum interference visibility. Our approach provides a practical design strategy for disorder-tolerant integrated
quantum photonic devices.
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All authors Jaesung Lim, Jihwan Kim, Dong-Gil Im, Kyungdeuk Park, Dongkyu Kim, Yonggi Jo, Yong Sup Ihn
Mesoscale and Nanoscale Physics
Boltzmann-constrained extraction of spin splitting and momentum relaxation in d-wave altermagnets
Y. X. Gao, Z. W. Fan, Q. S. Yao et al. (+2 more)
Altermagnets exhibit
spin-split electronic structure without requiring
spin-orbit coupling, but transport measurements generally mix intrinsic
spin splitting with extrinsic scattering. We examine this identifiability problem for a two-dimensional d-wave altermagnet within a unified semiclassical framework spanning ballistic to diffusive transport. The
spin-dependent
Fermi-surface anisotropy produces a pronounced size effect, where vastly different longitudinal velocities cause the two
spin channels to exhibit markedly different effective relaxation lengths within the same device geometry. However, the altermagnetic coupling $\alpha$ and the momentum relaxation time $\tau_0$ strongly compensate each other in longitudinal conductance, creating a severe parameter degeneracy. To lift this degeneracy, we formulate a physics-informed neural network (PINN) to act as a differentiable Boltzmann solver that strictly enforces contact injection, local particle conservation, and global current continuity. Driven by sparse conductance spectra, this neural solver leverages the
Fermi-level dependence of transport to unlock the coupled parameters simultaneously, achieving sub-percent accuracy even under moderate measurement noise. These results show that combining the
Fermi-level dependence of transport with strict physical constraints provides a robust route to separating
spin splitting from scattering in altermagnetic conductors.
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All authors Y. X. Gao, Z. W. Fan, Q. S. Yao, Y. D. Ji, H. Geng
High Energy Physics (Experiment)
Towards Engineering Scaling Laws with Pretraining Data Composition
Jan-Lucas Uslu, Kevin Greif, Daniel Whiteson et al. (+1 more)
Neural scaling laws describe how model performance improves as a power law in compute, model size, and
dataset size. While well-established for large
language models, these relationships are emerging for large models in particle physics. As with
language, empirical studies show that the performance scales as a power law. However, unlike natural
language or image domains, fundamental physics has high-fidelity simulators that produce synthetic data cheaply. This favors scaling regimes where additional data is cheaper than additional parameters, and allows the pretraining
dataset itself to be engineered to influence the scaling. For the task of classifying hadronic jets produced in collisions of high-energy particle beams, we show that the scaling behavior can be engineered towards requiring more data rather than larger models by inclusion of pretraining data which is more diverse and better aligned with the downstream classification task.
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All authors Jan-Lucas Uslu, Kevin Greif, Daniel Whiteson, Benjamin Nachman
Materials Science
Thickness-Dependent Interlayer Coupling and Semiconductor-to-Semimetal Crossover in Arsenene Multilayers
Jeonghwan Ahn, Seoung-Hun Kang and Jaron T. Krogel
Interlayer interactions in layered materials are often assumed to transfer from the
bilayer to the bulk, but this assumption can fail when chemically active out-of-plane orbitals participate in bonding. We combine
diffusion quantum Monte Carlo (DMC) and density functional theory (DFT) to determine how interlayer coupling evolves in arsenene multilayers. DMC shows that bulk gray arsenic is compact, whereas the corresponding few-layer structures remain at substantially larger interlayer separations despite sharing the same nominal A$_{1}$B$_{-1}$ adjacent-layer registry. Registry alone therefore does not determine the bonding regime; thickness and coordination reshape the interlayer interaction. Among the tested functionals, SCAN+rVV10 most closely reproduces DMC
equilibrium separations and stacking energetics. Using the DMC-benchmarked SCAN+rVV10 calculations, we predict a thickness-driven stacking sequence from A$_{1}$A$_{1}$ to A$_{1}$B$_{1}$ and finally bulk-like A$_{1}$B$_{-1}$. The structural crossover coincides with a stacking-dependent DFT band-gap collapse driven by enhanced interlayer As p$_{z}$ hybridization.
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Atmospheric and Oceanic Physics
A Stochastic-Thermodynamic Constraint on the Seasonal Phase Locking of the El Niño-Southern Oscillation
Yuki Yasuda and Tsubasa Kohyama
We investigate the seasonal phase locking of the El Niño-Southern Oscillation (ENSO) in a linear
stochastic recharge oscillator (SRO), a damped oscillator with additive noise and a time-dependent growth rate. Phase locking is reflected in the seasonality of the variance of the sea surface temperature anomaly (SSTA). In general, energy drives such a change, whereas
entropy governs whether it occurs; phase locking is thus subject to both an energy- and an
entropy-based constraint. We quantify this
entropy-based constraint using a thermodynamic uncertainty relation (TUR), a fundamental inequality in
stochastic thermodynamics. The TUR constrains the tendency of the SSTA variance by the partial
entropy production rate, which is dominated by the ratio of forward and backward transition probabilities and quantifies the irreversibility of SSTA transitions. The growth rate governs this irreversibility: its extrema occur in boreal autumn and late winter, and the
entropy production rate peaks at both times. These peaks relax the TUR constraint on the tendency of the SSTA variance, so that the variance itself can peak in boreal winter, consistent with observed ENSO phase locking. Conversely, when irreversibility is insufficient, ENSO cannot grow or decay. If this irreversibility were interpreted as dissipated energy, the constraint on ENSO growth and decay would require this dissipation to be exported from the equatorial Pacific. A more realistic model is needed to test this hypothesis and to further explore the physical connection between
entropy and dissipated energy.
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Physics and Society
Have Data Centers Raised Your Electric Bill? Causal Evidence from the United States
Asa Watten, John Bistline and Geoffrey Blanford
We estimate that data centers caused average retail electricity rates to fall modestly in the United States from 2015 to 2024 using an instrumental variables approach. Despite prevailing sentiment, the finding is consistent with economic
reasoning: existing large power system fixed costs, economies of scale in transmission and distribution, and declining unit costs for generation imply that durable demand growth lowers average prices. We find patterns of economies of scale for transmission, distribution, and generation costs as well as within and across retail customer classes. We caution that future supply constraints could reverse the effect.
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General Relativity and Quantum Cosmology
Polarization-Dependent Photon Propagation, Quasinormal Modes, and Gravitational Lensing in Higher-Curvature Effective Theories
Takamasa Kanai
We investigate the impact of higher-
curvature corrections on
photon propagation within an effective field theory framework and their observational consequences in strong gravitational fields. We consider polarization-dependent modifications to
photon trajectories in static and spherically symmetric spacetimes, focusing on Schwarzschild and Reissner–Nordström black hole backgrounds. Using the geometrical optics approximation, we derive the effective metrics governing
photon propagation and study the resulting polarization-dependent shifts of the
photon sphere. We compute the corresponding quasinormal modes in the eikonal limit and analyze their polarization dependence. We further investigate gravitational
lensing, focusing on polarization-dependent corrections to the deflection angle in both weak- and strong-field regimes. In the strong-deflection regime, we find that even perturbatively small EFT corrections modify the coefficient of the logarithmically divergent part of the deflection angle, resulting in a potentially observable difference from the uncorrected case. This suggests that strong gravitational
lensing may provide a sensitive probe of small higher-
curvature corrections. While extracting EFT information directly from QNM frequencies is more subtle, QNMs may provide complementary information to gravitational
lensing in future studies. Our results establish a framework for probing higher-
curvature effects through polarization-dependent strong-field observables.
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Optics
\mu-MOPA Architecture for Photonic Integrated Solid State Laser
Yu Guo, Yubo Wang, Haoqi Zhao et al. (+4 more)
Diode-pumped solid-state (DPSS)
lasers play a central role in modern photonics owing to their exceptional efficiency and ability to extend spectral coverage beyond the reach of
semiconductor diodes. These attributes have enabled breakthroughs in precision metrology,
quantum optics, and coherent communications. However, bringing the proven advantages of DPSS gain media such as Nd:YAG onto an integrated photonic platform has remained difficult, largely due to inefficient pump utilization and limited power-scaling in chip-scale implementations. Here, we demonstrate the first photonic-integrated Nd:YAG
laser-amplifier system that overcomes these challenges with a micro-chip based master-oscillator-power-amplifier (\mu-MOPA) architecture. The seed
laser, employing a double-resonant microring resonator, could reach a threshold as low as 2.9 \mu W. The single-pass waveguide amplifier, when optimized separately, provides up to 46.6 dB small-signal gain. Combining the low-threshold seed with cascaded waveguide amplifiers, the integrated \mu-MOPA delivers more than 12 dBm of amplified continuous-wave output power. These results establish Nd:YAG waveguide integration as a practical route to compact and high-performance solid-state light sources.
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All authors Yu Guo, Yubo Wang, Haoqi Zhao, Fengyan Yang, Guangcanlan Yang, Hao Xie, Hong X. Tang
Medical Physics · Cross-listed from eess.IV
Contour-Constrained Deformable Registration with Parameter Characterization for Head and Neck Surgical Guidance
Qingyun Yang, Jon S. Heiselman, Ayberk Acar et al. (+5 more)
With 890,000 annual new cases globally, head and neck squamous
cell carcinoma has one of the highest recurrence rates among solid malignancies. Although frozen section analysis is the standard of care for intraoperative margin assessment, accurately relocating detected positive margins on the resection bed remains challenging due to imprecise
alignment between resected specimens and their resection bed, compounded by post-resection mucosal tissue shrinkage. We present a biomechanics-driven deformable registration framework that corrects post-resection tissue deformation to provide intraoperative guidance. Our approach registers 3D specimen meshes to intraoperative resection bed point clouds using a deformable registration approach based on regularized Kelvinlet basis functions. The registration matches surface point clouds, fiducial landmarks, and boundary contour constraints that directly penalize perpendicular distance-to-agreement between specimen and resection bed boundaries. Across nine specimens from skin, buccal mucosa, and tongue sites, the overall mean target registration error was $11.11 \pm 4.07$ mm using rigid registration, which decreased to $8.20 \pm 2.68$ mm (26.19% reduction) using deformable registration without contour constraint. The proposed contour-constrained deformable registration further reduced the error to $5.62 \pm 2.28$ mm, a 49.41% reduction relative to rigid registration. We observed the largest reduction in the most clinically challenging tongue specimens. We also performed a systematic two-stage parameter search to characterize the relative importance of surface
alignment, fiducial correspondences, contour constraint, and strain energy regularization. This search revealed that contour weighting dominates registration accuracy for tissue types with large lateral deformation, while the
algorithm operates over a broad range of parameter combinations.
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All authors Qingyun Yang, Jon S. Heiselman, Ayberk Acar, Morgan J. Ringel, Michael I. Miga, Matthieu Chabanas, Michael C. Topf, Jie Ying Wu
Instrumentation and Detectors
Operational characterization of LAPPD Generation 2: charge sharing, delayed pulses, and dark-count behavior
S.-W. Stradleigh, J.A. Foot, R. Zhang et al. (+1 more)
We present a study of charge sharing and electronic cross-talk in second-generation Large-Area Picosecond Photodetectors (LAPPD Gen 2). The LAPPD is a
vacuum-based device consisting of a photocathode, two microchannel plates, and a resistive anode that capacitively couples to an 8 $\times$ 8 pixelated readout board (25.4 mm $\times$ 25.4 mm pixel area). Using a picosecond pulsed
laser, we measure signal distributions across the resistive anode and quantify coupling between target and neighboring pixels. We further examine the relationship between dark-count rate and LAPPD voltage settings, identifying decay behavior characterized by fast, intermediate, and slow relaxation timescales. We additionally observe the LAPPD behaving as a resonant cavity by injecting electrical pulses into the readout board. To further interpret observed signals, we develop a pulse-classification method and identify additional features at approximately 60 ns and 110 ns. Finally, we implement a first-principles Monte Carlo simulation to model the radial and temporal distributions of observed signals, including contributions from electron backscatter and potential ion afterpulsing. The simulation shows reasonable agreement with the experimentally derived pulse classifications.
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All authors S.-W. Stradleigh, J.A. Foot, R. Zhang, V.A. Li
Quantum Physics
Sparse positive maps on qutrits with exact nondecomposability thresholds and PPT-entanglement transitions
Davide Poderini, Angela Rosy Morgillo, Fabio Benatti et al. (+3 more)
We study a family of sparse positive maps on qutrits for which positivity, decomposability, and PPT
entanglement can all be analysed explicitly. The block structure of the associated Choi
matrices reduces positivity to a Hermitian biquadratic form and leads to exact positivity boundaries for three representative parametric families. For the same families we determine the exact transition between decomposable and non-decomposable maps and construct associated PPT states of two classes. The first consists of witness-adapted deformations naturally tied to the non-decomposability analysis. The second consists of analytically tractable families whose full PPT-entangled branch is detected by fixed positive maps, yielding exact thresholds between separability and bound
entanglement. For the trace-preserving subclass, we further compare positivity with a recent
eigenvalue bound for 2-positive maps, thereby making the gap between positivity and higher-order positivity fully explicit within this family.
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All authors Davide Poderini, Angela Rosy Morgillo, Fabio Benatti, Fabio Anselmi, Chiara Macchiavello, Massimiliano F. Sacchi
General Relativity and Quantum Cosmology
Graviton Floor
Himeka Matsuo, Asuka Ito, Kazunori Kohri et al. (+2 more)
It has been observed that the Universe is permeated by the
cosmic photon background, ranging from
radio waves to gamma rays. We investigate the conversion of the
photon background into gravitons in the presence of background
magnetic fields in the Milky Way
Galaxy and in blazar jets. We find that the resulting graviton background is dominated by the contribution generated in blazar jets. Importantly, this graviton background constitutes a graviton floor for high-frequency gravitational wave detectors searching for new physics, analogous to the
neutrino floor.
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All authors Himeka Matsuo, Asuka Ito, Kazunori Kohri, Teruaki Suyama, Ryutaro Tomomatsu
Astrophysics of Galaxies
Evolution of starless cores in massive clumps seen by the ALMA ASHES and QUARKS surveys
Dongting Yang, Hong-li Liu, Sheng-li Qin et al. (+28 more)
We present a systematic comparative analysis of 324 starless cores in early-phase infrared-dark clouds (IRDCs; ASHES survey) and evolved-phase infrared-bright clouds (IRBCs;
QUARKS survey) using 1.3 mm continuum and line data by the Atacama Large Millimeter/submillimeter Array (ALMA). Despite having comparable sizes ($\sim$2500 au),starless cores in IRBCs exhibit systematically higher median mass ($1.5\,M_{\odot}$ vs. $0.6\,M_{\odot}$), number density, and surface density–enhancements of approximately a factor of two relative to starless cores in IRDCs. Starless cores in IRBCs also display relatively stronger non-thermal motions ($\rm\sigma \sim 0.5\,km\,s^{-1}$ vs. $\rm0.3\,km\,s^{-1}$), higher total virial parameters (median $\alpha_{\mathrm{vir,tot}} \sim$ 2.3 vs. 1.0), and steeper density profiles, indicating more centrally concentrated structures in feedback-driven,
turbulence-enhanced environments. These findings support a dual evolutionary origin: (i) new core formation in evolved IRBCs under altered initial conditions, and (ii) subsequent dynamical mass growth via
accretion from extended reservoirs. The prevalence of low-mass starless cores–even in late-stage IRBC environments–challenges models requiring massive prestellar cores and instead favors competitive-like dynamical mass
accretion scenarios for high-mass
star formation.
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All authors Dongting Yang, Hong-li Liu, Sheng-li Qin, Tie Liu, Wenyu Jiao, Guido Garay, Patricio Sanhueza, Fengwei Xu, Lei Zhu, Sami Dib, Xindi Tang, Amelia Stutz, Xiaofeng Mai, Siju Zhang, A.Y. Yang, Anandmayee Tej, Shanghuo Li, Xunchuan Liu, Pablo Garc{\i}a, Mika Juvela, James O. Chibueze, Prasanta Gorai, kee-tae Kim, Chang Won Lee, Tapas Baug, Swagat Ranjan Das, Shivani Gupta, Jihye Hwang, Leonardo Bronfman, Archana Soam, L. K. Dewangan
Chemical Physics
Variational Polaron Theory for Ground States of Strongly Coupled Light-Matter and Electron-Phonon Systems
Nguyen Thanh Phuc
Strong light-matter and electron-
phonon coupling generate ground states dressed by virtual bosonic excitations, making bare-state truncations and perturbative treatments unreliable in the ultrastrong-coupling regime. We introduce a nonperturbative variational ground-state framework based on a state-dependent polaron transformation, combined with a product-state ansatz and a second-order perturbative correction for residual matter-
boson entanglement. We show that the optimized transformed frame becomes asymptotically decoupled at infinite coupling, because the leading linear coupling is canceled while off-diagonal matter transitions are suppressed by displaced-oscillator overlaps. The approach is asymptotically correct in both weak- and strong-coupling limits and remains accurate in the intermediate regime, where fixed polaron transformations are least reliable. Dicke-model
benchmarks reproduce ground-state energies, fidelities, and the superradiant transition, with second-order energy errors below 0.2%. Holstein-model
benchmarks yield errors below 0.5% and clarify how translational
symmetry affects wave-function quality. This dressed-basis framework enables nonperturbative modeling of strongly coupled light-matter and electron-
phonon systems.
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