Quantum Gases
Front-based construction of quantum droplets, bubbles, and hole states in a Bose mixture
Sherzod R. Otajonov and Fatkhulla Kh. Abdullaev
We study nonlinear holes, bubbles, kink fronts, and
quantum-droplet-like states in an elongated Bose mixture governed by an extended Gross-Pitaevskii equation with attractive cubic mean-field interactions and repulsive quartic Lee-Huang-Yang contribution. We classify the constant-amplitude backgrounds: the Bogoliubov-de Gennes spectrum shows that the upper branch is modulationally stable, whereas the lower branch is unstable to long-wavelength perturbations. Grand-potential and pressure determine the
vacuum-finite-density coexistence point and the unique background supporting stationary kink and antikink fronts. Symmetric holes on the stable background have a density deficit and integral width that diverge near coexistence as the hole separates into two nonlinear fronts. A multiplicative kink-antikink construction connects bell-shaped states to broad flat-top droplets and approaches the stationary
quantum-droplet family as the front separation increases. An antikink-kink sum with equal signs generates bubble-like density depletions without a phase jump, whereas their difference produces dark-hole-like profiles with a $\pi$ phase difference between the asymptotic backgrounds. Bubble depth increases with front separation, distinguishing gray-like and dark-like profiles. Real-time simulations show that deep bubbles persist under weak random perturbations, demonstrating finite-time robustness without establishing spectral stability. In the asymmetric two-component model, localized relative-density modes can induce spinor-driven breakup on a modulationally stable background, while robust holes persist near the kink limit. Collisions of kink-antikink droplet-like states display phase-dependent merging, asymmetric particle transfer, and effective reflection. These results connect nonlinear fronts with bubbles, phase-jump holes, and self-bound droplets in beyond-mean-field Bose mixtures.
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High Energy Astrophysical Phenomena
Long-term X-ray variability of the NLS1 Ark 564
Neha P R, Nikita S Arun, Savithri H. Ezhikode et al. (+4 more)
We present a systematic spectral study of the X-ray emission from the Narrow- Line Seyfert 1 (NLS1)
galaxy Ark 564 using Swift/XRT observations spanning sixteen years. The source exhibits significant variability in both the soft and hard X-ray bands, along with a strong positive correlation between them, indicating a closely coupled emission mechanism within the
accretion flow-corona system. A simple absorbed power-law model is statistically insufficient to describe the spectra, confirming the presence of an additional soft component. To investigate the origin of the soft excess, we performed multi-model spectral fitting. Incor- porating a warm Comptonization component yields a statistically improved fit, supporting the scenario in which the soft excess arises from Comptonization in a warm, optically thick corona. We also applied a relativistic reflection model to representative observations; however, given the moderate spectral resolution and limited high-energy coverage of Swift/XRT, the current data do not allow us to robustly determine whether reflection provides a superior or physically preferred description. Our results indicate that warm Comptonization offers a consistent explanation for the observed soft excess in Ark 564 within the limitations of the available data, while deeper broadband observations are required to defini- tively distinguish between competing models and comprehensively characterise the long-term X-ray spectral variability of the source
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All authors Neha P R, Nikita S Arun, Savithri H. Ezhikode, Ranjeev Misra, Bari Maqbool, Jeena K, Joe Jacob
Solar and Stellar Astrophysics
BS Cassiopeiae: A Contact Binary with Starspot-Driven Variability and Evidence for Additional Components
Min-Ji Jeong, Chun-Hwey Kim, Kyeongsoo Hong et al. (+5 more)
We present a comprehensive photometric and spectroscopic analysis of the contact eclipsing binary BS Cas, based on 22-yr multi-site light curves and 2-yr high-resolution spectra. The long-term photometry shows pronounced year-to-year changes in the light-curve shape, including eclipse-depth reversals between the primary and secondary minima and variations in the O'Connell effect. The first double-lined radial-velocity (RV) curves of BS Cas are derived from the spectra using broadening-function (BF) profiles. Sharp peaks absent from the 2018 BFs appear in the 2020 BFs, suggesting an additional component along the same line of sight as BS Cas. Simultaneous modeling of the BVR light curves and the RVs shows that BS Cas is a contact binary in which the more massive component is cooler than its less massive companion, with a mass ratio of 2.515 and a fill-out factor of 32.3%. Multi-epoch modeling suggests that the long-term photometric variations arise from evolving starspots and changes in the third-light contribution. The eclipse-timing variation diagram confirms a secular orbital period decrease at a rate of $-2.305 \times 10^{-7}~\mathrm{days\,yr^{-1}}$ consistent with angular momentum loss and mass transfer, along with an 18.376-yr modulation interpreted as a light-travel-time effect from a third body. The TESS timings reveal anti-correlated variations between the primary and secondary minima that appear to result from differential rotation of high-latitude starspots. These results suggest that BS Cas is a physically complex contact binary in which long-term photometric and eclipse-timing variations reflect multiple processes, including
magnetic activity and the influence of a third body.
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All authors Min-Ji Jeong, Chun-Hwey Kim, Kyeongsoo Hong, Mi-Hwa Song, Hye-Young Kim, Jang-Ho Park, Cheongho Han, Joh-Na Yoon
Superconductivity
Topological Superconducting Phases in a Strained Altermagnet-Superconductor Heterostructure
Keita Yoshizawa, Ryo Okugawa and Takami Tohyama
We investigate topological superconductivity in a
heterostructure consisting of a two-dimensional $s$-wave
superconductor and a $d$-wave altermagnet with Rashba
spin-orbit coupling. In particular, we study the effects of strain and hopping anisotropy on the topological superconducting phases. By calculating the Chern number, we obtain topological phase diagrams as functions of the chemical potential and the strength of the effective
magnetic field induced by the
magnetic proximity effect. We find that strain-induced
lattice distortion allows topological superconducting phases to emerge over a broad parameter region. Our findings suggest that strain that lowers
symmetry can serve as a route to realizing topological superconductivity in altermagnet-
superconductor heterostructures.
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Mesoscale and Nanoscale Physics
Observation of the electronic Pomeranchuk effect in generalized Wigner crystals of twisted MoS$_2$
Xinjie Fang, Linfeng Wu, Naitian Liu et al. (+9 more)
Moire superlattices in transition metal dichalcogenides provide a highly tunable platform for exploring strongly correlated electronic phases, such as generalized Wigner
crystals. While these crystalline states typically melt with increasing thermal fluctuations, an electronic analogue of the Pomeranchuk effect can stabilize the localized solid phase at elevated temperature through isospin
entropy. Here, we report the observation of an electronic Pomeranchuk effect at the fractional filling factors of $\nu = 1/3$ and $\nu = 1/4$ in AB-stacked twisted
bilayer MoS$_2$ with twist angles of 4.1$^\circ$ and 3.9$^\circ$, respectively. At ultra-low temperature, the system exhibits a highly conducting, itinerant behavior at these fractional fillings, characteristic of a compressible
Fermi-
liquid ground state. Upon heating, the system exhibits a counterintuitive increase in the longitudinal resistivity, signaling an isospin-
entropy-driven transition into a localized generalized Wigner
crystal state. Our findings highlight the unique capacity of flat bands in twisted
bilayer MoS$_2$ for stabilizing highly degenerate
magnetic configurations, offering new insights into the thermodynamic phase diagrams of low-dimensional correlated systems.
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All authors Xinjie Fang, Linfeng Wu, Naitian Liu, Le Zhang, Wenqiang Zhou, Jing Ding, Zhangyuan Chen, Hanxiao Xiang, Yue Xiao, Kenji Watanabe, Takashi Taniguchi, Shuigang Xu
Applied Physics
FSSDataBase: a reconstructable dataset of simulated frequency-selective surface structures and scattering responses
Xinke Kuang, Shiyun Ma, Yuanyuan Wang et al. (+1 more)
Data-driven design of frequency-selective surfaces (FSSs) requires reusable
datasets that link structural geometry to electromagnetic response under documented simulation conditions. Here we present FSSDataBase, an openly available collection of 5,000 procedurally generated single- and multilayer FSS unit
cells simulated using Ansys HFSS. The
dataset covers 10-20 GHz with transverse-electric and transverse-
magnetic relfection and transmission responses, including magnitude and phase, for recorded incidence angles of $0^{\circ}$ and $30^{\circ}$. Each record links binary structural masks and JSON-based reconstruction metadata to raw response samples and derived magnitude labels. Structural descriptors, response-distance measures and task-oriented cost functions characterize
geometric and electromagnetic variation and support screening for polarization stability, angular-selective bandwidth and matched-amplitude, 180{\deg} phase-separated structure pairs. Accompanying code supports model reconstruction, data processing and configuration-driven generation of additional samples. Beyond conditional forward modelling and response-based structure
retrieval, FSSDataBase has the potential to serve as a reference
dataset for deep-learning-based FSS inverse design, supporting fair comparisons across network architectures under shared data splits,input conditions and evaluation protocols.
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All authors Xinke Kuang, Shiyun Ma, Yuanyuan Wang, Jiang Wu
Earth and Planetary Astrophysics
Pulsed Accretion onto Eccentric Binaries in Highly Misaligned Circumbinary Disks
Ruiqi Yang, Jeremy L. Smallwood, Shang-Fei Liu et al. (+1 more)
We present three-dimensional smoothed particle hydrodynamics simulations of highly misaligned circumbinary disks (CBDs) around moderately eccentric equal-mass binaries ($e_\mathrm{b}=0.5$). We show that the binary
accretion is modulated on the binary orbital period and exhibits two pulses near periastron. The dominant pulse peaks before periastron for an initial binary-disk misalignment of $60^\circ$, shifts to after periastron at $90^\circ$, and occurs at an even later post-periastron phase at $120^\circ$. We further show that the two pulses are accompanied by a time-dependent response of the circumstellar disks (CSDs) and by different distributions of accreting material within the cavity and around the CSDs. The qualitative pre- versus post-periastron distinction is also present in individual binary orbits despite variations in pulse amplitude. Our results motivate future tests of whether pulse timing is related to binary-disk orientation.
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All authors Ruiqi Yang, Jeremy L. Smallwood, Shang-Fei Liu, Alessia Franchini
Materials Science
A hydrogen-informed Rice-Beltz model for crack-tip dislocation emission under mixed-mode loading
Kai Zhao
The fundamental competition between crack-tip cleavage and dislocation emission dictates the ductile-to-brittle transition in crystalline solids. In hydrogen-charged environments, this delicate balance is disrupted, yet existing models often struggle to self-consistently capture the atomic-scale thermomechanical modulation of the emission barrier. Here, we propose the hydrogen-informed Rice-Beltz framework to quantify the critical stress intensity factors (SIFs) required for initial dislocation nucleation under mixed-mode (I+II) loading. By integrating the elastic interaction of the dilatational field of interstitial hydrogen and the applied stress fields against the incipient dislocation core, the model recovers the non-monotonic relation between the most probable SIF and the hydrogen concentration. Unlike the classical pure mode-I (or mode-II) scenario, the minimization of the local strain energy density is employed to generate closed-form nominal driving forces, which are subsequently embedded into a transition-state-theory framework. This atomistically-informed approach yields the most probable SIF for the first dislocation emission event as a function of the loading rate, slip angle, and hydrogen concentration, providing a rigorous, parameter-free boundary condition for the onset of hydrogen-modulated crack-tip plasticity.
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Instrumentation and Detectors
Parnassus for the CLD Detector: A Generative Machine-Learning Surrogate for Detector Simulation and Reconstruction at the FCC-ee
Umar Sohail Qureshi, Benjamin Nachman and Caterina Vernieri
Detector simulation and event reconstruction will be computationally expensive for future $e^+e^-$
collider programs and are currently critical bottlenecks for accurate feasibility studies. To address this challenge, we build a Parnassus model for the CLD detector concept. Parnassus is a framework for automatically tuning a surrogate model, in our case, a conditional flow matching neural network, to emulate a full detector simulation and reconstruction. We train on $e^+e^-\to Z\to q\bar q$ events at $\sqrt{s}=91.2$ GeV processed through a Geant4 simulation of the CLD detector concept and the Pandora particle-flow reconstruction and reproduce single-particle kinematics, particle-IDs, and impact-parameter distributions. We also examine jet- and event-level features, inclusively and split by
flavor, and find excellent fidelity, significantly better than the parameterized program Delphes. Furthermore, we train a
transformer-based
flavor tagger on the reconstructed particle-flow constituents and show that the surrogate preserves the $b/c/s/q$ discrimination of the full CLD reconstruction. The Parnassus CLD model achieves a generation cost of about 1.2 ms (40 ms) per event on a single GPU (CPU), over three (two) orders of magnitude faster than full simulation and reconstruction. Our model is publicly available for feasibility and design studies.
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Chemical Physics
Efficient Spin-Orbit Coupling in Algebraic Diagrammatic Construction Theory: A State-Interaction Approach
Nicholas Yiching Chiang, Rajat Majumder, Terrence L. Stahl et al. (+2 more)
Spin-orbit coupling and electron correlation play important roles in a broad range of chemical and physical phenomena. In this work, we systematically assess the performance of single-reference algebraic diagrammatic construction combined with state interaction (SI-ADC) for describing electronic structure in the presence of
spin-orbit coupling. We find that second-order SI-ADC methods (SI-ADC(2)) achieve zero-field-splitting accuracies comparable to those of higher-level and more computationally demanding approaches, including variational four-component ADC and two-component ADC methods based on
spin-orbit effective
Hamiltonians. We further demonstrate the broad applicability of SI-ADC by evaluating a diverse range of
spin-orbit-coupled properties, including electron affinities, ionization potentials, neutral excitation energies, core-ionization energies, and
magnetic g-tensors, for systems ranging from small molecules to transition-metal complexes and f-block compounds. Across these applications, SI-ADC(2) methods provide consistently accurate results, likely benefiting in part from favorable error cancellation between electron-correlation and
spin-orbit effects. In contrast, SI-ADC(3) methods are generally less accurate, particularly for systems containing transition-metal and heavy elements. Overall, these results establish SI-ADC as an efficient and broadly applicable framework for incorporating
spin-orbit coupling into ADC calculations of electronic and spectroscopic properties.
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All authors Nicholas Yiching Chiang, Rajat Majumder, Terrence L. Stahl, Ning-Yuan Chen, Alexander Yu. Sokolov
Solar and Stellar Astrophysics
A Sample of Long-Period Binaries with Dormant Compact-Object Candidates from LAMOST DR13 MRS and Gaia DR3
Junxing Zhou and Wei-Min Gu
Identifying dormant compact objects in non-interacting binaries is crucial for constraining the hidden population of
stellar remnants. We present a systematic search for long-period compact-object candidates by combining
Gaia DR3 astrometry with multi-epoch LAMOST DR13 medium-resolution spectroscopy. Starting from sources with elevated RUWE values, we required at least five LAMOST spectroscopic epochs and peak-to-peak RV variations exceeding 20 km/s. After RV extraction, orbital fitting, and subsequent screening, we obtained
Bayesian Keplerian orbital solutions for 19 long-period single-lined binary candidates, with periods spanning approximately 30-1500 days. Multi-wavelength spectral energy distribution fitting was used to constrain the visible
stars and evaluate the expected luminosities of unseen companions under a main-sequence assumption. Two systems are identified as the highest-priority compact-object candidates in our sample, each with a minimum companion mass exceeding 1
solar mass. Their spectra and optical-to-infrared photometry show no detectable secondary-light contribution, although such a contribution would be expected if the unseen companions were normal main-sequence
stars. These systems therefore represent the strongest compact-object candidates in our sample, although further observations are required to distinguish massive white
dwarfs or
neutron stars from faint
stellar companions or unresolved hierarchical systems. We also identify five intermediate-priority and 12 lower-priority systems for follow-up spectroscopy, ultraviolet imaging, and future astrometric constraints.
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Quantum Physics
A Generalized Stein Lemma for Quantum Channels
Minbo Gao, Zhengfeng Ji and Chenghua Liu
We prove a generalized
quantum Stein lemma for parallel discrimination of an arbitrary finite-dimensional channel against families of alternative channels. The alternatives are compact and convex, closed under tensor products, and contain a faithful replacer. At every fixed type-I error tolerance, the optimal type-II error exponent equals the regularized Umegaki channel relative
entropy minimized over the alternatives, and both defining limits exist. Inputs may be entangled across channel uses and with a reference system. The main technical result constructs exactly trace-preserving approximations with exponentially small diamond error, dominated in completely positive order by free channels at every rate above the common exponent. The proof combines uniform auxiliary map approximation, iterative reduction of the domination rate, and tensor amplification. It yields asymptotic equipartition with trace-preserving smoothing at every subexponentially vanishing error, an exponential strong converse, and stability under vanishing diamond-norm perturbations. Under additional permutation invariance and closure under insertion of a fixed faithful input state and discarding of its output, we also prove an explicit finite-block completion bound. This quantitative construction uses weighted discarding, local operator corrections, and comparison with auxiliary extensions. Applications include state-preserving, coherence-restricted, covariant,
entanglement-breaking, and positive-partial-transpose channels. For isometric targets against
entanglement-breaking or positive-partial-transpose alternatives, we obtain exact finite-block testing and smoothing formulas.
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High Energy Physics (Theory)
Genuine Multi-Entropy of Fully Symmetric Gaussian States
Hugo A. Camargo and Mitsuhiro Nishida
We study the tri-partite genuine Rényi multi-
entropy of fully symmetric Gaussian states as a function of the squeezing parameter for different total number of bosonic modes under different subsystem configurations. Exact results for a few modes are obtained, and we
conjecture an asymptotic formula at the limit of large squeezing parameter as a function of the replica index $n$, while also finding subleading subsystem-size dependent terms for $n=3$ under a specific tripartition. We analytically show that the genuine $n=2$ Rényi multi-
entropy of any pure bosonic Gaussian states is zero for any number of modes and for any tripartition. Furthermore, to investigate the dependence on subsystem size, we plot the curve of genuine Rényi multi-
entropy as a function of the number of modes in the subsystems while keeping the total number of modes fixed. We discuss differences and similarities between this result and studies of the multi-
entropy curve for Haar random states. In particular, we identify a subsystem size configuration related with the multi-
entropy time in an evaporating black hole for which the behavior of the genuine multi-
entropy changes.
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Atmospheric and Oceanic Physics · Cross-listed from cs.LG
Mechanism-Aware Ensemble Conditioning for Data-Limited Emulation of Extreme Events
Isabella S. Thiel, Juan Bello-Rivas, Yannis G. Kevrekidis et al. (+1 more)
Extreme events in chaotic systems are difficult to learn from short trajectories because they are controlled by transient finite-time instability rather than by frequently observed bulk dynamics. We propose a mechanism-aware conditioning plug-in framework that turns a nudged coarse ensemble into a non-intrusive sensor of local instability geometry. In the small-noise regime, the ensemble covariance aggregates the same finite-time deformation kernels that govern local instability, providing a Jacobian-free proxy for the local amplification structure around a synchronized coarse trajectory. A small FiLM module injects statistics of this ensemble geometry into an otherwise unchanged backbone while leaving the coarse simulator unchanged. We demonstrate this interface in two distinct pipelines: a
Transformer-style residual-
attention corrector for a controlled low-dimensional chaotic system and a probabilistic recurrent STORN corrector for topographic two-layer quasi-geostrophic (QG) flow. In the low-dimensional
benchmark, ensemble covariance directions co-activate with OTD modes and FiLM conditioning improves 99th-percentile exceedance-frequency errors over an identical no-context
Transformer baseline. In QG, a fixed ensemble-conditioned FiLM-STORN model trained on only \(50\) time units substantially improves long-horizon rare-event statistics in the data-limited regime, including density-tail errors, exceedance frequencies, and spatial exceedance-area distributions relative to an unconditioned STORN trained on the same data; on averaged high-threshold exceedance diagnostics, it also outperforms the baseline STORN trained with $20$ times more high-resolution data. These results show that local instability geometry is not merely interpretable post hoc, but an actionable conditioning signal for data-efficient rare-event emulation.
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All authors Isabella S. Thiel, Juan Bello-Rivas, Yannis G. Kevrekidis, Themistoklis P. Sapsis
Materials Science
Strain-controlled topology and quantum control at a cubic Ce$^{3+}$ crystal-field crossing
A. Ghosh and J.T. Haraldsen
Field-tuned
crystal-field crossings provide a route to synthetic
topology in localized rare-earth degrees of freedom when
symmetry-resolved perturbations can independently control the crossing states. Here we show that a field-induced crossing in cubic Ce$^{3+}$ has precisely this structure. For $B\parallel[001]$, the crossing is protected by a twofold rotation, while the $T_{2g}$ shears $\epsilon_{xz}$ and $\epsilon_{yz}$ break that protection and mix the two states through orthogonal pseudospin components. Together with
magnetic-field detuning, these controls generate an isolated diabolical point with unit-magnitude Chern charge in a three-dimensional parameter space. Using the CeTe
crystal-field scale gives an ideal single-ion crossing near $35.5$ T. A calibrated point-charge calculation gives a representative projected shear coupling $|\alpha_{T_{2g}}|\simeq18.1$ meV per unit tensor strain, corresponding to gaps of $0.036$ and $0.072$ meV for tensor shears of $0.10\%$ and $0.20\%$. We identify the associated elastic and
magnetic signatures, discuss the limitations of the electrostatic estimate in a hybridizing Ce compound, and determine the adiabatic and coherence requirements for cyclic
geometric control. The result is a
symmetry-based framework that connects high-field
crystal-field reconstruction, strain response, and parameter-space
topology in rare-earth systems.
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Optics
Recent advances in poled lithium niobate
Kibret A. Messalea, Tim Weiss, Yang Yang et al. (+3 more)
Lithium niobate is a versatile material for both classical and
quantum photonics, recognized for its outstanding electro-optic and nonlinear optical properties. Through a process known as poling, periodic ferroelectric
crystal domains can be engineered to enable quasi-phase-matched frequency conversion, efficient modulation, and the generation of
quantum light sources. The emergence of lithium niobate on
insulator technology has further enhanced its suitability for scalable integrated photonics, offering ultra-low optical losses and strong light confinement while retaining the material's inherent advantages. Here, the techniques used to fabricate and characterize periodically poled lithium niobate are reviewed. Key developments are discussed, offering insights into the future of domain engineering of lithium niobate.
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All authors Kibret A. Messalea, Tim Weiss, Yang Yang, Hamed Arianfard, Brett C. Johnson, Alberto Peruzzo
General Relativity and Quantum Cosmology
Photon spheres, elliptic surfaces, and Seiberg-Witten geometry
Cordell Blankenship, Andreas Malmendier and Michael T. Schultz
We study null geodesics in Reissner-Nordström-de Sitter spacetime and in its $\omega=-2/3$ Kiselev deformation through the
elliptic curves defined by the radial equation. The relation of these curves to the non-critical $E_7$ Seiberg-Witten family yields differential equations for finite-distance light deflection, and explains the boundary source term through a suitable gauge of the Seiberg-Witten differential. This geometry separates the extremal point $Q^2=M^2$ from the Argyres-Douglas point $Q^2=9M^2/8$. We also determine the Kiselev critical and horizon loci, and show that, at fixed nonzero angular momentum, the Argyres-Douglas and ultracold loci meet only at zero Killing energy.
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Nuclear Theory
A new type of skin thickness in high-spin isomers to constrain equation of state of spin-polarized nuclear matter
Toi Tachibana, Kouichi Hagino, Kenichi Yoshida et al. (+1 more)
We explore experimental probes for constraining the equation of state (EOS) of
spin-polarized
nuclear matter, where
spins of nucleons are aligned along a particular direction. For this purpose, we calculate the $12^+$ isomeric state of the \ce{^{52}Fe}
nucleus with the relativistic point-coupling model. We argue that the
spin skin thickness of this high-
spin state, that is, the difference between the radius of the
spin-up density and that of the
spin-down density, strongly correlates with the
spin slope parameter of the EOS. This is in analogy to the well known linear correlation between the slope parameter of the
symmetry energy and the
neutron skin thickness of finite
nuclei. We show that this correlation is retained even when one considers the difference of the radii between the $12^+$ and the ground states, even though the correlation is much weaker than in the case of the difference between the
spin-up and the
spin-down radii. We also discuss the mean-square charge radii of the $12^+$ state. We find that by taking the square of the radii the dependence on the
spin slope parameter becomes much stronger, and thus it can serve as a good probe of the
spin slope parameter given a high resolution of
laser-spectroscopy experiments.
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All authors Toi Tachibana, Kouichi Hagino, Kenichi Yoshida, Qiang Zhao
General Relativity and Quantum Cosmology
Propagation delays and regional intensity changes in lensed hotspot images
Yong Li and Xiao-Gang Lan
Propagation delays cause an image recorded at a single observer time to combine radiation emitted at different stages of the source
evolution. Comparable changes in total intensity can accompany distinct and even opposite changes in apparent image size. Using regional intensities, centroids, and covariances, we apply the law of total covariance to separate changes in regional intensity weights from changes in internal widths and centroid separation. Ray tracing simulations of a finite Gaussian hotspot moving along a prescribed strong field trajectory show two events with comparable attenuation in screen integrated intensity but opposite changes in second moment size. In the contracting event, the regional weights move away from balance; in the expanding event, they move toward balance even as the centroids approach each other. Differential propagation delays therefore drive these opposite size responses by redistributing intensity between spatially separated image regions.
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Atmospheric and Oceanic Physics
On the Limits of Univariate Deep Learning for Significant Wave Height Forecasting
Yilin Zhai, Hongyuan Shi and Zaijin You
This study conducts a systematic hyperparameter search across five deep learning architectures, DLinear, LSTM, PatchTST, ResAttLstm, and Mamba2, and nine context lengths (1-168 h) for single-station significant wave height (Hs)
forecasting on NDBC buoy 41009, followed by re-evaluation of the best configurations on a 47-buoy, 37-year corpus. The five families converge to a common performance level on the multi-buoy evaluation (between-family SD = 0.0014 m^2, 0.8% of the grand mean), a spread dwarfed by the 4.83x cross-
dataset MSE shift between buoy corpora. All multi-buoy trials beat persistence (mean skill +0.062), but no architecture consistently outperforms the others. On the single-buoy experiment, skill peaks at 12-24 h where five trials fall below persistence, per-family Q4/Q3 test MSE ratios range from 2.4 to 2.6, and deep models underperform persistence for the most extreme 1% of waves. These findings are consistent with the interpretation that persistence already captures the dominant linear-inertial signal in univariate Hs, and that architecture engineering under this univariate input setting has reached diminishing returns: cross-buoy variance, not model class, dominates forecast error. Future work should prioritise atmospheric
covariates, zero-shot cross-buoy transfer, and decomposition of Hs into swell and wind-sea components. By establishing a rigorous reference baseline for what univariate Hs models can and cannot achieve, this study provides a
benchmark against which future multivariate and physics-informed approaches can be calibrated, and offers practical guidance for lightweight buoy-level
forecasting in mid-latitude storm-dominated and swell-mixed environments.
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Fluid Dynamics
Particle Trajectories Beneath Fully Nonlinear Waves Generated by Horizontal Seabed Motion
João Vitor P. Poletto, David Andrade, Marcelo V. Flamarion et al. (+1 more)
We investigate fully nonlinear water waves and fluid-particle dynamics generated by the horizontal motion of a seabed obstacle with prescribed time-dependent velocity. The governing equations are the full Euler equations, formulated in a time-dependent conformal domain that simultaneously maps the moving free surface and seabed onto fixed boundaries. The main contribution of this work is a Lagrangian formulation for computing particle trajectories in the resulting genuinely unsteady conformal domain. We derive a closed-form trajectory system in the canonical domain in which the time dependence of the conformal map is entirely represented by the real and imaginary parts of an analytic function that can be evaluated spectrally from the surface. We apply the formulation to waves generated by horizontal submarine landslide motion and characterize particle displacements throughout the fluid as functions of the initial particle position and Froude number. Our findings identify distinct regions in which particle motion is predominantly associated with the moving seabed, the generated wave, or the combined action of both. The results reveal a transition in the dominant mechanism driving particle motion: at low Froude numbers, particle displacements are primarily associated with the moving seabed, whereas at high Froude numbers the generated wave becomes increasingly dominant, particularly near the free surface and away from the obstacle path.The numerical predictions are benchmarked against laboratory data available in the literature, showing good agreement and providing a quantitative assessment of the model accuracy. Moreover, laboratory topographies beyond those considered here can be readily incorporated into the numerical framework through a Hermite interpolation procedure.
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All authors João Vitor P. Poletto, David Andrade, Marcelo V. Flamarion, Roberto Ribeiro-Jr
Medical Physics
A 2D autocorrelation-based frequency estimator reflecting spatial tissue distribution to improve Ultrasound H-scan tissue characterization
Jihye Baek, Thurston Brevett, Dongwoon Hyun et al. (+4 more)
H-scan is a promising quantitative ultrasound technique that estimates the frequency content of backscattered signals and maps the estimated frequencies onto a red/blue color scale to reflect underlying tissue properties. Although it relies on matched filters tuned to different frequencies, the broad spectral bandwidth of ultrasound produces noisy, granular displays. Here, we introduce an adaptive frequency
estimator designed to suppress the noise within homogeneous regions while preserving sharpness across tissue boundaries. The method combines 2D autocorrelation with a matched filter. In the first stage, a matched-filter-based estimation yields an a priori map of the spatial distribution of frequencies. The local heterogeneity of these estimates then defines a 2D weighting function that guides a second estimation stage. Drawing on the concept of Loupas's blood velocity
estimator, we apply autocorrelation over a 2D spatial kernel to recover the axial frequency components, employing a weighted summation that accounts for the spatial frequency distribution within the kernel. We benchmarked the proposed
estimator against conventional approaches, including the short-time
Fourier transform, the H-scan matched filter, and standard autocorrelation, using both Field II simulations and in vivo data from human subjects with hepatic steatosis. In simulation, our adaptive
estimator reduced the noisy texture in homogeneous regions while retaining clear boundary delineation, whereas the other
estimators could achieve only one of these objectives. Applied to the in vivo human liver, the
estimator improved H-scan image quality by lowering noise and enhancing the discrimination of steatotic liver from adjacent gallbladder and skin layers.
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All authors Jihye Baek, Thurston Brevett, Dongwoon Hyun, Ahmed El Kaffas, Aya Kamaya, Kevin J. Parker, Jeremy J. Dahl
Superconductivity
Electrochemical Growth of Full Volume Meissner Effect Superconducting BKBO
Oleksandr Foyevtsov, Kateryna Foyevtsova, Mohamed Oudah et al. (+2 more)
In this work we show the results of electrochemical synthesis of BKBO
crystals using three different experimental setup configurations. The setups differ between each other by varying level of control over physical variables and progressing from a two-electrode to a three-electrode configuration using highly oriented platinum counter electrode. By systematic analysis of the temperature dependence of the
magnetic susceptibility at the superconducting transition of the collected
crystals we observe that an order of magnitude sharper superconducting transition is achieved for the most comprehensive three-electrode setup. In addition, the level of chemical substitution can be controlled by the value of the overpotential versus reference electrode. We demonstrate that with this technique a full volume Meissner effect can be achieved with a sharp transition temperature for the superconducting
crystal.
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All authors Oleksandr Foyevtsov, Kateryna Foyevtsova, Mohamed Oudah, Dan Bizzotto, George Sawatzky
Soft Condensed Matter
Realignment of ferroelectric nematic by photoinduced electric field
Sathyanarayana Paladugu, Oleksandr Kurochkin, Ruslan Kravchuk et al. (+5 more)
Liquid crystal displays (LCDs) employ thin pixels of a paraelectric nematic, confined between two glass plates with transparent indium tin
oxide (ITO) electrodes. A voltage applied to the electrodes realigns the molecules, changing the optical appearance of the pixel. Here we demonstrate that a similar molecular realignment can be triggered by low-power light irradiation when the paraelectric nematic in the
cell with ITO electrodes is replaced with a ferroelectric nematic (NF). Irradiation creates an intrinsic electric field that is strong enough to realign the NF but too weak to affect the paraelectric nematic. The extraordinary sensitivity of the ITO/NF pair to light irradiation creates a platform for optical control of ferroelectric polarization and applications in photonics, sensing, smart windows, and beyond.
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All authors Sathyanarayana Paladugu, Oleksandr Kurochkin, Ruslan Kravchuk, Mykola Kravets, Volodymyr Sashuk, Bijaya Basnet Vassili G. Nazarenko, Sergij V. Shiyanovskii, Oleg D. Lavrentovich
Solar and Stellar Astrophysics
A Comprehensive Study of the Long-Period Cataclysmic Variable V630 Cassiopeiae
Ivan Mora Zamora, Gagik Tovmassian, Juan Echevarria et al. (+1 more)
We present a comprehensive review of V630 Cassiopeiae, which is a very long-period cataclysmic variable. Based on new observations combining spectroscopy and high-resolution photometry provided by TESS and precise distance data from
GAIA, we confirm and extend previously described characteristics. The light curves show differential behaviors between different epochs, attributed to changes in the disk's brightness distribution, likely due to non-axial structures such as precessing eccentric disks. The spectroscopy reveals complex Ha line profiles, with dual components and an emission distribution that suggests a large, asymmetric, and possibly precessing disk, rather than a classic shock structure in the matter-flow impact region. Doppler
tomography indicates that the emission originates at the periphery of the disk, distributed in an asymmetric pattern rather than a compact point, complicating the interpretation of radial velocities and limiting their use for accurately determining masses. Through photometric and spectroscopic analysis, we established a donor mass estimate with an approximate value of 0.38 Ms at the adopted distance of 2409 pc, with significant uncertainty related to distance and other systematic factors. Finally, using the parameters of V630 Cas, binary
evolution simulations were conducted with MESA incorporating CARB
magnetic braking prescription to identify an evolutionary sequence that explains its properties.
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All authors Ivan Mora Zamora, Gagik Tovmassian, Juan Echevarria, Diogo Belloni
General Relativity and Quantum Cosmology
Geometry as Thermodynamics:Entropy Stationarity and Horizon Residues
Wen-Xiang Chen
Thermodynamic descriptions of
gravity involve both variational conditions for spacetime dynamics and analytic structures associated with horizons. We examine their relation while keeping their assumptions distinct. First, we present an explicit derivation of the Einstein equation from the established null-vector
entropy functional, including the null constraint, the matter term, and the integration constant associated with the cosmological constant. Second, for an analytic static spherical geometry with a nondegenerate Killing horizon, we define a meromorphic radial one-form whose residue is the inverse of twice the surface
gravity. Euclidean regularity then fixes the Hawking temperature. Combining this residue with the Einstein–
Hilbert Noether charge gives a normalized contour representation of the Wald
entropy. The construction reproduces the Schwarzschild temperature,
entropy, and Smarr relation, but does not constitute an independent microscopic derivation of the area law. We establish the limits of a stronger identification between pole structure and dynamics: an asymptotically flat family can retain the Schwarzschild horizon residue, area, surface
gravity, and mass while violating the
vacuum Einstein equation, and an extremal charged solution possesses a higher-order pole. We also show why exponentiating an unspecified
entropy functional does not produce a universal
entropy residue. The resulting framework separates
entropy stationarity, horizon analyticity, and charge normalization, providing explicit consistency tests for further thermodynamic interpretations of gravitational singularities.
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Astrophysics of Galaxies
A Cyanopolyyne-rich but COM-poor Massive Protostar: The First Hot Carbon Chain Chemistry Source G28.28-0.36
Kotomi Taniguchi, Masao Saito, Prasanta Gorai et al. (+6 more)
We present molecular emission line data from the massive young
stellar object (MYSO) G28.28-0.36 (G28.28) obtained with the Atacama Large Millimeter/submillimeter Array Band 3. Cyanopolyynes (HC$_3$N and HC$_5$N) and three complex organic molecules (COMs; CH$_3$OH, CH$_3$CN, and CH$_3$CHO) are detected from the MYSO G28.28. In addition, strong emission regions of cyanopolyynes are identified between G28.28 and a nearby ultracompact H II region. The HC$_5$N emission is coincident with the
dust continuum peak, where an excitation temperature of 100 K is derived from CH$_3$CN. These results suggest that the Hot Carbon Chain Chemistry (HCCC) mechanism produces cyanopolyynes in the hot region around G28.28. We find that G28.28 exhibits a unique chemical feature: cyanopolyynes are abundant, but COMs are deficient, unlike the other MYSOs studied previously. These results imply that G28.28 is a counterpart of the Warm Carbon Chain Chemistry (WCCC) low-mass source L1527. G28.28 is the first HCCC source identified so far.
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All authors Kotomi Taniguchi, Masao Saito, Prasanta Gorai, Olli Sipilä, Kazuhito Dobashi, Paola Caselli, Tirupati Kumara Sridharan, Tomomi Shimoikura, Jonathan C. Tan
Astrophysics of Galaxies
A VLA Study of the Disturbed Massive Cluster PLCK G165.7 + 67.0 and Its Two Narrow Angle Tail Galaxies
Aurora Wilde, Eric F. Jimenez-Andrade, Brenda L. Frye et al. (+11 more)
Since spectroscopic measurements provide only the line-of-sight velocity, transverse motions are difficult to constrain. In the vast majority of cases, transverse velocities have been measured only for local
galaxies.
Radio galaxies whose jets are bent back by ram pressure into nearly parallel Narrow-Angle Tails (NATs) offer a way to extend such measurements to higher
redshifts. Here, we present proprietary 15~GHz (Ku-band) and archival 6~GHz (C-band) continuum observations from the Very Large Array (VLA) of six
radio galaxies in the
galaxy cluster field PLCK G165.7+67.0 (G165). VLA imaging resolves two of the cluster
galaxies into NATs whose tails both extend toward the Southwest, away from the cluster center of mass. Spectral index maps made at matched angular resolution resolve a steepening gradient consistent with radiative aging along the length of the tails. Physical properties of the NATs are measured and used to constrain two independent models: a Mach cone model and a nonrelativistic hydrodynamic flow model based on Euler's equation. The models returned transverse velocities of $\sim 2000 ~\rm km~ \rm s^{-1}$ for both
galaxies. One NAT is the brightest cluster
galaxy (BCG) and has a measured radial velocity of $-3300 ~\rm km ~\rm s^{-1}$, resulting in an even higher space velocity. The high inferred 3D velocity of the BCG may be explained if it is intercepted close to core passage.
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All authors Aurora Wilde, Eric F. Jimenez-Andrade, Brenda L. Frye, Patrick S. Kamieneski, Kevin C. Harrington, Megan Donahue, Min S. Yun, Anton M. Koekemoer, Marcel Neeleman, Massimo Pascale, Nicholas Foo, Reagen Leimbach, Seth Cohen, Rogier A. Windhorst
High Energy Astrophysical Phenomena
Deciphering the VHE gamma-rays spectra of Extreme High-Frequency peaked BL Lac Objects through a Photohadronic Model
Sarira Sahu, D. I. Páez-Sánchez, A. U. Puga Oliveros et al. (+7 more)
Extreme high-frequency peaked BL Lac objects (EHBLs) have their synchrotron peak above $\sim 1$ keV and their inverse Compton peak extends up to several TeVs. Due to low luminosity of EHBLs, these objects are often undetected, and only a small number of them are thus known. As a result, they are poorly understood. Using a photohadronic model and including extragalactic background light correction we analyzed 22 very high-energy (VHE) gamma-ray spectra of 15 EHBL sources observed in different periods. We find that the photohadronic model used can adequately describe the observed VHE spectral energy distribution and furthermore, we classify them according to the value of the
photon spectral index, $\delta$. The
redshift of the EHBL HESS J1943+213 is also tightly constrained using the same photohadronic model. Within the sample, a plurality of flaring epochs fall in the high-emission state which is followed by the low-emission state and the very-high-emission state respectively. These fractions of flaring epochs characterize only the present sample, not the EHBL population at large. Due to the anomalous behavior of the VHE gamma-ray spectra of the EHBL H 2356-309, we suggest it to be a new subclass of EHBL having hard and very soft intrinsic spectra during different flaring epochs.
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All authors Sarira Sahu, D. I. Páez-Sánchez, A. U. Puga Oliveros, M. E. Iglesias Martínez, Jose Guerra Carmenate, R.de J. Pacheco-Aké, G. Sánchez-Colón, Subhash Rajpoot, P. Fernández de Córdoba, Gaetano Lambiase