High Energy Physics (Phenomenology)
Baryon Asymmetry Transfer to Majorana Dark Matter from a Colored Partner
Wei Huang, Hongjian Du, Feng Luo et al. (+1 more)
We propose a mechanism in which a
primordial baryon asymmetry determines the relic abundance of self-conjugate dark matter through a heavier partner sector. In a simplified model with a Majorana
fermion $\chi$ and a colored scalar partner $\tilde q$, QCD annihilations deplete the symmetric partner population while a residual asymmetric component survives as a temporary reservoir. For feeble portal couplings, this asymmetry is transferred to $\chi$ at late times, after dark matter freeze-out. The final relic abundance is controlled by the amount of surviving asymmetry, the timing of its transfer, and the subsequent dark matter annihilation. Solving the coupled Boltzmann equations with the relevant chemical-potential effects, we find that an intermediate range of portal couplings can reproduce the observed relic abundance without requiring a compressed mass spectrum. The qualitative mechanism remains robust against variations in the mass hierarchy, dark matter annihilation mode, and
lepton asymmetry. The small portal couplings also make the colored partner potentially long lived, allowing LHC searches for heavy long-lived particles to constrain part of the viable parameter space.
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All authors Wei Huang, Hongjian Du, Feng Luo, Michihisa Takeuchi
High Energy Physics (Theory)
Heterotic string couplings at order $\alpha'^3$ in NS-NS sector
Alireza Pahlavan, Mehdi Ameri and Mohammad R. Garousi
We utilize the standard T-duality procedure to derive the classical effective action of heterotic string theory at the eight-derivative order within the NS-NS sector, which comprises the metric, the \(B\)-field, and the dilaton. Starting from the minimal basis at this order, consisting of 872 even-parity and 477 odd-parity couplings, we perform a dimensional reduction on a circle and impose invariance under T-duality transformations, specifically the Buscher rules supplemented by higher-derivative corrections. This invariance uniquely fixes a subset of the couplings to match those of type II theory up to an overall factor, while the remaining couplings are determined in terms of the coefficients at order \(\alpha'\). For these latter couplings, we adopt both the Metsaev-Tseytlin and Meissner schemes. Subsequently, through field redefinitions, we recast the action into a canonical form in which the dilaton appears solely through the overall factor \(e^{-2\Phi}\). In the Meissner scheme, the pure
gravity sector precisely reproduces the known S-
matrix results. In both schemes, the pure
gravity terms can be expressed as the double trace \((\Tr(R^2))^2\), and when combined with the corresponding Yang-Mills terms \((\Tr(F^2))^2\), they take the unified form \((\Tr(R^2-F^2))^2\), as anticipated in the literature.
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General Relativity and Quantum Cosmology
The Schwarzschild Black Hole in an External Gravitational Tidal Field: the Quasinormal Spectrum
Dimitrios Giataganas, Alex Kehagias and Antonio Riotto
A black hole need not ring down in isolation, since a nearby companion can subject it to an external gravitational tide. We calculate how a quadrupole tide modifies the Schwarzschild black hole resonances. Linearising the exact tidally distorted Schwarzschild solution in the
tidal amplitude $A$, we derive the diagonal odd- and even-parity perturbation equations on the deformed background and compute the formal first order displacements of analytically continued Schwarzschild resonances. Each diagonal first order shift factorises as $\delta\omega_{n\ell m}=A\,c_{\ell m}\kappa_{n\ell}$, giving one reduced complex coefficient for each $(n,\ell)$, expressed as a ratio of contour integrals, multiplied by a universal Zeeman-like pattern that splits the $2\ell+1$ azimuthal multiplet. For the $\ell=2$ and $\ell=3$ sectors analysed explicitly, the odd- and even-parity shifts coincide, so Schwarzschild isospectrality survives at first order in the
tidal amplitude. Quadratic
tidal forces, by contrast, can break this degeneracy. Moreover, for a physical companion, the astrophysically dominant $(n,\ell,m)=(0,2,2)$ mode oscillates faster and decays more slowly. Finally, we show that the eikonal shifts admit a
geometric description in terms of the Penrose limit about the tidally deformed
photon ring.
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Other Condensed Matter
Nonreciprocal Control of the Goos–Hänchen Shift via the Barnett Effect in Cavity Magnomechanics
Shah Fahad and Gao Xianlong
We propose a theoretical scheme for realizing a tunable nonreciprocal Goos-Hänchen shift (GHS) in a hybrid cavity magnomechanical system. The setup consists of a rotating yttrium iron garnet sphere embedded in a microwave cavity, with
magnetic-dipole and magnetostrictive interactions mediating
magnon-
photon and
magnon-
phonon couplings, respectively. Owing to the Barnett effect, the
magnon frequency acquires a rotation-induced shift whose sign can be reversed by changing the direction of the bias
magnetic field. We show that the output probe spectrum exhibits a Fano resonance, while the associated GHS responds asymmetrically to opposite field directions, providing a controllable mechanism for nonreciprocal beam shifts. The
magnon-
photon and
magnon-
phonon interactions are found to affect the GHS in opposite ways, while the cavity length offers an additional degree of tunability. These results provide a route toward magnetically reconfigurable microwave photonic devices and sensitive detection of Barnett-induced effective fields.
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Optics
Critical Topological Photonics in Synthetic Dimensions
Mingyuan Chen, Yuwei Jing, Franco Nori et al. (+1 more)
Topological states and criticality have long been regarded as incompatible ingredients: the former requires a finite spectral gap, whereas the latter demands its closure. Guided by this view, topological photonics has focused almost exclusively on gapped phases, treating gap-closing transitions as mere phase boundaries. In this work, we propose a class of topological states in which
topology coexists with criticality in experimentally accessible synthetic-frequency photonic platforms. In a one-dimensional (1D) synthetic
lattice, we identify such critical topological photonic states through midgap degeneracies in the single-particle
entanglement spectrum, and uncover a
topology-enforced multicritical point that reorganizes the
topology of neighboring critical states. We further extend this framework to two dimensions (2D). Our work provides an experimentally accessible route to critical topological photonics, and may also inspire novel applications such as critical topological sensing.
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All authors Mingyuan Chen, Yuwei Jing, Franco Nori, Xue-Jia Yu
Mathematical Physics · Cross-listed from cs.DM
Thermal Recurrence Orders of the Potts Model Partition Function in Grid Graphs
Yi-Zhong Wang
We study the linear recurrence order of the Potts model partition function on thermal 2D grid graphs. By restricting the transfer
matrix (TM) to the real coupling axis, the physical operator maintains diagonalizability under the Spectral
Theorem. We show that this thermal regularization allows the Krylov subspace to saturate the unconstrained planar state capacity, locking the recurrence order to the Dyck path up to reversal (OEIS A007123) for $q \ge 4$. Furthermore, the recurrence order collapses to height-restricted Dyck paths up to reversal (OEIS A001998) for $q=3$ due to finite-index Jones-Wenzl projections, and to the zero-magnetization conservation sector (OEIS A001405) for $q=2$. This framework bridges graph-theoretic combinatorics with the representation theory of physical loop gas models.
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Optics
Coexistence of Magnon-Induced Optical Vortex and Gaussian Beam Scattering Assisted by Rotational Umklapp Process
Ryusuke Hisatomi, Kotaro Taga, Hisakazu Matsuki et al. (+3 more)
The exploitation of
crystal-
lattice symmetries to engineer angular momentum transfer between structured light and
magnons marks a novel frontier for optomagnonic research. In Brillouin light scattering, when focused light propagates parallel to an external
magnetic field and interacts with
ferromagnetic uniform
magnons, only optical-
vortex scattering is expected to be permitted. Due to the combined effects of magneto-optical coupling and optical
spin-orbit interaction, the transfer of
magnon spin angular momentum to
photon orbital angular momentum allows for this distinctive scattering phenomenon. Here, we experimentally demonstrate that, for a specific
ferromagnetic crystal orientation, Gaussian-beam scattering coexists with the optical-
vortex scattering, contrary to conventional expectations based on angular momentum conservation between
magnons and
photons. We show that the
crystal lattice, via the rotational Umklapp process, provides the missing angular momentum required for the Gaussian-beam scattering. Furthermore, we predict that as the degree of light focusing increases, the relative efficiencies of the Gaussian-beam and optical-
vortex scattering processes reverse.
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All authors Ryusuke Hisatomi, Kotaro Taga, Hisakazu Matsuki, Shutaro Karube, Yoichi Shiota, Teruo Ono
Fluid Dynamics
On the degradation of hot spot performance due to mid-to-high-mode hydrodynamic instabilities
Dongxue Liu, Jiaqin Dong, Yunxing Liu et al. (+5 more)
In an ignited design of inertial confinement fusion, the role of mid-to-high-mode hydrodynamic instabilities in degrading hot-spot performance, beyond reducing temperature, remains unclear. To address this, we propose an isobaric criterion to assess the isobaric assumption that forms the theoretical basis of the hot spot. The most dangerous mode l = 12 is determined through a balance between perturbation growth and ablation stabilization induced by thermal conduction. Thermal conduction outperforms convection when the Peclet number is much less than 1. Therefore, for mid-to-high modes, thermal conduction makes the hot spot isobaric before the outer mass inflow restores the lost heat. Consequently, neglecting thermal conduction overestimates pressure and underestimates volume. These results enhance our understanding of mid-to-high modes in degrading hot-spot performance, and suggest that thermal conduction losses may reduce performance even if perturbations are nearly stabilized by ablation.
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All authors Dongxue Liu, Jiaqin Dong, Yunxing Liu, Zhiyu He, Wei Wang Jinren Sun, Yuqiu Gu, Xiuguang Huang, Jian Zheng
Quantum Physics
Reinventing the Single-pixel Imaging Paradigm via Quantum-Operator-Based Signal Processing
Bu-Ran Yu, Yi-Zhu Zhang, Kan-Xu Jia et al. (+3 more)
A fundamental bottleneck across modern computational imaging and high-dimensional sensing is the conventional decoupled acquisition-reconstruction hierarchy, which subjects high-dimensional spatial sensing to the classical shot-noise limit and intense computational overhead. As a prominent manifestation of this limitation, single-pixel imaging (SPI) suffers severely from this paradigm. We reinvent this paradigm by introducing a
quantum-operator-based SPI theoretical framework driven by coherent signal processing. Within this architecture, the spatial inverse problem is analytically mapped into the
eigenvalue spectrum of a
quantum operator via tailored light-matter interactions. By analytically synthesizing non-linear reconstruction operators via ultra-shallow
quantum architectures, we theoretically demonstrate an exponential decay of spatial approximation errors, completely bypassing traditional linear solvers. This operator-space
embedding not only shields reconstruction from noise via a strategic error-saturation zone but also bridges the gap from classical shot-noise scaling $\mathcal{O}(1/\sqrt{N_{\text{ph}}})$ to the ultimate Heisenberg limit $\mathcal{O}(1/N_{\text{ph}})$. Crucially, while formulated within SPI, this coherent operator paradigm fundamentally extends to general
photon-starved, high-dimensional imaging modalities. This work establishes a universal theoretical blueprint for next-generation
quantum-enhanced sensing, shifting the paradigm from iterative optimization to coherent operator-space
evolution.
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All authors Bu-Ran Yu, Yi-Zhu Zhang, Kan-Xu Jia, Qian-Qian Bao, Shao-Ying Meng, Xi-Hao Chen
Statistical Mechanics
Nonequilibrium statistics of harmonically trapped run-and-tumble particles: An exact convolution approach
Francisco J. Sevilla and Jair A. Meléndez Mora
We study one-dimensional run-and-tumble particles confined by a harmonic potential and coupled to an
equilibrium thermal bath. Exploiting the coupling of active and thermal degrees of freedom through the Ornstein-Uhlenbeck propagator, we show that the position distribution factorizes, as a convolution, into the Ornstein-Uhlenbeck distribution and the distribution of the athermal run-and-tumble problem. This yields closed-form results, correcting expressions from earlier treatments by identifying the Ornstein-Uhlenbeck propagator, rather than the free-
diffusion one, as the correct kernel. Results are confirmed both in
Fourier space and by direct Langevin simulation. We further focus our analysis on the stationary regime, characterized by two dimensionless parameters–the ratio of trapping to persistence length, and the ratio of thermal to active
diffusion–which control the crossover from a non-Gaussian, boundary-peaked distribution to the Gaussian,
equilibrium-like limit. Energy fluctuations and the Kullback-Leibler divergence from the
equilibrium distribution quantify the resulting non-
equilibrium character of the confined active particle.
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High Energy Physics (Phenomenology)
Direct renormalization of flavor-changing currents in vNRQCD for $B_c^{(*)}$ decays
Jichen Pan
We present a direct vNRQCD calculation of the two-loop anomalous dimensions of the leading
flavor-changing nonrelativistic currents that govern the leptonic decays of the $B_c$ and $B_c^*$
mesons. The calculation is performed at the matching scale $\nu=1$, where the anomalous dimensions are the ultraviolet counterterms required to cancel the residual infrared poles of the full-QCD short-distance coefficients. In contrast to the conventional extraction from those infrared poles, we determine the current renormalization constants directly in the effective theory. The pseudoscalar and vector channels are obtained from one
spin-unified formula, with the
spin dependence entering through $S(S+1)$. We also clarify the role of ultrasoft-induced mixing operators in the unequal-mass theory: they are essential for the full velocity running below $\nu=1$, but their Wilson coefficients vanish at the matching point and do not alter the fixed-order current anomalous dimensions reported here. The results agree with the known matching calculations and reduce smoothly to the equal-mass quarkonium limits.
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Quantum Gases
Breakdown of Aharonov-Bohm cage in Rydberg synthetic lattices: the roles of inhomogeneity and long-range exchange
Li Pan, Xinlu Chen, Hong Zhang et al. (+1 more)
While the interaction-induced breakdown of Aharonov-Bohm (AB) cage is typically attributed to uniform bound-pair transport, systems with inhomogeneous exchange interactions realized with Rydberg synthetic
lattices exhibit more complex dynamics. Employing the
evolution-path
symmetry (EPS) framework developed recently, we analyze the two-particle dynamics via path interference in Fock space. We find that a homogeneous nearest-neighbor exchange interaction cannot break the AB cage, regardless of whether the long-range exchange interaction is present or not. In contrast, we demonstrate that inhomogeneous nearest-neighbor exchange interaction breaks the destructive-interference EPS, and lifts the degeneracy of many-body compact localized states, thereby generating non-local dispersive eigenstates. Consequently, the initial state gains a non-zero overlap with these dispersive states, enabling delocalized transport. Furthermore, while long-range exchange interaction alone preserves the AB cage, its coupling with nearest-neighbor inhomogeneous exchange interaction opens non-canceling pathways that alter the
diffusion profile. Our work connects microscopic path interference with macroscopic spectral reorganization, offering an analytical understanding of the mechanism underlying exchange-interaction-induced transport in Rydberg synthetic
lattices.
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All authors Li Pan, Xinlu Chen, Hong Zhang, Jian-Song Pan
Quantum Physics
Markov Constraints Enhance Identifiability in Quantum Shadow Inversion
Zhixing Chen and Lin Chen
We study
quantum shadow inversion under Markovian locality constraints for four-partite systems arranged along the chain $A$–$B$–$C$–$D$. The goal is to reproduce the expectation value of a fixed endpoint observable $O_{AD}$ after an unknown global
unitary, without requiring full
unitary inversion. We formulate the task using Markov-admissible supermaps and introduce the Markov-implementable centralizer to describe the remaining endpoint gauge freedom. We show that unrestricted endpoint post-processing is too broad, and impose an endpoint-local refinement. Under this condition, every implementable endpoint
unitary must factorize across $A|D$, so the Markov constraint strictly reduces the centralizer-induced shadow ambiguity whenever the full centralizer contains non-product
unitaries. This provides a structural mechanism by which Markov locality enhances identifiability in
quantum shadow inversion.
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Geophysics · Cross-listed from cs.DC
Rapid Earthquake-to-Tsunami Waveform Generation via Large-Scale Multi-GPU FFT Convolution Applied to the Cascadia Subduction Zone
Bowen Shi, Sreeram Venkat, Stefan Henneking et al. (+1 more)
Data-driven methods for earthquake and tsunami early warning rely on large ensembles of rupture scenarios and their resulting waveforms, but generating such
datasets with repeated high-fidelity seismic and tsunami simulations is prohibitively expensive. We exploit the linear time-invariant structure of both dynamics to precompute elastic Green's functions and acoustic-
gravity adjoint responses, reducing the source-to-waveform map to two consecutive convolution operators. We evaluate these convolutions with a distributed, FFT-accelerated GPU pipeline that partitions the large seafloor grid across GPUs and directly generates the final observation waveforms. We demonstrate the scalability of this pipeline for the Cascadia Subduction Zone with 963 subfaults, 2,416,530 seafloor grid points, 64 observation locations, and 256 timesteps, requiring 9.45 TiB of aggregate GPU
memory. On 64 GB200 GPUs within one NVL72 domain, the pipeline generates waveforms in 24 ms per rupture once the response operators are resident, enabling large rupture ensembles to be evaluated within minutes.
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All authors Bowen Shi, Sreeram Venkat, Stefan Henneking, Omar Ghattas
Materials Science
Dynamic Magnetic Pair-Density Function of a One-Dimensional Ferromagnet
Shin-ichi Shamoto
The dynamic
magnetic pair-density function (DymPDF) $D_{\rm M}(r, E)$ is derived by extending the static
magnetic pair distribution function (mPDF) to finite energy transfer. The analytical DymPDF of a one-dimensional Heisenberg ferromagnet is obtained from the
magnon dispersion and compared with simulations performed using {\textsc SpinW}. Excellent agreement is achieved for energy dependence of the nearest-neighbor
spin-pair correlation, demonstrating that the DymPDF changes sign at the
magnon-mode transition occurring at one-half of the maximum
magnon energy. The r-dependence of DymPDF at low energy is also reproduced with a model including
magnon correlation length and
Fourier-termination effects. These results establish the theoretical foundation of DymPDF analysis for investigating local
spin dynamics in
magnetic materials.
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General Relativity and Quantum Cosmology
Probing Variations of Newton's Constant in Strong Gravitational Fields
T. D. Le
The constancy of Newton's gravitational constant G is a fundamental prediction underlying general relativity and a critical assumption in theories of
gravity beyond it. We report a high-precision test of a possible temporal variation of G in a strong gravitational field, using high-resolution ultraviolet spectra of Ni V absorption lines in the white
dwarf G191-B2B obtained with the Hubble Space
Telescope Imaging Spectrograph (HST/STIS). By comparing the measured line centroids with laboratory wavelengths and isolating the gravitational-
redshift contribution, we obtain dG/G = (-0.014 +/- 0.016) x 10^-15 yr^-1 at a strong-field potential phi approximately 10^4, corresponding to an absorption
redshift z_abs approximately 8.47 x 10^-5. The result is consistent with a constant G and places a stringent constraint on its secular variation in the strong-field regime. Our measurement demonstrates the potential of white-
dwarf stars as a sensitive probe of temporal variations in the gravitational coupling.
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Nuclear Experiment · Cross-listed from cs.LG
How Architecture and Training Affect TPC Representations Across Experiments
Tyler Wheeler, Michelle P. Kuchera, Raghuram Ramanujan et al. (+12 more)
Deep-learning efforts have increasingly shifted toward foundation model approaches. In experimental physics, this allows models and learned representations to be reused beyond the experiments in which they were developed. This work evaluates the reusability of representations across experiments and detector systems using probes on frozen encoders. These probes reveal task-relevant structure before downstream adaptation, complementing fine-tuning. Together with random-weight controls, they distinguish contributions from architecture and encoder training that downstream performance alone cannot resolve. Time projection chamber (TPC) data provide a useful testbed because events from TPC systems can be represented as variable-length sparse tensors, while detector geometries, event
topologies, and scientific tasks can differ substantially. We investigate whether fixed-dimensional TPC event representations can be reused across classification tasks, experiments, and detector systems. Sparse ResNet and PointNet-style encoders produce 512-dimensional
embeddings for four
datasets from the GADGET II TPC and AT-TPC. Randomly initialized encoders isolate the contribution from architecture before supervised training. We then train each encoder on a classification task, freeze its parameters, and train a linear or nonlinear probe for each downstream task. We find that this architecture-induced structure remains useful across experiments and detector systems. The randomly initialized PointNet-style representation is highly informative on several tasks. The two architectures organize their
embedding spaces differently, but neither exhibits a large, systematic loss of utility cross-detector. These results show that architecture is a major source of task-relevant structure in TPC
embeddings and should be treated explicitly when assessing representation learning and developing reusable detector models.
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All authors Tyler Wheeler, Michelle P. Kuchera, Raghuram Ramanujan, William Sieland, Ryan Krupp, Yassid Ayyad, Daniel Bazin, Connor L. Cross, Hoi Yan Ian Heung, Andrew J. Jones, Ruchi Mahajan, Saiprasad Ravishankar, Pranjal Singh, Benjamin Votaw, Chris Wrede
Statistical Mechanics
High-Efficiency Ising Machine with Time-Dimensional Exchange Coupling
Zhengyu Du, Haijie Xu, Kaiming Cai et al. (+2 more)
Conventional probabilistic Ising machines often suffer from inefficient exploration of configuration space, while replica-based
quantum Monte Carlo methods reduce sampling bottlenecks at the cost of large hardware overhead. Here we propose a time-dimensional exchange coupling (TEC) that replaces spatial replica coupling with a temporal exchange interaction between successive
spin configurations of a single p-bit network. This TEC improves sampling efficiency without duplicating replica hardware. At low temperatures,
antiferromagnetic TEC expands sampling range; at high temperatures,
ferromagnetic TEC stabilizes the optimal state. For MaxCut problems with up to 2000 vertices, TEC significantly accelerates convergence speed. SPICE simulations confirm hardware feasibility. TEC offers a scalable, hardware-efficient strategy to enhance combinatorial optimization on existing Ising machines.
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All authors Zhengyu Du, Haijie Xu, Kaiming Cai, Zhe Yuan, Yue Zhang
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Width-Independent Compressibility of Deep Neural Networks
Hong-Yi Wang, Mingze Wang and Liu Ziyin
It has long been known that well-trained neural networks can be compressed very strongly without affecting their performance, an important phenomenon that remains poorly understood. We prove a uniform compressibility
theorem for deep multilayer perceptrons with analytic activations. For a deep, wide fixed teacher network, there exists a narrow (same depth) network that approximately represents the same function as the original. The reachable compressed width is strikingly independent of the original width, but is $O((\log(1/\varepsilon))^{d_{in}})$, where $\varepsilon$ is the error budget and $d_{in}$ is the effective input dimension. Our construction involves a novel derivative-matching technique which is aware of the low-dimensional input, and a layer-wise reweighting that preserves the input-output mapping.
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Soft Condensed Matter
Pitch-controlled reorientational nonlinearity in chiral nematic liquid crystals: a reduced-order model for self-focusing and soliton formation
Homa Saadatmand, M. Javad Zakeri, Ahmed Sameh Ahmed et al. (+6 more)
We present a reduced-order semi-analytical model for reorientational nonlinearity in
chiral nematic
liquid crystals, showing that the
chiral pitch acts as the dominant physical length scale governing the onset of nonlinear self-focusing and
soliton formation. Starting from the full Frank-Oseen equation, we derive a closed-form expression for the optically induced molecular rotation that captures the essential saturable response of the medium while reducing computational cost by more than two orders of magnitude compared with standard relaxation-method solvers. Despite its simplicity, the model reproduces the essential features of the numerically obtained nonlinear refractive index, the onset of self-localization, and the transition from discrete to continuous
solitons in one and two dimensions. It further predicts the formation of fully localized astigmatic nematicons with only minor shifts in the self-localization threshold due to the neglect of nonlocal effects. The proposed model provides direct physical insight into light-matter interactions with soft matter media and offers a computationally efficient tool for the design and optimization of nonlinear photonic devices.
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All authors Homa Saadatmand, M. Javad Zakeri, Ahmed Sameh Ahmed, Suraj Bhandari, Loubna Benkoula, Ameer B. Batarseh, Andrea Blanco-Redondo, Miroslaw Karpierz, Pawel S. Jung
Materials Science
Thermodynamic and Kinetic Tests for Low-Pressure Metal-Flux Growth of Diamond, with an Extension to Cubic Boron Nitride
Rodney S. Ruoff
Diamond was grown from a
liquid Ga-Fe-Ni-Si
alloy near 1 atm, although bulk graphite is thermodynamically more stable under those conditions. This Perspective asks what must be true for a diamond growth front to continue advancing in such a metastable regime. I define a finite-difference transfer free energy for a specified interfacial event and identify the completed attachment of one carbon atom at a kink as the repeatable event that governs sustained growth. In the macroscopic limit, surface terms cancel, and the required carbon activity is fixed by the bulk free energy of diamond. On a graphite-normalized scale, the diamond
equilibrium threshold is about 2.0 at 1300 K, whereas graphite saturation occurs at unity. Diamond growth therefore requires kinetic selection above the graphite threshold, not a reversal of bulk phase stability. The analysis distinguishes thermodynamic driving force, kinetic accessibility, experimental detection limits, and the carbon retained after an experiment. It gives isotope-resolved tests for distinguishing sustained diamond growth from seed survival, transient carbon attachment, or failure to detect graphite. A $^{13}\mathrm{C}$-enriched diamond seed provides a test of natural-abundance gas or condensed carbon sources: a registered, crystallographically continuous $^{12}\mathrm{C}$-rich layer outside the original seed can establish source-attributed overgrowth without isotopically labeling each feed. The same accounting is extended to cubic boron nitride. Separate boron and nitrogen chemical potentials are required, and $^{10}\mathrm{B}/^{11}\mathrm{B}$ and $^{15}\mathrm{N}$ contrasts could distinguish reservoir supply from seed loss for each element. The resulting criteria make low-pressure metal-flux growth claims quantitatively testable and guide experiments, thermodynamic modeling, and atomistic simulation.
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Materials Science
First-Principles Atomistic Structure and Dynamics of Polyethylene During High-Pressure Radical Polymerization via Machine Learning Force Fields
Bharatha K. Gunawardana, Teresa Shah, Bicha Azizova et al. (+6 more)
Polyethylene (PE) is one of the most commonly used synthetic
polymers. While the synthesis and processing protocols for PE are well established, precise experimental assignment of microscopic structures at atomistic resolution (i.e., the position of each atom) remains largely limited to highly crystalline systems. This gap is often addressed via computer simulations using empirical interatomic potentials, which use approximate but efficient descriptions of interatomic interactions to reach the length and time scales needed to describe macromolecules. These empirical potentials typically perform well for bulk and/or collective properties but face challenges with chemical realism for complex systems, e.g., during reactive processes. In this work, we address this challenge by combining the computational efficiency of a deep potential (DP) machine-learning force field and the chemical realism of first-principles van der Waals (vdW) corrected hybrid density functional theory (DFT) enabled by a SeA high-throughput framework. Using this approach, we study the structure and dynamics of PE oligomers and
polymers in an ethylene solvent under common high-pressure (supercritical) radical polymerization conditions. We found that the local solvation environment of radical-containing PE oligomers converges for chain lengths greater than (n~6), suggesting extensibility of our oligomer-trained MLFF to significantly longer
polymers. We then confirmed the extensibility of these models to long PE chains by characterizing the molecular weight scaling of single-chain structure and dynamics, which showed classic good solvent behavior. Our PE MLFF retained a consistent level of fidelity and stability across a wide range of thermodynamic state points and chain lengths, at full atomistic resolution, therefore paving the way towards first-principles-based
polymer structure and property prediction.
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All authors Bharatha K. Gunawardana, Teresa Shah, Bicha Azizova, Deepa Ranabhat, Yizhi Song, Akshath Shastri, Srinjoy Ghose, Thomas E. Gartner III, Hsin-Yu Ko
Mathematical Physics · Cross-listed from math.AP
Existence of Large Boundary Layer Solutions for the Outflow Problem of Full Compressible Navier-Stokes Equations
Tianle Wang, Yi Wang and Qiuyang Yu
We investigate the existence and non-existence of large-amplitude boundary layer solutions to the
outflow problem for the one-dimensional full compressible Navier-Stokes equations on the half-line $\mathbb{R}_+$. Through a delicate global phase-plane analysis, we substantially extend the small-amplitude boundary layer solutions obtained via the center-
manifold approach to the large-amplitude regime. Based on the sign of $M_+-1$ (with $M_+$ denoting the Mach number at the right end state) and the Prandtl-number-related parameter $\zeta$, we provide a complete characterization of the existence and non-existence of large-amplitude boundary layer solutions for this half-space
outflow problem. In sharp contrast to the corresponding inflow problem, boundary layer solutions to the
outflow problem are permitted to be non-monotone, and their existence region in the phase plane can be an open set.
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Plasma Physics
State-Space Model-Enabled Reinforcement Learning for Magnetic Configuration Controlon EXL-50U
Pei Guo, Zhengyuan Chen, Jianguo Chen et al. (+17 more)
Accurate feedback control of the
plasma current ($I_p$) and centroid position $(R_c,Z_c)$ is essential for the stable operation of spherical
torus (ST)
plasmas. Conventional proportional-integral-derivative (PID) controllers require extensive manual tuning and struggle with the fast, strongly coupled dynamics that arise as
plasma performance improves. Reinforcement learning (RL) has recently emerged as a promising alternative to such complex
magnetic control problems, yet its practical deployment on ST devices remains challenging. This paper presents a practical RL controller for the EXL-50U ST, trained within a rigid RZIP state-space model (SSM) that enables efficient offline policy learning. A lightweight
plasma position reconstructor is developed to estimate $(R_c,Z_c)$ from
magnetic probe signals within the real-time control cycle. The trained policy is seamlessly deployed on the EXL-50U
plasma control system, achieving stable regulation of $I_p$ and $(R_c,Z_c)$ and sustaining discharges up to 650 ms under RL control. These results demonstrate the feasibility and practical potential of model-informed RL for
magnetic configuration control in ST devices, offering a promising direction beyond conventional PID-based schemes.
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All authors Pei Guo, Zhengyuan Chen, Jianguo Chen, Xuanhe Wang, Guoyang Shi, Siqi Ding, Yapeng Zhang, Lei Xing, Yong Liu, Xiang Gu, Tiantian Sun, Xiuchun Lun, Jia Li, Zhengxiong Wang, Huasheng Xie, Hanyue Zhao, Yuejiang Shi, Xianming Song, Tianyuan Liu, EXL-50U Team
Quantum Physics
Architectural scaling tradeoffs in modular 3D bosonic quantum processors
Shaojiang Zhu, Ugur Alyanak, Tanay Roy et al. (+7 more)
We propose a modular three-dimensional bosonic
quantum processor built from repeatable coupled-cavity modules linked by configurable interconnect networks. Using hardware-motivated graph-theoretic measures, we compare nearest-neighbor, hub-based, and hybrid architectures in terms of interconnect count, communication distance, resource concentration, and implementation complexity. Rather than identifying a universally optimal
topology, our analysis shows how these architectures redistribute the costs of scaling, including wiring and port requirements, nonlocal communication distance, exposure to shared resources, routing bottlenecks, and scheduling overhead. Case studies of a \(3\times3\) processor and a larger hierarchical architecture further distinguish finite-size performance from asymptotic scaling. The resulting framework provides a systematic basis for evaluating modular three-dimensional bosonic processors and for identifying the device-level parameters required for quantitative hardware design.
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All authors Shaojiang Zhu, Ugur Alyanak, Tanay Roy, Alessandro Reineri, Andy C. Y. Li, Taeyoon Kim, Srivatsan Chakram, Akshay Murthy, Anna Grassellino, Alexander Romanenko
Fluid Dynamics
Propagating fronts of convection rolls in Rayleigh-Bénard convection
Saikat Mukherjee and Mark Paul
We investigate the propagation of counter-rotating convection rolls in Rayleigh-Bénard convection initiated locally in a quiescent fluid layer under supercritical conditions. The velocity of the front separating quiescent fluid from the forming convection rolls, and the wavenumber of the convection rolls remaining behind the front, are explored. We numerically investigate fronts of forming convection rolls over five orders of magnitude of the reduced Rayleigh number, $\epsilon$, in 2D and 3D domains, for a broad range of boundary conditions, and for different front initiation approaches. In all cases, the front velocity increases as $\epsilon^{1/2}$ with increasing $\epsilon$ for $\epsilon \lesssim 1$ in agreement with predictions using the amplitude equation. The amplitude equation description of the front velocity remains accurate for $\epsilon \lesssim 10$ except when the Prandtl number is large which yields a velocity that is faster than predicted for a fluid layer far from threshold. The wavenumber of the convection rolls increases linearly with $\epsilon$ in agreement with the wavenumber that maximizes the growth rate of perturbations in the linear regime. Farther from onset, the wavenumber growth transitions to a reduced scaling of $\epsilon^{1/4}$ in agreement with predictions using the Swift-Hohenberg equation in the large $\epsilon$ limit. The scalings describing the wavenumber variation with $\epsilon$ are independent of the domain geometry, boundary conditions, and front initiation method. However, the front-selected wavenumber at criticality does not equal the critical wavenumber of the bulk instability, in general, and depends significantly upon these details. We compare our results with experimental measurements where possible.
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Computational Physics · Cross-listed from math.NA
Wasserstein Moment Nudging for Vlasov-Poisson Data Assimilation
Liyao Lyu, Xinyue Yu, David Schneidinger et al. (+1 more)
We introduce a continuous data assimilation method for particle-in-
cell simulations of the Vlasov-Poisson equation when only hydrodynamic moments are observed. The forecast state is an empirical measure on phase space, whereas the observed fields (density, bulk velocity, and temperature) constrain only a few velocity moments and leave the velocity-space shape of the distribution undetermined. We construct the moment feedback as a Wasserstein gradient flow of a moment-mismatch functional over phase-space measures. The resulting drift acts directly on particle positions and velocities, couples the density, momentum, and energy residuals through a single variational structure, and vanishes on the entire moment-compatible set. Under the standard Wasserstein metric, the energy residual produces a position correction that grows quadratically with the particle speed, and the particle system falls outside standard well-posedness theory. Our primary formulation pairs the quadratic moment mismatch with a velocity-weighted Wasserstein metric that penalizes spatial transport at large peculiar velocity relative to the observed bulk flow, which removes this growth. A direction-split variant retains the plain metric instead. Under the same weighted metric, an alternative moment-relative-
entropy functional yields an affine, shape-preserving velocity correction and explicit global moment balances for the space-inhomogeneous system. We prove that the finite-particle scheme with linear Lenard-Bernstein collisions is globally well posed. In 1D1V and 2D2V experiments with several collision models, the nudged formulations reduce bulk-velocity and temperature errors by up to two orders of magnitude relative to an unassimilated run.
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All authors Liyao Lyu, Xinyue Yu, David Schneidinger, Hayden Schaeffer
Fluid Dynamics
Translation of a spherical viscous drop driven by localized forcing in Stokes flow
Sho Kawakami, Yuan-Nan Young and Howard A. Stone
Localized forcing in the fluid inside or outside a viscous drop can drive drop translation. Using the Lorentz reciprocal
theorem, we derive an integral expression for the translational velocity of a spherical Newtonian drop subject to localized force and source distributions in either fluid and to interfacial traction. For a clean drop, we obtain explicit responses to Stokeslets, force dipoles, rotlets, general second force moments, and source dipoles as functions of position, orientation, and viscosity ratio. Interior forcing obeys a finite selection rule: only force moments through second order and the first source moment contribute directly to translation. Exterior forcing can couple to multipoles of all orders and produces distance-dependent responses. Although different enclosed singularities can produce the same drop velocity, resolving their exterior flows in drop-centered spherical Stokes modes provides additional constraints on the underlying forcing. We also distinguish regularized force distributions, governed by prescribed kernel moments, from resolved rigid particles, governed by low-order surface-traction moments and prescribed slip. The framework unifies these representations and shows how exterior-flow measurements provide information beyond drop translation, laying the foundation for constructing squirmer-like viscous drop solutions with controllable far-field behaviors.
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High Energy Physics (Phenomenology)
Thermal width shift of $\Delta^{++}$ in a pion gas
Ying Zhang, Peng-Yu Niu, Xin-yue Hu et al. (+2 more)
We compute the thermal width shift of the $\Delta^{++}$ resonance induced by a pion gas within a nonrelativistic effective field theory framework. The $\Delta^{++}$ self-energy is evaluated from pion-forward-scattering diagrams with intermediate
proton and $\Delta$ states, weighted by the thermal pion distribution. Analytical expressions for the imaginary part of the self-energy yield the temperature-dependent width correction $\delta\Gamma(T)$. The width increases with temperature, reaching approximately $6$~MeV at $T \approx 160$~MeV. When the temperature-dependent $\Delta$ and nucleon masses from an NJL-model
chiral restoration scenario are incorporated, the width shift becomes non-monotonic, peaking near $T \approx 140$~MeV—a consequence of the competition between collisional broadening and the shrinking $\Delta \to N\pi$ phase space as the $N$–$\Delta$ mass gap closes. Applying our formalism to
STAR data for $\Delta^{++}$ in d+Au collisions at $\sqrt{s_{NN}} = 200$~GeV, we extract a temperature $T \approx 300$~MeV at $p_t = 900$~MeV, consistent with the experimental extraction within errors. This value significantly exceeds the hadronic-phase temperature, explicitly demonstrating that the observed $\Delta^{++}$ width shift is not solely of pion-gas origin—genuine hot-medium and collective-flow contributions must be substantial.
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All authors Ying Zhang, Peng-Yu Niu, Xin-yue Hu, Kai-Jia Sun, Qian Wang
Earth and Planetary Astrophysics
A surviving pink spinel records an early aluminous melt on the ureilite parent body
Yaozhu Li, Phil J.A. McCausland, Roberta L. Flemming et al. (+2 more)
Ureilites are ultramafic achondrites interpreted as fragments of a differentiated parent body, yet their origin and
evolution remain debated because textural
equilibrium coexists with chemically primitive compositions. Here we report mineralogical, isotopic, and microstructural observations from polymict ureilite Elephant Moraine (EET) 87720. The sample contains unusually magnesian olivine (Mg# up to 98.7), Ca-poor pyroxene (Wo as low as 1.0), and rare coarse-grained pink aluminous spinel containing 56.4-58.7 wt% Al2O3 and 11.3-11.8 wt% Cr2O3. In situ triple oxygen isotope measurements of spinel and associated forsteritic olivine plot along the ~1-slope Carbonaceous Chondrite Anhydrous Mineral (CCAM) line, consistent with bulk ureilites. The clasts also follow the ureilitic Fe-loss/addition trend, with near-constant chondritic Mn/Mg ratios. These observations demonstrate that the clasts are indigenous to the ureilite parent body and extend the known ureilite oxygen isotope range to delta18O ~9.7 per mil. Three-dimensional dark-field X-ray microscopy reveals a hierarchical deformation microstructure in the spinel, comprising distributed
lattice curvature, localized slip-band-like boundaries, and coherent mosaic-domain boundaries, indicating multiscale accommodation of shock-induced
crystal-plastic deformation. We propose that the aluminous spinel crystallized from a locally Al-rich, Ca-poor melt under low oxygen fugacity. Al partitioning between coexisting spinel and olivine yields a crystallization temperature of 1318 +/- 43 K, consistent with a thermally elevated parent body. The spinel may therefore preserve a rare crystallization product of an early aluminous melt that has largely disappeared from the ureilite record, providing an archive of early planetary differentiation.
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All authors Yaozhu Li, Phil J.A. McCausland, Roberta L. Flemming, Noriko T. Kita, Carsten Detlefs