Peer Revenue Equity in science

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics

Watch Physics

Friday 2 October

Exactly Solvable and Integrable Systems

A novel extension of the canonical 2+1-dimensional Dym equation. Moving boundary problems solvable via Painleve' II Reduction

Colin Rogers and Sandra Carillo

An extension with temporal modulation is presented of the canonical 2 + 1-dimensional solitonic Dym equation as originally introduced by Konopelchenko and Dubrovsky. Application is made of admitted Painleve' II symmetry reduction to derive exact solution to a class of associated 2 + 1-dimensional nonlinear moving boundary problems of generalized Stefan-type.
Read the full abstract

Quantum Physics

Quasiparticle quantum simulation of materials with the Bethe-Salpeter equation

Jielun Chen, Jiace Sun and Garnet Kin-Lic Chan

The first-principles quantum simulation of the full electronic Hamiltonian of a material model of realistic size appears daunting even in a future era of fully fault-tolerant quantum computers. In contrast, classical simulations of material excited states rely on heuristic quasiparticle frameworks, such as the GW approximation and Bethe-Salpeter equation, where only a few quasiparticles are explicitly considered. Here we give a detailed description of quasiparticle quantum simulation for multi-excitonic states within the BSE. We develop an explicit first-quantized, orbital-based block encoding of the multi-exciton BSE Hamiltonian for qubitization, and reduce its cost using integral factorization and crystal symmetries. For a materials model of size $N$, and a fixed number of quasiparticles, the resulting algorithms require $\widetilde{O}(N)$ Toffoli gates and $O(\log N)$ logical qubits, or, using space-time tradeoffs, $\widetilde{O}(\sqrt{N})$ Toffoli gates and $\widetilde{O}(\sqrt{N})$ logical qubits, achieving up to a sixth power reduction in Toffoli count, or up to exponential reduction in qubit count, versus standard full Hamiltonian simulation techniques that have been explored in materials simulation. Resource estimates for the classically challenging problem of triexcitonic eigenvalue estimation across a range of semiconductor models of a realistic physical size of $O(10^3)$ atoms, show that our Toffoli-optimized implementation reduces the Toffoli count by $10^6-10^7$ relative to full Hamiltonian simulation estimates, while a qubit-optimized implementation requires only a few hundred logical qubits. More broadly, these results show that classical heuristic frameworks will be essential in the design of future fault-tolerant quantum algorithms for materials.
Read the full abstract

Chemical Physics

Preparation sequence controls oxygen partitioning between boron and lithium on tungsten

Predrag S Krstic, Meral Sharkass, Swarit Dwivedi et al. (+3 more)

Classical reactive molecular dynamics of boron- and lithium-conditioned tungsten surfaces show that the order in which boron and oxygen are introduced - not the boron inventory - controls surface chemistry. On a thin engineered tungsten oxide, boron captures 81% of oxygen and consumes the oxide; on an engineered ~2 nm mixed WO3/WO2 film, boron captures only 20% and leaves 52% of reaction-zone tungsten in WO3-like coordination; and in a co-deposited W-B substrate later exposed to oxygen, boron captures only 28% despite a tenfold larger inventory. Adding lithium leaves the oxide-first cases unchanged but transforms the co-deposited case, where lithium becomes the dominant oxygen captor (58%) and a lithium-borate-glass-like network form. We outline the expected, divergent responses of the boron-only and boron-plus-lithium materials to deuterium irradiation.
Read the full abstract

All authors Predrag S Krstic, Meral Sharkass, Swarit Dwivedi, Dalia Sayed Ahmed, Yun Kyung Shin, Adri CT van Duin

General Relativity and Quantum Cosmology

Uniform Strong-Deflection Lensing in Near-Extremal Kerr

Shakibul Chowdhury

Strong-deflection lensing by a subextremal Kerr black hole exhibits a logarithmic critical divergence, whereas the exactly extremal prograde problem develops stronger power-law behavior. We construct a uniform asymptotic description of the transition between these regimes for prograde equatorial null geodesics. The distinguished joint near-critical and near-extremal limit occurs when the impact-parameter offset from the exact critical value is of order \(M\kappa\), where \(\kappa=\sqrt{1-a^2/M^2}\). In this limit, the Kerr radial potential reduces to a quadratic normal form, yielding an analytic crossover function that connects the subextremal logarithmic and extremal power-law regimes. We derive a matched next-to-leading-order correction and validate it against high-precision integrations of the exact Kerr geodesic equations, finding improvement for all 55 trajectories tested. The same asymptotic structure yields a higher-order image-branch law interpolating between algebraic and exponential accumulation, with crossover order scaling as \(\kappa^{-1}\). We also derive and numerically validate the corresponding image-branch coordinate-time delay law, whose high-order extremal-like limit approaches the horizon-period spacing \(4\pi M\).
Read the full abstract

Fluid Dynamics

Radiometer effect on an infinitely thin circular disk

Takuma Tomita, Satoshi Taguchi and Tetsuro Tsuji

The radiometer effect is a self-thermophoretic phenomenon in which a thin body with a temperature difference between its two sides experiences a force in a rarefied gas. We numerically investigate this effect for an infinitely thin circular disk freely translating at its terminal velocity in an otherwise quiescent gas. The problem is formulated using the linearized Bhatnagar–Gross–Krook model of the Boltzmann equation with the diffuse reflection boundary condition. A major difficulty arises from the sharp disk edge, which generates discontinuities in the velocity distribution function that propagate into the gas. Accurate resolution of these discontinuities is essential for capturing the edge-localized stress associated with the radiometric force in the near-continuum regime. The discontinuities are explicitly accounted for using a characteristic-based numerical scheme, together with the appropriate far-field asymptotics for the unbounded domain. The radiometric force, the terminal velocity, and the flow and stress fields are obtained over a wide range of Knudsen numbers. The dimensionless radiometric force increases monotonically with the Knudsen number, scaling as $\mathrm{Kn}^{3/2}$ in the continuum limit and approaching a constant in the free-molecular limit. The terminal velocity exhibits a nonmonotonic dependence on the Knudsen number and slightly exceeds its free-molecular-limit value at intermediate Knudsen numbers. In the continuum limit, the magnitude of the edge-localized variation of the normal-stress difference appears to remain finite, whereas its characteristic width is of the order of the molecular mean free path. The resulting numerical data also provide reference solutions for future studies of sharp-edge kinetic problems. Finally, the computed radiometric force is independently validated using the symmetric relation for the linearized Boltzmann equation.
Read the full abstract

Optics

Non-Markovian Entanglement via Parametrically Mediated Molecular Cavity Optomechanics

Wenyao Hu, H. N. Liu, X. C. Zhang et al. (+3 more)

Quantum entanglement in molecular cavity optomechanical (COM) systems serves as a fundamental resource to explore quantum-enhanced sensing, coherent molecular dynamics, and quantum information processing, which has been studied under Markovian approximation but not yet explored in non-Markovian reservoirs. In this paper, we propose a scheme to manipulate quantum entanglement in molecular COM system coupling with degenerate optical parametric amplifier (DOPA) under Markovian approximation. We reveal that both strength and phase of DOPA can be tuned to enhance optical-vibration entanglement and suppress vibration-vibration entanglement. The optical-vibration entanglement can exist at room temperature, demonstrating strong robustness against thermal noise. Moreover, we extend results from Markovian to non-Markovian regimes, which can further enhance both types of entanglement with DOPA fixed. In particular, we find that non-Markovian effects can reverse influences of DOPA on vibration-vibration entanglement from suppression to enhancement, leading to regeneration of entanglement. The scheme provides an effective way to control and enhance quantum entanglement in molecular COM system through steering DOPA and non-Markovian effects.
Read the full abstract

All authors Wenyao Hu, H. N. Liu, X. C. Zhang, Cheng Shang, Yan-Hui Zhou, H. Z. Shen

Mathematical Physics · Cross-listed from math.PR

Rank-One HCIZ Integrals and Multiplicative Convolutions

Benoît Collins, Nicolas Delporte, Manasa Nagatsu et al. (+1 more)

We study how spectral averaging interacts with the logarithm in large-dimensional rank-one Harish-Chandra–Itzykson–Zuber (HCIZ) integrals. For independent bi-unitarily invariant matrices $A,B$ with uniformly bounded deterministic singular values and weakly convergent empirical spectral measures of their Gram matrices, the integral for $(BA)^*(BA)\otimes\mathbf{1}_N$ has two limiting descriptions at speed $N^2$ for small real parameters: averaging its logarithm gives free multiplicative convolution, whereas taking the logarithm after averaging gives classical multiplicative convolution. We also prove an exact finite-dimensional equality between this annealed integral and the one for $(A^*A)\otimes(B^*B)$. For every fixed number of factors $k\geq3$, we construct counterexamples showing that the analogous equality can fail even asymptotically. For tensor products with any fixed number $k$ of factors, global Haar vectors at speed $N^k$ and product-state vectors at speed $N$ yield classical and free multiplicative convolution, respectively, for small real parameters under the corresponding hypotheses. We also derive the known multiplicativity of the $S$-transform.
Read the full abstract

All authors Benoît Collins, Nicolas Delporte, Manasa Nagatsu, Reiko Toriumi

High Energy Astrophysical Phenomena

Study of the Ultra-Long GRB 220627A: Exploring a Possible Blue Supergiant Collapsar Origin

Ayush Garg, Amit Shukla, Dorottya Szécsi et al. (+1 more)

Ultra-long gamma-ray bursts (ul-GRBs) challenge standard collapsar models because their extreme durations require central engines active for $\sim10^{3}-10^{4}$ s. While the prompt spectral evolution of typical GRBs is difficult to resolve due to their short durations, ul-GRBs provide a unique opportunity to study spectral evolution on extended timescales. We present a time-resolved spectroscopic study of GRB 220627A, one of the most luminous ul-GRBs known ($E_{\rm iso}\sim10^{54}$ erg, $T_{90}>1000$ s), consisting of two bright emission episodes separated by $\sim600$ s quiescent interval. Using a novel HOP algorithm-based segmentation method, we identify optimal time intervals for time-resolved spectroscopy. A Comptonized power-law (CPL) model well describes the prompt emission ($\sim 10$ keV-40 MeV) across all timescales. Fermi-GBM spectroscopy reveals a transition from a hard, slow-cooling synchrotron spectrum ($\alpha_{\rm I}=-0.70$) during episode-I to a softer, fast-cooling synchrotron spectrum ($\alpha_{\rm II}=-1.29$) during episode-II. This evolution closely resembles that of the magnetar-candidate GRB 091024A, highlighting a potential progenitor degeneracy based solely on spectral evolution. However, the extreme isotropic-equivalent energy exceeds the maximum energy available from magnetar spin-down, strongly favouring a blue supergiant (BSG) collapsar origin. The prolonged activity and multi-episode structure are naturally explained by sustained accretion through an extended stellar envelope. Our results demonstrate that ul-GRBs can display magnetar-like spectral evolution while being powered by BSG collapsars. GRB 220627A highlights the need for combining time-resolved spectroscopy with energetic constraints to distinguish between progenitor scenarios and understand the physical origin of ul-GRBs.
Read the full abstract

All authors Ayush Garg, Amit Shukla, Dorottya Szécsi, G. C. Anupama

Mesoscale and Nanoscale Physics

Topological insulators on complex networks

Sunkyu Yu, Xianji Piao and Namkyoo Park

The landscape of topological insulators has expanded beyond its traditional domain of periodic lattices with short-range hopping. Related studies have explored topological phenomena under non-Euclidean geometries, disordered structures, and long-range hopping, progressively narrowing the gap between topological phases of matter and complex networks. Here we demonstrate that genuine complex networks, far beyond periodic lattices and their conventional variants, can themselves host topological insulating phases. By developing a nonconflicting design framework for multiple topological objectives, we realize topological insulators in high-degree Hofstadter lattices and across regular, small-world, and random networks. This generalization uncovers distinct network-specific features, including an expanded range of attainable topological characteristics, a degree-dependent transition from Hofstadter-type to Haldane-type Chern insulators, and, most notably, the superior robustness and reconfigurability of small-world topological insulators. Our graph-theoretic framework establishes network complexity as a resource for realizing high-capacity and reconfigurable topological insulators.
Read the full abstract

Soft Condensed Matter

Orientational origin of nonlinear shear rheology in unentangled polymer melts

Souta Miyamoto, Takeshi Sato, John J. Molina et al. (+1 more)

Universal rheological properties of unentangled polymer melts are investigated through the stretch-orientation decomposition of polymer dynamics. By externalizing stretch from the explicit state of each Rouse mode, we construct a constitutive model with orientational kinetics that preserves the Rouse relaxation spectrum. The resulting model yields the observed steady-shear scalings of the shear viscosity and first normal-stress coefficient, predicts a finite second normal-stress coefficient, and approximately reproduces the Cox-Merz and Gleissle-Osaki rules. The derived steady-oscillatory shear correspondence further identifies an elastic contribution, associated with the first normal stress difference, that is absent from the conventional Cox-Merz rule.
Read the full abstract

All authors Souta Miyamoto, Takeshi Sato, John J. Molina, Takashi Taniguchi

Statistical Mechanics

Structural crossover of complex networks: bridging degree correlation and fractality

Shogo Mizutaka, Jun Yamamoto and Kousuke Yakubo

We investigate the relationship between long-range degree correlations and fractality in scale-free random networks. By analyzing degree correlations in scale-free random networks at the percolation threshold, at which a giant component emerges, we derive the ball volume $\tilde{\nu}_k(l)$, defined as the average number of nodes within distance $l$ from a root node with degree $k$. The resulting expression predicts a degree-dependent structural crossover. For $l\ll k^{1/(\df-1)}$, the ball volume grows as $\tilde{\nu}_k(l)\sim kl$, whereas for $l\gg k^{1/(\df-1)}$, it crosses over to the global fractal scaling $\tilde{\nu}_k(l)\sim l^{\df}$. Here, $\df$ is the fractal dimension of critical scale-free random networks. We further show that the structural crossover can be naturally understood in terms of critical branching processes and is also observed in empirical fractal networks.
Read the full abstract

Classical Physics · Cross-listed from cs.DC

PaxosLease in Relativistic Inertial Frames

Márton Trencséni

A lease grants one holder exclusive authority over a resource for a fixed term, and its safety property guarantees that at most one holder has the lease at any time. Under special relativity “at any time” has no frame-independent meaning for participants in relative motion. This note first restates the classical safety property with light cones, requiring a holder's expiry to lie in the causal past of any later acquisition by a different holder, an order every observer agrees about. Second, the paper modifies classical PaxosLease: the core change is that the containment and quarantine rules each gain a factor of $k = \sqrt{(1+\beta)/(1-\beta)}$, the relativistic Doppler factor, where $\beta$ is relative speed as a fraction of the speed of light.
Read the full abstract

Materials Science

Orientation refinement for nanobeam precession electron diffraction patterns using spot intensity profiles

Arthur Després, Muriel Vérion and Edgar F. Rauch

We develop a method to measure crystallographic orientations with high angular resolution for nano-beam precession electron diffraction patterns, and applicable to 4D scanning precession electron diffraction. We show that internal variations of intensity in the diffraction spots can be simulated and correlated to experimental variations to measure the crystallographic orientation with a much better angular resolution that with the standard method of automated crystal orientation mapping (ACOM). In a tilt series carried out with long exposure time on a monocrystal of silicon around the main goniometer tilt axis, the imposed tilt angles are retrieved with a 0.044{\deg} to 0.054{\deg} precision with refinement, against 0.25{\deg} to 0.33{\deg} with the standard method. Shorter exposure times, introducing Poisson noise, marginally degrade the precision to a 0.054{\deg} to 0.066{\deg} range. The method also corrects a systematic error of ACOM near zone axis.
Read the full abstract

Quantum Physics

From Heat to Homology: Spectral Gap Transfer for Exact Quantum Gibbs Sampling at All Temperatures

Caesnan M. G. Leditto, Kuo-Chin Chen and Min-Hsiu Hsieh

Preparing Gibbs states through dissipative dynamics requires controlling convergence for the chosen Hamiltonian $H$ and coupling operators. However, efficient implementation requires convergence guarantees from the spectral gap of the generator of the dynamics, which remains a crucial challenge. Recent results address the challenge by restricting the dynamics with structural assumptions about the Hamiltonian and its interactions. For the Chen-Kastoryano-Gilyen (CKG) construction and arbitrary finite-dimensional Hamiltonians, we prove an explicit comparison that converts a spectral gap estimate for the infinite-temperature generator into a lower bound on the spectral gap of the CKG quantum Gibbs sampler at every finite positive inverse temperature $\beta$. It allows a single spectral gap estimate at infinite temperature to certify convergence across Hamiltonians and temperatures. Such an estimate is often known from a classical spectral gap estimate, such as the classical random walk spectral gap. For Hodge Laplacians of simplicial complexes as Hamiltonians, we construct coupling operators whose generator at infinite temperature has the same spectral gap as a classical simplicial down-up walk. A positive spectral gap of the walk and bounded spectral width $W=\lambda_{\max}(H)-\lambda_{\min}(H)$ give a generator spectral gap independent of the number of simplices at every fixed temperature. We then establish conditions under which the sampler approximately prepares zero-energy (harmonic) states in polynomial evolution time. This provides a conditional convergence guarantee for the state preparation in the thermal approach to quantum topological data analysis.
Read the full abstract

High Energy Physics (Experiment)

First measurement of the low-momentum negative-muon beam for the muon-to-electron conversion experiment at J-PARC

The COMET Collaboration: K. Oishi, R. Abramishvili, G. Adamov et al. (+182 more)

The COMET Phase-$\alpha$ experiment, the initial beam-operation stage of the COMET muon-to-electron conversion programme at J-PARC, took place in 2023 and marked the first beam operation at the COMET facility. It served to commission the delivery of a bunched, slow-extracted 8 GeV proton beam and the muon beamline. Its objective was to demonstrate experimentally that low-momentum negative muons could be transported to the experimental area through the Transport Solenoid (TS). We report a measurement of the transported muon beam using the Range Counter, a dedicated detector that identifies stopped negative muons by detecting delayed electrons emitted after the muons stop in a copper absorber. From the measured decay-time spectra, we reconstruct the number of stopped muons, the corresponding momentum spectrum, and the transverse beam profile. The observation of the stopped-muon component demonstrates that slow negative muons were transported through the TS to the experimental area. The reconstructed momentum spectrum indicates that the transported beam is concentrated in the low-momentum region. The non-uniform transverse profile is qualitatively consistent with charge drift in the curved solenoidal magnetic field. A Geant4-based simulation reproduces the overall dependence on degrader thickness and detector position; the measured yields are systematically higher by roughly 30%. These results provide the first experimental benchmark of low-momentum negative-muon transport in COMET and establish the basis for future beam characterisation and production studies.
Read the full abstract

All authors The COMET Collaboration: K. Oishi, R. Abramishvili, G. Adamov, J. C. Angelique, K. Aoki, M. Aoki, Y. Arimoto, A. N. B. Az, I. Bagaturia, D. Bauer, T. Bouillaud, L. Del Buono, C. Cârloganu, N. Chadeau, Y. Chen, P. Chetry, D. Chokheli, T. Clouvel, P. D. Dauncey, S. Dekkers, R. Derveni, G. Devidze, P. J. Dornan, M. T. Dubouchet, L. B. Epshteyn, I. Evtoukhovitch, P. Evtoukhovitch, G. Faure, S. Fayer, G. V. Fedotovich, Y. Fujii, Y. Fukao, E. George, E. L. Gillies, M. Gouzevitch, D. N. Grigoriev, E. Hamada, I. H. Hashim, S. Hashimoto, M. Higashide, Y. Higuchi, N. Hiroshima, Y. Igarashi, F. V. Ignatov, M. Iio, M. Ikeno, K. Ishibashi, T. Itahashi, A. Jansen, R. Jeena, O. Jeremy, X. Jiang, P. M. Jonsson, Y. Kageyama, V. Kalinnikov, E. Kaneva, F. Kapusta, K. Kawagoe, R. Kawashima, N. Kazak, A. Khvedelidze, Y. Kojima, A. N. Kozyrev, B. Krikler, Y. Kuno, S. Kuribayashi, Y. Kurochkin, N. Kurosawa, A. Kurup, K. Ladhams, P. Lebrun, M. J. Lee, H. Li, W. Li, R. P. Litchfield, D. Lomidze, I. Lomidze, G. Macharashvili, Y. Makida, S. Makimura, G. Matsumoto, S. Matsumoto, A. Melnik, H. Miao, S. Mihara, A. Miles, M. Miyataki, Y. Miyazaki, T. Mizuno, M. Moritsu, R. Muto, R. Nagai, H. Nagashima, Y. Nakai, T. Nakamoto, Y. Nakamura, Y. Nakatsugawa, Y. Nakazawa, J. Nash, M. A. S. Nasrullah, T. M. Nguyen, V. Niess, Y. S. Ning, H. Nishiguchi, M. Nishihara, K. Noguchi, N. H. M. Nor, N. Norjoharuddeen, T. Ogitsu, H. Ohata, N. Ohuchi, K. Okabe, T. Okamura, H. Okurano, M. Oonaka, J. Pasternak, A. Paulau, D. Pieters, V. Raspal, R. Razali, A. Razquin, W. Roth, B. Sabirov, T. Saito, H. Sakamoto, P. Sarin, K. I. Sasaki, R. Sasaki, A. Sato, J. Sato, H. Sendai, N. Shigyo, M. Shinjo, Z. Shioya, M. Shoji, Dz. Shoukavy, W. Da Silva, A. Simonenko, D. Stöckinger, N. Sumi, A. Sumimura, S. Sun, J. Suzuki, S. Takami, S. Tanaka, J. Tang, J. Tojo, M. Tomizawa, T. Toriashvili, N. Tran, Z. Tsamalaidze, N. Tsverava, T. Uchida, Y. Uchida, Y. Uchiyama, S. Ueda, K. Ueno, Y. Uesaka, D. Vasileuskaya, E. Velicheva, M. L. Wong, T. S. Wong, C. Wu, T. Xing, Y. Xu, C. Yamada, H. Yamaguchi, M. Yamanaka, Y. Yang, W. Yao, B. Yeo, H. Yoshida, M. Yoshida, M. Yoshii, D. Yoshikawa, T. Yoshioka, Y. Yuan, Yu. V. Yudin, N. Yussup, I. Yusuff, J. Zhang, Y. Zhang, Z. Zhang, Y. Zhou, K. Zuber

Quantum Physics

Thermalization in a repeated-interaction model with memory effects

Kanji Nishii, Ryo Nagai and Yoshihiko Abe

We study how memory affects the thermalization of a qubit in a repeated-interaction model. In our model, a memory qubit interacts repeatedly with the system, while both qubits undergo collisions with fresh thermal ancillas. We derive exact closed evolution equations for their populations and mutual coherence, and demonstrate memory effects using a causal-break operation. Although the system converges to the target thermal state, the thermalization behavior shows non-monotonic approach. We also find a Mpemba-like reversal, in which the number of collisions required for thermalization depends non-monotonically on the temperature of the target state. Within the initial-state family considered, both phenomena require initial coherence between the system and memory or an imbalance in their excited-state populations.
Read the full abstract

Soft Condensed Matter

Nonlocal, nonlinear electrostatics: like-charge attraction and asymmetric solvation

V. Stepanyan, Y. Sh. Mamasakhlisov and A. E. Allahverdyan

We study an equilibrium system, where linear molecules with a rigid charge distribution interact via the mean-field generated by the Coulomb coupling. We focus on the nonlinear regime, which is valid close to external charges immersed in the system. The finite molecular size in this regime leads to a nonlocal response at short distances. First, we show that the mean-field potential is non-monotonic, i.e., like charges can attract each other. Second, we show that the polarization induced by an external charge (and hence its solvation structure) depends on the sign of this charge, violating the effective C-symmetry of the macroscopic electrodynamics. We identify several scenarios of this effect, characterize it with the free energy and entropy differences, and compare it with analogous effects in asymmetric electrolytes described by nonlinear Poisson-Boltzmann equations.
Read the full abstract

Chaotic Dynamics

An Arrow of Time in Stable Autonomous Generation

Zhixin Lu

Does stable autonomous generation select a direction of time? This question matters both for learning models that autonomously generate prescribed dynamics and for designing controllers that make an invariant set attracting without changing its dynamics. Periodic motion and quasiperiodic torus rotations admit stable generation in either direction. For a chaotic attractor, however, reversing the equations reproduces its backward trajectories while turning attraction into repulsion. Can additional latent variables or autonomous feedback restore attraction without changing the reversed motion? We prove an obstruction to such exact generation by finite-dimensional autonomous systems with $C^2$ vector fields, compact attracting sets, and continuous readouts. The result applies to the classical Lorenz attractor and, more generally, to dynamics with an ergodic invariant measure of positive metric entropy whose intrinsic local stable fibers are totally disconnected on a set of positive measure. The proof connects this geometry to an entropy contradiction: a hypothetical attracting realization would force the output entropy to vanish, contrary to the prescribed chaotic dynamics. We use reservoir-computing examples to illustrate the difficulty of stable autonomous generation for time-reversed chaos: both time directions are closely tracked while the networks are driven by data, but only the forward example retains Lorenz geometry during autonomous generation. The theorem identifies a class of dynamics that cannot be learned for exact, stable autonomous generation by finite-dimensional smooth models satisfying the stated assumptions, regardless of the learning procedure or the number of latent variables.
Read the full abstract

Optics

Fast Nanophotonic Inverse Design using Precomputed Numerical Green Functions

Thi Phuong Thao Nguyen, James Wang and Constantine Sideris

Inverse design has been transformative in nanophotonics, providing an automated means of realizing high-performance, non-intuitive devices. However, the primary bottleneck of existing inverse design approaches is their reliance on time-consuming and computationally expensive full-wave electromagnetic simulations. In this work, we extend the Precomputed Numerical Green Function (PNGF) method for the first time to nanophotonic inverse design, accelerating evaluation of the forward problem by multiple orders of magnitude with no loss in accuracy compared to the full-wave solution. After a single, fully parallelizable precomputation step, both the objective function and its gradient can be evaluated through simple calculations whose cost scales linearly with the size of the design region. A low-rank matrix update technique further reduces the cost of objective function evaluation, yielding sub-millisecond computation times per iteration. Design examples using both gradient-based level-set optimization and tile-flipping direct binary search often achieve more than three orders of magnitude speedup in design time, resulting in an ultrafast photonic inverse design platform that can design new devices from scratch in seconds.
Read the full abstract

High Energy Physics (Phenomenology)

Kinetic Equilibrium between SIMP Dark Matter and Radiation via Internal Bremsstrahlung

Xiaoyong Chu, Ajay Kaladharan and Yassine El Mohtadi

As an alternative to standard dark matter freeze-out via two-body annihilation, strongly interacting massive particles are proposed to regulate their relic abundance through three/four-body self-annihilation. During such freeze-out, dark matter must undergo both number reduction and energy dissipation. The former requires number-reducing processes, and the latter requires an efficient energy-dissipation mechanism. In this work, we propose a novel mechanism where internal Bremsstrahlung processes establish kinetic equilibrium between dark matter and radiation, and thus dissipate energy. More appealingly, this mechanism can be naturally realized in a class of strong dynamics models with flavor-universal quarks and a light axion. To demonstrate our results in a $Sp(4)_c$ dark-color model, we compute all relevant interaction terms and numerically solve the full Boltzmann equations. The same mechanism can also be applied to vector dark matter models.
Read the full abstract

Mesoscale and Nanoscale Physics

Extracting the anyon charge from shot noise in complex fractional quantum Hall edges

Jinhong Park and Christian Spånslätt

Shot-noise measurements with a quantum point contact provide a direct probe of the quasiparticle charge in Laughlin fractional quantum Hall (FQH) states. However, the interpretation of such measurements becomes more subtle for multichannel edges, where the point-contact tunneling noise coexists with noise generated by intermode equilibration and heating. We develop a general framework that incorporates both these contributions and apply it to the paradigmatic $\nu=2/3$ FQH edge. We derive expressions for the drain auto- and cross-correlations in a four-terminal QPC geometry and show that equilibration-induced heating affects the auto- and cross-correlations in parametrically different way than the intrinsic partition noise. This distinction permits us to propose a specific combination of the two correlations which strongly suppresses the heating contribution and fully recovers the tunneling quasiparticle charge. Our results thereby provide a systematic framework for interpreting shot-noise measurements in complex FQH edges and can be further extended to more general counterpropagating edge structures.
Read the full abstract

Materials Science

Emergent Noncoplanar Spin Chirality through Magnetic and Nonmagnetic Substitution in the Kagome Antiferromagnet Mn$_3$Sn

Anupam Barik, Achintya Low, Susanta Ghosh et al. (+2 more)

Controlling noncoplanar spin textures in centrosymmetric magnets remains a central challenge for realizing emergent Berry-phase phenomena. Here, we demonstrate that magnetic (Cr) and nonmagnetic (Cu) substitution at the Mn site provide distinct routes to engineer spin chirality and topological transport in the kagome antiferromagnet Mn$_3$Sn. Cr substitution enhances low-temperature spin canting, stabilizing a dense noncoplanar texture that yields a pronounced topological Hall effect (THE) at low temperatures. In contrast, Cu substitution drives a spin-reorientation transition accompanied by an easy-axis rotation, creating a broad temperature window (150–208 K) where competing magnetic anisotropies stabilize noncoplanar spin textures and generate a large THE. A concurrent carrier-type crossover signals an underlying electronic-structure reconstruction. These results reveal that exchange enhancement and exchange dilution represent two fundamentally different pathways for tuning real-space Berry curvature, establishing chemical substitution as a powerful strategy for engineering topological transport in kagome antiferromagnets.
Read the full abstract

All authors Anupam Barik, Achintya Low, Susanta Ghosh, Kapildeb Dolui, Setti Thirupathaiah

Quantum Physics

Quantum Error-Corrected Memories Keep Proper Time

Sebastian P. Kish and Simon J. Devitt

What does quantum error correction do to relativistic proper time? We show that when two error-corrected quantum memories follow distinct worldlines and are controlled by local references, their local correction histories factor exactly from the proper-time difference between them. Error correction therefore does not erase time dilation: when the memories are compared, the accumulated difference appears as a relational phase rotation. During locally referenced operation this rotation is invisible to every local error syndrome; at discrete phases admitted by a code, the final relational evolution instead returns exactly as a deterministic logical gate, including an $S$-type Clifford gate at a $\pi/2$ excursion. These results connect fault-tolerant quantum information with relativistic clocks and establish protected quantum memories as a platform for preserving proper-time information and for long-coherence tests of quantum evolution involving relativistic proper time.
Read the full abstract

Earth and Planetary Astrophysics

Joint RV-Astrometric Analysis of two-planet system HD 65216: Prospects for Gaia DR4

Alexander L. Wallace, Robert A. Wittenmyer and Jonathan Horner

We provide updated mass and orbital constraints on the planetary system around HD 65216, consisting of at least two giant planets on eccentric orbits. We first analyse new RV data to constrain the periods and eccentricities of both planets, before applying the Hipparcos-Gaia proper motion anomaly to constrain the inclination of HD 65216 c. From this joint analysis, we find that HD 65216 c is most likely in an eccentric orbit ($e$ = 0.42$\pm$0.05) with a longer period (7007$^{+192}_{-161}$ days) than previously determined. The proper motion anomaly is consistent with a bimodal distribution of inclinations, with peaks at sin$i\sim$0.5, producing true masses of 2.23$^{+0.96}_{-0.77}$ M$_{\mathrm{J}}$ and 3.32$^{+1.40}_{-1.16}$ M$_{\mathrm{J}}$ for HD 65216 b and c respectively, assuming the planets are co-planar. Finally, we simulate Gaia DR4 epoch astrometry and the DR3-DR4 proper motion anomaly. We find that these methods will be sensitive enough to further constrain orbital parameters and true mass.
Read the full abstract

Mathematical Physics

Stratification of the space of density matrices via invariant theory and Uhlmann's connection

Howy Jordan, Markus J. Pflaum and Gerd Rudolph

The space of $n\times n$ density matrices is the full state space of an $n$-level quantum system. While it has been asserted in the literature on quantum information theory that decomposing this state space into equirank pieces yields a Whitney stratification, rigorous proofs have remained absent. Using methods from invariant theory, this work provides a proof that the rank decomposition of the matrix algebra constitutes a (b)-regular stratification in the sense of Whitney. Furthermore, we demonstrate how the Uhlmann connection - which describes the adiabatic holonomy of mixed states and reduces to the Berry connection on pure states - can be geometrically treated as a stratified connection on a stratified vector bundle. Finally, our appendix provides a self-contained exposition of stratified fiber bundles and the new concept of stratified connections, which may be of independent interest.
Read the full abstract

Nuclear Theory

Precise description of spontaneous fission half-lives of Rutherfordium isotopes within the relativistic Hartree-Bogoliubov theory

Jie Zhao

I investigate the spontaneous-fission (SF) half-lives of $^{254,256}$Rf within the multidimensionally constrained relativistic Hartree-Bogoliubov (MDC-RHB) model combined with the local quasiparticle random-phase approximation (LQRPA) method. The collective inertia is evaluated using the finite-amplitude method (FAM), which enables a fully self-consistent treatment of dynamical residual effects beyond the conventional cranking approximation. The effective collective potential is constructed by subtracting both the vibrational zero-point energy and rotational energy correction from the deformation energy surface. The SF half-lives are evaluated within the Wentzel-Kramers-Brillouin (WKB) approximation. Compared with the nonperturbative and perturbative cranking approximation, the FAM-LQRPA collective inertia is significantly enhanced, especially around the ground-state minimum, due to the dynamical residual interaction included in the QRPA. As a consequence, the predicted SF half-lives increase by several orders of magnitude and become consistent with experimental data. The calculated SF half-lives are 5.65 $\mu$s for $^{254}$Rf and 0.95 ms for $^{256}$Rf, both within approximately two orders of magnitude of the corresponding experimental values. These results indicate that a self-consistent treatment of dynamical residual effects and beyond mean-field correlations is crucial for quantitative microscopic descriptions of SF within covariant density functional theory.
Read the full abstract

Optics

Absence of universal backscattering immunity in reciprocal photonic waveguides

Yecheng Hu, Ming Gao, Wei Xie et al. (+6 more)

Suppressing parasitic back-reflection caused by imperfections, such as random defects, material inhomogeneities, localized inclusions, and fabrication-induced geometric deviations, has long been a central objective in optical-waveguide engineering. In this Letter, we theoretically establish that universal immunity to backscattering from arbitrary disorder is fundamentally impossible in reciprocal optical waveguides, irrespective of whether the underlying structure is topologically trivial or nontrivial.We establish this result through two complementary constructions of physically admissible reciprocal perturbations. The first considers weak permittivity perturbations of finite spatial extent within the first Born approximation, whereas the second considers optically small dielectric perturbations of finite contrast. In each construction, an admissible realization exists that produces a nonzero leading-order backward-scattering amplitude. We trace the fundamental origin of this limitation to the absence in photons of the intrinsic spin-$\tfrac{1}{2}$ and fermionic time-reversal structure underlying Kramers protection in electronic systems. Consequently, any mechanism that enforces photonic backscattering suppression throughout a prescribed class of disorder must instead be engineered into the underlying electromagnetic structure and its constitutive response, which can itself be modified by generic reciprocal perturbations. Numerical examples in representative reciprocal topological waveguides further illustrate these limitations for random defects and sharp bends. We further identify several constructive strategies for suppressing back-reflection within certain prescribed classes of disorder.
Read the full abstract

All authors Yecheng Hu, Ming Gao, Wei Xie, Yinxiang Xiong, Canqiu Dong, Zhuoyuan Lu, Yuerui Lu, Sid Assawaworrarit, Alex Y. Song

Quantum Physics

Design Automation for Gray-Code Quantum Read-Only Memory

Hao-Yu Lu, Yu-Ting Kao, Yeong-Jar Chang et al. (+2 more)

We propose a programmable quantum read-only memory based on Gray code encoding, termed GQROM, designed to efficiently load classical data into quantum circuits. This architecture mitigates critical bottlenecks in near-term quantum computing by reducing initialization overhead and gate-induced errors. By utilizing Gray code, in which consecutive addresses differ by only a single bit, GQROM minimizes state transition complexity. We demonstrate the architecture's flexibility in accessing targeted data through initial-state modification. The entire design, including a systematic EDA flow, was implemented and validated on the Qiskit platform, confirming its practical feasibility. These results underscore GQROM's potential as a scalable and hardware-friendly solution for efficient state preparation in quantum circuits.
Read the full abstract

All authors Hao-Yu Lu, Yu-Ting Kao, Yeong-Jar Chang, Chao-Hung Wang, Darsen D. Lu

Solar and Stellar Astrophysics

Formation and Eruption of a Vortex-driven Magnetic Flux Rope in the Simulated Quiet Sun

Zhizhen Ye and Feng Chen

Magnetic flux ropes (MFRs) are key structures for understanding flares and coronal mass ejections in active regions, but their characteristics in the quiet Sun remain poorly understood. With a radiative MHD simulation spanning from the upper convection zone to the corona, we analyze the formation and eruption of a supergranular-scale flux rope. We use a clustering method to group the closed field lines by their connectivity. The clusters are gathered further into 8 persistent cluster assemblies (CAs) that correspond to a flux rope and ambient magnetic structures. A persistent counterclockwise vortex is maintained at the converging point of the supergranules, i.e. the positive footpoint of the flux rope. The vortex continuously injects helicity into a magnetic flux tube and wraps ambient magnetic structures around the central flux tube. On a time scale of one hour, the flux tube evolves to a strongly twisted flux rope and erupts. The eruption exhibits similar current sheet structures as inferred from the flux rope eruption in active regions; however, the mass ejection and heating are much weaker and give rise to very insignificant observable features. The synthetic EUV images show mostly dimming features caused by density rarefaction in the expanding flux rope. This work helps elucidate the dynamic and complex evolution of flux ropes formed in the quiet Sun and suggests that similar events in the real Sun may have been underestimated due to their stealth behavior.
Read the full abstract

Computational Physics

AI-Assisted GPU optimization of the Stochastic Variational Method for Few-Body Boson System

Noritaka Shimizu, Shigeyoshi Aoyama, Yusuke Tsunoda et al. (+1 more)

The stochastic variational method (SVM) is one of the most powerful methods to solve quantum few-body systems precisely in various fields, such as nuclear and atomic physics. To the best of our knowledge, no SVM code optimized for GPUs has been reported. We developed a parallel SVM code for few-body clusters of $^4$He atoms and optimized it for two GPU architectures, NVIDIA GH200 and AMD Instinct MI300A, with the entire code written by an AI coding agent. On the algorithmic side, we introduce the secular-equation method with the Gu–Eisenstat prescription for solving the generalized eigenvalue problem within the SVM framework. The main part of the code tuning is to batch the many small matrices so that the GPUs are used efficiently, together with an array layout in memory optimized for coalesced addressing. For the five-body system with 4800 SVM basis states, the tuned SVM code runs 16.2 (14.7) times faster on the NVIDIA GH200 (AMD MI300A) than the same tuned code on the Intel Xeon Max CPU system, and 168 (153) times faster than the first working CPU implementation. The achieved performance brings 6-body and larger cluster systems within reach.
Read the full abstract

All authors Noritaka Shimizu, Shigeyoshi Aoyama, Yusuke Tsunoda, Akira Nukada