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Physics

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Tuesday 22 September

Mathematical Physics

Finite images of braid group representations and algebraic solutions of KZ-type equations

Haru Negami

Finite monodromy provides a bridge between group representations and algebraic solutions of differential equations. We study this connection for the Katz-Long-Moody construction, which transforms representations of the semidirect product of a free group and a braid group into new representations of the same group and is related to Knizhnik-Zamolodchikov (KZ)-type equations. For a fixed finite-image input, we classify the parameter values for which the resulting representations have finite image, both on the semidirect product and on its free-group and braid-group subgroups. In particular, finiteness of the braid-group image is independent of the admissible parameter. These results give necessary and sufficient conditions for all solutions of the corresponding regular-singular KZ-type equations to be algebraic. On restriction to the free group, they also characterize finite monodromy and algebraicity of all solutions of the associated Fuchsian systems, connecting the classification to classical questions about algebraic hypergeometric functions.
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Pattern Formation and Solitons

Is there an accelerating nonspreading wave packet in the Schrödinger equation with higher even-order dispersions?

Farrell Theodore Adriano and Hadi Susanto

Probably not. For Airy-type initial data, although nearly all lobes accelerate, the principal lobe remains essentially stationary. Moreover, the overall wave packet gradually disperses.

Computational Physics · Cross-listed from math.NA

Uniform approximation of spectra of linear second order differential operators via discrete sine transform based discretisation

Oliver Křenek, Vít Průša, Rebecca Tozzi et al. (+1 more)

We study various discretisation schemes for the regular Sturm–Liouville operator on a bounded interval and for the Laplace operator on an arbitrary planar domain, in both cases subject to zero Dirichlet boundary conditions. The objective is to identify a discretisation scheme such that the corresponding discretised operator—a matrix of size $N \times N$—produces $N$ eigenvalues that approximate as closely as possible the first $N$ eigenvalues of the corresponding operator at the continuous level. By means of numerical experiments we examine several conventional discretisation schemes, and we corroborate the known fact that the conventional discretisations fail to achieve the objective, with the failure attributable to the poor approximation of high-index eigenvalues, and, as a result, to the non-uniform spectrum approximation. In contrast, the newly proposed discrete sine transform based discretisation scheme is designed in such a way that it replicates the asymptotic behaviour of high-index eigenvalues, thereby providing the sought uniform spectrum approximation. Of equal significance is the fact that the proposed discrete sine transform based scheme can be, unlike many Fourier transform based methods, applied to non-rectangular domains.
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All authors Oliver Křenek, Vít Průša, Rebecca Tozzi, Martin Vejvoda

Quantum Physics

An asymmetric atom-photon architecture for device-independent quantum key distribution over 25 km

Jonas Meiers, Christian Haen, Max Bergerhoff et al. (+4 more)

Device-independent quantum key distribution (DIQKD) can guarantee security without trusting the internal workings of the measurement devices, but extending it to fiber networks demands high-quality entanglement, reliable heralding, and faithful photon transmission simultaneously. Here, we address these requirements in an event-ready asymmetric atom-photon architecture implemented over $25\,\mathrm{km}$ of spooled telecom fiber. A single trapped $^{40}\mathrm{Ca}^{+}$ ion forms one party of the protocol while a single transmitted photon measured at the remote station forms the other. Double quantum frequency conversion and active polarization stabilization preserve the atom-photon quantum correlation across the full link. We obtain a Clauser-Horne-Shimony-Holt parameter of $|S|=2.75^{+0.16}_{-0.15}$, exceeding the threshold $|S|=2.362$ required for a positive asymptotic secret-key fraction under the DIQKD model used. Within the same asymptotic model, this corresponds to a conservative estimate of 69 secret-key bits out of 10908 detected Bell states. The demonstrated architecture establishes a route towards DIQKD in heterogeneous, repeater-compatible quantum networks.
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All authors Jonas Meiers, Christian Haen, Max Bergerhoff, Pascal Baumgart, Tobias Bauer, Christoph Becher, Jürgen Eschner

Optics

Meta-Optics-Based Diffractive Learning Machine for Angle-Multiplexed Multi-Task Processing

Mingcheng Luo, Jianmin Xiong, Jiayong Peng et al. (+4 more)

All-optical diffractive neural networks (DNNs) offer low latency, low energy consumption, and massive parallelism. However, their scalability in terms of network scale and multi-task processing remains limited. Here, we experimentally demonstrate a large-scale metasurface-based diffractive learning machine for angle-multiplexed multi-task processing. Our system employs a metasurface-based reflection cavity to realize a five-layer DNN comprising 115 million fixed, untrained diffractive nodes within a compact volume of 216 mm^3. By integrating this large-scale, untrained DNN with a lightweight, trainable digital backend containing only 7,680 parameters, our system experimentally achieves an accuracy of 95.3% on the standard full-scale CIFAR-10 dataset, significantly outperforming previous optical neural networks and rivaling large-scale digital models. Using a novel incident-angle-multiplexing scheme, our system experimentally achieves parallel processing of 11 tasks with negligible performance degradation, representing the largest multi-task processing capacity reported to date. Our work provides a scalable and energy-efficient solution for high-performance edge computing.
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All authors Mingcheng Luo, Jianmin Xiong, Jiayong Peng, Jingtian Hu, Hongwei Chen, Chester Shu, Chaoran Huang

Earth and Planetary Astrophysics

Molecular mapping of an exoplanet with JWST: NH3 detection in the temperate super-Jupiter Epsilon Indi Ab

R. Kravtchenko, O. Berné, I. Schroetter et al. (+2 more)

Epsilon Indi Ab is currently the coldest, and one of the closest, directly imaged exoplanets (T_eff = 275 K, d=3.6 pc), offering a unique opportunity to test our understanding of the physical and chemical properties of gas giants across the full temperature range spanned by hotter directly imaged exoplanets and the cooler giants of the Solar System. We aim to characterize the atmosphere of Epsilon Indi Ab using infrared spectroscopic observations. We present JWST spectroscopic observations of Epsilon Indi Ab obtained with MIRI in the Medium Resolution Spectrograph mode (4.9-27.9 microns, October 2025) and NIRSpec in the Integral Field Unit mode (2.87-5.27 microns, May 2026). The data are highly contaminated by the stellar light from the bright host star. We therefore adopt a high-pass filtering and cross-correlation approach based on petitRADTRANS atmospheric models to detect the planetary signal and specific molecules. The cross-correlation analysis enables a robust detection of the planet with both instruments (up to S/N = 15.2). Using molecular mapping, we securely identify the presence of NH3 (maximum S/N = 15.6), H2O (maximum S/N = 10.8), CH4 (S/N = 3.8) and marginally detect CO2 (S/N = 2.5). These first results confirm the potential of infrared spectroscopy combined to cross-correlation techniques to characterize the atmosphere of directly imaged exoplanets with JWST, even the in case where the contamination by the host star is critical.
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All authors R. Kravtchenko, O. Berné, I. Schroetter, P. Amiot, F. Debras

Medical Physics

A wearable, stretchable radio-frequency coil for extremity imaging in low-field MRI systems

Jesús Conejero, Marina Fernández-García, José Borreguero et al. (+10 more)

Purpose: To develop a wearable, stretchable radio-frequency (RF) coil that conforms to the extremities and improves the filling factor in low-field MRI. Methods: A stretchable solenoid RF coil was fabricated by stitching a sinusoidally arranged Litz-wire conductor onto an elastic textile. The coil was compared with four rigid coils, including two routinely used designs and two prototypes designed to isolate the effects of conductor material and stretchability. Performance was characterized through quality-factor, loading-factor, transmit-efficiency, and image-based signal-to-noise ratio (SNR) measurements. Phantom and in-vivo knee experiments for one volunteer were performed using two portable MRI systems operating at 3.53 and 3.04 MHz. Results: The electrical performance of the selected Litz wire decreased with increasing frequency, becoming a slight disadvantage at 3.53 MHz. Nevertheless, the stretchable coil provided the highest phantom SNR in both systems, exceeding that of the best-performing rigid coil by approximately 8 % at 3.53 MHz and 20 % at 3.04 MHz. In vivo, its global SNR was 5 % lower than that of the best rigid coil at 3.53 MHz and 19 % higher at 3.04 MHz. Compared with the larger rigid coil required when knee positioning is constrained, the corresponding SNR improvements were approximately 18 % and 80 %. Conclusion: Anatomical conformity can compensate for the frequency-dependent electrical limitations of Litz wire in stretchable low-field RF coils. The proposed design provided SNR comparable to or greater than the best rigid designs while facilitating coil placement in subjects for whom smaller rigid coils may be impractical.
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All authors Jesús Conejero, Marina Fernández-García, José Borreguero, Teresa Guallart-Naval, Pablo García-Cristóbal, Lorena Vega-Cid, Eli G. Castañón, Rubén Bosch, Eduardo Pallás, Pablo Moreno, Fernando Galve, Joseba Alonso, José Miguel Algarín

High Energy Physics (Phenomenology)

Impact parameter and transverse charge densities of the pion and kaon

Fernando Chandra, Parada T. P. Hutauruk and Terry Mart

The impact parameter and transverse charge densities provide spatially resolved information on hadron structure and probe the interplay between dynamical chiral symmetry breaking and SU(3)-flavor symmetry breaking. We investigate the valence-quark distributions of the pion and kaon using their unpolarized vector GPDs at nonzero skewness $\xi$ within the covariant Nambu–Jona-Lasinio model, with ultraviolet divergences regulated by the Schwinger proper-time scheme. Increasing $\xi$ shifts the distributions toward smaller $x$, reduces their central magnitude at $b_\perp=0$, and broadens their transverse profiles. These results provide insight into the spatial structure of the pion and kaon and offer stringent tests of nonperturbative QCD dynamics, with relevance to forthcoming measurements at Jefferson Lab and the Electron-Ion Collider.
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Strongly Correlated Electrons · Cross-listed from math.AC

Poincaré Duality and Quadratic Refinements over Laurent Rings

Błażej Ruba and Bowen Yang

We develop a Poincaré duality theory for defects of nondegenerate sesquilinear pairings over Laurent polynomial rings. A key ingredient is a novel flat resolution of the character module, constructed from a triangulation of the sphere at infinity associated with a fan. The cup product on this resolution turns Poincaré duality on the sphere into canonical pairings between the resulting defect modules. In middle degrees, we construct distinguished quadratic refinements using equivariant cohomology of the sphere with the antipodal action. The effective replacement of the sphere with a projective space provides a geometric substitute for division by two. Applied to translation-invariant Pauli stabilizer codes, our results establish the nondegeneracy of higher-dimensional braiding pairings. They extend the two-dimensional T-junction formula for topological spin to higher dimensions, while giving it a geometric interpretation.
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General Relativity and Quantum Cosmology

Thermodynamics of arbitrary spherical surfaces in FLRW spacetimes

Xun Gong, Jun Wang and Chen-Yang Zhang

In this work, we investigate the thermodynamics of arbitrary spherically symmetric surfaces in non-flat FLRW spacetimes within general relativity. Adopting the gravity-to-thermodynamics perspective, the Clausius relation and the unified first law follow directly from the gravitational field equations and matter dynamics, with a central role played by the matter-flux measure derived from energy-momentum conservation. The cosmological apparent-horizon and event-horizon thermodynamics are both recovered as special cases. In particular, the event-horizon temperatures derived from the gravitational dynamics satisfy both thermodynamic relations without introducing phenomenological modifications, and the corresponding temperature reduces to the Gibbons-Hawking temperature in the de Sitter limit. We further show that previous inconsistencies originate from incompatible temperature prescriptions rather than from any intrinsic deficiency in the thermodynamics of the cosmological event horizon. These results demonstrate that the gravity-thermodynamics correspondence is a generic feature of gravitational dynamics rather than a property unique to causal horizons.
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Astrophysics of Galaxies

Mass Distribution of M31 from its Rotation Curve up to 167 kpc

Hao Wu, Yang Huang, Huawei Zhang et al. (+2 more)

The mass distribution of the Andromeda galaxy (M31) is fundamental for understanding its dark matter content, assembly history, and dynamical role within the Local Group. However, estimates of M31's total mass remain quite uncertain, partly because of limited dynamical constraints at large galactocentric radii. Moreover, M31's recent merger history has produced abundant tidal substructures and may have left its outer halo out of dynamical equilibrium, complicating equilibrium-based mass estimates. We use over 8,500 tracers with line-of-sight velocities to constrain the rotation curve (RC) of M31 over R=2–167 kpc. In the disk, we derive the RC from a clean tracer sample using the Jeans equation and find good agreement with previous H I measurements. In the halo, we use Gaussian mixture modeling to account for tidal substructures and Galactic foreground contamination and constrain the kinematics of the residual dynamically hot halo. Assuming this halo population can be treated as an equilibrium tracer, we infer the outer RC and constrain M31's mass distribution for different velocity anisotropies beta and dark matter halo profiles. The NFW and Dekel–Zhao (DZ) models yield broadly consistent total masses ranging from 1.12(+0.11/-0.10) to 1.63(+0.21/-0.17)x10^12 Msun for beta=0.3–0.7. In contrast, the Einasto profile favors substantially lower masses of 0.41(+0.09/-0.06) to 0.86(+0.21/-0.16)x10^12 Msun, highlighting significant dependence on the adopted halo profile, although Einasto solutions are more in tension with independent mass estimates based on M31 satellite galaxies than the NFW and DZ models at fixed beta. Overall, our analysis provides a comprehensive measurement of M31's mass distribution under the assumption of dynamical equilibrium, while also quantifying the systematic uncertainties associated with halo velocity anisotropy and the choice of dark matter density profile.
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All authors Hao Wu, Yang Huang, Huawei Zhang, Qikang Feng, Cheng Liu

Quantum Physics

Photon-Statistics Control of Strong-Field Rydberg-State Excitation

Tao Jiang, Jinlei Liu, Haopu Dou et al. (+8 more)

Photon statistics provides a new control dimension for strong-field bound-state formation. Using a quantum-optical phase-space formulation coupled to time-dependent Schrödinger-equation calculations, we show that field fluctuations enhance multiphoton Rydberg excitation by broadening AC-Stark-shifted resonances, but suppress tunneling-mediated recapture even as ionization increases. A quantum-statistical recapture model attributes the latter to ensemble-induced dispersion of relative path phases. Photon statistics also reshapes Rydberg-manifold parity, linking field statistics to recapture coherence and final-state symmetry.
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All authors Tao Jiang, Jinlei Liu, Haopu Dou, Lingyi Zhao, Peng Xiang, Liangjun Peng, Renyu Wang, Jing Zhao, Xiaowei Wang, Yue Lang, Zengxiu Zhao

Superconductivity

Analysis of Josephson junctions switching time distributions for the detection of single microwave photons

A. S. Piedjou Komnang, C. Guarcello, C. Barone et al. (+5 more)

We investigate an optimal scheme for the detection of single microwave photons by a Josephson junction through the analysis of its switching times distribution. The proposed analysis is of support for the decision about the existence of the photon field, which is important in the case of rare events. We assume that the cavity and the transmission line are ideal (each photon absorbed to the cavity gives a current pulse as the output of the transmission line) and the photon source is periodic. The employed methodology consists in comparing the switching probabilities of a Josephson junction exposed to a train of current pulses, simulating a weak photon field, with that of the same device in absence of pulses. In both cases, thermal noise can induce thermal activated switchings. The investigation of the unbalance in the number of switching events in the two cases, gives an estimate of the efficiency of the detection. Furthermore, in the assumption of escapes described by Kramers model, it is possible to provide a relationship between the properties of the photons field, the quantum efficiency of the detection process, and the Josephson junctions switching features at finite temperatures.
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All authors A. S. Piedjou Komnang, C. Guarcello, C. Barone, C. Gatti, S. Pagano, Vincenzo Pierro, A. Rettaroli, G. Filatrella

Nuclear Theory

Electronic-Structure Control of Nuclear Excitation by Electron Capture in Finite-Density $^{229}$Th

Yang-Yang Xu, Jin-Tao Qi, Qiong Xiao et al. (+4 more)

Nuclear excitation by electron capture (NEEC) provides a unique pathway for coupling electronic and nuclear dynamics, but its description in dense matter commonly relies on electronic structures of isolated ions. Here we show how dense environments reshape the available NEEC capture channels. Using a finite-temperature average-atom model, we assess channel availability by jointly considering electronic localization, resonance energy matching, and vacancy availability. Near solid density, the shallow $6p$ states remain sufficiently localized to support resonant electron capture that drives the 8.356-eV isomeric transition in $^{229}$Th, whereas higher valence-like states merge into the continuum and no longer constitute localized capture channels. Calculations at different temperatures and densities reveal distinct windows of channel availability arising from the interplay among pressure-induced delocalization, shifts in resonance energy, and vacancy formation. Coupling the reconstructed channels to particle-in-cell simulations of laser-driven $^{229}$Th further shows that electronic structure at finite density can substantially alter the predicted cumulative NEEC yield. These results demonstrate how the electronic environment governs resonant capture pathways, highlighting its essential role in nuclear excitation driven by electrons in dense matter.
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All authors Yang-Yang Xu, Jin-Tao Qi, Qiong Xiao, Jun-Hao Cheng, Xin-Yan Li, Tai-Wu Huang, Tong-Pu Yu

Optics

Intra-bandgap Bound-State Magnonics in a Photonic Crystal Waveguide

Chong-Xin Run, Xue-Feng Pan, Bang-Yao Wu et al. (+5 more)

Cavity and waveguide magnonics have recently emerged as frontiers for investigating light-matter interactions. In these systems, coupling magnons into meticulously engineered photonic lattices with rich band structures provides a promising platform for tailoring magnon-photon interactions. However, how these hybrid interactions behave in the bandgaps of photonic lattices—specifically, the formation of magnon-photon bound states (MPBSs)—remains largely unaddressed. Crucially, these bound states arise through a mechanism that is fundamentally distinct from bound states in the continuum (BICs). Here, we experimentally demonstrate intra-bandgap bound-state magnonics by coupling yttrium iron garnet (YIG) spheres to a microwave photonic crystal waveguide. At room temperature, we observe MPBSs featuring highly tunable spatial localization, power-dependent interaction modulation under microwave pumping, and long-range magnon-magnon interactions mediated by mode overlap. These unique features bridge fundamental insights into intra-bandgap light-matter interactions with practical applications, offering an avenue for scaling up coherent networks and investigating many-body physics through engineered interactions.
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All authors Chong-Xin Run, Xue-Feng Pan, Bang-Yao Wu, Kai-Min Hsieh, Wei-Min Zhou, Anton Frisk Kockum, Peng-Bo Li, Io-Chun Hoi

Materials Science

Realization of quantum spin Hall insulator superlattice with emergent multigap-like helical edge states

Hui Guo, Xianghe Han, Fang Qin et al. (+15 more)

The functional quantum spin Hall insulators (QSHI), protected by time-reversal symmetry against single-particle backscattering, hold great promise for dissipationless quantum electronics. Realization of QSHI with gapped helical edge states, which would enable deterministic on/off switching of the edge-channel conductance, is a key requirement for programmable topological circuits. Here, we report realization of superlattice-modulated QSHI HfTe5 hosting emergent multigap-like helical edge states. Using scanning tunneling microscopy and spectroscopy, we identify a reconstruction-induced periodic superlattice modulation in epitaxial monolayer HfTe5 and directly observe multiple gap-like features in the edge channel, accompanied by a series of sharp peaks in the density of states. Combined with theoretical modelling, we attribute the observed edge gap to the finite-width coupling between the two edges significantly enhanced by the superlattice modulation, whereas the sharp peaks are the manifestations of mini-gaps opening at the reduced Brillouin zone boundaries by the periodic modulation of spin-orbit coupling. Notably, these sharp peaks exhibit clear Zeeman splitting under magnetic fields, consistent with the helical nature of the topological edge states. Our results establish a viable route to engineering gapped helical edge states in QSHI and provide a promising platform for topological devices with desired on/off switchability.
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All authors Hui Guo, Xianghe Han, Fang Qin, Xiaoshuai Fu, Hao Peng, Hongqin Xiao, Hengxin Tan, Chen Liu, Zihao Huang, Jiayi Wang, Qian Fang, Rui Chen, Haitao Yang, Wang Yao, Li Huang, Hai-Zhou Lu, Hui Chen, Hong-Jun Gao

Quantum Physics

The Failure of Simultaneous Quantum Typicality

Benoit Collins

We establish exact thresholds for the failure of simultaneous quantum typicality: three parties for mixed states and four for pure states. For the four-qubit Higuchi–Sudbery state, every sequence satisfying the expected purity bounds on three overlapping marginals, with sufficiently small fixed positive entropy slack, is asymptotically perfectly distinguishable from the tensor powers of the input: its trace distance from them tends to the maximum value $2$. This maximal separation persists, with a common positive slack, throughout an open neighborhood in the full four-qubit state space. Tracing out one party yields a mixed tripartite example. The proof connects simultaneous quantum smoothing with polynomial concentration on $\CP^1$. Symmetry reduces the problem to a frame inequality on $\Sym^n(\mathbb C^2)$, where a linear entropy deficit competes with a quadratic cost of polynomial concentration. Bernstein–Markov estimates and a subharmonic barrier control this cost, yielding an exponential obstruction to simultaneous typicality. These results disprove Dutil's multiparty quantum typicality conjecture, formulated in 2011, and the one-shot simultaneous min-entropy-smoothing conjectures of Drescher–Fawzi and Colomer–Winter. Together with the positive results for smaller systems, they determine the smallest numbers of parties at which simultaneous typicality can fail.
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High Energy Physics (Phenomenology)

Dark Diffraction at LZ from a Screened Neutral Composite Baryon

Hyunjoo Jung and Seong Chan Park

The LUX-ZEPLIN (LZ) experiment recently reported a nuclear-recoil-like candidate at $E_R=248\pm23_{\rm stat}\pm23_{\rm sys}$ keV. We show that such an energetic recoil can arise from the elastic form factor of composite dark matter, without invoking an inelastic mass splitting or a boosted population. A neutral baryon of $N$ dark quarks can have a charge form factor that is suppressed at low momentum transfer but recovers at higher momentum transfer, providing a momentum-space band-pass filter. Modeling the form factor with one Gaussian per charged constituent species, we prove that two terms cannot produce a hard recoil spectrum and find that three yield too few events in the LZ signal window, while four suffice. A confining $SU(4)_D\times U(1)_D$ gauge theory provides a concrete realization through a neutral bosonic baryon made of four dark quarks. For a 200 GeV benchmark normalized to one accepted event, we predict approximately 1.5 true recoils beyond the current LZ region of interest. The form factor also produces diffraction nodes at fixed momentum transfers, placing them at recoil energies that scale as $1/m_A$ across target nuclei.
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Atmospheric and Oceanic Physics

A dataset of one-dimensional idealized probabilistic fields

Gregor Skok and Romain Pic

Verification of probabilistic weather forecasts remains a crucial aspect of numerical weather prediction, as new AI-based models become more widely used alongside the more traditional physics-based ensemble forecasting systems that continue to be developed and improved. We present a first-of-its-kind idealized probabilistic dataset composed of one-dimensional cases aimed at analyzing the behavior and properties of verification methods for probabilistic forecasts and comparing their behavior. It covers a wide range of probabilistic cases, such as constant, localized events, gradients, fronts, noisy, bimodal, and limiting cases. Moreover, the code associated with the dataset provides great flexibility for customizing the experiments it covers. The dataset represents the first building block of the more extensive comparison dataset of the Bridging The Gap project, which aims to facilitate the development and comparison of spatial verification methods for probabilistic forecasts.
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Quantum Physics

Enhanced Atomic Magnetometry with a Pinched Spin State

Tingxuan Guo, Xiangyu Li, Yang Li et al. (+1 more)

The sensitivity of an atomic spin sensor is fundamentally constrained by the quantum Fisher information (QFI) of the probe state. The pinched state, $|{F,0}\rangle$, has an $(F+1)$-fold larger single-particle QFI for transverse-field sensing than the stretched state, $|{F,F}\rangle$, corresponding to a predicted $\sqrt{F+1}$ reduction in the spin-projection-noise-limited field uncertainty. We show that this advantage can be accessed in an rf sensing scheme by engineering a spectrum symmetric about $m=0$, yielding an ideal $(F+1)$-fold enhancement of magnetic-field response. For $^{87}\mathrm{Rb}$ with $F=2$, we observe up to 2.7-fold response enhancement. Implementing this approach in a compact $0.8~\mathrm{cm}^3$ anti-relaxation-coated multipass cell, we realize a single-beam, dual-axis, zero-field magnetometer, achieving $13$–$23$~$\mathrm{fT}/\sqrt{\mathrm{Hz}}$ over $3$–$100$~Hz at room temperature.
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All authors Tingxuan Guo, Xiangyu Li, Yang Li, Kaifeng Zhao

Fluid Dynamics

CFD-Machine Learning Driven Pod Optimization and Staged Pressure-Area Management for Supersonic Evacuated Tube Transport

Jaydip Patel and Dhwanil Shukla

This study investigates the aerodynamic feasibility of high-speed evacuated tube transport (ETT) using an integrated CFD-machine learning framework for pod geometry optimization and a staged converging-diverging (CD) tube concept for supersonic operation. The pod geometry is parameterized using composite cubic Bezier curves with seven design variables. Latin Hypercube Sampling is used to generate 200 configurations across subsonic and supersonic regimes, which are evaluated using two-dimensional axisymmetric ANSYS Fluent simulations validated against published compressible-flow data. The resulting CFD dataset is used to train surrogate models for rapid drag prediction. XGBoost provides the best overall performance, achieving a test R^2 of 0.9524, and is coupled with Differential Evolution and Particle Swarm Optimization to identify low-drag geometries that are subsequently verified using CFD. The study further examines a staged CD tube architecture combining controlled area variation with gradual pressure reduction to mitigate choking during supersonic acceleration. In the idealized axisymmetric simulations, the proposed strategy enables transition from atmospheric entry at Mach 1.6 to near-vacuum cruise at Mach 2.5 and a blockage ratio of 0.50 without forming a choked annular flow region. Total drag decreases from 68,913.7 N under atmospheric supersonic conditions to 120.5 N in the final near-vacuum stage, associated with a transition from wave-drag-dominated to viscous-shear-dominated resistance. The results demonstrate the potential of combined pod-shape optimization and staged pressure-area management for reducing aerodynamic resistance in supersonic ETT systems.
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Biological Physics

How do incorrect ligands help detect a correct ligand?

Yan-Ru Chen, Kwan-tai Leung and Hsuan-Yi Chen

Intrigued by the response of T cell receptors to the presence of a few agonist ligands, we propose a minimal model that can achieve similar performance. The model consists of a small cluster of immobile receptors that bind reversibly to two types (correct/incorrect) of ligands in the environment, with slightly weaker binding strength for the incorrect one. It features binding-state coupling between nearest-neighbor receptors, and receptors in the bound/free states are activated/deactivated by specific enzymes, with rates that allow kinetic proofreading. It is found that, for a range of binding-state coupling strength, incorrect ligands alone cannot activate the receptors, but the binding of merely one correct ligand to a receptor is sufficient to promote the activation of other receptors via induced binding to incorrect ligands. Both response time and signal amplification increase as the receptor binding-state coupling strength increases until it reaches an optimal range to achieve the most rapid and sensitive response. These results suggest a possible mechanism for a speedy and specific response of receptors to very few correct ligands in biological and artificial systems at the subcellular scale.
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Atmospheric and Oceanic Physics

Precursors, Pathways, and State-Dependent Reliability of Long-range ENSO Prediction in the CESM2 Seasonal-to-Multiyear Large Ensemble

Yudi Mao, Gan Zhang, Hui Li et al. (+3 more)

Understanding the sources of ENSO prediction skill and error is essential for improving long-range climate prediction. Here we examine ENSO precursors in CESM2 Seasonal-to-Multiyear Large Ensemble (SMYLE) hindcasts initialized in February and August during 1970-2019, using ensemble sensitivity analysis and an extended nonlinear recharge oscillator (XRO) benchmark. SMYLE exhibits meaningful long-lead skill, with February-initialized predictions remaining skillful through the following winter, and August-initialized predictions retaining useful skill at the December target sixteen months ahead. However, the predictions are under-dispersive in a state-dependent manner. Rank histograms reveal overconfidence issues for strong ENSO events and a warm bias for weak events. February predictability arises from canonical Bjerknes feedback dynamics reinforced by subtropical-tropical interactions resembling the North Pacific Meridional Mode (NPMM). The best February-initialized predictions feature warm western Pacific subsurface anomalies and La Nina anomalies at initialization, with equatorially confined anomalies and relatively weak sensitivities to extratropical influences thereafter. Second-year ENSO predictability in August-initialized predictions instead emerges through a delayed pathway characterized by cross-basin preconditioning. Skillful cases begin with a cold tropical equatorial South Atlantic and a warmer tropical western Indian Ocean, while Pacific processes play a reduced role until the following year. SMYLE matches the skill of the cross-validated XRO at both December targets, and its sensitivities agree with the observationally fitted benchmark, though the Atlantic couplings appear misrepresented. These findings suggest that improving the initial Pacific state and cross-basin coupling fidelity in GCMs may help improve ENSO prediction.
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All authors Yudi Mao, Gan Zhang, Hui Li, Dillon J. Amaya, Stephen G. Yeager, Sen Zhao

Quantum Physics

Post-Selection-Based Stochastic Quantum Battery

Aman Verma, Roson Nongthombam and Amarendra K. Sarma

Quantum batteries are quantum systems that store useful energy, which can be subsequently extracted to perform work. In this paper, we investigate the charging dynamics of the quantum battery under continuous measurements and post-selection. By post-selecting the trajectories with no quantum jump $|1\rangle \rightarrow |0\rangle$ in a three-level system, the dynamics is effectively confined to a two-level $(|2\rangle-|1\rangle)$ manifold. We analyze the resulting charging dynamics under both $\sigma_x$- and $\sigma_y$-driving protocols and investigate the roles of detuning, coherent driving, non-linearity, and measurement backaction. The generation and dynamics of quantum coherence, which plays a pivotal role in quantum battery, are also analyzed under post-selection. The advantage and comparison of our results over those of a generic two-level system and with the Lindblad dynamics are also highlighted. Our work explores the interplay between the measurement axis and the driving protocols that govern the charging rate, ergotropy, and quantum coherence of the non-Hermitian, highly tunable, and controllable quantum battery.
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Nuclear Theory

Physical interpretation and limits of photon–dilepton radial-flow tomography

Lipei Du

Thermal photons and dileptons provide complementary information on the temperature and collective expansion of matter created in relativistic heavy-ion collisions. Their combination has been proposed as an electromagnetic probe of radial flow: a comparatively flow-insensitive dilepton invariant-mass inverse slope is used to infer the photon inverse slope expected without transverse flow and compared with the observed photon slope. Here the physical basis and leading limitation of this construction are examined using a controlled expanding-fireball calculation. The dilepton and flow-free photon inverse slopes are tightly correlated because they respond similarly to changes of the underlying thermal scale, although the numerical relation depends on the spectral window and electromagnetic source. The flow-induced change of the photon inverse slope correlates more strongly with the photon-emission-weighted velocity component along the photon momentum than with a bulk-like radial-flow average. Prethermal source variations can bias the inferred flow-free photon reference and generate apparent flow even when the direct photon spectral-flow signal vanishes, while multiple photon and dilepton windows provide independent response patterns that can help diagnose this source ambiguity. These results clarify both what photon–dilepton radial-flow tomography measures and the source consistency required for its interpretation.
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Materials Science · Cross-listed from cs.CV

Real-Time Atomic-Resolution Electron Phase Imaging without Probe Calibration via Ptychography-Supervised Learning

H. Yue, C.-C. Chen, C.-N. Hsiao et al. (+4 more)

Atomic-scale phase imaging is central to resolving defects, interfaces, and weakly scattering atoms that govern the behavior of nanoscale materials. Electron ptychography delivers sub-ångström phase sensitivity but remains an offline technique, because its iterative reconstruction is computationally expensive and sensitive to experimental calibration, preventing live use during data acquisition. Here, a ptychography-supervised local inference framework is presented that converts four-dimensional scanning transmission electron microscopy (4D-STEM) into an acquisition-compatible phase-imaging workflow. Physics-constrained reference phase maps reconstructed from a single experimental AuPd dataset serve as teacher labels for a compact model that predicts local phase patches directly from diffraction measurements, without explicit probe input or online iterative optimization. Full-field images are assembled by deterministic overlap stitching. The workflow reaches an online latency of about 0.27 ms per probe position and a throughput of about 20,000 positions per second, an approximately 1,000-fold speed-up over GPU-accelerated ePIE, while preserving atomic-scale lattice contrast and reciprocal-space fidelity. Without fine-tuning, the same model transfers across materials (WS2), defocus conditions (high-entropy alloy nanoparticles), and instruments (hBN at 300 kV). The approach amortizes ptychographic redundancy into a fast, generalizable workflow that enables real-time atomic-scale phase imaging for materials microscopy.
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All authors H. Yue, C.-C. Chen, C.-N. Hsiao, J. Cheng, Y. Liu, X.Z. Liao, Steve F. Shu

High Energy Physics (Experiment)

Search for the $^{16}\text{O}(ppp) \rightarrow ^{13}\text{C} \pi^+ \pi^+ e^+$ Decay Mode in Super-Kamiokande Using Machine Learning Techniques

The Super-Kamiokande Collaboration: J. Feng, K. Abe, Y. Asaoka et al. (+296 more)

We report a new partial lifetime limit of $4.2 \times 10^{32}$ years for the trinucleon decay mode $^{16}\text{O}(ppp) \rightarrow ^{13}\text{C} \pi^+ \pi^+ e^+$, obtained from a search conducted using the Super-Kamiokande detector with 0.401 megaton-years of exposure across five operational periods (SK-I: 1996–2001, SK-II: 2002–2005, SK-III: 2006–2008, SK-IV: 2008–2018, SK-V: 2019–2020). This represents an improvement of six orders of magnitude over previous experimental constraints. The analysis utilizes a convolutional neural network (CNN) incorporating an attention mechanism—a computational technique that enables the model to focus on the most relevant regions of Cherenkov ring patterns—to enhance event classification, thereby improving the sensitivity of the search. This is the first application of a CNN to a nucleon decay search in Super-Kamiokande. Furthermore, the large dataset available in Super-Kamiokande (hereafter "SK") strengthens the statistical power of the study, enabling a more stringent constraint than those set by prior experiments.
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All authors The Super-Kamiokande Collaboration: J. Feng, K. Abe, Y. Asaoka, M. Harada, Y. Hayato, K. Hiraide, T. H. Hung, K. Ieki, M. Ikeda, J. Kameda, Y. Kataoka, S. Mine, M. Miura, S. Moriyama, K. Nakagiri, M. Nakahata, S. Nakayama, Y. Noguchi, G. Pronost, K. Sato, H. Sekiya, R. Shinoda, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takemoto, H. Tanaka, S. Chen, Y. Itow, T. Kajita, R. Nishijima, K. Okumura, T. Tashiro, T. Tomiya, X. Wang, F. J. de Garay Arcones, P. Fernandez, L. Labarga, D. Samudio, C. Yanagisawa, B. Jargowsky, E. Kearns, J. Mirabito, L. Wan, T. Wester, B. W. Pointon, J. Bian, B. Cortez, N. J. Griskevich, Y. Jiang, M. B. Smy, H. W. Sobel, V. Takhistov, J. Hill, B. D. Xu, D. Jung, D. H. Moon, R. G. Park, B. S. Yang, K. Scholberg, C. W. Walter, T. P. Leplumey, O. Drapier, A. Ershova, M. Ferey, Z. Hu, E. Le Blévec, Th. A. Mueller, P. Paganini, C. Quach, R. Rogly, T. Nakamura, J. S. Jang, R. P. Litchfield, L. N. Machado, F. J. P. Soler, J. G. Learned, K. Choi, S. Cao, T. V. Ngoc, L. H. V. Anthony, N. W. Prouse, M. Scott, Y. Uchida, V. Berardi, N. F. Calabria, M. G. Catanesi, N. Ospina, E. Radicioni, A. Langella, G. De Rosa, G. T. Burton, G. Collazuol, M. Feltre, M. Mattiazzi, L. Ludovici, M. Gonin, L. Périssé, B. Quilain, H. Tanigawa, Z. Utagawa, M. Fukazawa, S. Horiuchi, A. Kawabata, Y. M. Liu, Y. Maekawa, Y. Nishimura, A. Oka, R. Akutsu, M. Friend, T. Hasegawa, Y. Hino, T. Ishida, T. Kobayashi, T. Matsubara, T. Nakadaira, Y. Oyama, A. Portocarrero Yrey, K. Sakashita, T. Sekiguchi, N. Bhuiyan, F. Di Lodovico, T. Katori, R. Kralik, N. Latham, R. M. Ramsden, V. Siccardi, S. Aoyama, H. Bambara, Y. Inaba, H. Ito, M. Nishigami, T. Sone, A. T. Suzuki, Y. Takeuchi, S. Wada, H. Zhong, L. Feng, S. Han, J. Hikida, N. Fujimoto, M. Kawaue, T. Kikawa, F. Nakanishi, T. Nakaya, R. A. Wendell, U. Limbu, S. J. Jenkins, N. McCauley, M. Fanì, M. J. Wilking, Z. Xie, Y. Fukuda, H. Menjo, Y. Yoshioka, J. Lagoda, J. Zalipska, T. Yano, M. Mori, J. Jiang, Y. Asano, K. Hamaguchi, H. Ishino, Y. Koshio, S. Ohshita, T. Tada, T. Ishizuka, G. Barr, D. Barrow, D. Wark, A. Holin, F. Nova, M. Jo, S. Jung, J. Yoo, L. Kneale, T. Peacock, P. Stowell, H. Okazawa, S. M. Lakshmi, S. Hong, E. Kwon, M. W. Lee, J. W. Seo, I. Yu, Y. Ashida, A. K. Ichikawa, S. Kobayashi, K. D. Nakamura, S. Abe, S. Goto, H. Hayasaki, S. Kodama, Y. Kong, Y. Masaki, Y. Mizuno, T. Muro, Y. Nakajima, W. Cai, Y. Endo, M. Sekiyama, N. Taniuchi, T. Yamazumi, M. Yokoyama, P. de Perio, S. Fujita, C. Jesús-Valls, K. Martens, Ll. Marti, A. D. Santos, K. M. Tsui, M. R. Vagins, M. Kuze, S. Izumiyama, R. Matsumoto, C. Ise, M. Ishitsuka, M. Sugo, M. Wako, K. Yamauchi, Y. Nakano, A. Yankelevich, F. Cormier, R. Gaur, M. Hartz, A. Konaka, X. Li, B. R. Smithers, S. Chen, Y. Wu, A. Q. Zhang, B. Zhang, H. Adhikary, M. Girgus, P. Govindaraj, M. Posiadala-Zezula, Y. S. Prabhu, S. B. Boyd, R. Edwards, D. Hadley, M. O'Flaherty, B. Richards, A. Ali, B. Jamieson, C. Bronner, D. Horiguchi, A. Minamino, Y. Sasaki, K. Hosokawa, Y. Kanemura, S. Miki, K. Shimizu, B. Zaldivar, M. C. Jang, S. H. Lee, B. Bodur, A. Beauchêne, N. Iovine, D. Martin, M. Kobayashi, R. Okazaki, M. Jakkapu, K. Nakamura, T. Tsukamoto, J. Gao, J. Migenda, S. Zsoldos, Y. Takagi, J. R. Hu, K. Yasutome, A. Tarrant, M. Mandal, M. Jia, C. K. Jung, W. Shi, S. Sakai, T. Tano, L. Cook, S. Samani, J. Y. Yang, J. E. P. Fannon, M. Malek, J. M. McElwee, M. D. Thiesse, L. F. Thompson, S. T. Wilson, S. Tairafune, A. Eguchi, E. Watanabe, J. Xia, K. Terada, R. Asaka, M. Shinoki, T. Yoshida, V. Gousy-Leblanc, M. Nicholson, S. Amanai, R. Shibayama, R. Shimamura

Quantum Physics

$\mathsf{BQP} \subseteq \mathsf{IP}$ Does Not Relativize

Adam Bouland, Andrew Huang, Anand Natarajan et al. (+2 more)

We construct an oracle relative to which $\mathsf{BQP} \not\subseteq \mathsf{IP}$, resolving a long-standing open question in quantum complexity theory. Together with recent work due to Aaronson et al., our work also gives the first oracle separation between $\mathsf{IP}$ and $\mathsf{MIP}$, answering a question dating back to Fortnow's thesis. Our separation is based on the Forrelation problem, where given Boolean functions $f$ and $g$, the goal is to determine if $f$ is correlated with the Fourier spectrum of $g$. While this task is solvable by a query-efficient quantum algorithm, we show that it admits no classical interactive protocol with polynomial communication and a polynomial-query verifier. Our proof is based on (i) a new structural result showing how to approximate Avg-Max circuits (which are well-known to capture the power of interactive proofs in the oracular setting) by convex functions with small first and second derivatives and (ii) a novel analysis establishing that the Forrelation distribution suggested by Aaronson and Ambainis fools such functions. Our results imply that any prover-efficient classical interactive protocol for $\mathsf{BQP}$ must rely on non-relativizing techniques. This might serve as a partial explanation for the lack of progress towards doubly-efficient, unconditionally sound classical verification of quantum computation.
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All authors Adam Bouland, Andrew Huang, Anand Natarajan, Itay Shalit, Avishay Tal

Quantum Physics

Post-selected enhancement of phase sensitivity in a two-path interferometer

Ryuya Fukuda, Katsuki Tanaka, Masataka Iinuma et al. (+1 more)

Post-selected metrology can exceed the standard quantum limit of single photon interference by concentrating all of the available Fisher information in a subset of post-selected outcomes. Here we apply this principle to a standard two-path interferometer, activating the Fisher information concentrated in the low probability output port by transferring the phase sensitivity to the circular polarizations of the photon. We obtain a phase gradient of the post-selected interference fringe that corresponds to that of a four-photon NOON state, providing a direct comparison of the performance of multi-photon interference with single-photon post-selection.
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All authors Ryuya Fukuda, Katsuki Tanaka, Masataka Iinuma, Holger F. Hofmann

High Energy Astrophysical Phenomena

A Multi-Mission Detection Framework for High-Energy Transients: Application to a 13-year Fermi/GBM and Swift/BAT Sample

Ariel Perera, Barak Zackay and Tejaswi Venumadhav

The detection of faint high-energy transients is becoming increasingly important in time-domain and multi-messenger astronomy, particularly for identifying electromagnetic counterparts to binary neutron star mergers, high-energy neutrino events, and other weak transient phenomena. At present, the sensitivity of gamma-ray and hard X-ray searches is often limited by the detection threshold of individual instruments, leaving a population of faint transients inaccessible to single-mission analyses. To address this limitation, we develop a joint detection framework that combines trigger information from multiple detectors and assigns each candidate a joint association probability, $p_{\text{joint}}$, as a function of the individual detector signal-to-noise ratios. We apply this framework to archival Fermi/GBM and Swift/BAT rates data from 2013-2025. The method effectively separates coincident signals from accidental background associations, suppressing inconsistent coincidences while enhancing the significance of faint events observed by both instruments. We find that, under optimal conditions, a two-mission search can increase the accessible volume for short gamma-ray bursts by up to $60\%$. This framework provides a practical foundation for generalized multi-mission searches, enabling more sensitive exploration of the faint high-energy transient sky and improving the prospects for future multi-messenger discoveries.
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