Geophysics
Generative wave propagator
Shijun Cheng and Tariq Alkhalifah
Seismic wavefield simulation is fundamental to seismology, but conventional finite-difference (FD) methods remain limited by numerical dispersion and stability constraints, which often require dense spatial grids and small time steps and thereby severely limit the effectiveness of iterative inversion workflows. We introduce a conditional
diffusion-based wavefield propagator that advances seismic wavefields recursively from one time step to the next. Instead of learning an unconditional data distribution of wavefield
evolution, the model is conditioned by a short history of recent wavefield time steps (snapshots), the velocity model, and the wavefield time step index, allowing it to represent the conditional transition between adjacent physical states. By training the network to directly predict the clean next wavefield snapshot, this strong physical conditioning makes it possible to replace the iterative reverse
diffusion process with a single network evaluation for each predicted snapshot. To improve stability over long recursive rollouts, we further introduce a causal time-weighted loss, in which adaptive weights, accumulated as exponential moving averages of per-snapshot training errors, emphasize training directions that are consistent with the forward propagation sequence and reduce the amplification of one-step prediction errors. Because the learned propagator is tied to the temporal spacing of the training snapshots rather than to the FD stability limit, it can advance the wavefield using a physical time step ten times larger than that required by the underlying solver. Experiments on the Overthrust, SEG/EAGE, and Marmousi models show that the proposed method accurately reproduces wavefield snapshots and shot gathers and achieves an end-to-end speedup of 2.17 x over a GPU-accelerated tenth-order staggered-grid FD implementation under matched hardware conditions.
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Plasma Physics
Turbulent Magnetogenesis and Large-scale Magnetic Dynamo Amplification in Ion–electron Plasmas
Fabio Bacchini, Francesco Pucci, Sergio Servidio et al. (+2 more)
Using fully kinetic simulations that capture unprecedentedly large (from electron to ion) scales, we study magnetogenesis driven by continuous large-scale forcing until nonlinear dynamo saturation. We uncover a two-stage mechanism in collisionless ion-electron
plasmas whose dynamics diverge dramatically from the pair-
plasma case. In the first phase, electron pressure anisotropy triggers electron-Weibel modes, seeding small-scale
magnetic fields. Then, a second growth phase emerges when the more massive ions develop their own strong anisotropy and drive ion-Weibel-type modes; concurrently, a Biermann-battery mechanism contributes to amplifying the
magnetic field. This combined dynamics provides a tenfold amplification of the
magnetic field in comparison to the pair-
plasma case. Over long times, dynamo action continues until the system reaches a statistical steady state. This self-consistent kinetic mechanism provides a plausible explanation for robust magnetogenesis wherever an external forcing continuously stirs the
plasma.
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All authors Fabio Bacchini, Francesco Pucci, Sergio Servidio, Francesco Valentini, William H. Matthaeus
Fluid Dynamics
Quadrature-Aware Complex-Linear Neural Operator for Boundary-to-Field Prediction in Resonant Acoustics
Muhammad Idrees Khan and Hua-Dong Yao
Repeated prediction of acoustic fields from spatially distributed boundary excitation is computationally expensive when each source realization requires a new wave simulation. This work introduces a quadrature-aware complex-linear boundary operator (CLBO) that maps complex normal velocity on a vibrating surface to complex pressure at receiver locations. The model couples learned source and receiver basis functions through an explicit complex surface-quadrature contraction, so the boundary excitation enters linearly by construction. This preserves complex superposition, homogeneity, and zero response to zero excitation, while representing the source through coordinates, normals, and quadrature weights rather than a fixed flattened input vector. Reference data were generated using a verified three-dimensional multiple-relaxation-time (MRT)
lattice Boltzmann solver and stored in a solver-agnostic boundary-to-field format. CLBO was compared with a fixed-sensor complex DeepONet under matched case splits and optimization settings, with additional tests of structural consistency, receiver-coordinate interpolation, source discretization, source-family holdout, label efficiency, physics-informed ablations, unseen source mixtures, and computational cost. Across five training seeds, CLBO achieved a mean complex relative field error of 0.184 +/- 0.00771, compared with 0.367 +/- 0.00742 for DeepONet. Its measured source-superposition error was 1.31 x 10^-7, and its mean error on newly simulated mixed-source cases was 0.237, compared with 0.415 for DeepONet. Inference was 1.83 x 10^4 faster than the reference calculation for the reported query size. These results show that enforcing the known complex-linear boundary-to-field structure improves physical consistency and generalization under distributed acoustic excitation.
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Atomic Physics
Atomic oven with rapid thermal response for atom experiments
Weilong Huang, Congjun Zou, Feiyu Dong et al. (+3 more)
Atomic oven generating controllable atomic beam flux plays a fundamental role in
quantum gas experiments. Here, we report a new heater design that can heat up an high temperature atomic oven with fast thermal response. The new heater shows a heating rate improved by 7.65 times comparing to that of the conventional resistive heater while the crucible temperature can heated up to 1200K. With this oven, we generated a collimated ytterbium beam with flux exceeding $10^{14} \text{ atoms/s}$ at 823 K. We believe that our design offers a promising solution for shortening experimental dead time and improve the experiment efficiency in cold atom researches.
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All authors Weilong Huang, Congjun Zou, Feiyu Dong, Huirong Xiao, Zejian Ren, Shanchao Zhang
Plasma Physics
Machine-Learning-Enabled Full-State Reconstruction of Fusion Plasmas from Minimal Sensor Measurements
Maryam Reza and Farbod Faraji
Plasma in
nuclear fusion reactors is only partially observable: diagnostics are constrained by limited access, cost, and the harsh
plasma environment, while high-fidelity simulations remain prohibitively costly at reactor-relevant scales to address the observability gap. This paper presents an ML model for reconstructing full-domain
plasma states from a small number of accessible measurements. The model combines temporal encoding of sparse sensor histories with spatial decoding into complete
plasma-field maps. Demonstrations using high-fidelity kinetic simulation data show that multiple coupled
plasma quantities can be reconstructed from only a few density sensors, with robustness to sparse and randomly located probes. The approach provides a route toward diagnostic augmentation, real-time state estimation, and data-driven digital twins for fusion-relevant
plasmas.
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Plasma Physics
Particle dynamics in nonlinear electromagnetic waves: chaos onset, diffusive heating, and wave surfing
Maxim Lyutikov
We investigate the dynamics of charged particles interacting with ultra-intense electromagnetic X-modes in strongly magnetized
plasmas. We demonstrate that particle motion becomes chaotic for relative wave intensities $\delta = B_w/B_0 \gtrsim 0.25$ (not above the field reversal threshold $\delta \geq 1$). The transition to chaos occurs via the Chirikov resonance overlap mechanism and the related destruction of Kolmogorov-Arnold-Moser (KAM)
tori. The maximum Lyapunov exponent increases logarithmically with $\delta$, even though the unmagnetized $\delta \to \infty$ limit is strictly integrable. In the $\delta \gg 1$ regime, incomplete re-laminarization of the phase space flow leads to two distinct populations: (i) the majority of particles undergoing
stochastic diffusion, and (ii) a fraction of particles that become phase-locked with the wave, experiencing macroscopic intermittent surfing (Lévy flights). The 1D Particle-In-
Cell simulations using the EPOCH code in the highly magnetized ($\sigma \gg 1$) and under-dense regime are generally consistent with the
Hamiltonian single-particle theory. The dissipation fraction of the initial EM energy remains mild.
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Physics and Society
Macro-level reinforcement tunes the transition order of reversible social contagion
Guanyu Zhang and Peng-Bi Cui
Social contagion is often shaped by reinforcement: individuals become more likely to adopt a new behavior, opinion, or product as exposure accumulates or adoption becomes widely visible. Existing network models mainly capture this effect through local mechanisms, such as threshold responses or higher-order interactions. However, how macro-level reinforcement reshapes reversible spreading remains unclear. Here we study a SIS-like process in which pairwise transmission is reinforced by global prevalence. Combining quasistationary simulations and bifurcation analysis, we show that global feedback can produce first-order transition and hysteresis loop, with distinct activation and collapse thresholds. We further show how network localization promotes local ignition while weakening the global prevalence signal required for abrupt macroscopic activation, thereby raising the reinforcement threshold. Our results reveal how onset–retreat asymmetry emerges from global feedback coupled to network structure, providing a minimal mechanism for abrupt, history-dependent reversible social contagion.
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Optics
An orthogonal-to-non-orthogonal multiplexing format converter
Zijian Li, Chen Ding, Zixian Wei et al. (+5 more)
Time-frequency orthogonality has been a foundational principle in the historical development of optical communications, whether in dense wavelength division multiplexing (WDM) within long-reach high-capacity coherent optical transmission or in time-frequency division multiple access within short-reach dense passive optical networks. Towards next-generation agile optical networks, jointly programmable orthogonal and non-orthogonal regulation offers flexible spectral allocation, ultra-dense packet distribution, and increased capacity. For bridging the fundamental differences of physical implementation, we propose and demonstrate a versatile orthogonal to non-orthogonal multiplexing format converter, with application to high-speed coherent optical transmission network enabled by a Talbot-based processor. The programmable Talbot-processed pumps coherently transfer and superpose optical signals of distinct wavelength channels onto a single channel through cross-phase modulation. We first demonstrate flexible conversion of two 80-Gbps WDM QPSK channels separated by 200-250 GHz into a non-orthogonal power-division multiplexing channel, while maintaining the high-quality encoded information in the digital domain. We then validate a digital-subcarrier-multiplexing dense access scenario in which eight 20-Gbps sub-channels are combined, converted, transmitted, and successfully decoded over a field-deployed fiber. The multiplexing format converter promises potential for applications in next-generation optical systems and networks with complex
topologies and dense populations.
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All authors Zijian Li, Chen Ding, Zixian Wei, Qiarong Xiao, Ka-Suen Lee, Chaoran Huang, Changyuan Yu, Chester Shu
Accelerator Physics
Beam-excited resonant modes in RF cavities
Yanxu Wang, Demin Zhou, Ji Li et al. (+4 more)
Beam-excited resonant modes in RF cavities are important sources of beam-coupling impedance and coupled-bunch instabilities in high-current storage rings. We develop a unified framework for longitudinal and transverse resonant impedances based on Maxwell's equations and generalized cavity-voltage definitions, and derive analytical expressions for impedances obtained from finite-length truncated wakefields. The formulation enables the resonant frequencies, normalized longitudinal and transverse shunt impedances, and, when sufficiently constrained, the quality factors to be extracted from practical wakefield simulations without requiring fully converged long-range wakes. The method is validated with an axisymmetric pillbox cavity through comparison with analytical results and eigenmode calculations. It is then applied to the RF cavity of the Storage-Ring-based Coherent Light Source (SRCLS), where the extracted HOM parameters are used to reconstruct total impedance spectra, evaluate coupled-bunch instability thresholds, and guide cavity-geometry optimization. The results demonstrate an efficient connection between wakefield analysis, eigenmode characterization, and beam-stability evaluation for practical RF-cavity designs.
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All authors Yanxu Wang, Demin Zhou, Ji Li, Weijie Fan, Qinglei Zhang, Chao Feng, Zhentang Zhao
Medical Physics
Comorbidity Network Analysis Reveals Diagnostic Disparities Between Austrian and Non-Austrian Inpatients: A Population-Wide Cohort Study
Elma Dervic, Andrea Vismara, Remah Dahdoul et al. (+2 more)
International migrants face well-documented barriers to healthcare access, yet the extent to which these barriers shape patterns of disease co-occurrence remains poorly understood. Drawing on a nationwide
dataset of approximately 13 million hospital admissions from around 4 million individuals in Austria (2015-2019), we constructed and compared comorbidity networks between Austrian nationals and non-Austrian migrants, matched 1:1 by age, sex, and time of first hospital admission (272,779 per group). Following matching, metabolic and cardiovascular diagnoses, including type 2 diabetes and myocardial infarction, were more common among non-Austrians, while depression was more common among Austrians. Comorbidity network analysis showed that among all disease pairs that differed significantly between groups, 70% showed stronger co-occurrence in Austrian patients and 30% in non-Austrian patients. Distinct sex-specific patterns appeared: Austrian males showed stronger associations between alcohol use disorder and mental health diagnoses, whereas non-Austrian males more frequently presented with acute somatic conditions. Among non-Austrian women, a pronounced cluster of recurrent depression, somatoform disorders, and dorsalgia was observed. We interpret the disproportionately fewer comorbidity links observed in non-Austrians not as evidence of lower disease burden, but as a likely reflection of structural access barriers, including
language differences, cultural factors, and crisis-oriented admission patterns, that prevent comprehensive diagnostic assessment, though a contribution from the healthy migrant effect cannot be excluded. These findings stress the need for culturally aware care strategies and earlier identification of high-risk multimorbidity profiles in migrant populations.
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All authors Elma Dervic, Andrea Vismara, Remah Dahdoul, Marion Aichberger, Nilufar Mossaheb
Physics and Society
Self-Reference in Large Language Models: The Introspection Threshold for Recursive Self-Improvement
Jiang Zhang, Bing Yuan and Qian Zhang
The pursuit of self-evolving AI raises a critical question: when is autonomous self-improvement sustainable rather than degenerative? Drawing an analogy to von Neumann's complexity threshold for self-reproducing automata, we argue that sustainable recursive self-improvement in Large
Language Models (LLMs) requires a functional analogue: introspection – the system's capacity to simulate its own operations and target modifications. Grounded in Kleene's Second Recursion
Theorem, we demonstrate the theoretical existence of such introspective programs. However, an empirical review reveals that while current LLMs exhibit quasi-introspection (e.g., partial metacognition), they fall short of true introspection due to structural bottlenecks: a lack of complete self-access, the feedforward nature of the
Transformer, and computational class constraints that prevent fixed-point iteration. We conclude by outlining architectural paths to cross this complexity threshold and discussing the associated safety implications.
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Plasma Physics
Particle dynamics and confinement in moving multi-mirror
Tal Miller, Eli Gudinetsky, Ilan Be'ery et al. (+1 more)
The moving multi-mirror (MMM) concept mitigates axial losses in
magnetic mirrors by using inward-propagating multi-mirror sections to transport escaping particles back toward the central
cell. Single-particle simulations are used to establish the underlying dynamics, while a modified rate-equation model provides quantitative estimates of the resulting confinement enhancement. It is found that the steady-state outgoing flux can be robustly suppressed by several orders of magnitude. The analysis uncovered confinement challenges in the MMM concept, indicating that additional scattering processes are required in both the central
cell and the MMM sections to achieve the desired confinement.
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All authors Tal Miller, Eli Gudinetsky, Ilan Be'ery, Ido Barth
Applied Physics
Enhanced LIBS Emission Using Laser Beam Splitting: Interacting Multi-Plume Plasma Dynamics
Girum Abebe Beyene, Inam Mirza, Jijil JJ Nivas et al. (+3 more)
The optical emission in
laser-induced breakdown spectroscopy (LIBS) is governed by the spatial intensity distribution of the incident
laser beam, which influences
plasma formation and
evolution. Beam shaping therefore offers a route to control
plasma dynamics and emission yield; however, its effects in LIBS remain insufficiently quantified, particularly under conditions relevant to compact instrumentation. In this work, a diffractive optical element (DOE) is used to transform a Gaussian beam into a 2x2 array, producing simultaneously expanding, co-propagating ablation plumes that interact during expansion.
Plasma evolution from Cu and Si targets is investigated in
vacuum using a Nd:YAG
laser (1064 nm, 5 ns, 10 J/cm2), combining time-resolved imaging with optical emission spectroscopy. The multi-spot configuration results in enhanced emission intensity compared to single-spot irradiation, with increases of ~9 for Si and ~3 for Cu. The observed enhancement is attributed to plume-plume interaction effects that modify
plasma density and emission characteristics. These results demonstrate that DOE-based beam shaping provides an effective and technically simple approach to increasing the LIBS signal without additional system complexity.
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All authors Girum Abebe Beyene, Inam Mirza, Jijil JJ Nivas, Oleksandr Gatsa, Nadezhda M. Bulgakova, Alexander V. Bulgakov
Medical Physics · Cross-listed from eess.SP
Light Coils: MRI with Fully Optical Data and Power Transmission
Zining Liu, Morteza Teymoori, Jakob Gerlach et al. (+5 more)
In MRI, dense receiver coil arrays with a high number of coil elements are used to efficiently detect and encode the signal. Further increasing the number of coils is hampered by electrical cabling and massive electronics that introduce electromagnetic coupling, integration complexity and even safety constraints. Here we introduce the novel Light Coils concept, a fully optical MRI receive architecture in which data transmission, front-end power delivery, and coil detuning are all implemented optically, thereby reducing the massive galvanic cabling to a few optical fibers. For signal encoding, Mach-Zehnder modulators (MZM) are used to convert the MR signal from each coil onto a C-band optical carrier. The preamplifiers are driven via a power-over-fiber (PoF) system that uses a high-efficiency photovoltaic (PV)
cell for optical-to-electrical power conversion. A pulse-sequence-triggered optical path controls active detuning. Jointly optimizing modulator bias, optical power and front-end gain under realistic receiver chain conditions, Light Coils can match the signal-to-noise ratio (SNR) of conventional RF coil systems with galvanic cables at MZM input powers of 5-10mW and photonic power converter inputs of 80-100mW. At a clinical 3T MRI system, we show in vivo human
brain imaging with a single-channel Light Coil element with an image quality and SNR comparable to a conventional coaxial readout using the identical coil element. Extending the concept to a four-channel array using dense wavelength-division multiplexing over a single fiber, we demonstrate wavelength-selective routing with inter-channel optical isolation exceeding 28dB, reduced noise correlation compared with the galvanic reference, and parallel imaging. These results establish a scalable route towards lightweight, modular, and potentially ultra-dense MRI receive arrays based on integrated photonics and power-over-fiber.
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All authors Zining Liu, Morteza Teymoori, Jakob Gerlach, Reza Aghabagheri, Henning Helmers, Michael Bock, Caglar Ataman, Ali Oezen
Biological Physics · Cross-listed from q-bio.PE
A loser in both environments can survive by switching between them
Riz Fernando Noronha and Kunihiko Kaneko
How can a species persist in an environment where it is always outcompeted? Using a minimal predator-prey model with environment-dependent parameters, we show that a predator driven to extinction in each of two static environments can survive indefinitely once the environment alternates between them fast enough. We derive the critical switching rate above which persistence occurs, and show that random (Poisson) switching needs to be faster than periodic switching in order to offset prolonged spells in the unfavorable environment. We then generalize the mechanism to any two-species system, and can predict persistence solely based on the sign of a single “switching rescue function" assembled from the two boundary vector fields. This general result has broad reaching consequences: for instance, when applied to a standard model of viral dynamics, it predicts that two drugs which each clear a pathogen on their own can fail when alternated, giving a non-resistance-based explanation for the failure of drug-cycling strategies. Our results demonstrate that the tempo of environment change, as opposed to the environments themselves, can lead to species survival.
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Instrumentation and Detectors · Cross-listed from astro-ph.IM
The Amerigo Vespucci as a traveling laboratory for studying the cosmic-ray fluxes at sea level
Davide Cerasole, Federica Cuna, Gaia De Palma et al. (+13 more)
We have installed and operated a plastic scintillator detector counter to measure the flux of
cosmic radiation during the 2023-2025 tour of the historical vessel Amerigo Vespucci. The Vespucci is the oldest ship of the Italian Navy and serves as a training vessel for Navy cadets. During its tour, some experiments were hosted onboard the vessel, providing unique opportunities for scientists working in different fields. We installed our detector upon the Vespucci's departure from Darwin in early October 2024. The detector collected
cosmic-ray data during the journey from Darwin to Trieste, where the worldwide tour ended in March 2025. After about one month of stop in Trieste, the ship continued its tour in the Mediterranean sea, and arrived in Genova on June 10, 2025. We performed measurements of the
cosmic radiation reaching the sea level across a wide latitude range, from 15{\deg} S to about 45{\deg} N. The lowest rate (averaged over all azimuth angles) was measured at a geographic latitude of about 7{\deg} N, and was about 16% less than the highest value, which was measured at Trieste, the northernmost location of the journey. Latitude effects on the
cosmic radiation flux at sea level are due to the quasi-dipole geomagnetic field configuration, tilted by an angle of about 11{\deg} with respect to Earth's rotational axis.
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All authors Davide Cerasole, Federica Cuna, Gaia De Palma, Riccardo Di Tria, Leonardo Di Venere, Fabio Gargano, Mario Giliberti, Francesco Licciulli, Antonio Liguori, Pierpaolo Loizzo, Francesco Loparco, Leonarda Lorusso, Mario Nicola Mazziotta, Giuliana Panzarini, Roberta Pillera, Davide Serini
Optics
Thermal vacuum friction of objects with different dimensionality
Gor Chalyan and F. Javier García de Abajo
Radiative forces acting on neutral bodies moving through a thermal bath represent a unique manifestation of the interplay between relativistic kinematics and thermal fluctuations.
Vacuum friction is commonly formulated using the fluctuation–dissipation
theorem or related statistical approaches, but such treatments can obscure the elementary momentum-transfer processes, especially in relativistic regimes. Here, we develop a kinetic momentum-transfer framework based on relativistic kinematics in which the radiative force and pressure are obtained by summing individual scattering and absorption events. This approach offers a transparent physical picture while ensuring a self-consistent treatment of Doppler shifts and relativistic transformations. We apply the method to three representative geometries: an isotropic dipolar particle, a thin resonant plate moving normal to its surface, and a thin resonant plate moving parallel to its surface. In the nonrelativistic limit, we derive explicit radiative drag coefficients, providing compact expressions for predicting
vacuum friction in moving structures.
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Chemical Physics
ML and AI for density functional theory: different priorities for Kohn-Sham and orbital-free DFT, for electronic and nuclear DFT
Xin-Hui Wu and Sergei Manzhos
We overview similarities and, importantly, differences in computational bottlenecks and accuracy requirements that can be addressed with machine learning (ML) and artificial intelligence (AI) techniques in electronic and
nuclear DFT. From these follow different promising methodological and algorithmic choices depending on whether one machine learns the exchange correlation (XC) functional, the kinetic energy functional (KEF), the density or the basis functions. In particular, while the popular deep neural networks remain a potent choice in the context of KS DFT, we highlight their disadvantages when building KEFs and highlight conceptual advantages - yet to be fully realized - of symbolic regression for both electronic and
nuclear DFT. We point out promising approaches that can be carried from the more extensively investigated ML-enhanced electronic DFT to
nuclear DFT.
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Optics · Cross-listed from quant-ph
Coherent quantum control of dark excitons in hybrid metal organic chalchogenolates
Christian L. McCoy, Tobias Saule, Mariya Aleksich et al. (+5 more)
Artificial atom-like systems are a promising candidate for next generation
quantum processing. Among them, dark
excitons exhibit one of the longest lifetimes at high temperatures. Here, we demonstrate coherent control of dark excitonic states in metal-organic chalcogenolates (MOChas) by using an ultrafast pulse shaper at room temperature. These dark
exciton states are optically accessed via two-
photon absorption and directly read out with a four-wave mixing process. The system is described by a non-perturbative, two-
photon Hamiltonian based on well-known atomic physics and applied to a three level system comprised of two dark
excitons. Empirical and theoretical state specific optical access is shown via a simple optical pulse shape. The developed
Hamiltonian-based description is a first step towards a
quantum processing platform using three-level systems and two
photon transitions, one example being dark
excitons in the MOCha silver benzeneselenolate (mithrene). Simple conditions for gate operations are laid out and described.
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All authors Christian L. McCoy, Tobias Saule, Mariya Aleksich, Maggie C. Willson, J. Nathan Hohman, Thomas Weinacht, George N. Gibson, Carlos A. Trallero-Herrero