Accelerator Physics
White Paper on a Novel FFA-Based CEBAF Upgrade to 22 GeV
S. A. Bogacz, R. M. Bodenstein, K. E. Deitrick et al. (+11 more)
We present a conceptual design for a cost-effective upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) to 22 GeV using non-scaling fixed-field alternating-gradient (FFA) arcs built from Halbach-style permanent magnets. Building on the eight-pass energy-recovery demonstration at the Cornell–BNL CBETA test accelerator, the design replaces the highest-energy recirculation arcs with a pair of FFA arcs that simultaneously transport six passes spanning a factor-of-two momentum range. We describe the machine layout; including the injector, recirculating linacs, spreaders and recombiners, FFA arcs, splitters, transition and extraction regions; together with beam-dynamics validation studies covering emittance growth, synchrotron-radiation-driven depolarization, and orbit correction, and we summarize permanent-magnet design, prototyping, and radiation-resiliency results. This white paper documents the accelerator physics underpinning a staged path to 22 GeV that preserves CEBAF's multi-
hall, high-luminosity, polarized-beam capabilities.
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All authors S. A. Bogacz, R. M. Bodenstein, K. E. Deitrick, B. R. Gamage, R. Kazimi, D. Khan, E. Nissen, S. Ogur, Y. Roblin, P. Rossi, J. S. Berg, S. J. Brooks, D. Trbojevic, V. Morozov
Atomic Physics · Cross-listed from quant-ph
Dual-Isotope Sympathetic Cooling in a Long Ion Chain
Tianyi Wang and Marko Cetina
Owing to their high controllability and connectivity, one-dimensional ion chains are attractive building blocks for near-term
quantum computers. However, long ion chains are susceptible to motional heating caused by fluctuating external electric fields. To enable deep computations, this source of noise must be suppressed without inducing
qubit decoherence or degrading
qubit connectivity. We demonstrate steady-state mid-
circuit sympathetic cooling of all computationally-relevant motional modes of a 23-ion chain consisting of \qubit
qubit and \coolant coolant ions without using any
qubit operations. In a room-temperature system, our cooling scheme preserves the mean
phonon occupations of the long-wavelength axial and radial modes near their values following state preparation, while keeping the modes used to implement entangling gates near their ground states throughout a 56-ms
circuit. Crucially, we show that our cooling sequence preserves
qubit coherence, and evaluate its impact on single- and two-
qubit gate operations. Additionally, we demonstrate a parallel
qubit reset protocol leveraging the shared radial mode coupling between species. Our sympathetic cooling scheme represents a critical step toward reducing gate errors in individually-addressed long ion chains and establishes a versatile platform for simulating open
quantum systems.
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Instrumentation and Detectors
Performance Evaluation of a High-Granularity LYSO-SiPM-Based Position-Sensitive Detector for a One-Shot Gamma-Scanning System with Sub-Millimeter Spatial Resolution
Katyayni Tiwari, Arzoo Sharma, Jürgen Gerl et al. (+5 more)
A compact position-sensitive {\gamma}-detector based on a thin monolithic LYSO
crystal and a 96-channel SiPM array is developed for the spatial characterization and calibration of segmented {\gamma}-ray detector systems used in
nuclear-physics experiments. The detector is designed to provide localized irradiation and rapid two-dimensional response mapping. A 7 cm diameter and 3 mm thick LYSO
crystal is optically coupled to the SiPM array, and the position of the incident {\gamma}-ray interaction is reconstructed from the relative scintillation-light signals collected by neighboring SiPM channels. An asymmetry-based charge-sharing method is employed to determine the interaction position from the spatial distribution of the detected scintillation light. Detailed GEANT4 simulations, including optical
photon transport, were performed to investigate the detector response and estimate its intrinsic spatial resolution. The simulations predict a spatial resolution of approximately 0.5 mm for 60 keV and 511 keV {\gamma}-rays under idealized conditions. A prototype detector was developed and experimentally characterized using coincidence measurements with the {\gamma}-scanning facility at GSI, Germany. The experimental measurements demonstrate a spatial resolution better than 1 mm in the central detector region, while the position-dependent response and degradation near the detector boundaries are investigated. The experimental results are compared with GEANT4 predictions to identify the contributions of optical
photon transport, charge sharing, and detector geometry to the measured spatial resolution. The developed detector provides a compact solution for the three-dimensional characterization of highly segmented {\gamma}-ray detector arrays in
nuclear physics experiments.
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All authors Katyayni Tiwari, Arzoo Sharma, Jürgen Gerl, Ivan Kojouharov, P. Herrmann, H. Schaffner, G. Aggez, Pushpendra P. Singh
Space Physics · Cross-listed from astro-ph.SR
Breakout/Interchange Reconnection as a driver of Jets, Fast CME, and Solar Energetic Particles
Pankaj Kumar, Judith T. Karpen, David Lario et al. (+4 more)
Understanding how energetic particles are accelerated and released from the low corona into the interplanetary medium during
solar eruptions is crucial for space weather research. Here, we present multiwavelength observations of a
solar eruption that are consistent with breakout reconnection playing an important role in driving a fast coronal mass ejection (CME) and the associated
solar energetic particle (SEP) event. Extreme-ultraviolet and
radio observations reveal evidence of breakout reconnection within a fan-spine
topology. The filament eruption begins after the pre-eruption opening, accompanied by quasiperiodic jets and associated downflows near the null point, as well as recurrent faint Type III
radio bursts during the ongoing slow breakout reconnection. Furthermore, the observations also reveal the formation of pre-eruption coronal rain via slow interchange reconnection near the null point. A large-scale circular ribbon, along with simultaneous four hard X-ray footpoint sources and intense Type III
radio bursts, was observed during the explosive breakout reconnection that enabled opening of field lines and allowed energetic particles to escape into interplanetary space. In situ measurements by PSP and Wind confirm the
prompt injection of electron beams consistent with the timing of the explosive breakout reconnection. A fast shock associated with the erupting flux rope during interchange reconnection played a major role in producing the gradual SEP event. These observations highlight the key role of breakout reconnection in producing a fast CME/shock with the SEP release and acceleration process. These results have broader implications for particle acceleration and release processes in multiscale null-point
topologies, which produce a continuum of eruptions ranging from small-scale jets to large-scale CMEs.
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All authors Pankaj Kumar, Judith T. Karpen, David Lario, Benjamin J. Lynch, Peter F. Wyper, Spiro K. Antiochos, P. K. Manoharan
Optics
Nonlocality is the missing design rule for topological photonics
Fatemeh Davoodi
Topological photonics has provided powerful design rules for routing and localizing light through geometry,
symmetry and engineered coupling. However, fabricated nanophotonic and plasmonic devices rarely realize only the local or short-range interaction networks assumed in compact topological models. Long-range near-field coupling, retardation, radiation leakage, substrate-assisted hybridization, material dispersion and fabrication disorder can reshape the optical modes that are interpreted as topological. In this Perspective, I argue that nonlocality should be treated as a design parameter rather than as a residual perturbation. This shift requires moving from ideal phase labels toward calibrated interaction models, finite-structure observables, robustness maps and graded confidence measures. I discuss how full-wave simulations, experiments and physics-informed learning can connect
geometric design variables to effective electromagnetic interaction networks. Such calibrated workflows can clarify when a topological design rule is reliable, when it fails, and how nonlocal coupling can be exploited for robust nanophotonic devices.
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Optics · Cross-listed from q-bio.OT
Beyond chlorophyll: machine learning estimates of diagnostic phytoplankton pigments from multispectral ocean colour data
David Moffat, Angus Laurenson, Victor Martinez-Vicente et al. (+4 more)
Phytoplankton play a central role in marine ecosystems and the global carbon cycle, with different groups contributing differently to ocean biogeochemical processes. While standard techniques exist for monitoring phytoplankton concentration from ocean-colour data, their community composition remains difficult to observe at large scales. Chlorophyll-a, widely available from satellite ocean-colour observations, is commonly used as a measure of phytoplankton biomass but provides limited information on taxonomic composition. Accessory pigments, some of which are diagnostic of important phytoplankton groups, offer additional information on community structure, but their
retrieval from ocean-colour data is challenging because of limited spectral resolution and strong covariance with chlorophyll-a. In this study, we evaluate machine learning methods for estimating diagnostic pigment concentrations from multispectral satellite observations. Using a global
dataset of 33,640 High Performance
Liquid Chromatography (HPLC) measurements matched with ESA Ocean Colour
Climate Change Initiative (OC-CCI) reflectance data, we compare Random Forest and TabPFN models trained on multispectral reflectance with baseline models using chlorophyll-a alone. A temporally stratified validation scheme is employed to reduce the effects of autocorrelation. Results show that multispectral models consistently outperform approaches based solely on satellite-derived chlorophyll-a, demonstrating that ocean-colour reflectance contains additional information relevant to pigment discrimination. Improvements vary by pigment, with those strongly correlated with chlorophyll-a showing limited gains, while others exhibit substantial improvement. These findings highlight the potential of machine learning to extract ecologically relevant information from satellite data beyond conventional chlorophyll-based approaches.
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All authors David Moffat, Angus Laurenson, Victor Martinez-Vicente, Gemma Kulk, Xuerong Sun, Robert J. W. Brewin, Shubha Sathyendranath
Computational Physics
First-Principles Electron-Magnon Coupling with Machine-Learning Hamiltonians: From Band Renormalization to Transport
Shixu Liu, Xingding Li, Haozhe Li et al. (+4 more)
In analogy to electron-
phonon coupling (EPC), electron-
magnon coupling (EMC) is expected to shape electronic structure, transport, and possibly unconventional superconductivity in
magnetic materials. However, unlike EPC, which is now routinely treated within first-principles frameworks, a quantitative description of EMC, especially for transport, remains elusive because of the lack of theoretical formalism. Consequently, even for elemental iron, EPC-only calculations miss both the magnitude and the $T^2$ component of resistivity. This discrepancy has long been attributed to EMC, although direct computational evidence has been lacking and the underlying transport mechanism remains unresolved. Here we develop a unified first-principles formalism for EMC in collinear
magnetic systems within many-body perturbation theory, complemented by machine-learning spinful
Hamiltonians that supply quantities not directly accessible from conventional first-principles methods. Our framework enables ab initio transport calculations including EMC effects for the first time. Applied to
ferromagnetic $\alpha$-Fe, our approach yields electron spectral functions consistent with previous studies. More importantly, we recover the full $T^2$ component of resistivity with a coefficient in quantitative agreement with measurement and reveal that the $T^2$ component cannot be attributed solely to EMC, as has long been assumed, but is dominated by the strong EPC-EMC interplay. Extending to
antiferromagnetic K-doped $\mathrm{BaMn_2As_2}$, our method captures the ARPES-observed
magnon-induced kink and a large EMC strength of $\sim 3$ comparable to experimental measurements, demonstrating the generality of the framework. Our work closes a longstanding gap in the quantitative understanding of transport in
magnetic systems and provides a predictive foundation for examining
magnon-mediated phenomena.
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All authors Shixu Liu, Xingding Li, Haozhe Li, Yang Zhong, Hongjun Xiang, Xin-Gao Gong, Ji-Hui Yang
Chemical Physics
Tracking molecular hydrogen formation from ionized water in real time
Chuan Cheng, Chi-Hong Yuen, Eleanor Weckwerth et al. (+8 more)
Removing an electron from a water molecule can drive its two hydrogen atoms to pair up and depart as molecular hydrogen. However, even for this elementary reaction, the route from start to finish has remained hidden because measurements have yet to follow the electronic and
nuclear motion simultaneously. Combining correlated photoelectron and ion imaging, few-femtosecond pump–probe measurements, and nonadiabatic simulations, we track the complete pathway in isolated heavy water (D$_2$O) molecules. The reaction takes an indirect route and dissociates along three distinct pathways (direct, roaming, and delayed) with formation times of about 34 and 72 femtoseconds for the direct and delayed branches. Yet bond formation requires the molecule to first break its own
symmetry. Only random asymmetric motion enables the electronic-state switch at a conical intersection, joining the two hydrogen atoms before the oxygen–hydrogen bond breaks. These results establish a time-resolved picture of molecular hydrogen formation from water and provide a general strategy for linking electronic excitation to chemical outcomes in settings from radiation damage to hydrogen production.
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All authors Chuan Cheng, Chi-Hong Yuen, Eleanor Weckwerth, Ian Gabalski, Aaron M. Ghrist, Haoran Ma, Andrew J. Howard, Mathew Britton, Yunquan Liu, Eric Wells, Philip H. Bucksbaum
Biological Physics
Roles of vortices and turbulent eddies in particle preferential concentration and deposition in the human respiratory tract
Mengtao Li, Yawei Wang, Wentao Feng et al. (+1 more)
Precise targeting of pharmaceutical aerosols is critical to the efficacy and safety of inhaled therapies. This study focused on the influences of
vortices and turbulent eddies on preferential concentration and deposition of pharmaceutical aerosols within the human respiratory tract. By reconstructing a high-fidelity respiratory tract geometry spanning the nasal cavity down to sequential bronchi from computed
tomography (CT) images and assigning physiologically realistic transient breathing profiles, an unsteady Reynolds-averaged Navier-Stokes (URANS) framework using the shear stress transport (SST) k-w
turbulence model and a stress-blended eddy simulation (SBES) framework of human respiratory tract were built. Beyond flow field analyses, Vorono diagrams and a set of newly-defined spatial accuracy metrics were adopted to quantitatively characterize particle distributions and localized prediction discrepancies. Spectral analysis revealed that the SBES simulations adequately recovered the prominent Kolmogorov -5/3 inertial scaling law. Such turbulent motion induces pronounced radial turbulent dispersion, forming particle clusters with higher cluster fractal dimensions D> 1.2 on the mid-plane of the laryngopharynx. Spatial accuracy metrics uncovered a critical dual deficiency of the URANS model: globally over-smears near-wall deposition by roughly 20%, simultaneously fails to resolve most high-concentration `hotspots' (the top 5% local extrema). These findings highlighted that the numerical resolution of transient
vortices and turbulent eddies constitutes an indispensable prerequisite for accurately predicting of particle transport and deposition in the human respiratory tract.
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All authors Mengtao Li, Yawei Wang, Wentao Feng, Yubo Fan
Applied Physics
Which transition can be used in sodium mirrorless lasing for mesospheric magnetometry?
Yucheng Yang, Chunyang Lei, Kai Guo et al. (+1 more)
Directed mirrorless lasing from the mesospheric sodium layer has been proposed as a way to overcome the isotropy of
laser-guide-
star fluorescence, with demonstrated
cell-scale analogues and a demonstrated stand-off magnetometry application. Several transition paths on the Na ladder compete for the same pump
photons, and which of them can sustain a population inversion—and under what pumping format—is usually settled by numerical scans of a multi-level rate model. Here the same question is answered in closed form, and three design-relevant results follow from the atomic data alone. (1) A cascade inversion on $u\to l$ requires $\tau_u/\tau_l>(g_u/g_l)b_{ul}$. The inequality reproduces the full continuous-wave classification—admitting $4P_{3/2}\to4S_{1/2}$ (2.21~\textmu m), $4P_{3/2}\to3D_{5/2}$ (9.1~\textmu m) and the fine-structure companion $4S_{1/2}\to3P_{1/2}$ (1138~nm), excluding $4D_{5/2}\to4P_{3/2}$ (2.34~\textmu m) and $3D_{5/2}\to3P_{3/2}$ (819~nm)—and shows the 2.34~\textmu m line to miss by only 9%, which is why it is transiently accessible. (2) Velocity selectivity reverses the naive scheme ranking because a Doppler-averaged treatment, exact for one-step pumping, underestimates two-step pumping by a participation factor of order the Doppler-to-natural width ratio, $\sim$$10^{2}$; equal division of power between two pump beams is exactly optimal. (3) The transient window on 2.34~\textmu m closes after $\sim$2$\tau(4P)\approx210$~ns, set by the reservoir lifetime rather than by the pump. Each conclusion is traceable to a lifetime, a branching ratio or a linewidth, and transfers to another species without rerunning a model.
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All authors Yucheng Yang, Chunyang Lei, Kai Guo, Chi Peng
Physics Education · Cross-listed from math-ph
Elements of Topology, Differential Geometry and General Relativity for Physicists: A Mathematica-based Tutorial Approach
Balasubramanian Ananthanarayan, Souvik Bera, Subhasish Chakrabarty et al. (+4 more)
This book is a self-contained, tutorial introduction to
topology, differential geometry, and general relativity for students and researchers in physics. Its distinguishing feature is a Mathematica-based approach that makes abstract constructions concrete through explicit, runnable notebooks and worked examples. A key contribution is a large collection of original Mathematica notebooks, written by the authors themselves, that let readers run, verify, and extend every demonstration. The first part covers point-set
topology, topological spaces, continuity of maps, homotopy, and the fundamental group with applications that highlight the role of
topology in modern physics. The second and largest part develops differential geometry from the ground up:
manifolds, tangent and dual spaces, vector fields, pullbacks and pushforwards, Lie brackets and Lie
algebras, local flows, and the Lie derivative. It then treats tensors, differential forms, the exterior derivative, volume forms, the metric tensor, and Hodge duality, emphasizing coordinate-free formulations and their computational realization. These tools are applied to Maxwell's equations in the
language of forms and the generalized Stokes
theorem, while Lie groups, fiber bundles, connections, and
curvature bridge geometry and gauge-theoretic physics. The final part uses this framework to present general relativity, computing
curvature tensors and field equations for standard spacetimes with dedicated Mathematica packages. Throughout, the book balances mathematical rigor with hands-on computation, enabling readers both to understand the theory and to reproduce every result themselves.
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All authors Balasubramanian Ananthanarayan, Souvik Bera, Subhasish Chakrabarty, Souradeep Das, Amitabha Lahiri, Suhas Sheikh, Sarthak Talukdar
History and Philosophy of Physics
Does the Actuality of Life Favor Many Actual Histories?
Jonathan Baxter
This essay develops a simple conditional argument for many-history ontologies from the fact that life exists. The question is not why our exact evolutionary sequence occurred, but why reality contains the broad class of life-bearing histories at all. If such histories are sufficiently rare, then a single-history ontology makes the existence of life surprising, while an ontology containing many histories can make it unsurprising. In the limiting case, life may be vanishingly unlikely in any one history while almost certain to occur somewhere if many histories are actualized. Everettian
quantum mechanics is a natural candidate for this kind of ontology because its multiplicity is not introduced for anthropic purposes, but arises from taking universal
unitary quantum mechanics seriously. The
Fermi paradox is discussed as pressure against the claim that life is common within a single history.
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Optics
Revealing Hidden Orbital Pathways in NonThermal Hot Carrier Relaxation of MXenes via NonSecular Redfield Quantum Kinetics
Ali Asghar Molavi Choobini, Abbas Chimeh and Jinhui Zhong
Non-thermal carrier relaxation is routinely inferred from population dynamics or spectroscopic observables, yet neither class of quantity uniquely identifies the microscopic channels through which energy and coherence are redistributed. We introduce a pathway-resolved
quantum-kinetic framework that simultaneously projects ultrafast relaxation onto orbital populations, directional inter-orbital transferes, coherence, spectroscopic visibility, and a hidden-pathway sector of the dynamical transfer network. Application to MXenes exposes strongly non-uniform orbital redistribution together with material-specific hierarchies of microscopic transfer channels. Temperature, excitation amplitude, and dissipative parameters modulate pathway competition and spectral amplitudes while leaving the identity of the dominant channels largely intact. Instantaneous transfer contributions, cumulative directional transfer, coherence, and spectroscopic visibility are shown to follow inequivalent hierarchical orderings. This non-equivalence isolates a set of hidden pathways that remain dynamically consequential despite weak conventional spectroscopic signatures. The resulting time energy coherence representation recasts nonthermal relaxation as a structured dynamical network comprising observable and hidden sectors, thereby providing a general methodology for resolving microscopic orbital transfer pathways in driven
quantum materials.
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Chemical Physics · Cross-listed from cond-mat.mes-hall
Electrostatic control of Li+ density and transport rate in double-gated van der Waals devices
E. Hoenig, X. Zhang, C. Li et al. (+7 more)
Ion transport in crystalline hosts is controlled by an applied potential that simultaneously sets ionic distribution and transport rate, restricting operation to a one-dimensional control space. Here we show that the transport rate of Li+ ions in double-gated van der Waals devices can be modulated while the system occupies fixed ionic-density states. We measure the ionic current along the van der Waals interfaces between hexagonal boron nitride and
graphene or MoS2 while simultaneously monitoring the in-plane electronic response. The ionic current exhibits pronounced hysteresis, with plateaus marking discrete ionic-density states balanced by electronic charge, while an independently tuneable electrochemical-potential drop controls the ionic transport rate. The devices sustain over 1,000 switching cycles and function as hybrid ionic-electronic transistors capable of logic operations and
memory retention, with ON/OFF ratios exceeding two orders of magnitude. This work demonstrates a two-dimensional control space for ions intercalated in layered materials.
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All authors E. Hoenig, X. Zhang, C. Li, J. Tong, G. Chen, L. Chen, D. Domaretskiy, D. R. da Costa, F. M. Peeters, M. Lozada-Hidalgo
Classical Physics
The Photon Gas in Classical Mechanics: A Statistical-Mechanical Treatment of Classical Field Theory
Farhang Loran and Saman Moghimi-Araghi
The thermodynamics of cavity radiation is usually introduced through the
quantum theory of a
photon gas. In contrast, we investigate which features of thermal radiation follow from classical electrodynamics alone. We show, using two complementary approaches, that the proportionalities between energy density, radiation pressure, and energy flux arise without invoking
photons or
quantum statistics. The first approach is based on explicit solutions of Maxwell's equations and spatio-temporal averaging of electromagnetic waves. The second approach develops the classical statistical mechanics of the electromagnetic field from first principles by constructing the canonical
Hamiltonian, implementing the gauge constraints, formulating the partition function as a functional integral, and evaluating the corresponding field correlation functions. By combining wave analysis, statistical mechanics, constrained
Hamiltonian dynamics, and functional methods within a single classical framework, this work provides a coherent classical formulation of electromagnetic radiation thermodynamics.
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Optics
Quantum Hydrodynamic Framework of Coherent Terahertz Emission in MXenes Driven via Engineered Femtosecond Waveforms
Ali Asghar Molavi Choobini, Abbas Chimeh and Jinhui Zhong
Coherent terahertz (THz) emitters based on low dimensional
quantum materials have attracted significant interest for compact broadband photonic technologies. However, theoretical descriptions that consistently connect microscopic
quantum dynamics to emitted THz radiation remain limited for MXenes, whose electronic properties are governed by transition metal d orbitals and chemically tunable surface terminations. A multiscale density-
matrix formalism for coherent THz generation in metallic MXenes driven by engineered three color femtosecond waveforms is developed. Material-specific electronic structures are described by parameterized multiband tight binding
Hamiltonians, while ultrafast carrier dynamics are treated using a non-secular Redfield master equation that explicitly retains interband coherence, carrier populations, electron
phonon interactions,
impurity scattering, and environment-induced relaxation. The transient photocurrent is explicitly decomposed into population and coherence driven contributions and linked to the emitted THz field through its time derivative, establishing a direct connection between microscopic
quantum dynamics and macroscopic radiation. The results show that environmental coupling does not merely attenuate THz emission, but redistributes coherent and population currents and reshapes the emitted waveform in both the time and frequency domains. Systematic investigations of optical waveform parameters, effective electronic structure, and open system relaxation identify physically grounded strategies for enhancing broadband THz generation. The proposed methodology establishes a transferable microscopic design platform for connecting material specific electronic structure,
quantum coherence, open system relaxation, nonlinear carrier transport, and coherent THz emission across MXenes and related low dimensional
quantum materials.
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Plasma Physics
AI Surrogate Modeling for Real-Time Tokamak Equilibrium Prediction: Benchmarking Neural Architectures and Validation on EXL-50U
Guoyang Shi, Zitong Zhang, Siqi Ding et al. (+5 more)
Fast and reliable
plasma equilibrium prediction is essential for real-time tokamak operation and control, but conventional Grad-Shafranov (GS) solvers are often too costly for real-time deployment. We develop an AI surrogate framework and
benchmark five architectures (MLP, CNN, FNO,
Transformer, and KAN) on a numerical GS database with 100,000 IID and 10,000 OOD samples. Under a unified protocol, we evaluate accuracy, inference efficiency, model scaling, and robustness. We also establish device-level validation on the EXL-50U tokamak by linking numerical GS solutions, surrogate predictions, and the standard Shape Editor reference to assess simulation-to-device consistency. The surrogates achieve errors of $10^{-3}$-$10^{-2}$ relative to GS solutions, while the GS-to-device discrepancy remains at $10^{-3}$.
Transformer gives the best IID accuracy, whereas CNN offers the best balance of accuracy, robustness, and speed, reaching 0.7 ms TensorRT latency. On unseen
plasma geometries and parameter regimes, CNN and FNO show the strongest extrapolation stability, with 4%-5% relative $L_2$ error, while models with weaker inductive biases degrade more substantially. Scaling data and model capacity improves interpolation but not necessarily extrapolation, revealing a trade-off between capacity and OOD generalization. Overall, this work provides a systematic, device-consistent
benchmark for AI-based GS prediction and practical guidance for selecting reliable surrogates for real-time
plasma control and fusion applications.
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All authors Guoyang Shi, Zitong Zhang, Siqi Ding, Jianguo Chen, Yapeng Zhang, Jiayi Zhi, Hanyue Zhao, Tianyuan Liu
Biological Physics · Cross-listed from cond-mat.mtrl-sci
The Achilles tendon enthesis rebuilds its mineralization front on reloading but retains a nanoscale imprint of unloading
M.L. Stammer, C. Camy, M. Frewein et al. (+16 more)
The enthesis is a graded fibrocartilaginous interface that transfers load between tendon and bone, yet the nanoscale mechanisms stabilizing its mineralization front remain unclear. Here, we combine
multimodal 2D/3D X-ray imaging with nonlinear optical microscopy to map structural, crystalline and extracellular
matrix organization across the murine Achilles tendon enthesis under unloading and reloading. Unloading reduces the tidemark-associated two-
photon fluorescence (2PF) peak and is accompanied by diffuse mineralization into previously unmineralized fibrocartilage. This unloading-associated mineral exhibits increased apparent crystallite size, an enlarged c-axis
lattice parameter, reduced crystalline texture and a diminished collagen order gradient, consistent with an altered mineralization environment. Upon reloading, the 2PF peak recovers, but a new tidemark forms ~20 um from the original boundary, creating a zone with a persistent nanoscale imprint in the mineral tessellation. These findings establish the enthesis as a mechanically governed graded interface in which
matrix-mediated boundary control constrains mineral formation and in which a record of mechanical history is imprinted into the nanostructure.
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All authors M.L. Stammer, C. Camy, M. Frewein, I. Silva Barreto, C. Genovesio, M. Eckermann, A. Karimbana, K. Iliopoulos, R. Ranjan, N. Wittig, T. Fovet, T. Brioche, A. Chopard, M. Burghammer, S. Brasselet, H. Birkedal, M. Pithioux, S. Roffino, T.A. Grünewald
Fluid Dynamics
Lagrangian Curvature Statistics from Gaussian Subensembles in Turbulent Flows
Yasmin Hengster, Johannes Bosbach, Daniel Schanz et al. (+2 more)
A salient feature of fully turbulent flows far from onset is the intermittent occurrence of extreme fluctuations at small spatial and temporal scales. These have a qualitative and quantitative effect on the instantaneous
curvature of a tracer particle trajectory as an intrinsically multi-scale observable. Here, we provide a complete statistical description of the
curvature of tracer particle trajectories in turbulent flows that includes and quantifies intermittency effects. We derive an exact expression and a closed-form approximation for the
curvature probability density function, both agree well with data obtained from laboratory experiments of different types of turbulent flows, and quantify the generic behavior of the system. The method can be extended to more complex systems such as
plasma turbulence.
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All authors Yasmin Hengster, Johannes Bosbach, Daniel Schanz, Andreas Schröder, Moritz Linkmann
Atmospheric and Oceanic Physics
Statistics of Temperature Extremes and Implications for Electrical Power Infrastructure in Continental France
Peter Werner, Bastien Cozian, Yoann Robin et al. (+2 more)
In this article, we present extreme value statistics of temperature extremes over continental France with a focus on their implications for electrical power infrastructure. These are obtained by fitting a non-stationary generalised extreme value distribution using a
Bayesian setup, which also provides errors or uncertainty values for all estimates. Within this method, a combination of simulated data from a collection of 28 CMIP6 models and measured records from the E-OBS
dataset is used. The investigated
climate scenarios are SSP2-4.5, SSP3-7.0 and SSP5-8.5, considering both historical and future climates spanning the years from 1850 to 2099. The method provides full spatial resolution on a 0.25 degree grid, allowing to asses extreme temperatures at arbitrary locations. Leveraging this particular aspect, various maps revealing the spatial structure of annual maximum high temperature extremes over continental France for the median and the statistical upper bound are shown together with summary information for the administrative regions in France towards the end of the century. It is statistically possible that the south west region of Occitanie could reach temperatures of up to 57{\deg}C under a high emission scenario by 2080, which is the highest compared to all other regions in continental France. We also perform a comparison to the reference
climate adaptation trajectory for France (TRACC - Trajectoire de réchauffement de Référence pour l'Adaptation au Changement Climatique), showing that it potentially underestimates the stated maximum temperatures which could be surpassed by up to +8{\deg}C. Furthermore, five reference electrical power infrastructure locations are investigated on how they are potentially affected by temperature extremes with the quantified intensities.
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All authors Peter Werner, Bastien Cozian, Yoann Robin, Laurent Dubus, Freddy Bouchet
Physics and Society
The power law in human mobility is a mixture artifact: evidence from a pandemic natural experiment
Leo Ferres and Bruno Gonçalves
For nearly two decades, human mobility has been read as scale free. Displacement distributions follow heavy tails that look like truncated power laws, traced to individual Lévy flights. A rival account holds that movement within each spatial container is lognormal, and the aggregate power law is an artifact of mixing containers of different sizes. The two fit the same aggregate data, so the debate has been hard to settle. We use the COVID-19 lockdowns as a natural experiment that removes long-distance travel and leaves local travel intact. We analyze 2.1 billion displacements from 4.4 million mobile-phone users across three distinct periods. The aggregate exponent increases under lockdown, from 1.66 to 1.74. Resampling the pre-lockdown traveling population to match the lockdown population reproduces that shift on its own, so we must look at the individual level to decides the question. Lognormal classification is a stable attractor (81% retained) while the power-law classification is fragile (32% retained), and the users who switch are the ones whose travel range collapsed the most. Matching the sample size we find that single users' tails reject the power law and pooled mixtures of equal size pass, so the heavy tail behavior originates in the aggregate behavior and not on the individual. Tail tests find no power-law threshold at full sample size, and the apparent power law disappears above ten thousand points. A level mixture rebuilds the aggregate ($R^2$ up to 0.98), the radius-of-gyration collapse fails and worsens under lockdown (CV $= 0.62$ to $0.76$), and the steepening concentrates in wide-ranging users ($P = 0.0003$). The power law of human travel is a feature of aggregation, not of individual movement.
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Geophysics · Cross-listed from quant-ph
Quantum observables as Fréchet sensitivity kernels
Rafael Abreu
We present a variational–adjoint interpretation of
quantum mechanics in which the interaction between forward and adjoint wavefunctions defines a general sensitivity kernel of the system. This Fréchet interaction density quantifies how perturbations in the wavefunction (or system parameters) influence a chosen observable. The familiar Born probability density appears as a special case when the adjoint wavefunction is chosen as the complex conjugate of the forward wavefunction, for which the interaction density becomes real and non-negative. Within this framework, probability is a particular positive-definite form of sensitivity described by the Fréchet interaction density. In general, the variational–adjoint interpretation also produces Fréchet sensitivity kernels associated with other
quantum observables, including momentum, energy, and
spin. This suggests that the Born probability density belongs to a broader class of Fréchet sensitivity kernels associated with
quantum observables. The proposed interpretation also provides a connection with time-symmetric interpretations of
quantum mechanics and possible future applications in
quantum control and
quantum metrology.
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General Physics
Model dependent analytic spin torsion corrections to Blandford Znajek energy extraction in Einstein Cartan gravity
Jingxu Wu, Liangyu Luo, Zhenzhou Lei et al. (+1 more)
We investigate the leading near-horizon response of Blandford-Znajek energy extraction to a compact, neutral
spin-polarized source within minimally coupled Einstein-Cartan-Dirac-Maxwell theory. Eliminating the algebraic contortion yields an effective axial contact interaction, which we embed into a conserved, anisotropic phenomenological completion. Working at leading order in the torsion parameter $\epsilon_T$, spatial anisotropy $\xi$, and slow rotation $\chi=a/M$ on the fixed-ADM branch, we derive the modified energy extraction rate at optimal load. We find that the leading-order power ratio $P_{\rm BZ}^{\rm EC}/P_{\rm BZ}^{\rm K}$ receives distinct contributions from rotational dragging ($\ell=1$) and magnetostatic flux redistribution ($\ell=2$). In the isotropic limit ($\xi=0$), the power is enhanced for a co-rotating completion and suppressed for a counter-rotating one, whereas for $\xi\neq0$ the net shift depends on the polar quadrupole response. We also formulate the generalized Znajek identity and linearized Grad–Shafranov framework, demonstrating that undetermined load-factor shifts leave the leading power coefficient invariant due to stationarity at the matched load point.
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All authors Jingxu Wu, Liangyu Luo, Zhenzhou Lei, Xiao Heng
Applied Physics
Movable Gate MOSFETs as Readout Devices for Cantilever-Based Nano-Electromechanical Sensors
Z. Geng, A. Hessel, S. C. Scholz et al. (+3 more)
This work proposes a novel readout mechanism for highly sensitive cantilever-based mass sensors using movable-gate (MG) MOSFETs. Traditional dynamic-mode cantilever sensors measure mass through shifts in resonance frequency, which offer high precision but require complex analog circuitry and large device areas, limiting integration and miniaturization. In contrast, the proposed approach exploits strong short-channel effects in MG MOSFETs, where the drain current depends exponentially on cantilever position, allowing for orders-of-magnitude changes without analog-to-digital conversion. Numerical simulations and initial experiments demonstrate the feasibility of this approach, which also avoids pull-in instability by using the electrostatic behavior of the gate-channel system to stabilize and even excite oscillations. The concept paves the way for scalable, low-complexity, high-resolution mass sensing with full
circuit integration potential.
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All authors Z. Geng, A. Hessel, S. C. Scholz, F. Schwierz, M. Ziegler, J. Knoch
Computational Physics · Cross-listed from cond-mat.mtrl-sci
First-Principles Spin-Lattice Coupling from Downfolded Electron-Phonon Interaction
Xu He, Álvaro Adrián Carrasco Álvarez, Gian-Marco Rignanese et al. (+3 more)
We present a method to calculate
spin-
phonon coupling parameters from first-principles perturbation theory by downfolding the electron-
phonon coupling (EPC). We exploit the localized nature of
magnetic moments and atomic displacements by working in the Wannier representation of the electronic
Hamiltonian and the EPC
matrix. The
spin system is mapped to a classical Heisenberg
Hamiltonian, whose parameters are obtained by treating local
spin rotations as a perturbation within a Green's-function formalism. The
spin and
phonon perturbations are connected through the EPC parameters, which enter as
lattice-induced perturbations to the tight-binding
Hamiltonian. By combining these
lattice perturbations with local
spin rotations, we obtain real-space derivatives of
magnetic exchange parameters without performing displaced
magnetic supercell calculations. We illustrate the method on SrMnO$_3$ and show that it can be integrated directly into standard workflows.
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All authors Xu He, Álvaro Adrián Carrasco Álvarez, Gian-Marco Rignanese, Eric Bousquet, Samuel Poncé, Matthieu J. Verstraete
Optics · Cross-listed from cs.MA
First Demonstration of Multi-Agent LLM System for Million-Scale Optical Link Management in Global Production AIDCs
Jingyi Su, Yihao Zhang, Dianxuan Fu et al. (+15 more)
We present the first LLM-powered multi-
agent system for autonomous fault management across millions of optical links in production AIDCs. Refined via SFT and continuous
memory evolution, it achieves 97.7% F1 and over 60% fault-incident reduction, outperforming SOTA LLMs on a ten-week field data evaluation.
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All authors Jingyi Su, Yihao Zhang, Dianxuan Fu, Leiyan Fei, Juan Wang, Mengfan Dai, Qing Liu, Xiong Wu, Yufeng Jiang, Cheng Chen, Bowen Zhang, Peilong Wang, Xi Chen, Zonglong He, Hongchen Yu, Zhicheng Ye, Weisheng Hu, Qunbi Zhuge
Instrumentation and Detectors
A Cosmic Muon Tomography System with Machine Learning based Momentum Measurement for Multi-Object Reconstruction and Material Characterization
Bharat Kumar Sirasva, Rohit Gupta and Satyajit Jena
Cosmic muon tomography is a powerful non-destructive imaging technique for inspecting dense and shielded materials through multiple Coulomb scattering. In this work, we present the design, simulation, and performance evaluation of a complete
muon tomography system comprising six scintillator-strip tracking stations for trajectory reconstruction and a four-station
magnetic spectrometer for
muon momentum estimation. The detector geometry is implemented in the GEANT4 framework and optimized for object localization and material characterization. The reconstructed momentum is combined with the scattering angle to define the scattering density $\rho_s = {(\theta p)^2}/{L_{\mathrm{eff}}}$, which enhances sensitivity to material-dependent scattering. Point-of-Closest-Approach (PoCA) reconstruction is used to estimate scattering locations within the imaging volume. To detect and separate multiple unknown objects, Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) is applied to the reconstructed PoCA cloud. Cluster-level scattering and
geometric features are then extracted for object characterization. The proposed framework enables object detection, localization, volume estimation, shape reconstruction, and material ranking within a unified analysis pipeline. Simulation studies with multiple objects of different compositions demonstrate accurate reconstruction of object positions and geometries, while providing reliable material discrimination based on scattering density. The developed system offers a scalable approach for next-generation
cosmic muon tomography applications in security screening,
nuclear waste characterization, and non-destructive inspection.
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Computational Physics · Cross-listed from quant-ph
Efficient Quantum Simulation of Linearized Vlasov–Poisson Dynamics Using Trotter and THRIFT Hamiltonian Simulation Methods
Kartick Paul, Rahul V, S. Aravinda et al. (+1 more)
The Vlasov–Poisson system provides the fundamental kinetic description of
plasma and plays a central role in understanding collective phenomena such as Landau damping and wave–particle interactions. Efficient numerical simulation of these dynamics remains challenging because of the high dimensionality of phase space. In this work, we studied magnetized and non-magnetized
plasma using a
quantum simulation framework for the linearized Vlasov-Poisson equation by reformulating the discretized system as a Hermitian
Hamiltonian suitable for gate-based
quantum computation. The time
evolution is implemented using first, second and fourth-order Trotter–Suzuki product formulas and the recently proposed Time-Resolved Interaction Framework (THRIFT). The performance of the different simulation methods is systematically evaluated through electric field
evolution, state fidelity, convergence behavior, energy conservation,
entanglement entropy and
quantum resource requirements, including
circuit depth and two-
qubit gate complexity, for both magnetized and non-magnetized
plasma models. To further reduce finite time step errors without increasing
circuit depth, Richardson extrapolation is incorporated as a error-mitigation technique. The results provide a comprehensive comparison of Trotter and THRIFT approaches and establish practical guidelines for accurate and resource-efficient
quantum simulation of
plasma dynamics on gate-based
quantum computers.
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All authors Kartick Paul, Rahul V, S. Aravinda, Reetesh K. Gangwar
Computational Physics · Cross-listed from cs.CE
A variational framework for bond-based peridynamics with spatially varying horizons and its asynchronous time integration
Prateek Prateek, Giuseppe Capobianco, Kai Partmann et al. (+3 more)
Bond-based peridynamics provides a non-local framework for modelling fracture without requiring spatial derivatives of the displacement field. However, when spatially varying horizons are used together with non-uniform discretisations, the classical single-horizon bond-based peridynamics formulation leads to asymmetric interactions between material points. These asymmetric interactions violate balance laws and can introduce non-physical artefacts such as ghost forces and spurious wave reflections. In this work, we develop a variational formulation for bond-based peridynamics with spatially varying horizons. Starting from the Lagrange-d'Alembert principle, we derive the governing equations of motion and show that the dual-horizon peridynamics formulation emerges naturally from the variation of the internal energy. Building on this variational structure, we construct asynchronous variational integrators that allow different time step sizes in different regions of the domain. This is particularly useful for dynamic fracture simulations with local refinement, where small time steps are required only near regions of high resolution or expected crack growth. Numerical examples involving wave propagation, a pre-cracked plate under tension, and the Kalthoff-Winkler impact experiment demonstrate that the proposed framework removes spurious reflections caused by non-uniform horizons, preserves physically consistent fracture patterns, and achieves results comparable to uniformly refined simulations. At the same time, the asynchronous variational integrator reduces the number of internal force evaluations compared to the standard velocity-Verlet method. The proposed approach therefore provides a consistent variational foundation and an efficient time-integration strategy for bond-based peridynamic simulations with spatially varying horizons.
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All authors Prateek Prateek, Giuseppe Capobianco, Kai Partmann, Kerstin Weinberg, Michael Ortiz, Sigrid Leyendecker
Fluid Dynamics
Weakly Compressible Subcycling for Accelerating Simulations of Surface-Tension-Dominated Incompressible Two-Phase Flows
Shu Yamashita, Shintaro Matsushita and Tetsuya Suekane
Simulations of surface-tension-dominated incompressible two-phase flows are computationally expensive due to the severe capillary time-step constraint. Although many studies have proposed time-implicit discretizations of surface tension to allow larger time-step sizes and accelerate simulations, these methods suffer from either artificial dissipation or complex implementation. Here, we propose a simple and novel approach: an incompressible solver with weakly compressible subcycling. The proposed approach relaxes the capillary time-step constraint, thereby accelerating simulations by more than $8.6\times$ without relying on artificially dissipative stabilization or requiring complex implementation. The key idea is to introduce lightweight substeps using a weakly compressible solver to assist the main incompressible solver. These substeps enable the main incompressible solver to use accurately computed fluxes and surface tension force, even with large time-step sizes. Numerical tests demonstrate the effectiveness of the proposed approach for practical problems, including the Rayleigh–Plateau instability and two-phase flows in porous media. This study paves the way for a new paradigm in which a weakly compressible solver serves as an assistant to an incompressible solver.
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