Plasma Physics
Direct Optimization of Stellarator Omnigenity from the Second Adiabatic Invariant
Hanlin Chen, Zhiyuan Lu, Guosheng Xu et al. (+4 more)
Stellarators offer a steady-state, disruption-free path to fusion energy but suffer from enhanced particle losses due to their three-dimensional geometry. Existing optimization methods rely on
geometric proxies rather than the actual trapped-particle orbit condition. We present a differentiable framework that directly optimizes the fundamental orbit action governing particle confinement. The approach yields compact stellarator designs with excellent fast-ion confinement, finite-pressure stability, and coil compatibility, demonstrating that first-principles orbit optimization can be integrated with engineering constraints in a single computational workflow for fusion reactor design.
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All authors Hanlin Chen, Zhiyuan Lu, Guosheng Xu, Shuai Cao, Yang Han, Dehong Chen, Baonian Wan
Physics and Society · Cross-listed from cs.SI
Network Information Enhances Unreliable News Domain Detection
Raphaela Keßler, Roman David Ventzke, Viola Priesemann et al. (+1 more)
Content-based detection of unreliable news is increasingly difficult, as low-reliability sources mimic credible journalism and generative AI makes fabricated content harder to flag. We ask whether network structure can improve news reliability classification, taking a domain-level approach that shifts the focus from individual articles to source reliability. From URL-sharing patterns in Telegram chats, we build a statistically validated domain co-sharing network and find assortative mixing by reliability: low-reliability domains group together, as do reliable ones. Exploiting this structure, we compare Graph Neural Networks against network-unaware baselines using both content-aware features (
multilingual text
embeddings) and content-agnostic features (spreading dynamics). GNNs consistently outperform Multi-Layer Perceptrons on identical features, with GraphSAGE best in both settings (accuracy 0.63 with content, 0.53 without), a 13-14% relative gain over the network-unaware baseline. Network
topology thus systematically improves domain reliability assessment, and remains effective even when content analysis is infeasible.
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All authors Raphaela Keßler, Roman David Ventzke, Viola Priesemann, Giordano De Marzo
Chemical Physics
Degradation of Proton Exchange Membrane Water Electrolyzers in Accelerated Stress Tests of Dynamic Load Cycling
Yunyi Zhang, Qingbo Gao, Jiawei Yang et al. (+4 more)
Proton exchange membrane water electrolysis (PEMWE) is a promising technology for harnessing intermittent renewable energy. This study experimentally investigates the degradation of PEMWE under fluctuating power supply, characterized by dynamic load cycling under accelerated stress test (AST). We focus on the effects of key parameters of dynamic loading, including the peak voltage and cycling frequency, in a set of simplified AST protocols designed to represent selected features of dynamic load fluctuations associated with variable renewable-energy operation. The results unveil the intricate relationship between the structural characteristics of the catalyst layer and the electrochemical performance. An elevated peak voltage accelerates the degradation in the initial phase of the AST. However, a low cycling frequency can mitigate the degradation by limiting the rise in various resistance forms, whereas a higher cycling frequency exacerbates the degradation primarily by increasing mass transport resistance, suggesting a frequency-sensitive deterioration of the system's components.
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All authors Yunyi Zhang, Qingbo Gao, Jiawei Yang, Zhen Zeng, Rui Chen, Tianyou Wang, Zhizhao Che
Optics
A high-Q Split Cavity Enabling Independent Electrical Tuning of two Quantum Dots
Lan Hoang Mai, Nazifa Tasnim Arony, R S Joshya et al. (+3 more)
Cavity-mediated strong coupling is an essential tool for
quantum photonics. However, the inherent inhomogeneity in ensembles of matter-based
qubits necessitates independent tuning to bring more than one
qubit into resonance with a single cavity mode. We present the design, fabrication, and characterization of a GaAs-based photonic
crystal split cavity that consists of two electrically-distinct portions, which preserves the ability to apply independent electric fields that would independently tune two distinct
qubits based on InAs
Quantum Dots (QDs) into resonance with a cavity mode. We show that this device, despite the cut required to electrically isolate the two halves, achieves an average Q $\geq 20,000$, sufficient to enter the strong coupling regime. Moreover, we show that the Q is limited primarily by the precision and accuracy of the e-beam lithography tool, rather than by sidewall scattering. This result creates a realistic experimental path toward devices that use controlled interactions between two InAs QDs, mediated by strong coupling to a single cavity mode, to generate multi-dimensional
photon graph states.
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All authors Lan Hoang Mai, Nazifa Tasnim Arony, R S Joshya, Tyler Manfre, Joshua M. O. Zide, Matthew F. Doty
Geophysics · Cross-listed from cs.SD
An End-to-End Workflow for Fin Whale Song Detection, Note Characterization, and Localization with Distributed Acoustic Sensing
Dídac Diego-Tortosa, Miriam Romagosa, Arantza Ugalde et al. (+4 more)
Submarine fiber-optic cables instrumented with distributed acoustic sensing (DAS) provide an effective approach for large-scale monitoring of fin whales. We present an end-to-end workflow for detecting, characterizing, and localizing fin whale notes, tested on two submarine telecom cables in the Strait of Gibraltar and western Alboran Sea. The workflow applies a kurtosis-value picker adapted to narrow-band fin whale notes. Channel-wise detections are grouped into individual notes using density-based spatio-temporal clustering, cluster agglomeration, and
hyperbolic fitting to reject incoherent picks. The retained clusters are characterized through temporal, spectral, and energy-related descriptors that support note-type discrimination and estimation of inter-note intervals. Relative arrival times across DAS channels are then used in a grid-search procedure to estimate candidate source locations. Evaluation against manually annotated detections from six fin whale songs yielded median pick-level precision of 0.990 and recall of 0.744, and median cluster-level precision of 0.880 and recall of 0.806. Representative applications demonstrate separation of overlapping vocalizations, characterization of type-A and type-B notes, and the inference of apparent source movement. By transforming dense DAS recordings into compact note-level bioacoustic information, the workflow provides an integrated framework for fin whale monitoring and a basis for adaptation to other synchronized acoustic receiver arrays.
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All authors Dídac Diego-Tortosa, Miriam Romagosa, Arantza Ugalde, Hugo Latorre, Sergi Ventosa, Jose Enrique García, Antonio Villaseñor
Space Physics · Cross-listed from astro-ph.SR
Statistical insights on the decorrelation lengths of solar wind parameters at L1 point under varying conditions
Yogesh, Aparupa Apsara Baruah, Dibyendu Chakrabarty et al. (+3 more)
Understanding the spatial coherence of
solar wind
plasma and
magnetic field properties is essential for interpreting multi-spacecraft observations and for characterizing the large-scale structure of heliospheric transients. In this study, we quantify the spatial correlation of six key
solar wind parameters - interplanetary
magnetic field components, bulk flow speed,
proton number density, and the alpha-to-
proton abundance ratio - using simultaneous measurements from the ACE and Wind spacecraft as a function of their instantaneous separation distance. The analysis is performed separately for intervals of background
solar wind, Interplanetary Coronal Mass Ejections (ICMEs), and Stream Interaction Regions (SIRs). The decay of the Pearson correlation coefficient with distance is modeled using an exponential function to infer characteristic de-correlation length scales. We find that the bulk
solar wind speed is the most spatially coherent parameter in all regimes, while
plasma composition exhibits the weakest coherence.
Magnetic field coherence shows strong dependence on
solar wind structure: ICMEs display near-unity correlations and the largest
magnetic coherence scales, consistent with organized, flux-rope-like configurations, whereas SIRs exhibit reduced coherence - particularly in the north - south
magnetic field component - reflecting compressed and turbulent
plasma. The background
solar wind exhibits intermediate behavior, with large-scale coherence in bulk
plasma properties but shorter coherence lengths in
magnetic fluctuations. These results provide a quantitative framework for distinguishing
solar wind structures based on their spatial coherence properties and have important implications for multi-point
solar wind studies and space weather applications.
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All authors Yogesh, Aparupa Apsara Baruah, Dibyendu Chakrabarty, Kalyan Bhuyan, Aakash Gupta, Gregory G. Howes
Geophysics
Network-Based Subbasin-Scale Mapping of Streamflow Alteration in Ontario, Canada
Hongren Shen, Bryan A. Tolson, James R. Craig et al. (+3 more)
Dams, reservoirs, and waterpower facilities support regional water management but can alter streamflow far downstream through connected river networks, complicating hydrologic modeling and aquatic ecosystem assessment. Existing indicators typically quantify alteration only at discrete locations, limiting spatially continuous mapping of potential infrastructure influence. We propose the Streamflow Alteration Index (SAI), a network-based screening metric that propagates point-based alteration signals downstream through a routing network. The framework includes paired indices, SAI_I and SAI_II (0-100%), representing influence from confirmed (Level I) and potential (Level II) alteration sources. We implemented SAI for Ontario, Canada, using the Ontario Lake and River Routing Product Version 2 (OLRRP v2) and an inventory of 643 alteration signal sources compiled from provincial
datasets. The resulting SAI v1.0 database provides seamless, high-resolution, subbasin-scale mapping and estimates at gauged and ungauged network nodes. We validated SAI by classifying gauged subbasins as natural, conditional, or altered and comparing these classes with two independent references: Reference Hydrometric Basin Network gauges and Water Survey of Canada (WSC) Natural and Regulated labels. SAI classified 86% of RHBN natural gauges and 86% of WSC-natural gauges as natural. Among WSC-regulated gauges, 74% were classified as conditional or natural. SAI v1.0 therefore provides an objective screening product for large-domain hydrologic and aquatic applications without requiring detailed dam operating information and offers a scalable basis for national- to global-scale mapping of potential streamflow alteration.
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All authors Hongren Shen, Bryan A. Tolson, James R. Craig, Robert A. Metcalfe, Jonathan Romero-Cuellar, James J. Luce
Fluid Dynamics
Aerodynamic Drag and Heat Transfer Corrections for Dehydrated Pollen Particles: CFD-Based Modeling of Airborne Allergen Transport in Smart Urban Environments
Omar Hamad, Samer Ali, Mahmoud Khaled et al. (+1 more)
Airborne pollen transport is a key concern for urban air-quality assessment, allergy-risk
forecasting, and smart-city planning. However, conventional dispersion models generally assume smooth spherical particles, neglecting how pollen dehydration alters particle morphology and impacts aerodynamic and thermal behavior. To address this gap, this study presents, for the first time, advanced CFD simulations evaluating the aerodynamic drag forces and convective heat transfer of realistically dehydrated (dry) pollen particles. Investigations are conducted at Reynolds numbers ($0.1 \leq Re_p \leq 15$) at the particle's scale corresponding to realistic atmospheric wind speeds ranging from 0.27 to 30 km/h. The findings reveal that dry pollen particles exhibit drag coefficients 8% to 15% higher than those predicted for hydrated pollen spherical particles. Conversely, their Nusselt numbers are 5% to 15% lower than those for hydrated pollen particles. These considerable deviations confirm that conventional spherical correlations are inadequate for simulating dry pollen Lagrangian transport and evaporation. These findings highlight the need to account for realistic dehydrated shapes when modeling airborne allergen transport in urban environments.
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All authors Omar Hamad, Samer Ali, Mahmoud Khaled, Talib Dbouk
Optics
Metaphotonic Catalysis: Amorphous silicon metasurfaces encode photochemical activity
Elif Nur Dayi, Priscila Vensaus, Milad Sabzehparvar et al. (+3 more)
Solar-to-fuel conversion can benefit from photoelectrodes with engineered light-matter interactions, yet most nanostructured designs provide limited control over the spatial and spectral distribution of photochemical activity. Here, we present an all-dielectric amorphous-silicon metasurface photoelectrode that confines resonant light-matter interactions within a 220-nm-thick active layer. Tunable Mie-type and guided-mode resonances spectrally encode chemical reactivity and produce absorptance above 80% near the silicon band edge, compared with less than 30% for an unpatterned film of the same thickness. The metasurface simultaneously functions as the light absorber, carrier-transport layer, and catalytic interface without an added co-catalyst or engineered passivation layer. Operando photo-scanning electrochemical microscopy reveals wavelength- and structure-dependent redox activity and a tenfold enhancement in internal
quantum efficiency near the silicon band edge relative to planar films. Power-dependent measurements support a
photon-driven rather than nonlinear photothermal origin of the enhancement, while surface-sensitive ultrafast transient-reflectivity measurements probe the underlying carrier dynamics. Light-coupled scanning electrochemical
cell microscopy further shows hydrogen-
evolution enhancements of up to 21-fold under photocatalytic conditions and 15-fold under photoelectrochemical bias, corresponding to 11.2-fold and 7.7-fold enhancements after accounting for the estimated surface-area increase. The metasurfaces remain stable during more than 10 hours of immersion and prolonged
laser illumination. These results establish amorphous silicon as a stable and versatile platform for resonantly programmed photocatalysis and
solar-fuel generation.
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All authors Elif Nur Dayi, Priscila Vensaus, Milad Sabzehparvar, Michele Puppin, Omer Can Karaman, Giulia Tagliabue
Applied Physics · Cross-listed from quant-ph
Revealing and reducing growth-induced interfacial disorder in preferentially aligned nitrogen-vacancy centers in diamond
Cheng-I Ho, Marina Davydova, Patrik Straňák et al. (+4 more)
Nitrogen-vacancy (NV) centers in chemical-vapor-deposition (CVD) diamond can form preferentially oriented ensembles with high sensing performance and low densities of
lattice defects. Thin films of this material are a cornerstone of various imaging modalities. However, nitrogen injection needed to produce such films can transiently drive growth out of
equilibrium, generating interfacial strain and
spin defects that degrade NV coherence. Here, we investigate this disorder in $^{12}\text{C}$-enriched, preferentially oriented NV layers grown on (111) diamond using two nitrogen-injection procedures, combined with nanometer-scale selective
plasma etching and NV
spin-coherence measurements. Pulsed nitrogen injection produces a pronounced nitrogen overshoot within a 60–80 nm interfacial region, generating excessive amounts of defects. By contrast, smooth nitrogen delivery through mass flow controllers substantially suppresses interfacial disorder, yielding coherence properties close to the theoretical limit imposed by
spin-bath noise. A 50-nm NV layer is used to demonstrate
proton nuclear magnetic resonance detection. This work reveals the role of interfacial disorder associated with the nitrogen-doping procedure and provides a route to growing high-quality, thin NV-doped layers for
quantum-sensing applications.
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All authors Cheng-I Ho, Marina Davydova, Patrik Straňák, Felix Hoffmann, Peter Knittel, Andrej Denisenko, Jörg Wrachtrup
Optics
Gallium phosphide on insulator for nanophotonics and quantum technologies
Tobias Bucher, Otto Arnold, Muyi Yang et al. (+7 more)
Gallium phosphide is a promising material platform for visible and near-infrared photonics and
quantum technologies owing to its high refractive index, low optical absorption, and strong second-order nonlinearity. Here, we demonstrate the fabrication of GaP-on-
insulator substrates by ion slicing. The splitting depth and exfoliation behavior of bulk GaP are tailored by controlling the He$^{+}$ ion implantation energy and fluence, enabling thin-film transfer onto amorphous substrates by anodic bonding and
plasma-enhanced direct wafer bonding. Channeling Rutherford backscattering spectrometry and X-ray diffraction confirm that the transferred layers retain their single-crystalline structure, while implantation-induced disorder and optical absorption are substantially reduced by annealing at 500 {\deg}C and subsequent polishing. The annealed films exhibit linear optical properties approaching those of bulk GaP. In addition, a (110)-oriented GaP thin film shows the characteristic polarization dependence expected from the zinc-blende second-order nonlinear susceptibility tensor, demonstrating a near-pristine second-order nonlinear response. This flexible fabrication approach enables the integration of high-quality single-crystalline GaP with variable orientation for free-space and integrated nanophotonics as well as nonlinear and
quantum optical devices.
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All authors Tobias Bucher, Otto Arnold, Muyi Yang, Zifei Zhang, Katsuya Tanaka, Annkathrin Köhler, Berit Marx-Glowna, Duk-Yong Choi, Isabelle Staude, Carsten Ronning
Chemical Physics · Cross-listed from cond-mat.soft
Colloidal Systems
Darrell Velegol
This book has one primary goal: To get you moving quickly from learning basic principles of colloid science, to designing colloidal systems for function or motion in the lab. It is not intended to provide encyclopedic knowledge about all aspects of colloid and surface science; rather, I have chosen not to include many topics of genuine importance. In reaching the intended goal, I use two parallel strategies. First, I give practical results that can be used immediately. If there is a cumbersome calculation, I have worked to reframe it into a table or figure. This is the case for Hamaker constants and hydrodynamics of spheroids, for instance. Second, I describe the physics of various colloidal phenomena, so that you as a researcher can think about alternative strategies. In balancing
algorithms with explanations, I provide plug-and-chug example problems to familiarize you with units, constants, and typical values. The practice problems provide extensions to the most basic theory that open new possibilities, while also giving results that are useful in practical and research studies. Throughout the book, I provide data we commonly use for viscosities,
zeta potentials, ionic phenomena, and other parameters. Rather than providing every reference and every technique, I have provided those references and techniques that we most often use in our lab. In the end, this book aims not to be an exhaustive study of colloids, but rather to be a doorway to producing desired colloidal systems as quickly as possible.
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Optics
Direct Wafer Bonding of Crystal-Ion-Sliced GaP Thin Films for Photonic Applications
Hossein Esfandiar, Emanuel Glück, Fabian Ganss et al. (+11 more)
Gallium phosphide (GaP) is a promising material platform for integrated photonics because of its high refractive index, broad optical transparency, and strong second-order nonlinear response. Here, we demonstrate GaP-on-
insulator thin films fabricated by
crystal ion slicing and direct wafer bonding, using fused silica and SiO$_2$/Si/Si thermally oxidized silicon substrates as representative platforms. Unlike GaP thin-film platforms that rely on heteroepitaxial growth or sacrificial-layer release, the presented approach enables the flexible integration of crystalline GaP thin films, independent of both donor and target substrates. Following post-transfer annealing, the films exhibit near-bulk crystalline quality with low residual strain, smooth surfaces suitable for nanophotonic fabrication, and homogeneous bonding interfaces. Furthermore, annealing restores the linear optical dispersion (n and k) approaching that of epitaxially grown GaP with estimated plane wave absorption loss of 0.9 dB/cm at 1550 nm in the telecom C-band. The demonstrated approach establishes a scalable pathway toward high-quality GaP thin-film photonics compatible with versatile heterogeneous integration and back-end-of-line CMOS processing.
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All authors Hossein Esfandiar, Emanuel Glück, Fabian Ganss, Ulrich Kentsch, Dennis Arslan, Jana Paeschke, Sebastian Ritter, Andreas Ihring, Muyi Yang, Isabelle Staude, Stefan Facsko, Falk Eilenberger, Carolin Rothhardt, Sebastian W. Schmitt
Optics
Phase-Drift Limits and Adaptive Quadrature Readout in Programmable Photonic Processors
Gökhan Elmas, Igor A. Litvin and Janis Nötzel
Phase fluctuations between optical inputs limit programmable photonic processors because their output powers depend on coherent interference. We study the phase-drift penalty that arises when sine and cosine quadratures are measured sequentially rather than simultaneously. The analysis is motivated by measurements from an eight-mode programmable photonic processor, including 35 free-running recordings of 300 s acquired at approximately 125 samples per second per channel. These recordings provide an empirical route for estimating the phase-increment variance at a selected reconfiguration interval. The estimate is defined at the time of the second measurement. For fixed quadrature order, perturbation of the atan2 reconstruction gives $e_{C\to S}=-\delta_\tau\sin^2\phi_0+O(\delta_\tau^2)$ and $e_{S\to C}=-\delta_\tau\cos^2\phi_0+O(\delta_\tau^2)$. Writing $Q_\tau=\operatorname{Var}(\delta_\tau)$, uniform phase averaging gives the first-order drift mean-square error $3Q_\tau/8$. A phase-predicted ordering rule measures the locally less informative quadrature first and the more informative quadrature second. Its uniform first-order penalty is $(3/8-1/\pi)Q_\tau$, which is 84.9 percent below the fixed-order value. We also derive an increment-aware
estimator from a local state-space model. Marginalizing the unknown phase increment increases the variance of a stale phase observation by $Q_\tau$, reducing its Fisher information from $I$ to $I/(1+IQ_\tau)$. For ideal balanced Poisson detection, the Fisher information of each quadrature equals its detected signal-
photon number. This yields dimensionless architecture boundaries in spatial information and phase-increment variance. Nonlinear Monte Carlo simulations validate the perturbative laws, quantify robustness to prediction error, and compare simultaneous, fixed-order, increment-aware, and adaptive receivers under a common noise model.
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Accelerator Physics
Beam energy measurement at the European XFEL with high-performance trajectory fitting
Lars Fröhlich
This contribution presents the method used for beam energy monitoring at the European XFEL. It relies on high-performance trajectory fitting of beam position monitor data against an online model of the accelerator
lattice. Unlike most other methods, it can be applied to virtually any section of the
lattice with sufficient dispersion without the need for manual adaptation. Our implementation is fast enough to measure the energy of many thousands of bunches per second in realtime on conventional x86 hardware shared with other processes. A short outline of the technique is presented and illustrated with data from the accelerator.
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Plasma Physics
Mass Spectrometry Studies of Hydrogen Ions Energy Distributions in an ECR- based Large Volume Plasma Source
Bibekananda Naik, Ramesh Narayanan, Debaprasad Sahu et al. (+2 more)
Plasma is produced in a Large Volume
Plasma Source (LVPS; dia. = 1 m, height = 1m) using CW microwaves (= 400 - 600 W, 2.45 GHz), in a compact ECR
plasma source (CEPS) attached to LVPS, at hydrogen gas pressures = 1 - 3 mTorr.
Plasma expands along the CEPS
magnetic field into LVPS. A Hiden Analytical HPR 60 molecular beam mass spectrometer (MBMS) is used to measure the H^- ion energy distribution functions (IEDFs) in the downstream
plasma. Previous
plasma characterization studies in LVPS indicated favourable downstream
plasma conditions for volume production of H^- ions. Measurements conducted with the MBMS probe aligned facing the
plasma flow = 80 cm downstream, gave typical H^- count rates = 3 x 10^5 counts /s, at = 400 W, = 1 mTorr, along with a distinct high energy tail (<= 20 eV). These and other results are analyzed in detail. The positive ion spectrum showed the H_3^+ count to be consistently high in all cases (= 60-70 %); the counts for H_2^+ and H^+ were =30-35 % and a =few %. Combining the Langmuir probe (LP) and MBMS data it is possible to determine the approximate densities in front of the MBMS probe aperture. At = 500 W and = 2 mTorr, one finds: n_(H^+) = 9.6 x 10^9 cm^(-3), n_(H_2^+) = 1.7 x 10^10 cm^(-3) and n_(H_3^+) = 4.3 x 10^10 cm^(-3). The corresponding H^- density, = 80 cm downstream is n_(H^-) = 3.9 x 10^8 cm^(-3). Accounting for all H^- losses due to scattering and destruction, one finds the effective mean free path for H^- loss to be = 12.4 cm. Noting that H^- formation takes place about = 10 - 30 cm downstream of the source exit, the approximate average H^- density in the formation zone is determined as = 5.5 x 10^10 cm^(-3). This value is remarkably encouraging for H^- production in volume mode, considering the large chamber volume and area, as well as the very moderate power used for the experiments.
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All authors Bibekananda Naik, Ramesh Narayanan, Debaprasad Sahu, Mainak Bandyopadhyay, Ashish Ganguli
Optics
A subsurface array of photonic crystal slabs produces green stripes in a scarab beetle
Laura Ospina-Rozo, Nicola S. Kubzdela, Zezheng Zhu et al. (+4 more)
Vivid colours in nature often arise from photonic nanostructures that have inspired diverse technologies. Yet most known examples fall within a limited set of structural themes. Here, we describe a biologically and optically novel structure in the bright green, violin-shaped stripes of the fiddler beetle Eupoecila australasiae. The green colour is produced by a composite, hierarchical structure comprising dense arrays of microscopic, fin-like elements located beneath the cuticle. Each vertical fin, patterned with complementary
lattices of nanospheres and indentations, can be approximated by two photonic
crystal slabs mounted on a solid central core. Optical modelling shows that the fins are strongly iridescent, reflecting light with longer wavelengths near the normal and light with shorter wavelengths at oblique angles. However, disorder in fin orientation and filtering by the overlying cuticle converts the opaline cyan appearance of the fins into the bright diffuse green seen externally. Our work expands the known diversity of biological photonic nanostructures and offers new inspiration for biomimetic designs.
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All authors Laura Ospina-Rozo, Nicola S. Kubzdela, Zezheng Zhu, James A. Hutchison, Mia Wansbrough, Nanfang Yu, Devi Stuart-Fox
Classical Physics
Solving the Dissipation Inequality not as a constitutive restriction
Maximiliano Larrain Silva and Amit Acharya
A solution procedure is formulated and solved for treating the nonlinear Dissipation Inequality as a constraint equation within continuum mechanics, and allowing for incomplete knowledge of constitutive behavior. The scheme is demonstrated in the context of the rate-dependent, elastoplastic response of a bar, resulting in a nonlinear problem of constrained optimization. Both closed form and computational results are developed. The computational solutions utilize a sequence of convex optimization problems, and are shown to be accurate. In the example considered, the approach is shown to automatically correct an (intentionally) faulty constitutive specification, resulting in the solution to be in accord with the fundamental postulates of continuum mechanics.
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Geophysics
Thermo-Hydro-Mechanical Modeling of a TBM Tunnel in Opalinus Clay: Thermal Coupling Effects on Long-term Lining Pressures and Excavation Damage Zone Development
Saeed Tourchi, Martin Ziegler and Arash Alimardani Lavasan
Tunnels in argillaceous formations such as Opalinus Clay (OPA) develop a coupled thermal, hydraulic, and mechanical response. This study examines the New Belchen Tunnel (STB), excavated by tunnel boring machine through faulted OPA shale. Field measurements show a strong relation between lining temperature and radial pressure. We use a two-dimensional plane-strain THM model to examine excavation, construction heat, seasonal temperature cycles, pore-pressure transients, and stress redistribution. The model reproduces the phasing and approximate magnitude of the seasonal pressure cycles and shows how the thermal expansion mismatch between the lining, grout, and OPA modifies lining load and near-field pore pressure. It underestimates the monotonic long-term pressure increase at several sensors. Comparison with radial extensometer measurements indicates that moisture-driven swelling, local geological structure, grout or interface damage, and three-dimensional construction effects also contribute. The model therefore supports a thermal interpretation of the cyclic response while defining the processes required for a fuller long-term back-analysis.
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Atmospheric and Oceanic Physics
Arctic bimodality reflects enhanced variability in the clear-cloudy transition rather than bistability
Nadja Omanovic, J. Antoon van Hooft, Valentina Zeni et al. (+1 more)
The wintertime Arctic boundary layer is characterized by two distinct states, radiatively clear (cloud-free) and radiatively opaque (cloudy), which is reflected in observations as a bimodal distribution. Previous studies hypothesized that these regimes are related to an underlying bistability of the system's dynamics. We apply a drift-
diffusion framework based on the two leading terms of the Kramers-Moyal expansion to observations from 15 winter periods in Ny-Alesund, Norway. Our model captures the bimodality; we find a single stable point for the deterministic drift, however, which questions the existence of bistable deterministic dynamics. Instead, the observed regimes can be attributed to state-dependent
stochastic fluctuations with maximum amplitude close to the clear-cloudy transition. The position of the stable point depends on the meteorological conditions. Controlling for synoptic variability does not remove the state-dependence of
diffusion, however. The cloudy regime is associated with southwesterly winds, high specific humidities, and uplifting motion, the latter two being conducive for cloud formation, while the cloud-free regime occurs under drier conditions and northeasterly winds. Through an illustrative example, we suggest a possible process-based interpretation of our statistical analysis. The nonlinear onset of cloud formation, once atmospheric humidity reaches saturation, could map state-independent fluctuations in humidity to state-dependent fluctuations in cloudiness.
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All authors Nadja Omanovic, J. Antoon van Hooft, Valentina Zeni, Franziska Glassmeier
Applied Physics · Cross-listed from eess.AS
MEMS Microphones as Ultrasonic Transducers: Nonlinear Electrostatic Actuation and a Parametric Array Prototype
Xiaoyu Niu, Zihuan Liu, Ehsan Vatankhah et al. (+2 more)
This paper investigates commercial-style capacitive MEMS microphone dies as air-coupled ultrasonic transmitters under nonlinear pull-in and snap-back actuation and demonstrates a compact parametric-array prototype. A single die produces large diaphragm displacement and measurable ultrasonic pressure in air. A 28-die array driven at 83 and 93 kHz generates a directional component at the 10 kHz difference frequency. Measurements are compared with analytical radiation theory and finite-element modeling, and the effects of aperture, fill factor, device uniformity, and receiver nonlinearity are discussed.
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All authors Xiaoyu Niu, Zihuan Liu, Ehsan Vatankhah, Yuqi Meng, Neal A. Hall
Plasma Physics · Cross-listed from astro-ph.SR
Performance of radio-based detection to operational monitoring M5+ class solar flares
Julia van Ravenswaaij, Ines Wilms, Ivan Ricardo et al. (+1 more)
Early detection of major
solar flares is critical for defense operations due to their potential to disturb radar and
radio systems. Typically, soft X-ray flux is used to monitor and classify
solar flares, but since this flux has to be measured in space, it means that its availability itself is dependent on space weather conditions. For this reason, in this paper, we investigated the feasibility of using ground
radio observations to monitor major (M5+ class)
solar flares. We made use of
datasets from the GOES-16 satellite and the
Radio Solar Telescope Network in the time range between March 2023 and March 2025. An elastic net regularized logistic regression model was trained on this data, optimized through a grid search and with incorporated class weighting for class imbalance. It was found that especially higher frequencies (8800 MHz) had a reasonable ability in monitoring and predicting major
flares (precision and recall for
flare events are 53% and 65%, respectively - implying that roughly one third of
flares were not detected - with signals appearing, on average, 3 to 4 minutes before the M5 threshold is exceeded).
Radio measurements at super high frequencies can thus serve as an alternative method to monitor major
solar flaring activity.
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All authors Julia van Ravenswaaij, Ines Wilms, Ivan Ricardo, Michaela Brchnelova
Physics and Society
Microscopic dynamics of consensus formation in multi-agent LLM Naming Games
Cristiano De Nobili, Vijayasri Iyer, Alessandro Codello et al. (+1 more)
Decentralized populations of Large
Language Model (LLM)
agents can spontaneously reach consensus on shared conventions, yet the microscopic mechanisms by which their internal stochasticity shapes macroscopic ordering remain unexplored. We study a minimal LLM Naming Game in which the listener's decision is a single-
token LLM call at decoding temperature $T$, replacing the inventory check of the deterministic Naming Game. Each interaction decomposes into an in-inventory and an out-inventory channel with conditional rates $\pi(T)\!\equiv\!P(\text{YES}\mid w\in P_j)$ and $\phi(T)\!\equiv\!P(\text{YES}\mid w\notin P_j)$, whose balance controls an ordering-disordering drift. A mean-field theory of the two-rate dynamics yields an analytical ordering condition that generalizes the consensus threshold of the
stochastic Naming Game to a critical line in the $(\pi,\phi)$ plane. Across three open-weight architectures, consensus is always reached, but through three distinct listener regimes: permissive (repaint-noise dominated), near-deterministic, and conservative (missed-collapse dominated). The effective finite-size exponent $\beta(T)$ in $t_{\rm conv}\!\sim\!N^{\beta}$ shifts with temperature, and the temperature-sensitivity $\alpha$ in $t_c\!\sim\!e^{\alpha T}$ ranges from ${\approx}\,0.67$ to ${\approx}\,0$ across architectures. Decoding temperature thus emerges as an architecture-dependent control parameter for decentralized LLM populations, quantitatively characterized by the statistical-physics toolkit.
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All authors Cristiano De Nobili, Vijayasri Iyer, Alessandro Codello, Raffaella Burioni
Optics
Generalized Temporal Coupled Mode Theory (g-TCMT) applied to Coupled Resonator Optical Waveguides with Exchange Symmetry (CROWe)
Tianrui Li, Matthew P. Halsall and Iain F. Crowe
In this paper, we extend our generalized Temporal Coupled Mode Theory (g-TCMT) model, developed earlier [1], from a simple, dual-coupled micro-ring resonator (MRR) system to higher-order, n-serially coupled MRRs. By treating each pair of adjacent MRRs as a single `equivalent resonator', we demonstrate excellent agreement in spectral resonance position, between the g-TCMT and numerical results obtained using the transfer
matrix method (TMM), for systems up to and including order n=4. The validity of this approach hinges on the existence, or otherwise, of exchange
symmetry, and so we refer to these structures as Coupled Resonator Optical Waveguides with exchange
symmetry (CROWe's). We explore the limitations of our approach with illustrative examples of strongly coupled systems of order n \geq 5. Finally, we explore the properties of such higher order CROWe's for applications in non-Hermitian photonics, i.e., in which gain in some of the component MRRs and loss in the others leads to Parity-Time (PT)
symmetry.
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Medical Physics
Cardiovascular Digital Twins from Physics Based to Data Driven Approaches
Emmanuel Lwele and Francis Chikweto
Cardiovascular digital twins aim to create patient-specific computational models that evolve with clinical data to support diagnosis, prognosis, and therapy optimisation. Mechanistic models provide physiological interpretability but remain computationally demanding, whereas data-driven approaches improve scalability yet risk limited robustness. Emerging physics-informed, graph-based, and hybrid methods integrate physical constraints with relational learning across vascular networks. We review modelling paradigms, data assimilation frameworks, validation challenges, and translational pathways toward clinically deployable cardiovascular digital twins.
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Plasma Physics
Hybrid Kinetic-MHD Simulations of Drift-Orbit Effects on the Stability and Non-Linear Dynamics of Runaway Electron Beams
Shi-Jie Liu, Hao-Wei Zhang, Hannes Bergstroem et al. (+2 more)
During tokamak disruptions, the Ohmic current may be replaced by a non-inductive runaway electron (RE) current, affecting resistive stability. Previous studies suggest that, in the linear phase, the presence of REs acts destabilizing for tearing modes (TM) compared to a scenario with Ohmic current. In the non-linear regime, this translates to larger saturation amplitudes. These results are based on the assumption of zero drift-orbit deviation from the
magnetic flux surfaces corresponding to the low-energy limit. This work investigates the importance of this kinetic effect by studying the linear and non-linear TM dynamics in RE beams with different RE energies, providing a clear picture of finite-orbit-width (FOW) effects. We use a hybrid fluid-kinetic model in the 3D non-linear magnetohydrodynamic (MHD) code JOREK, treating REs kinetically with a full-f Monte Carlo approach in self-consistent interaction with the MHD mode dynamics. The study shows that the presence of REs modifies the characteristics of the instability in several ways. First, we find that the major-radial displacement of drift orbits from flux surfaces induces an $m=1$ perturbation to the
equilibrium current, introducing additional mode coupling between $(m,n)$ instabilities and the $(m\pm1,n)$ sidebands. Second, we find that increasing RE energy has a stabilizing effect on the MHD modes because REs cannot support narrow current sheets on rational flux surfaces owing to the drift-orbit displacement. This counteracts the destabilizing effect that REs have on TMs in the low-energy limit. For the scenario investigated, the stabilizing effect dominates over the additional mode coupling, reducing the development of
stochastic magnetic regions with increasing RE energy and thereby lowering radial particle transport. Overall, we find that FOW effects can substantially alter the MHD stability and non-linear dynamics of RE beams.
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All authors Shi-Jie Liu, Hao-Wei Zhang, Hannes Bergstroem, Matthias Hoelzl, the JOREK Team
Atomic Physics · Cross-listed from quant-ph
Better accuracy with fewer qubits: Single-particle basis set optimization for quantum chemistry on quantum computers
Subimal Deb and V. S. Prasannaa
In spite of recent advances,
quantum computers are expected to be sufficiently noisy in the coming few years to the extent of limiting
quantum chemical calculations to relatively small number of orbitals. However, even with reasonable quality single particle basis sets, small active spaces with limited orbitals can result in a significant fraction of correlation energy being lost, motivating the design of moderate quality
qubit-efficient basis sets for
quantum algorithms. We begin by reoptimizing the existing minimal basis sets using a genetic
algorithm-inspired approach in conjunction with aggressive refinement strategies, and generate modified minimal basis sets (MSTO-kG basis; k = 2-11) for atoms from H through F. The ground state energies of H through F using our MSTO bases at FCI level of theory yield ground state energies that are comparable or sometimes even lower than those obtained using 6-31G basis sets. In the case of Li, the MSTO bases surpass the performance of cc-pVQZ bases. Thus, we obtain better atomic energies with same number of
qubits relative to STO bases, and better/comparable energies with fewer
qubits relative to higher quality bases. In the case of molecules, H2 performs poorly; a finding that is consistent with an earlier work in literature. For other molecules, Li2, C2, LiH, BeH and BeH2, the FCI results (except C2 for which we employ CISD) from our bases are comparable to/outperform those from 6-31G basis. Finally, we compare the resources required between different bases and find that MSTO bases yield better energies than the competing basis sets while incurring fewer
qubits and two-
qubit gates with VQE, QPE, and HHL. The logical T-gate counts are also found to be considerably lower for QPE and HHL respectively. Overall, our work paves way for more accurate yet less
qubit-hungry
quantum chemical calculations using near-term
quantum computers.
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Optics
Deep Inverse-Designed Nanophotonic Processors with Structural Nonlinearity from Repeated Phase Encoding
Azka Maula Iskandar Muda and Uğur Teğin
Passive nanophotonic scattering regions implement linear optical transformations, and cascading input-independent regions alone does not create functional depth because the resulting transformations collapse into a single linear operator. Here, we introduce repeated phase encoding between inverse-designed passive transformations to generate an input-conditioned multilayer optical map without interlayer photodetection. Each re-encoding introduces additional phase-dependent optical pathways, producing structural nonlinearity with respect to the encoded variables while every scattering region remains passive and linear in the optical field. Under a controlled MNIST depth sweep, classification accuracy increases from 83.53% with one layer to 93.61% with seven layers, whereas the input-independent passive control saturates at 86.34%. The depth trend also persists in a time-multiplexed CIFAR-10 patch model. We further realize three jointly trained $16\times16$ transformations, each independently implemented as an inverse-designed nanophotonic region, with relative complex transmission errors of 7.63%, 7.59%, and 8.80%. The reconstructed electromagnetic stack reaches 91.79% accuracy after phase calibration, compared with 91.95% for its surrogate model. These results establish repeated input encoding as a route to functional depth in compact inverse-designed nanophotonic processors.
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Atmospheric and Oceanic Physics
Crucial role of subsurface ocean variability in tropical cyclone genesis
Cong Gao, Lei Zhou, I.-I. Lin et al. (+4 more)
The upper ocean provides thermal energy to tropical cyclones. However, the impacts of the subsurface ocean on tropical cyclogenesis have been largely overlooked. Here, we show that the subsurface variabilities associated with the variation in the 26 {\deg}C isothermal depth have pronounced impacts on tropical cyclogenesis over global oceans. The sea surface wind stress and its curl before tropical cyclogenesis are large enough to perturb the ocean interior down to more than one hundred meters due to entrainment and upwelling. The 26 {\deg}C isothermal depth can fluctuate by tens of meters to significantly modify the upper ocean heat content. Consequently, sea surface temperature anomalies under nascent tropical cyclones are induced, and tropical cyclogenesis is modulated. Our results substantiate an unexpected relation between ocean interior variations and tropical cyclogenesis.
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All authors Cong Gao, Lei Zhou, I.-I. Lin, Chunzai Wang, Shoude Guan, Fei-Fei Jin, Raghu Murtugudde
Classical Physics
Wave Scattering at temporal interfaces with spatial-translation-symmetry mismatch
Cong Chen, Kaijun Yi, Guoliang Huang et al. (+1 more)
Temporal interfaces enable wave manipulation through broken time-translation
symmetry, but conventional formulations generally assume that spatial-translation
symmetry is preserved across the interface. Here we consider temporal interfaces between periodic media with mismatched spatial
symmetries. It is discovered that the reciprocal-
lattice vectors of the pre- and post-switching media enter a generalized quasi-momentum-matching condition, giving rise to reciprocal-
lattice-assisted wave-vector conversion. We then develop a multichannel temporal-scattering theory and validate it in one- and two-dimensional elastic
lattices. A single incident Bloch mode can thereby excite multiple post-interface Bloch modes with distinct wave vectors and frequencies, a response inaccessible at conventional temporal interfaces. These results establish
symmetry mismatch as a new degree of freedom for simultaneous control of wave vector and frequency in time-modulated periodic media.
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All authors Cong Chen, Kaijun Yi, Guoliang Huang, Gengkai Hu