Physics and Society
Collective impact of opinion formation on agent-based epidemic dynamics
Andrea Bondesan, Riccardo Vecchio, Chiara Barbati et al. (+3 more)
Epidemic spread and collective opinion formation are tightly coupled processes: individual beliefs about the severity of an outbreak and the value of protective measures shape behavior, while the evolving epidemic itself reshapes public sentiment through risk perception. We propose an
agent-based framework that couples opinion dynamics with a compartmental epidemic model, in which each
agent carries both a health status and a continuous opinion variable describing adherence to protective measures. Opinion
evolution is driven by binary interactions among
agents and by an exogenous background field that reflects the current state of the epidemic, while the disease transmission rate depends explicitly on the opinions of interacting
agents. Using methods of statistical mechanics, we characterize the resulting macroscopic system for the compartmental mass fractions and mean opinions in both far-from-
equilibrium and close-to-
equilibrium regimes. The calibration shows that incorporating behavioral opinion dynamics substantially improves the interpretation of epidemic
evolution. In particular, the inferred risk perception function evolves consistently with the observed epidemic burden, indicating that behavioral adaptation can explain part of the temporal variation that would otherwise be absorbed into time-dependent transmission parameters. Our results illustrate how integrating opinion heterogeneity in kinetic epidemic models offers quantitative insights into the feedback between behavior and disease spread.
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All authors Andrea Bondesan, Riccardo Vecchio, Chiara Barbati, Jonathan Franceschi, Anna Odone, Mattia Zanella
Accelerator Physics
Generation of 10-TW Attosecond X-Ray Pulses in a Free Electron Laser
E.A.Schneidmiller, S.Serkez, I.Zagorodnov et al. (+35 more)
Attosecond pulses provide direct access to electron dynamics in atoms, molecules, and solids on their natural timescales. While table-top sources have achieved attosecond pulse durations at moderate intensities, extending attosecond science to high peak powers in the x-ray regime requires free-electron
lasers (FELs). Here we report the generation of soft-x-ray pulses with a duration of $\sim\!100$ as and peak power on the order of 10 TW at the European XFEL. The unprecedented combination of pulse duration and peak power is enabled by operation of a soft-x-ray undulator at high electron energy together with five-stage bunch compression, producing ultrahigh peak currents. These millijoule-level attosecond x-ray pulses establish a new regime for attosecond science.
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All authors E.A.Schneidmiller, S.Serkez, I.Zagorodnov, N.Gerasimova, M.Scholz, N.Golubeva, M.Guetg, G.Geloni, S.Karabekyan, F.Sottocorona, A.Trebushinin, G.Perosa, S.Tomin, F.Mayet, Th.Maltezopoulos, J.Gruenert, J.Laksman, H.Ahmadi Rashtabadi, T.M.Baumann, R.Boll, F.Calegari, G.Catacchio, S.Dold, D.E.Ferreira de Lima, L.Funke, W.Helml, M.Ilchen, T.Mazza, M.Meyer, T.Mullins, M.Robinson, S.Savio, K.Scharei, Ph.Schmidt, A.Thiel, S.Usenko, L.Wuelfing, W.Decking
Accelerator Physics
Fabry-Pérot Resonance Shifts as a Novel Non-destructive In Situ Surface Damage Diagnostic
Gregory Blume, Colin Kirk, Sushil Poudel et al. (+6 more)
Current surface damage evaluation for nanostructured electronic devices requires specialized equipment or conditions outside the designed operating environment and cannot be used for in situ evaluation of surface damage. In this work, we developed a non-destructive method to probe the surface sublimation of a
semiconductor heterostructure which can be applied to other
semiconductor damage mechanisms. This approach employs shifts in the resonances of an optical cavity comprising the surface and an integrated distributed Bragg reflector fabricated below the
semiconductor heterostructure undergoing sublimation. We performed the demonstration of this technique under
vacuum, but surface damage effects can be observed in any operational environment either in situ or ex situ.
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All authors Gregory Blume, Colin Kirk, Sushil Poudel, John Hill, Alimohammed Kachwala, Joseph Grames, Marcy L. Stutzman, Matt Grau, Sylvain Marsillac
Optics · Cross-listed from cond-mat.mes-hall
Rydberg excitons in core-shell nanostructures II. Plasmon-exciton interaction and enhancement
David Ziemkiewicz, Gerard Czajkowski and Sylwia Zielińska-Raczyńska
Interaction between Rydberg
excitons in core-shell Cu$_2$O nanostructures and surface plasmons is investigated. An enhancement of a quadrupole transitions to the Rydberg
exciton states in copper oxide plasmonic nanaostructures is examined. A possibility of a modification of plasmonic enhancment (i.e., an average amplification factor) of electric field distributions in the vicinity of nanostructures, which depends on its shape and geometrical size, is also discussed.
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Chemical Physics
HOMO-LUMO Intervals from Modern Density Functionals as Fundamental Gap Estimators
H. Francisco, Javier Carmona-Espíndola, A. C. Cancio et al. (+2 more)
Use of the Kohn-Sham
eigenvalue gap (highest occupied molecular orbital to lowest unoccupied, HOMO-LUMO) as a fundamental gap (I-A, I= ionization potential, A= electron affinity)
estimator is a long-standing challenge for relatively simple exchange-correlation functionals, e.g. meta-GGAs. The LAK meta-GGA [T. Lebeda et al. Phys. Rev. Lett. 133, 136402 (2024)] was developed to emphasize certain constraints in ways intended to make the LAK KS gaps close to the HSE06 hybrid functional [A.V. Krudau et al. J.Chem. Phys. 125, 224106 (2006)] gaps. The LAK functional was tested against a small atomization data set and a very small bond length set, with no molecular HOMO-LUMO gap testing. Here we test LAK against widely used, large reference data sets for molecular heats of formation, bond lengths, harmonic frequencies, I, and A and compare with r2SCAN [J.W. Furness et al., J. Phys. Chem. Lett. 11, 8208 (2020)] as well as HSE06 and PBE0, a quite different hybrid. On these tests LAK does not give meaningfully better geometries, heats of formation, HOMO-LUMO gaps, or DFT IP
theorem satisfaction than r2SCAN. Compared against experimental I and A values the same holds; LAK results resemble r2SCAN results, not HSE06. Moreover, the HOMO and LUMO shifts generated by the NCAPR GGA [J. Carmona-Espindola et al., J. Chem. Phys. 157, 114109 (2022)] as derivative discontinuity estimates, correct the bare NCAPR HOMO and LUMO
eigenvalues to substantially better agreement with experiment for both fundamental gap and IP
theorem than do the meta-GGAs (LAK, r2SCAN) or hybrids (HSE, PBE0). We discuss possible reasons why LAK behaves differently for molecules and solids.
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All authors H. Francisco, Javier Carmona-Espíndola, A. C. Cancio, José Luis Gázquez, S. B. Trickey
Chemical Physics
Scaling Density Functional Theory with Gaussian Splatting
Andrés Guzmán-Cordero, Cindy Zhang, Majdi Hassan et al. (+3 more)
Density functional theory (DFT) strikes a practical balance between accuracy and computational cost in many problems of computational chemistry and materials science. However, many DFT calculations are limited by fixed atom-centered basis sets, which dictate how accuracy and cost scale with system size. We propose Gaussian Splatting for Density Functional Theory (GS-DFT), which represents molecular orbitals as a cloud of Gaussians whose positions, shapes, and mixing coefficients are optimized jointly by gradient descent to minimize the energy without training data. Conceptually, GS-DFT is 3D Gaussian splatting with the renderer replaced by
quantum mechanics. We introduce two key solver components: adaptive density fitting with screening for efficient evaluation of two-electron integrals, and a regularized differentiable orthogonalization of the molecular orbitals. Empirically, the optimized basis reaches the accuracy of the largest conventional basis sets with a fraction of the parameters, converging systematically in energy, density, and nuclear forces. At equal parameter count, it captures the stretched-bond and anion physics that fixed bases only recover with specialized basis augmentation. The resulting solver exhibits quadratic peak
memory scaling in the cloud size, allowing us to simulate systems of up to 2,742 atoms (10,406 electrons) without any modifications at triple-zeta scale using a single four-GPU node.
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All authors Andrés Guzmán-Cordero, Cindy Zhang, Majdi Hassan, Marta Skreta, Kirill Neklyudov, Matija Medvidović
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Ferroelectric Switching in ZnO/Zn1-xMgxO Heterostructures: Atomistic Insights into Interfacial Coupling and Layer Architecture
Alireza Sepehrinezhad, Ali Mohammadi Dinani, Ece Gunay et al. (+4 more)
Ferroelectric switching in
heterostructures couples composition, layer
topology, temperature, and interfacial boundary conditions. ReaxFF molecular dynamics isolates these variables in ZnO/ Zn1- xMgxO/ZnO and Zn1-xMgxO/ZnO/ Zn1-xMgxO stacks. Within pristine, initially single-domain models, coupling to switchable Zn1-xMgxO reduces the applied field required to reverse ZnO by up to fivefold. Temperature generally lowers the coercive field, whereas Mg concentration produces a nonmonotonic response. At equal ZnO and Zn1-xMgxO (ZMO) proportions, structures with ZnO at the center switch at lower fields than those with ZMO at the center at all four temperatures examined, demonstrating a
topology-dependent response. Layer-resolved trajectories reveal
topology-dependent switching sequences with direction-dependent redistribution of normal stress near the heterointerfaces, consistent with a stress-assisted cooperative pathway. Limiting MgO-containing structures exhibit sequential multilevel switching or low-polarity trapping, depending on thickness and temperature. Fixed-charge atomistic simulations complement previous continuum descriptions by resolving structural, energetic, and local stress
evolution under a common applied field. TEM and STEM-EDS observations provide experimental structural context for the modeled architectures. Together, the results establish layer
topology and interfacial mechanical confinement as design variables for wurtzite ferroelectric
heterostructures.
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All authors Alireza Sepehrinezhad, Ali Mohammadi Dinani, Ece Gunay, Elizabeth C. Dickey, Jon-Paul Maria, Susan Trolier-McKinstry, Adri C.T. van Duin
Fluid Dynamics
A parallel solver for vortex-induced vibrations at zero mass ratio
Arthur Bawin, Joan Le Pouhaër, Stéphane Étienne et al. (+1 more)
We present a parallel strategy for the study of the
vortex-induced vibrations (VIV) of a rigid, massless cylinder mounted on translational springs, in two and three dimensions. Without mass or damping, its motion is governed solely by the fluid forces and the spring restoring force, and is an immediate response to the flow. We focus on low spring stiffness, yielding high reduced velocity and maximal oscillation amplitude. A monolithic finite element method in an arbitrary Lagrangian-Eulerian framework with implicit time stepping is proposed, solving the fluid flow, cylinder dynamics, and mesh motion simultaneously. Mesh movement is modelled with a linear elastic pseudo-solid with variable Lamé coefficients, and the no-slip condition on the cylinder is enforced with a Lagrange multiplier coupled to the position degrees of freedom; three strategies are explored to enforce this force-position coupling in a distributed framework. To the best of our knowledge, this work is the first to propose a distributed solver for three-dimensional fluid-structure interaction at zero mass ratio. The solver is verified with manufactured solutions, and exhibits second-order accuracy in time. A numerical study of two- and three-dimensional VIV for Reynolds numbers from 100 to 300 reproduces the VIV responses obtained in previous two-dimensional studies, and predicts nonperiodic 3D oscillations starting at $Re = 300$. Using the direct solver MUMPS, the proposed method scales to up to 768 compute cores.
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All authors Arthur Bawin, Joan Le Pouhaër, Stéphane Étienne, Cédric Béguin
Optics
Direct Observation of Switching-Wave Dynamics in 20 GHz Normal Dispersion Spiral Microresonators
Van Doan Le, Julien Fatome and Erwan Lucas
Integrated Kerr frequency combs are powerful tools for microwave photonics, spectroscopy, and optical communications. While traditional architectures rely on the anomalous-dispersion regime, this typically requires thick, highly strained silicon nitride layers that complicate standard CMOS-foundry fabrication. Thinner layers circumvent these fabrication constraints but yield normal-dispersion microcombs that generally require specific trigger mechanisms, such as deterministic seeding, due to the absence of spontaneous modulational instability. Here, we demonstrate the generation of a 20 GHz microcomb in the normal-dispersion regime, driven by a synchronized dual-pump scheme via electro-optic sidebands modulation. The platform leverages an Archimedean spiral geometry on a foundry-compatible, 350 nm-thin SiN platform. By employing adiabatic
curvature engineering, the resonator balances a compact footprint with an intrinsic quality factor exceeding $7 \times 10^6$, while effectively eliminating avoided mode crossings with higher order modes. This strong-dispersion architecture yields a low-repetition-rate microcomb featuring high power-per-line and picosecond-scale temporal profile, which enables the direct optical sampling and characterization of the out-coupled switching wave waveforms. The measured dynamics across a range of pump desynchronizations demonstrate excellent agreement with simulations. Our work establishes a scalable, strategy for footprint-efficient normal-dispersion microcomb generation at microwave frequencies, with potential for scaling to other wavelength ranges.
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Chemical Physics
Communication: Becke Weights as a Partitioning Scheme for Phase Space Electronic Structure Theory
Ben Curlee, Zheng Pei, Xinchun Wu et al. (+4 more)
We implement the Becke weight for atom A ($w_A$) as the partitioning scheme needed for phase space electronic structure theory. We show that this ansatz can lead to very efficient electronic structure calculations at nonzero nuclear momentum ($P \ne 0$). We further show that using Becke weights leads to efficient VCD calculations that are very stable with respect to basis set size. We hypothesize that, as far as
quantum chemistry simulations in an atomic orbitals basis, the choice of Becke weights as a partitioning scheme will be adopted for all future phase space electronic structure calculations in an atomic orbital basis, as theorists learn to efficiently simulate coupled nuclear electronic dynamics through a new framework.
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All authors Ben Curlee, Zheng Pei, Xinchun Wu, Titouan Duston, Todd J. Martinez, Yihan Shao, Joseph E. Subotnik
Geophysics
Explaining Ground-Motion Residuals at Two Strong-Motion Stations in Southeastern New York: Sediment Resonance and Topographic Amplification
Aser Abbas, Patrick Daniele, James Kaklamanos et al. (+3 more)
Sites hosting strong-motion stations in the Central and Eastern United States are commonly characterized using proxy-based parameters, limiting the ability to identify the physical causes of large ground-motion residuals. This study investigates the amplification mechanisms at two New York strong-motion stations that recorded some of the largest positive 1-Hz pseudospectral-acceleration residuals during the 2024 Mw 4.8 Tewksbury, New Jersey, earthquake. Station N62A is located at Caumsett State Historic Park in the Atlantic Coastal Plain, whereas station PAL is located at the Lamont-Doherty Earth Observatory atop the Palisades cliffs. Detailed geophysical site characterization at both sites combined active-source and ambient-noise surface-wave testing with HVSR measurements. At Lamont-Doherty, additional ambient-noise arrays were deployed across the Palisades ridge to evaluate topographic amplification. At Caumsett, surface-wave testing resolved a thick sedimentary column overlying a major impedance contrast, with a spatially representative fundamental site frequency of 0.93 Hz. Amplification in the same frequency range was also independently evident in observed amplifications computed from site-to-site (S2S) residuals. The fundamental-resonance band also encompasses the 1-Hz frequency at which the large Tewksbury residual was observed, supporting deep sediment resonance as the dominant mechanism. At Lamont-Doherty, surface-wave testing indicated hard-rock conditions with a thin, laterally variable sediment cover. The ambient-noise arrays showed repeatable, directional amplification near 2 Hz at PAL, and the earthquake-based S2S amplifications show a peak between approximately 0.6 and 2 Hz, a pattern reproduced by neither the transfer functions nor the ergodic linear amplification models. These observations support topographic amplification as the primary mechanism at PAL.
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All authors Aser Abbas, Patrick Daniele, James Kaklamanos, Laurie Baise, Kyle Cannon, Ellie Meyer
Applied Physics
Depth-resolved elastic property tomography using higher-order shear-horizontal modes
Peter Huthwaite
Early material degradation can produce weak, local changes in elastic stiffness before a crack or void forms, but conventional ultrasonic measurements dilute these changes through path and thickness averaging. This paper introduces DEPTH (Depth-resolved Elastic Property
Tomography using Higher-order modes), which uses mode-to-mode scattering among higher-order guided waves to reconstruct elastic-property variations as a function of axial position and depth through a plate. The formulation is developed using shear-horizontal (SH) modes, for which the reconstructed property is shear modulus. A Born formulation shows that each incident-received mode pair contains at most two cosine depth orders, allowing the through-thickness field to be recovered from diverse modal mixtures across mode pairs and frequency. The
matrix-free regularised inverse is evaluated using direct two-dimensional modal data, practical single-surface excitation and reception, and full three-dimensional finite-element data. In a 10 mm plate, the ideal two-dimensional case gives a through-thickness point-spread FWHM of 0.84-1.03 mm, while the single-surface configuration recovers four compact targets at the correct depths. This provides the first demonstration of depth-resolved elastic-property
tomography from multimode guided-wave transmission with excitation and reception confined to a single physical plate surface. With full three-dimensional propagation and finite-width transduction, the reconstruction retains the compact-target positions with a whole-image correlation of 0.899 against a matched acquisition-limited reconstruction. These simulation results demonstrate that higher-order guided-wave mode conversion can provide local depth-resolved elastic-property
tomography from surface-access measurements, with potential for characterising early-stage damage such as fatigue.
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Optics
High-Yield, 150 ps Polymer Scintillators via Synergistic Purcell and High-Z Enhancement
Xiaohe Zhou, Hiba H. Karakkal, Chenger Wang et al. (+12 more)
Developing plastic scintillators that simultaneously achieve high light yield (LY), ultrafast timing, and scalable processability remains a formidable challenge in radiation detection. Here, we report a solution-processable hybrid scintillator that integrates high-Z sensitization with Purcell-enhanced radiative recombination within a conjugated-
polymer platform. By
embedding HfO2 nanoparticles and resonant Ag-SiO2 plasmonic nanoantennas into a poly(9,9-dioctylfluorene)
matrix, we exploit the intrinsic sub-nanosecond kinetics of conjugated
polymers while overcoming their characteristic low stopping power. The HfO2 nanocrystals amplify energy deposition and suppress interchain aggregation, preserving high photoluminescence
quantum yields in the solid state. Simultaneously, the nanoantennas induce strong plasmon-
exciton coupling, accelerating radiative decay to ~150 ps. This synergistic architecture yields LY=6.1
photons/keV, comparable to standard commercial plastics with nanosecond lifetimes, yet over an order of magnitude higher than current sub-nanosecond state-of-the-art materials. This performance represents one of the most favourable combinations of efficiency and timing resolution reported to date. Our versatile strategy provides a framework for next-generation organic scintillators, merging record-breaking temporal response with high efficiency for advanced radiation-sensing architectures.
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All authors Xiaohe Zhou, Hiba H. Karakkal, Chenger Wang, Andrea Fratelli, Francesco Bruni, Matteo L. Zaffalon, Leonardo Poletti, Saptarshi Chakraborty, Emanuele Mazzola, Roberto Lorenzi, Francesco Carulli, Francesca Rossi, Francesco Meinardi, Luca Gironi, Sergio Brovelli
Instrumentation and Detectors
Time-Resolution Function of the RADEX Neutron Source
R. M. Djilkibaev
The time-resolution function is one of the key factors determining the accuracy of
neutron-resonance parameter reconstruction in time-of-flight experiments. A method is proposed for determining the time-resolution function of the RADEX
neutron source associated with
neutron slowing down in the target, based on detailed Geant4 modeling. The
neutron time spectra obtained in the Geant4 simulations are approximated by a sum of three Gamma functions with dimensionless parameters. This model is shown to describe the shape of the time distributions well over the
neutron-energy range 50–300 eV. To test the applicability of the proposed approach to a source of a different design, a comparison is made with the calculated n\_TOF time-resolution function. Its shape is also shown to be well described by a three-component Gamma model.
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Plasma Physics
Impact of magnetic drift configuration on the edge radial electric field in the TCV tokamak
S. Rienäcker, L. Vermare, P. Hennequin et al. (+8 more)
The edge radial electric ($E_r$) in the Tokamak à Configuration Variable (TCV) is compared in matched L-mode discharges with opposite ion
magnetic drift directions (favorable versus unfavorable $B \! \times \! \nabla B$ configurations). As previously reported on the WEST and AUG tokamaks, the $E_r$ profile—measured by Doppler backscattering (DBS)—exhibits a "well" just inside the separatrix in the favorable drift case, which is absent or less pronounced in the unfavorable counterpart. This observation holds over a broad range of
plasma conditions, notably also in Ohmic discharges with nearly identical edge density and temperature profiles. Density fluctuation characteristics inferred from DBS are not drastically different: Under Ohmic heating, edge fluctuation levels tend to be higher in the favorable configuration, while radial correlation lengths are similar. The edge $E_r$ difference appears uncorrelated with carbon toroidal rotation behavior. Reducing density, or increasing auxiliary heating power tends to accentuate the edge $E_r$ disparity.
Plasma current has little impact on both favorable and unfavorable $E_r$ profiles—in contrast to results from WEST. Approaching the L-H transition via auxiliary heating, edge $E_r \times B$ shear and pressure grow more readily in the favorable configuration, and DBS fluctuation levels are reduced relative to the unfavorable case. Overall, our results confirm that the edge $E_r$ sensitivity to
magnetic drift configuration is a robust, multi-machine phenomenon, with a plausible connection to confinement level and H-mode access.
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All authors S. Rienäcker, L. Vermare, P. Hennequin, C. Honoré, B. Labit, S. Coda, L. Frassinetti, B. Vincent, O. Panico, Y. Wang, K. Singh
Chemical Physics
Multivariate conformal uncertainty propagation in multitask atomistic simulation: Successes and pitfalls
Katharine Fisher, Michael Herbst, James Kermode et al. (+1 more)
Machine learning has become the standard tool for the design of interatomic potentials which balance efficiency and accuracy, but uncertainty quantification remains an open problem. Multiscale simulations introduce an additional challenge: robust uncertainty quantification across scales. Even within one scale, computations are often multistage, producing a sequence of target quantities, each dependent on the previous, and each with some uncertainty. Conformal methods have emerged as a model agnostic framework for recalibrating surrogate predictions to produce sets which contain the truth at a user-specified rate. For multistage workflows, we require uncertainty calibration for multiple chemical properties and atomistic configurations, and we want to propagate uncertainty sets to downstream quantities of interest. Such propagation should capture the error cancellations which occur in many downstream targets in materials science; for instance, an approximate energy difference is often more accurate than individual energy predictions. We present the first exploration of multivariate conformal methods for chemical properties, including Bonferroni-corrected hyperrectangles, hyperellipsoidal sets based on the Mahalanobis distance, and custom loss functions within conformal risk control. Calibration is applied directly to predicted energies, atomic forces, and virial stresses, then propagated to elastic constants and vacancy formation energies employing a variety of commonly considered approximate protocols in materials modeling. We highlight the benefits of building correlation predictions into the conformal procedure, making it possible to build sets which capture near
symmetries and error cancellation. We conclude with a discussion of the interplay of the employed approximate computational protocol and conformal guarantees.
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All authors Katharine Fisher, Michael Herbst, James Kermode, Youssef Marzouk
Fluid Dynamics
Controlling three-dimensional falling liquid films: from weighted-residual models to direct numerical simulation
Oscar A. Holroyd, Susana N. Gomes and Radu Cimpeanu
We consider the problem of controlling a three-dimensional falling
liquid film using same-fluid blowing and suction through the substrate. Building upon recent results for the corresponding two-dimensional problem, we employ a reduced-dimensional weighted-residual model for the film height and downstream flux as the basis for controller design. Linear stability analysis is used to estimate the number of actuators required to stabilise the film, while a linear-quadratic regulator (LQR) framework is used to construct feedback controls for the linearised system. The resulting gain
matrix is then combined with observations from direct numerical simulation (DNS) of the three-dimensional Navier-Stokes equations, allowing controls derived from the reduced-dimensional model to be applied directly to the full flow. Through systematic numerical tests, we demonstrate that these controls successfully stabilise the flat-film solution across a physically relevant range of Reynolds numbers and domain configurations. We further show that both the number and placement of actuators play a crucial role in control performance, with spanwise instabilities requiring additional actuator coverage in the cross-stream direction. Although the extension from two to three dimensions substantially increases the cost of controller construction, this cost is incurred entirely offline during the computation of the gain
matrix, making the overall framework computationally tractable. Our results demonstrate that LQR feedback controls derived from a three-dimensional weighted-residual model retain predictive value when applied to fully resolved DNS, extending previous two-dimensional control methodologies and helping bridge the gap between theoretical control design and experimentally relevant falling-film flows.
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Optics
Probing the formation of femtosecond laser-induced periodic surface structures on silica films by ultrafast small-angle X-ray scattering
Dominik Kaczmarek, Jean-Luc Déziel, Thies Johannes Albert et al. (+16 more)
Ultrashort X-ray pulses, as provided by X-ray Free Electron
Lasers (XFELs), offer unique opportunities to probe the formation of
laser-induced nanostructures with sizes even below the optical diffraction limit, with sub-micometer and sub-picosecond spatial and temporal resolution. Using ultrafast small-angle X-ray scattering (SAXS), we probe the formation of nanoscatterers and nanocracks in reciprocal space as they evolve into different types of
laser-induced periodic surface structures (LIPSS) on silica films. Our focus is on the dynamics and
evolution of nanoscatterers and high spatial frequency LIPSS (HSFL), with spatial periods below 100 nm. Our experiments include an in-situ analysis of the pulse-by-pulse
evolution of HSFL at a fixed sample location, as well as fs time-resolved delay and fluence scans using an ultrafast pump-probe scheme. We find that nanoscatterers and periodic nanocracks form at delay times of hundreds of picoseconds and subsequently evolve into HSFL. At low
laser fluences, inter-pulse incubation effects become important during multi-pulse irradiation. Simultaneously, inter-pulse feedback leads to an ordering and improve the regularity of the HSFL. The experiments are complemented by theoretical analyses, including numerical Finite-Difference Time-Domain (FDTD) simulations. These combined analyses allow us to propose a five-stage model of LIPSS formation on silica films upon irradiation with fs-
laser pulses.
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All authors Dominik Kaczmarek, Jean-Luc Déziel, Thies Johannes Albert, Matthias Weise, Jerzy Antonowicz, Robert Carley, Devesh Chopra, Loïc Le Guyader, Laurent Mercadier, Giuseppe Mercurio, Roman Minikayev, Mianzhen Mo, Andreas Scherz, Ryszard Sobierajski, Yanwen Sun, Martin Teichmann, Peter Zalden, Klaus Sokolowski-Tinten, Jörn Bonse
Instrumentation and Detectors · Cross-listed from hep-ex
Suitability studies of exotic muon decay at the High Intensity heavy-ion Accelerator Facility
Lingzhi Dong, Jinning Li, Leyun Gao et al. (+8 more)
We present a detailed feasibility study of exotic
muon decay searches using the
muon beam at the High Intensity heavy-ion Accelerator Facility (HIAF). For the decay channel mu to eX0, where X0 denotes a new
boson featuring LFV couplings, the produced electron carries very low energy when the mass of X0 approaches the
muon mass, making detection challenging. Nevertheless, the high-energy beam at HIAF can boost these electrons up to a measurable energy range. The detector system proposed here comprises front-end scintillators for particle identification (PID) and a main detector consisting of an RPC stack to track decay products and a scintillator for energy measurement. Leveraging the kinematic properties of low momenta and small emission angles of signal electrons, we employ optimized momentum and angular acceptance cuts on the RPC detector to efficiently suppress background events. With this strategy, we obtain an upper limit of 1e-5 on the branching ratio of the exotic
muon decay at 95% confidence level, achieving state-of-the-art sensitivity.
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All authors Lingzhi Dong, Jinning Li, Leyun Gao, Cheng-en Liu, Yu Xu, Xuecheng Zhang, Liangwen Chen, Qite Li, Chen Zhou, Qiang Li, Zhiyu Sun
Atomic Physics
Highly elastic collisions of ultracold asymmetric top molecules in a static electric field
Reuben R. W. Wang
We propose that the application of static electric fields to reactive CaNH$_2$ molecules can result in large ratios of elastic to lossy collisions at ultracold temperatures. In the first rotationally excited
manifold, the asymmetric top structure of CaNH$_2$ results in a $\approx 226$ MHz splitting of the opposite parity $K$-doublet states. This modest splitting allows electric fields below a kilovolt per centimeter to polarize the molecules and induce long-range dipole-dipole interactions. By increasing the electric field, we find that dipole-dipole attraction can become sufficiently large to induce weakly bound octatomic field-linked states of [CaNH$_2$]$_2$. In the absence of these field-linked states, we identify select molecular states where dipolar interactions allow elastic collisions to dominate over lossy collisions by up to three orders of magnitude, while maintaining loss rate coefficients at the $10^{-14}$ cm$^3$s$^{-1}$ level. These results establish that evaporative cooling is a viable route to
quantum degenerate gases of
laser coolable asymmetric top molecules. Access to such low
entropy ensembles of asymmetric top molecules holds promise to push the frontiers of
quantum simulation, state-resolved chemistry, and searches for beyond the Standard Model physics.
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Atmospheric and Oceanic Physics
Learning Aerosol Coagulation Dynamics in Latent Space with a Scale-Covariant Neural ODE
Wenhan Tang, Ruqi Yang, Jeffrey H. Curtis et al. (+5 more)
Particle-resolved aerosol models preserve the joint size-composition structure that governs cloud activation, optical properties, and freezing, but their computational cost limits their use in large-scale atmospheric models. We extend AeroMELD from a compact representation of aerosol populations to a prognostic model of coagulation. The resulting AeroMELD-Coag advances nine learned coordinates for population shape and one for total particle number through a scale-covariant neural ordinary differential equation that incorporates the known concentration dependence of coagulation. Across 2,000 held-out trajectories spanning 48 h, median symmetric errors are 3.5% for latent shape and 0.52% for total number. This ten-coordinate state also retains the evolving size-resolved composition and associated cloud-condensation-
nuclei (CCN) activation, optical properties, and frozen fraction. Compared with the evaluated 20-bin sectional model with 320 prognostic coordinates, AeroMELD-Coag lowers pooled mean CCN activation error from 1.98% to 1.38% and frozen-fraction error from 1.72% to 0.56%. In a matched integration
benchmark, GPU integration time per trajectory, amortized over a batch, is more than three orders of magnitude lower than for both single-core CPU references. These coagulation results provide a proof of concept for advancing aerosol microphysics efficiently in a compact learned state while retaining information about aerosol mixing state. They establish a foundation for future large-scale atmospheric models to represent aerosol microphysics with greater mixing-state detail within practical computational budgets.
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All authors Wenhan Tang, Ruqi Yang, Jeffrey H. Curtis, Ehsan Saleh, Lekha Patel, Peter A. Bosler, Nicole Riemer, Matthew West
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Multiscale computational study of the dielectric response of semi-crystalline polyethylene with chemical defects
Roshal Perepadan Shaju, Guido Roma and Xavier Colin
Polymers are widely used as functional insulating materials, but predicting their dielectric behavior is challenging because multiple mechanisms, acting across different spatial and temporal scales, contribute to their response. In polyethylene (PE), one of the most common
polymers, electronic, atomic, and mesoscale dynamics must all be considered. In this work, semicrystalline models of polyethylene were developed and investigated using a multiscale approach.
Quantum simulations were employed to describe electronic and vibrational contributions to the dielectric response, while classical molecular dynamics simulations captured the behavior of
polymer chains at room temperature and frequencies down to the 10-100 MHz range. The study focuses on the impact of
radio-oxidation defects on the dielectric properties of polyethylene.
Quantum calculations reveal how electronic and vibrational contributions depend on the local atomic environment surrounding these defects. Comparison with molecular dynamics results highlights the influence of temperature on the static dielectric constant. Structural analyses further assess the effect of each defect type on PE crystallinity. Analysis of dipolar correlation functions shows that different defects interact with one another and with the
polymer matrix in distinct ways, affecting permittivity and dielectric loss peaks. For all defect types, defect-defect interactions provide the largest contribution to dielectric response. While most oxidized groups exhibit positive coupling with the PE
matrix, alcohol defects display a negative cross-correlation, partially offsetting their impact on the dielectric properties. Our results also show that ketone groups produce the largest dielectric loss between the defects studied.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Electron lattice potentials for ultracold atoms using circular Rydberg orbitals
Aileen A. T. Durst, Einius Pultinevicius, Homar Rivera-Rodríguez et al. (+3 more)
Recent advances in experiments using individually trapped atoms have enabled precise control over circular Rydberg electrons with exceptionally long lifetimes. We show that these giant and stable electron orbits can form toroidal
lattice potentials for ultracold atoms with a period set by the electron's de Broglie wavelength. Unlike conventional static optical
lattices, this electron
lattice is formed via the electron-atom interaction, which mixes Rydberg circular states with opposite azimuthal phase winding into a standing electronic matter wave. The
lattice phase is thereby intrinsically coupled to the atom position. For a pair of atoms, this results in ballistic tunneling motion in the two-atom spatial correlations along the ring, while the single particle dynamics is essentially free rotation. We simulate the dynamics for an experimentally realistic setting that exploits optical tweezers for individual atom control. Our results open a route toward incorporating long range atom-atom interactions mediated by a single electron and, ultimately, realizing small Bose and Fermi gases confined in these microscopic electronic atom traps.
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All authors Aileen A. T. Durst, Einius Pultinevicius, Homar Rivera-Rodríguez, Tilman Pfau, Matthew T. Eiles, Florian Meinert
Chemical Physics
Multiphysics Simulation Framework for Continuous Ion Transport and Energetics in Atmospheric Pressure Interfaces
Yihui Yan, Jozef Lengyel, Frederic Rosu et al. (+1 more)
Optimizing atmospheric pressure interfaces requires balancing efficient ion transport with unwanted collision activation. The complex environment at the inlet region, including rapid pressure drops, RF/DC electric fields, ion-gas collisions, and space charge effects, makes simulation of this system challenging. In this work, we introduce MuCITE (Multiphysics simulation for Continuous Ion Transport and Energetics), which combines continuous ion injection, precomputed electric and gas flow fields, and particle-in-
cell space charge updates. Furthermore, by employing improved impulsive collision theory, it can not only predict transport but also analyze the loss position of ions and the
evolution of their kinetic energy, internal energy, and dissociation probability during transport. Transport predictions with ion currents and activation trends of in-source fragmentation were compared with experimental measurements using a custom-built source and a Q-Exactive HF source. The results show that the simulation predictions agree well with the experimental results and can serve as a reference before experiments. MuCITE allows users to derive ion transport, output beam characteristics, and ion energy through the configurable interface geometry and operating conditions. It supports simulation-guided design and tunable parameters to achieve predicted efficient ion transport or in source activation.
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All authors Yihui Yan, Jozef Lengyel, Frederic Rosu, Valerie Gabelica
Chemical Physics
A General Non-Markovian Electronic Friction and Langevin Dynamics Framework for Nonequilibrium Systems
S. L. Rudge, R. J. Preston, D. S. Kosov et al. (+1 more)
We present a general framework for simulating the nonequilibrium vibronic dynamics of molecules interacting with metal surfaces, which utilizes non-Markovian electronic friction and the corresponding generalized Langevin equation. The method employs a Markovian
embedding scheme to sample coordinate-dependent
quantum colored noise, with the underlying
memory kernels represented systematically by exponential decompositions obtained directly from the electronic forces. In doing so, the approach extends the widely used electronic friction and Langevin dynamics formalism beyond the conventional Markovian approximation while retaining the coordinate dependence of the electronic back-action. We demonstrate the method for nonequilibrium charge transport through a vibrationally coupled molecular junction, where comparisons with numerically exact hierarchical equations of motion simulations show that the non-Markovian formulation is both more accurate and more robust than its Markovian counterpart. In particular, we find that non-Markovian electronic forces play a decisive role in the nonequilibrium vibrational dynamics, stabilizing regimes in which the conventional Markovian approximation fails.
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All authors S. L. Rudge, R. J. Preston, D. S. Kosov, M. Thoss
Geophysics
Structure-dependent failure modes of neural priors in acoustic full-waveform inversion
Ziye Yu, Xin Liu and Yuqi Cai
Frequency continuation does not improve every neural representation, and better velocity recovery need not imply better prediction of unseen waveforms. We compare a velocity grid with total-variation regularization, an adapted sinusoidal coordinate network (SIREN), and a frozen image generator with a full-grid residual in two-dimensional acoustic full-waveform inversion. All methods use the same frozen SWEEP discretization, acquisition, observations, background, and budget of 1,500 shot–model gradient evaluations. Three exposed synthetic targets represent inclined layering, curved layering, and a high-contrast curved interface drawn from a fault-labelled family. With 2-to-10 Hz continuation, the generative-residual model attains velocity RMSEs of 218.7, 108.0, and 341.9 m/s, compared with 232.5, 100.3, and 412.9 m/s for Grid+TV. Thus the latter wins on curved layering, while the former improves model RMSE by 5.9% and 17.2% on the other targets. Grid+TV nevertheless predicts held-out 10 Hz shots better on all three. SIREN is worse than the common background in every
cell; continuation worsens two targets but improves one. A five-weight TV sensitivity study preserves the CurveFault model-error ranking. An equal-budget variational extension fails both recovery and interval coverage. These results establish conditional rankings, not universal superiority or an isolated spectral-bias mechanism. Full-grid residuals also prevent attributing gains uniquely to the generator. We advocate joint reporting of model recovery, unseen-shot prediction, optimization cost, and negative outcomes when auditing neural FWI.
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Applied Physics · Cross-listed from quant-ph
Frequency- and Power-Dependent Optical Response of a Cesium Rydberg Microwave Receiver
Jure Pirman, Ema Stopar, Katja Gosar et al. (+2 more)
We show experimentally obtained frequency- and power-dependent optical response of a room-temperature cesium vapor
cell used as a Rydberg microwave receiver based on electromagnetically induced transparency. An applied microwave field couples the ${70S_{1/2}}$ Rydberg state to the nearby ${70P_{1/2}}$, ${70P_{3/2}}$, ${69P_{1/2}}$, and ${69P_{3/2}}$ states, modifying the probe-transmission spectrum. Probe transmission is recorded over a 800 MHz range of coupling
laser detunings. These EIT spectra are measured for RF frequencies from 9 to 13.5 GHz and over a 40 dB range of RF power. We analyze the RF induced splittings in the recorded EIT spectra. We observe both limiting cases, where the EIT peak separation is either dominated by the RF detuning or by the RF power. At higher powers we are also able to observe complex features due to coupling of multiple nearby Rydberg states. We further analyze the probe-transmission signal at zero coupling-
laser detuning. Sigmoidal fits to the power-response curves are used to determine the midpoint power and the 10-90% transition interval as functions of RF frequency.
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All authors Jure Pirman, Ema Stopar, Katja Gosar, Erik Zupanič, Peter Jeglič
Geophysics
Wave-Propagation Geometry Emerges from Scalar Travel-Time Relations
Ziye Yu
Scalar travel-time relations can identify propagation geometry without velocity inputs, ray labels or equation supervision during learning. Physical interpretation is applied after learning through the high-frequency isotropic eikonal relation (Aki and Richards, 2002). Here we show that local value differences constrain derivatives through sampling geometry and smoothness. Controlled neural fields recover propagation directions with $5.34\pm0.07^{\circ}$ median angular error, and local P- and S-wave velocities in a prospectively locked, test-sealed realization. Classical representations also recover geometry. Scalar-matched perturbations separate value accuracy from derivative reliability; regularized inversion can recover structure when direct gradients fail. A field trained on 2.90 million Chinese arrivals retains continental crust–mantle boundary structure: correlation with a withheld reference is $\rho=0.910$ raw and 0.592 after quadratic detrending (spatial-shift $p=0.020$). Direct catalogue values yield $\rho=0.909$, and thickness contrasts are compressed. Manual-only California arrivals support broad velocity organization with limited lateral fidelity. Synthetic
quantum fields containing phase information support probability-flow and trajectory readouts without supervising those quantities. These results establish conditional identification across representations and physical settings: informative scalar relations can constrain geometry, while known physical relations supply its interpretation. They do not imply that accurate scalar fitting alone guarantees reliable physical derivatives.
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Geophysics
From Image Morphology to Multiphysics Earth Posteriors
Ziye Yu, Xin Liu and Yuqi Cai
Structural learning and physical-property inference can draw on different sources of knowledge. We learn morphology from 33,140 natural, satellite, and texture images, without geological training models, then infer Earth properties from physical observations. Identical frozen weights map 128 coordinates into each $256\times256$ compressional-velocity, shear-velocity, or density field. Fixed adapters assign physical meaning; observation-specific likelihoods determine new posteriors without retraining. Across 256 unseen Earth models, image coordinates reduce projection error fourfold relative to a dimension-matched cosine basis. Matched inversions favor image coordinates for the tested curved-velocity targets and a smooth radial basis for the tested faulted targets. A simplified 2.5-dimensional application with 915 measured observations along one 120.9-km southern-California profile constrains a velocity–density contrast. Grouped arrival-time and
gravity errors fall by 43% and 44% relative to the pretrained image prior, although the matched smooth radial basis predicts better. Direct layered-Rayleigh updating reduces blind phase-velocity error by 28% at five sites, whereas P-and-
gravity-only sharing worsens it, distinguishing reusable morphology from beneficial cross-property coupling. These results establish a practical separation: images supply structural alternatives, and heterogeneous physical observations determine their experiment-specific posterior probabilities.
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Applied Physics
Black silicon avalanche photodiode with dopant-free multiplication region achieves >98% EQE
O. Leiviskä, O. Setälä, A. Haarahiltunen et al. (+3 more)
Conventional silicon avalanche photodiodes (Si APDs) rely on highly doped regions to enable impact ionization and achieve internal gain. However, inefficient charge collection in these regions, combined with front surface reflection, degrades the external
quantum efficiency (EQE) of these devices. In this work, we mitigate both loss mechanisms by integrating black silicon (b-Si) surface nanostructuring with Al2O3 induced carrier collection in an inverted-mesa Si APD architecture. This design confines the electric field and defines the multiplication region without requiring ion implantation. The resulting devices display near-ideal responsivity (at M = 1) across the UV-visible spectrum, with EQE exceeding 100% at 200-400 nm (peak ~130%) and exhibiting 92-100% at 400-700 nm. Avalanche gains of M ~ 4 at 80 V, M ~ 10 at 100 V, and M ~ 23 near breakdown at ~110 V are obtained. Dark current remains in the picoampere range up to ~80 V but rises to the nanoampere range near breakdown, narrowing the practical bias window. Capacitance-limited rise times of ~30-570 ns are measured for device diameters of 1-5 mm. The results demonstrate that the developed architecture enables APDs capable of detecting every single
photon over wide range of wavelengths.
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All authors O. Leiviskä, O. Setälä, A. Haarahiltunen, J. Heinonen, V. Vähänissi, H. Savin