Chemical Physics
Systematic incorporation of nuclear quantum effects into atomistic simulations by smoothed trajectory analysis
Ádám Madarász, Bence Balázs Mészáros and János Daru
Nuclear quantum effects (NQEs) play an essential role in many atomistic systems, yet their explicit inclusion in molecular simulations remains challenging. Path-integral molecular dynamics (PIMD) provides a rigorous framework for incorporating NQEs, but its practical applicability is often limited by the slow and strongly system-dependent convergence with respect to the number of beads. Here we introduce path-integral generalized smoothed trajectory analysis (PIGSTA), a post-processing framework for the systematic incorporation of NQEs into atomistic simulations, using either classical or path-integral molecular dynamics trajectories. By applying analytically defined convolution kernels to simulation trajectories, PIGSTA corrects the frequency-dependent discretization error associated with a finite number of beads, without modifying the underlying dynamics. For harmonic systems, PIGSTA recovers the exact
quantum-mechanical limit at any bead number, whereas standard PIMD becomes exact only in the infinite-bead limit. More generally, the method significantly improves the convergence of thermodynamic and structural observables at finite bead numbers and provides an internal, reference-free diagnostic of bead-number convergence based on the consistency of energy and force
estimators. We assess PIGSTA for ambient
liquid water and for the Zundel cation at ultralow temperature, representing a particularly demanding case for bead-number convergence. In both systems, PIGSTA reproduces the converged PIMD limit and enables physically consistent results at reduced bead numbers when convergence criteria are satisfied. Owing to its post-processing nature and negligible additional computational cost, PIGSTA offers a practical and broadly applicable approach for incorporating NQEs into atomistic simulations.
Read the full abstract ▾
Optics
Universal Bright-Bright Integrated Soliton Molecule via Parametric Binding
Pradyoth Shandilya, Shao-Chien Ou, Alioune Niang et al. (+4 more)
Dissipative Kerr
solitons (DKSs) have emerged as the preferred solution for on-chip integrated optical frequency comb (OFC) generation in metrology. A multi-pumped DKS enables either all-optical trapping in the Kerr-induced synchronization regime, or a multi-component OFC with \greg{a locked repetition rate yet with constant frequency offsets between the components} in the multi-color DKS regime. The multi-color DKS regime is of particular interest since nonlinear mixing between the DKS and the secondary pumped component generates idler waves at different frequencies that are useful for spectral extension of the DKS comb. Here, we explore multi-color idler generation at frequencies in which the resonator free spectral range matches that at the DKS. We demonstrate theoretically and experimentally that without phase matching, the idler forms a bright pulse fundamentally bound to the bright DKS through parametric interaction, despite occurring in normal dispersion. Our work can enable new applications in metrology and spectroscopy of
quantum systems toward visible wavelengths, as the parametric nature of our bright-bright state eliminates dependence on dispersion regime or visible wavelength pumping.
Read the full abstract ▾
All authors Pradyoth Shandilya, Shao-Chien Ou, Alioune Niang, Gary Carter, Curtis R. Menyuk, Kartik Srinivasan, Grégory Moille
Classical Physics
Hessian-Enhanced Alternating Frequency/Time method for Computing Resonance Backbone Curves
Wei Wen, Weikai Qi and Weidong Wen
Computing resonance and anti-resonance backbone curves in complex nonlinear mechanical systems is of high engineering relevance but remains computationally challenging, especially for large finite-element (FE) models. Existing
manifold-based approaches often rely on
polynomial parameterizations, limiting their effectiveness for general smooth, non-
polynomial nonlinearities. To overcome these limitations, we develop a direct optimization framework that employs a Lagrange multiplier formulation to determine the resonance backbone curve on the response surface constrained by the harmonic balance governing equations. Crucially, solving this formulation efficiently requires second-order sensitivity information. Therefore, the primary innovation of this work is the derivation of a analytical Hessian Tensor for generic $C^2$-continuous nonlinear elements. This is achieved by combining an extended Alternating Frequency/Time (AFT) method for computing second-order derivatives with local-coordinate tensor transformations. By integrating this analytical Hessian into the solver, the proposed framework ensures robust convergence and significantly reduces runtime, making it practical for large-scale models where numerical differentiation is computationally prohibitive. The method is validated on three
benchmarks of increasing complexity: a two-degree-of-freedom (2-DOF) system with cubic nonlinearity, a beam with cubic stiffness or
hyperbolic tangent (tanh) friction nonlinearities, and an industrial-scale finite element model of a compressor bladed disk (blisk) with a friction ring damper. Results demonstrate that the proposed framework accurately and efficiently computes both resonance and anti-resonance backbone curves, providing a robust frequency-domain tool for structures with non-
polynomial nonlinearities.
Read the full abstract ▾
Geophysics
Theoretical constraints on tidal triggering of slow earthquakes
Yishuo Zhou, Ankit Gupta, Hideo Aochi et al. (+4 more)
Tidal stress is a globally acting perturbation driven primarily by the gravitational forces of the Moon and the Sun. Understanding how
tidal stresses can trigger seismic events is essential for constraining tectonic environments that are sensitive to small stress perturbations. Here, employing a spring-block model with rate-and-state friction, we investigate
tidal triggering on velocity-weakening stable sliding faults with stiffness slightly exceeding the critical stiffness. We first apply a step and a boxcar with finite duration normal stress perturbation to demonstrate a resonance-like amplification of slip velocity for specific boxcar durations. Next, we perform nondimensional analyses and numerical simulations with harmonic perturbations to identify the key parameters controlling
tidal triggering and their admissible ranges. Triggered slip events are further characterized using physically observable quantities, including radiation efficiency and
tidal phase. Our results show that even small stress perturbations can trigger periodic as well as temporally complex slip events on stable sliding faults. The triggering behavior is primarily controlled by the normalized perturbation period and the normalized perturbation amplitude. An increase in the normalized period shifts event timing from the peak of
tidal stress toward the peak of stress rate, whereas increasing the normalized amplitude promotes a transition from slow to fast events. This framework helps explain the period-dependent sensitivity and the observed phase preference between
tidal stress and maximum slip velocity. Comparison between observed and model-predicted
tidal correlation patterns may therefore help constrain the instantaneous frictional strength of the interface, as well as the characteristic slip distance for frictional weakening.
Read the full abstract ▾
All authors Yishuo Zhou, Ankit Gupta, Hideo Aochi, Alexandre Schubnel, Satoshi Ide, Pierpaolo Dubernet, Harsha S. Bhat
Fluid Dynamics
Purified Two-Relaxation-Time Lattice Boltzmann Method: Removing Ghost Modes from TRT for Enhanced Stability
Yuan Yu, Yaolong Yu, Yuting Zhou et al. (+3 more)
The two-relaxation-time (TRT)
lattice Boltzmann model is widely adopted for its simplicity and tunable boundary accuracy. However, its collision operator relaxes the full symmetric non-
equilibrium component, implicitly retaining non-hydrodynamic ghost modes that degrade stability at high Reynolds numbers. In this work, we establish a rigorous connection between ghost-mode filtering and regularization within the TRT framework. By decomposing the discrete velocity space into hydrodynamic and non-hydrodynamic subspaces, we prove that the TRT-regularized
lattice Boltzmann (TRT-RLB) model is mathematically equivalent to the standard TRT model with ghost modes explicitly removed. This equivalence holds exactly for D2Q9 and D3Q19
lattices, where the symmetric and antisymmetric subspaces are completely spanned by the physically relevant Hermite modes and identifiable ghost modes. Based on this finding, we propose the Purified TRT (P-TRT) model, which achieves regularization-level stability through simple algebraic ghost-mode subtraction rather than expensive tensor projections. For D2Q9, the non-
equilibrium collision cost is reduced from 180 to 52 floating-point operations per node, a 71% reduction. Linear stability analysis in moment space further reveals that the P-TRT operator annihilates the ghost
eigenvalue, proving its spectral radius is bounded above by that of standard TRT and that stability is governed exclusively by hydrodynamic modes.
Benchmarks including the double shear layer at Re up to 10^7, Taylor–Green
vortex decay, force-driven Poiseuille flow, and creeping flow past a square cylinder confirm that P-TRT preserves the stability, second-order accuracy, and zero-slip boundary properties of TRT-RLB while retaining the simplicity of the TRT family.
Read the full abstract ▾
All authors Yuan Yu, Yaolong Yu, Yuting Zhou, Siwei Chen, Haizhuan Yuan, Shi Shu
Accelerator Physics
First results from the E302 efficiency$\unicode{x2013}$instability experiment at the FACET-II facility
O. G. Finnerud, E. Adli, R. Ariniello et al. (+18 more)
The beam-breakup (BBU) instability in
plasma accelerators is seeded by a transverse offset between the driver and a trailing bunch. The BBU instability induces oscillations in the trailing bunch, which are detrimental to its beam quality. When the instability is large, assuming little mitigation from ion motion and energy spread, the beam suffers emittance growth, and charge can be kicked transversely out of the
plasma channel. The detrimental effect on beam quality is substantially worse at high efficiencies, which places constraints on the achievable power efficiency in applications such as linear
colliders, where maintaining the beam quality is required. In this paper, we present the first experimental signatures of the BBU instability in data taken in the E302 experiment at the FACET-II facility at SLAC National Accelerator Laboratory. We use a specific beam-optical setup and a novel method to probe for transverse instabilities on diagnostic screens downstream of a
magnetic dipole spectrometer. We complement the analysis with full 3D particle-in-
cell (PIC) simulations of the
plasma interaction using similar driver and trailing bunch parameters on a simulated FACET-II spectrometer.
Read the full abstract ▾
All authors O. G. Finnerud, E. Adli, R. Ariniello, S. Corde, T. N. Dalichaouch, C. Emma, S. Gessner, C. Hansel, M. J. Hogan, C. Joshi, D. Kalvik, A. Knetsch, C. A. Lindstrøm, M. Litos, N. Majernik, K. A. Marsh, B. D. O'Shea, I. Rajkovic, S. Rego, D. Storey, C. Zhang
Optics
Diffusion Schrödinger Bridges with enhanced posterior sampling for metasurface inverse design
Mathys Le Grand, Pascal Urard, Denis Rideau et al. (+5 more)
Metasurface inverse design is challenged by the intricate relationship between structural parameters and electromagnetic responses, as well as the high dimensionality of the optimization space. Local models, while commonly employed, quickly become infeasible for complex and locally coupled structures. Conventional iterative optimization techniques, on the other hand, are computationally intensive, time-consuming, and susceptible to convergence in local minima. This study explores a versatile generative methodology based on enhanced posterior sampling within the Schrödinger Bridge framework. By decomposing posterior sampling into amplitude and directional contributions, we effectively integrated different kind of posterior sampling. This approach is further supported by refined training strategies to enhance performance and reduce the complexity of hyperparameter optimization. The proposed framework demonstrates exceptional accuracy and robustness, representing a significant advancement in metasurface design. Notably, it enables high-precision inverse design for large-scale configurations of up to $350 \times 350$ pillar arrays, despite being trained on significantly smaller arrays of $23 \times 23$ pillars.
Read the full abstract ▾
All authors Mathys Le Grand, Pascal Urard, Denis Rideau, Loumi Trémas, Damien Maitre, Adam Fuchs, Louis-Henri Fernandez-Mouron, Régis Orobtchouk
Fluid Dynamics
Band-Ensemble Spectral Proper Orthogonal Decomposition with Frequency Attribution
Jakob G.R. von Saldern, Oliver T. Schmidt, Philipp Godbersen et al. (+2 more)
This study presents band-ensemble Spectral Proper Orthogonal Decomposition (bSPOD). The approach is inspired by frequency smoothing, a method used to reduce
estimator variance in power spectral density estimates, and is here extended to SPOD. The
algorithm estimates SPOD modes from consecutive
Fourier coefficients obtained from a single
Fourier transform of the full time record and thus avoids time
segmentation. In this study, bSPOD is applied to artificial test data and to a PIV data set of a broadband-tonal cavity flow. Compared to the more commonly used Welch-based SPOD formulation, bSPOD reduces spectral leakage, permits increased frequency resolution, and retains frequency information of tonal components at comparable computational cost. These features enable reduced
estimator variance while maintaining low bias for tonal components, making bSPOD particularly effective for broadband-tonal flows.
Read the full abstract ▾
All authors Jakob G.R. von Saldern, Oliver T. Schmidt, Philipp Godbersen, J. Moritz Reumschüssel, Tim Colonius
Atomic Physics
Stability, degeneracy, and scalability of a 600-site cavity array microscope
Anna Soper, Danial Shadmany, Adam L. Shaw et al. (+3 more)
Optical cavities are a foundational technology for controlling light-matter interactions. While interfacing a single cavity to either an atom or ensemble has become a standard tool, the advent of single atom control in large atomic arrays has spurred interest in a new frontier of “many-cavity QED,” featuring many independent resonators capable of separately addressing individual
quantum emitters. In this fast-evolving landscape, the cavity array microscope was recently introduced – employing free space intra-cavity optics to engineer a two-dimensional array of tightly spaced cavity TEM$_{00}$ modes with wavelength-scale waists, ideally suited for interfacing with atom arrays. Here we realize the next-generation of this architecture, achieving hundreds of degenerate cavity modes with improved, uniform finesse, and explore the technical features of the system which will enable further scalability. In particular, we study imperfections, including optical aberrations, field of view constraints, array non-degeneracies, and losses from optical elements. We identify the sensitivity to these various vectors and exposit the control knobs and techniques necessary to align and operate the system in a stable manner. Ultimately, we lay out a pathway towards operation with tens of thousands of independent cavities while maintaining compatibility with existing atom arrays, paving the way to myriad applications including highly parallelized remote
entanglement generation, fast and non-destructive mid-
circuit readout, and the implementation of hybrid atom-
photon Hamiltonians.
Read the full abstract ▾
All authors Anna Soper, Danial Shadmany, Adam L. Shaw, Lukas Palm, David I. Schuster, Jonathan Simon
Optics · Cross-listed from cond-mat.mes-hall
Optically tunable nonlinear mechanical damping in an optomechanical resonator
Hideki Arahari, Motoki Asano, Hiroshi Yamaguchi et al. (+1 more)
We theoretically propose and experimentally demonstrate optically tunable nonlinear mechanical damping in a cavity optomechanical system utilizing a partly resolved sideband regime. Optomechanical coupling provides a delayed nonlinear backaction to the mechanical modes, resulting in nonlinear mechanical damping. This optically induced nonlinear damping is observed in the frequency and time domains, and we show using both theory and experiment that it can be tuned via
laser detuning. Specifically, we observe positive nonlinear damping in the blue-detuned regime and negative nonlinear damping in the red-detuned regime. We also observe optically mediated cross-nonlinear damping between two mechanical modes: the amplitude of one mode modulates the damping of the other. The presented results show a tunable scheme of nonlinear mechanical damping that will be applicable to various non-trivial systems, governed by nonlinear, nonequilibrium, and non-Hermitian phenomena.
Read the full abstract ▾
All authors Hideki Arahari, Motoki Asano, Hiroshi Yamaguchi, Hajime Okamoto
Optics · Cross-listed from astro-ph.IM
Joint optical-digital design strategy for adaptive optics systems: application to wavelength selection for satellite imaging
Florian Cheyssial, Laurent Mugnier and Cyril Petit
Adaptive optics can be used to mitigate the effects of atmospheric
turbulence on imaging systems, but the correction is only partial, and deconvolution is often required to improve the resolution. This results in entire optical/digital systems, which are traditionally designed sequentially, i.e. , the adaptive optics system is optimised first, and the restoration
algorithms are designed a second time. Studies on optical/digital systems have shown that jointly optimizing the whole system is a better alternative. We propose to extend these co-design strategies to the design of an adaptive optics-assisted imaging system. We derive a simple criterion that takes into account the source properties and the entire optical/ digital system performance. To illustrate its interest, we use it to optimize the wavelength distribution between the wavefront sensor and the imaging camera. In addition, we explore the potential of using multiple imaging channels operating at different wavelengths as a means of making an imaging system robust to
turbulence strength and source magnitude variations. Later, any parameter of the optical/digital system, if not the entire system itself, could be optimized this way.
Read the full abstract ▾
Atomic Physics
Ab initio calculations of the electronic structure of Ac$^+$
Genevieve Geehan, Marten Luit Reitsma, Johan David Polet et al. (+3 more)
Accurate spectroscopic investigations of the heaviest elements are inherently challenging, due to their short lifetimes and low production yields. Success of such measurements requires both dedicated experimental techniques and strong theoretical support.
Laser resonance chromatography (LRC) is a promising approach for heavy ion spectroscopy, in particularly for metals with low vapour pressure, such as actinium. We have employed the state-of-the-art relativistic Fock space coupled cluster approach as well as the configuration interaction with many-body perturbation theory method to calculate the energy levels, the transition amplitudes, the branching ratios, and the hyperfine structure parameters of the lowest excited states in Ac+. Knowledge of these properties is required for the design of experiments. Our calculations are in close agreement with experimental transition energies, leading us to expect a similar level of accuracy for the calculated hyperfine structure parameters. Based on these predictions, two possible experimental schemes are proposed for the planned LRC measurements.
Read the full abstract ▾
All authors Genevieve Geehan, Marten Luit Reitsma, Johan David Polet, Mustapha Laatiaoui, Julian Berengut, Anastasia Borschevsky
Physics and Society
Smart On-Street Parking: Survey of Actual Implementations in Cities and Insights from Practitioners
Enock Ndunda and Alexandre Nicolas
Smart solutions for on-street parking, which collect and leverage real-time information about on-street parking space availability to guide drivers or adjust policies, have attracted considerable
attention in academia and in the corporate world, but comprehensive feedback on actual implementations was still missing. Here, we survey around 25 smart parking (SP) implementations in cities across the world using online sources. To get more candid insights, we complement this objective review with case studies centred around interviews that we conducted with practitioners from ten cities across continents (San Francisco, Saint Pete Beach, Penang, Douala, Soissons, Grand Paris Seine Ouest, Montpellier, Frauenfeld, Zurich, Perth). Summing up our observations, we underline the broad diversity of SP implementations in terms of contexts and scales, from 2-to-3-year small-scale pilot studies to large deployments that take centre stage in a city's mobility policy. Technological choices also vary widely, from the ground sensors used in pioneering deployments in the early 2010s and still in use, to static cameras (which cover more spaces per device), and to mobile cameras with automatic licence-plate recognition embarked in roaming cars, a more and more popular solution for parking control. Different attitudes to the role given to smartphone applications are also noticed. But, importantly, not only means, but also goals differ: facilitating parking control and enhancing revenue, or providing data for a curb-pricing strategy, or feeding live data into
navigation algorithms to reduce parking search times. Unfortunately, their level of achievement is seldom gauged with robust metrics. Hardware durability issues are mentioned as causes of premature termination, particularly for `first-generation' ground sensors, but so, too, are fluctuating political will and changing priorities. Smaller-scale, geographically isolated implementations and pilots are particularly vulnerable to these fluctuations, to discontinued funding or defaulting start-ups, and to limited public awareness.
Read the full abstract ▾
Physics and Society · Cross-listed from cond-mat.stat-mech
Tensor network dynamical message passing for epidemic models
Cheng Ye, Zi-Song Shen and Pan Zhang
While epidemiological modeling is pivotal for informing public health strategies, a fundamental trade-off limits its predictive fidelity: exact
stochastic simulations are often computationally intractable for large-scale systems, whereas efficient analytical approximations typically fail to account for essential short-range correlations and network loops. Here, we resolve this trade-off by introducing Tensor Network Dynamical Message Passing (TNDMP), a framework grounded in a rigorous property we term Susceptible-Induced Factorization. This theoretical insight reveals that a susceptible node acts as a dynamical decoupler, factorizing the global
evolution operator into localized components. Leveraging this, TNDMP provides a dual-mode algorithmic suite: an exact
algorithm that computes local observables with minimal redundancy on tractable
topologies and a scalable and tunable approximation for complex real-world networks. We demonstrate that widely adopted heuristics, such as Dynamical Message Passing (DMP) and Pair Approximation (PA), are mathematically recoverable as low-order limits of our framework. Numerical validation in synthetic and real-world networks confirms that TNDMP significantly outperforms existing methods to predict epidemic thresholds and steady states, offering a rigorous bridge between the efficiency of message passing and the accuracy of tensor network formalisms.
Read the full abstract ▾
Computational Physics · Cross-listed from astro-ph.IM
A Demonstration of a Neural Network as a Bridge Between Galaxy Simulations and Surveys
E. Elson
This paper demonstrates that the
stellar masses of
galaxies in the
Galaxy and Mass Assembly (GAMA) survey, originally derived via
stellar population synthesis modelling, can be accurately predicted using only their absolute magnitudes and colour indices. A central contribution of this work is the demonstration that this long-standing inference problem can be solved using an exceptionally simple machine-learning model: a fully connected, feed-forward artificial neural network with a single hidden layer. The network is trained exclusively on synthetic
galaxies generated by the SHARK semi-analytic model and is shown to transfer effectively to real observations. Across nearly 3.5 dex in
stellar mass, the predicted values closely track the GAMA SED-derived masses, with a typical scatter of ~0.131 dex. These results demonstrate that complex deep-learning architectures are not a prerequisite for robust
stellar mass estimation, and that simulation-trained, lightweight machine-learning models can capture the dominant physical information encoded in broad-band photometry. The method is further applied to 17,006 GAMA
galaxies lacking SED-derived masses, with photometric uncertainties propagated through the network to provide corresponding error estimates on the inferred
stellar masses. Overall, this work establishes a computationally efficient and conceptually transparent pathway for simulation-to-observation transfer learning in
galaxy evolution studies.
Read the full abstract ▾
Accelerator Physics · Cross-listed from nlin.AO
Synchronization of Synchrotron Radiation Bursts during a spatio-temporal Instability in accelerator-Based source
C. Evain, A.-A. Diallo, E. Roussel et al. (+9 more)
Synchronization is a fundamental phenomenon in dynamical systems, occurring in a wide range of contexts such as mechanical, chemical, biological, and social systems. In this work, we explore a novel manifestation of synchronization in accelerator-based light sources, specifically in storage rings where relativistic electron bunches circulate and emit synchrotron radiation, used for user experiments. In such systems, a systematic spatio-temporal instability arises when the bunch contains a large number of electrons. This instability is characterized by the spontaneous formation of microstructures within the bunch, which appear with a bursting behavior. We demonstrate that these bursting events can be synchronized with an external sinusoidal signal by modulating the electric field in a radiofrequency (RF) cavity. This external modulation induces typical synchronization features such as Arnold tongues at fundamental, harmonic, and subharmonic frequencies of the natural bursting rate, as well as phase-slip phenomena near the synchronization threshold. The synchronization mechanism is analyzed using numerical simulations based on the Vlasov-Fokker-Planck equation, and a proof-of-principle experiment is conducted at the SOLEIL synchrotron facility.
Read the full abstract ▾
All authors C. Evain, A.-A. Diallo, E. Roussel, C. Szwaj, M. Herda, M.-A. Tordeux, F. Ribeiro, M. Labat, N. Hubert, J.-B. Brubach, P. Roy, S. Bielawski
Fluid Dynamics
On large-scale wind-drift ocean currents: An asymptotic approach in spherical coordinates
Christian Puntini, Luigi Roberti and Eduard Stefanescu
Starting from the Navier–Stokes equations in rotating spherical coordinates with depth-varying density and eddy viscosity, we derive an asymptotic model describing non-equatorial wind-generated ocean drift currents. Our approach allows for large-scale flows that cannot be captured by classical tangent-plane approximations. The strategy is to perform a careful scaling and to perform a double asymptotic expansion with respect to two small parameters arising from the scaling: the Rossby number and the ratio between the Ekman depth and the Earth's radius. We obtain a system of linear ordinary differential equations with nonlinear boundary conditions governing the leading-order dynamics, highlighting that the dynamics is governed by the linear terms, whereas the nonlinear ones, related to the injection and dissipation of kinetic energy, appear only at higher order. We use the leading-order equations to compare our model with the simplest theory of ocean circulation due to Sverdrup and note that, even at this level of simplification, our equations have the potential to provide deeper insight. Subsequently, focusing on Ekman flows, we prove existence and uniqueness of the leading-order solution, which retains the classical Ekman spiral structure for arbitrary eddy viscosity profiles. Finally, we compute the surface deflection angle of the wind-driven current for three explicit eddy viscosity profiles, obtaining results consistent with observations. In addition, we derive the governing equations for the first-order correction with respect to the Rossby number and provide a priori bounds for its solution.
Read the full abstract ▾
Data Analysis and Statistics · Cross-listed from cond-mat.stat-mech
Relativity of Observation: Operational Intensive Variables in Nonequilibrium Thermodynamics
Akihisa Ichiki
We formulate nonequilibrium thermodynamics in which intensive variables acquire operational meaning through measurement protocols consistent with local reciprocity. Using physical
equilibrium as a reference, conjugate observables are constructed by continuously adjusting devices along the local tangent space of the statistical
manifold. In this relativity of observation, Onsager reciprocity holds locally, allowing inference-based Lagrange multipliers to be directly measured. This provides a systematic method to extend operational definitions of intensive variables to nonequilibrium states, highlighting their context-dependent nature and offering a concrete experimental strategy.
Read the full abstract ▾
Optics
Burst-mode fs-laser direct writing for full-thickness oxidation of Ta thin films
Lina Grineviciute, Hsin-Hui Huang, Haoran Mu et al. (+5 more)
Direct fs-
laser (1030~nm/200~fs) write of a throughout
oxide Ta$_{2}$O$_{5}$ on a 200~nm Ta film was achieved using a combined ps- and ns- burst mode (Burst-in-Burst or BiB) of fs-pulse exposure at a high 0.6~MHz repetition rate. Few micrometers-wide lines were formed at the center of 12~$\mu$m focal spot by controlled oxidation without ablation. The oxidized regions were flat and optically transparent. Wavelength-scale self-organized ripples of oxidized Ta$_{2}$O$_{5}$ sub-1~$\mu$m gratings were recorded by rastering a $1\times 1$~mm$^2$ area. The oxidized ripples with periodic pattern $\sim wavelength$ were aligned with the polarization of the writing beam. Energy deposition in the burst-mode oxidation is discussed by comparing 200~fs and 20~ps BiB-mode writing modes. The presented strategy of self-guided oxidation with heat deposition by BiB fs-
laser opens an opportunity for debris-free and annealing-free oxidation on a sub-wavelength scale.
Read the full abstract ▾
All authors Lina Grineviciute, Hsin-Hui Huang, Haoran Mu, Nguyen Hoai An Le, Andrew Siao Ming Ang, Dan Kapsaskis, Tomas Katkus, Saulius Juodkazis
Optics
Broadband Continuous Frequency Tuning in Non-Hermitian Laser Arrays Enabled by Mode-Switching Boundary Topology
Chuanfeng Yan, Cheng Tan, Kai Wang et al. (+6 more)
Broadband and continuous frequency tuning is central to the versatility of
semiconductor lasers, yet existing approaches typically rely on external moving components, limiting scalability and integration. Here we demonstrate broadband continuous frequency tuning in a non-Hermitian
laser array achieved solely by controlling the pump currents. We show that in two coupled sub-
lasers with frequency detuning ($\Delta\omega$) and relative loss ($\Delta\alpha$), a mode-switching boundary emerges in the ($\Delta\omega$, $\Delta\alpha$) parameter space, shaping the frequency landscape of the lower-loss supermode. The
topology of this boundary comprises pseudo-symmetric (PS) and pseudo-
symmetry-broken (PSB) branches connected at an exceptional point (EP). When tuning trajectories cross the PS branch, frequency tuning is discontinuous, whereas trajectories crossing the PSB branch enable continuous tuning; trajectories through the EP yield the maximum continuous tuning range. Experiments using two coupled terahertz
quantum cascade
lasers demonstrate continuous tuning over 10 GHz, enabled by arbitrarily many combinations of pump currents. Extending this approach to a multi-element array further expands the continuous tuning range to 163 GHz. These results establish a general route to broadband continuous tuning in moving-part-free
semiconductor lasers and highlight the potential for dynamic
eigenvalue engineering in non-Hermitian photonics and beyond.
Read the full abstract ▾
All authors Chuanfeng Yan, Cheng Tan, Kai Wang, Hongzhou Bai, Shanhai Gao, Lianghua Gan, Yueheng Zhang, Qijie Wang, Gangyi Xu
Physics and Society
An attention economy model of co-evolution between content quality and audience selectivity
Masaki Chujyo, Isamu Okada, Hitoshi Yamamoto et al. (+2 more)
Human
attention has become a scarce and strategically contested resource in digital environments. Content providers increasingly engage in excessive competition for visibility, often prioritizing
attention-grabbing tactics over substantive quality. Despite extensive empirical evidence, however, there is a lack of theoretical models that explain the fundamental dynamics of the
attention economy. Here, we develop a minimal mathematical framework to explain how content quality and audience
attention coevolve under limited
attention capacity. Using an evolutionary game approach, we model strategic feedback between providers, who decide how much effort to invest in production, and consumers, who choose whether to search selectively for high-quality content or to engage passively. Analytical and numerical results reveal three characteristic regimes of content dynamics: collapse, boundary, and coexistence. The transitions between these regimes depend on how effectively audiences can distinguish content quality. When audience discriminability is weak, both selective
attention and high-quality production vanish, leading to informational collapse. When discriminability is sufficient and incentives are well aligned, high- and low-quality content dynamically coexist through feedback between audience selectivity and providers' effort. These findings identify two key conditions for sustaining a healthy information ecosystem: adequate discriminability among audiences and sufficient incentives for high-effort creation. The model provides a theoretical foundation for understanding how institutional and platform designs can prevent the degradation of content quality in the
attention economy.
Read the full abstract ▾
All authors Masaki Chujyo, Isamu Okada, Hitoshi Yamamoto, Dongwoo Lim, Fujio Toriumi
Physics and Society
Impact of seed node position on network robustness under localized attacks
Masaki Chujyo, Shu Liu and Fujio Toriumi
Localized attacks (LAs), where damage propagates from a single seed node to its neighbors, pose significant threats to the robustness of complex networks. Although previous studies have extensively analyzed network vulnerability under such attacks, they typically assume random seed node placement and evaluate average robustness. However, the structural position of the seed node can significantly impact the extent of damage. This study proposes the Localized Attack Vulnerability Index (LAVI), a node-level metric that quantifies the potential impact of a LA initiated at a specific node. LAVI quantifies the cumulative number of severed links during attack progression, capturing how local connectivity and topological position amplify the resulting damage. Numerical experiments on synthetic and real-world networks demonstrate that LAVI correlates more strongly with network robustness degradation than standard centrality measures, such as degree, closeness, and betweenness. Our findings highlight that classical centrality metrics fail to capture key dynamics of spatially localized failures, while LAVI provides an accurate and generalizable indicator of node vulnerability under such disruptions.
Read the full abstract ▾
Geophysics · Cross-listed from cs.LG
Reclaiming First Principles: A Differentiable Framework for Conceptual Hydrologic Models
Jasper A. Vrugt, Jonathan M. Frame and Ethan Bollman
Conceptual hydrologic models remain the cornerstone of rainfall-runoff modeling, yet their calibration is often slow and numerically fragile. Most gradient-based parameter estimation methods rely on finite-difference approximations or automatic differentiation frameworks (e.g., JAX, PyTorch and TensorFlow), which are computationally demanding and introduce truncation errors, solver instabilities, and substantial overhead. These limitations are particularly acute for the ODE systems of conceptual watershed models. Here we introduce a fully analytic and computationally efficient framework for differentiable hydrologic modeling based on exact parameter sensitivities. By augmenting the governing ODE system with sensitivity equations, we jointly evolve the model states and the Jacobian
matrix with respect to all parameters. This Jacobian then provides fully analytic gradient vectors for any differentiable loss function. These include classical objective functions such as the sum of absolute and squared residuals, widely used hydrologic performance metrics such as the Nash-Sutcliffe and Kling-Gupta efficiencies, robust loss functions that down-weight extreme events, and hydrograph-based functionals such as flow-duration and recession curves. The analytic sensitivities eliminate the step-size dependence and noise inherent to numerical differentiation, while avoiding the instability of adjoint methods and the overhead of modern machine-learning autodiff toolchains. The resulting gradients are deterministic, physically interpretable, and straightforward to embed in gradient-based optimizers. Overall, this work enables rapid, stable, and transparent gradient-based calibration of conceptual hydrologic models, unlocking the full potential of differentiable modeling without reliance on external, opaque, or CPU-intensive automatic-differentiation libraries.
Read the full abstract ▾
Fluid Dynamics · Cross-listed from cond-mat.soft
Interfacial dynamics induced by impacts across rigid and soft substrates
Ishin Kikuchi, Hiroya Watanabe, Yuto Yokoyama et al. (+2 more)
We investigate impact-induced gas-
liquid interfacial dynamics through experiments in which a
liquid-filled container impacts substrates with elastic
moduli from $O(10^{-1})$ MPa to $O(10^{5})$ MPa. Upon impact, the concave gas-
liquid interface inside the container deforms and emits a focused jet. When the jet velocity is normalized by the container impact velocity, all data collapse onto a single curve when plotted against the Cauchy number, $Ca = \rho_{\rm e} V_{\rm i}^2 / E$, which represents the ratio of the inertial force of the container-
liquid system to the elastic restoring force of the substrate. The dimensionless jet velocity remains nearly constant for $Ca< 10^{-4}$, but decreases significantly for $Ca > 10^{-4}$. Based on this observation, we define the boundary between the rigid-impact and soft-impact regimes using the Cauchy number, providing a quantitative criterion for what constitutes “softness” in impact-driven interfacial flows. To explain the reduction in jet velocity observed in the soft-impact regime, we introduce a framework in which only the impulse transferred within the effective time window for jet formation contributes to interface acceleration. This concept, referred to as the partial impulse, captures the situation where the impact interval (the duration of contact between the container and the substrate) exceeds the focusing interval (the time required for jet formation). By modelling the contact force using an elastic foundation model and solving the resulting momentum equation over the finite impulse window, we quantitatively reproduce the experimental results. This partial impulse framework unifies the dynamics of impact-driven jetting across both rigid and soft substrate regimes, extending the applicability of classical impulse-based models.
Read the full abstract ▾
All authors Ishin Kikuchi, Hiroya Watanabe, Yuto Yokoyama, Hiroaki Kusuno, Yoshiyuki Tagawa
Optics · Cross-listed from quant-ph
Lunar Silicon Cavity
Jun Ye, Zoey Z. Hu, Ben Lewis et al. (+5 more)
The Moon's permanently shadowed regions (PSRs) are among the coldest places in the
Solar System and are expected to become key landing sites for upcoming international space agency missions. Their proximity to peaks of perpetual
solar power and potential resource richness makes them
prime candidates for lunar exploration and future Moon bases. Here we propose to deploy a passive, ultrastable optical resonator in these regions that will enable
laser systems with unprecedented phase-coherence. The unique physical environment of lunar PSRs greatly benefits the construction of a cryogenic monolithic silicon cavity that exhibits low $10^{-18}$ thermal noise-limited stability and coherence time exceeding 1 minute, more than a decade better than the current best terrestrial system. Such a stable
laser will form an enabling infrastructure for
quantum technology in space to serve many applications, including establishing a lunar time standard, building long-baseline optical interferometry, distribution of stable optical signals across networks of satellites, testing general relativity and gravitational physics, and forming the backbone for space-based
quantum networks.
Read the full abstract ▾
All authors Jun Ye, Zoey Z. Hu, Ben Lewis, Wei Zhang, Fritz Riehle, Uwe Sterr, Yiqi Ni, Julian Struck
Fluid Dynamics
Validation of a high-order finite difference compressible solver
Yujoo Kang and Sang Lee
The verification and validation of a high-order compressible in-house solver based on a compact finite difference scheme are presented. Validation is performed using five canonical cases: the one-dimensional Sod shock tube problem, two-dimensional shock-shear layer interaction, compressible channel flow, compressible turbulent boundary layer, and shock-turbulent boundary layer interaction. Comparisons against exact solutions and reference direct numerical simulation data demonstrate accurate shock capturing, resolution of vortical structures, and good agreement for first and second order statistics.
Read the full abstract ▾
Physics and Society
Mean-Field Theory for Heider Balance under Heterogeneous Social Temperatures
Zhen Li and Yuki Izumida
Heider balance theory provides a fundamental framework for understanding the formation of friendly and hostile relations in social networks. Existing
stochastic formulations typically assume a uniform social temperature, implying that all interpersonal relations fluctuate with the same intensity. However, studies show that social interactions are highly heterogeneous, with broad variability in stability,
volatility, and susceptibility to change. In this work, we introduce a generalized Heider balance model on a complete graph in which each link is assigned its own social temperature. Within a mean-field formulation, we derive a distribution-dependent self-consistency condition for the collective opinion state and identify the criteria governing the transition between polarized and non-polarized configurations. This framework reveals how the entire distribution of interaction heterogeneity shapes the macroscopic behavior of the system. We show that the functional form of the inverse-temperature distribution, in particular whether it is light-tailed or heavy-tailed, leads to qualitatively distinct phase diagrams. We also establish universal bounds for the critical transition, where the homogeneous-temperature limit provides a universal lower bound for the critical mean of an inverse-temperature distribution governing the transition. Numerical simulations confirm the theoretical predictions and highlight the nontrivial effects introduced by heterogeneity. Our results provide a unified route to understanding structural balance in realistic social systems and lay the groundwork for extensions incorporating fluctuations beyond mean field, external fields, and network
topologies beyond the complete graph.
Read the full abstract ▾
Applied Physics
Shallow Trap States Control Electrical Performance of Amorphous Oxide Semiconductor Thin-Film Transistors
Måns J. Mattsson, Jinhan Lee, Christopher E. Malmberg et al. (+10 more)
The performance of n-type amorphous
oxide semiconductor thin-film transistors (TFTs) is largely controlled by the density of states (DoS) near the conduction band mobility edge. Here, the full subgap DoS of amorphous InGaZnO (a-IGZO) TFTs, used in display panels and dynamic random-access
memory (DRAM) development, is measured by ultrabroadband photoconduction (UP-DoS) microscopy to within 0.1 eV of the mobility edge. The measured subgap DoS for 25 TFT processing conditions accurately predicts each transfer curve, showing how shallow defect states are electron traps that rigidly tune subthreshold swing, threshold voltage and drift mobility. For a set of TFTs, the subthreshold transfer characteristics can be independently simulated from the experimental shallow defect DoS, with no adjustable parameters. The full transfer curve is simulated by introducing a single parameter: the conduction band tail energy. Additionally, the simulation reveals that the shallow trap density controlling subthreshold behavior can be directly extracted from transfer curves. Finally, a systematic In-enrichment study, combined with DFT+U DoS simulations, enables identification of vacancy cation coordination environments for all experimentally observed subgap peaks. The dominant trap controlling conventional a-IGZO TFT performance is centered at ~0.32 eV below the conduction band mobility edge and is assigned to a Ga-Ga-In oxygen vacancy defect.
Read the full abstract ▾
All authors Måns J. Mattsson, Jinhan Lee, Christopher E. Malmberg, Jared Parker, Kyle T. Vogt, Hyemi Kim, Minji Hong, Pilsang Yun, Daewon Ha, Taeyoon Lee, Paul H.-Y. Cheong, John F. Wager, Matt W. Graham
Optics
Direct laser writing of high aspect ratio nanochannels for nanofluidics
Stoffel D. Janssens, Meissha Ayu Ardini, David Vázquez-Cortés et al. (+2 more)
Nanochannels with high width-to-height aspect ratios are desirable for many applications, particularly those requiring optical access, but remain challenging to fabricate. In this work, the direct
laser writing of such channels between diamond films and glass substrates is introduced. As previously reported,
laser light can transform a portion of diamond film into a nanostrip. The strip induces delamination of the surrounding film, causing the formation of two nanochannels with triangular cross-sections. Here, it is demonstrated that nanochannels with rectangular cross-sections and width-to-height aspect ratios exceeding fifty can form between pairs of nanostrips. With atomic force microscopy, the maximum strip spacing that produces these nanochannels is investigated, and it is demonstrated that the reflectance of the channels can be measured by microspectrophotometry. The microstructure of the nanochannels, including nanostrips, and processes that occur during
laser writing are inferred from transmission electron microscopy and electron energy loss spectroscopy. By fabricating a nanofluidic device and using microspectrophotometry, it is found that the nanochannels fill with water through capillary action, are resistant to clogging, and are mechanically stable against water filling. A versatile platform for producing high-aspect-ratio nanochannels that are optically accessible and fluidically functional is presented, thereby expanding opportunities for advanced applications.
Read the full abstract ▾
All authors Stoffel D. Janssens, Meissha Ayu Ardini, David Vázquez-Cortés, Cathal Cassidy, Eliot Fried
Fluid Dynamics
Comparison of inviscid and viscous vortex shedding from translating and rotating plates
Yu Jun Loo and Silas Alben
We compare an inviscid
vortex sheet model with continuous leading-edge shedding with direct Navier-Stokes simulations over a wide range of unsteady plate motions at moderate Reynolds number ($\mathrm{Re} \approx 1000$). Approximately $70$ distinct kinematic configurations are examined, spanning both body-dominated and flow-dominated regimes. In body-dominated motions, where the fluid dynamics are primarily driven by prescribed plate accelerations, the inviscid model accurately reproduces normal force histories and the qualitative structure of the induced vorticity field. In flow-dominated configurations, with quasi-periodic
vortex shedding, agreement with force predictions is good but reduced at low angles of attack, reflecting the greater sensitivity of
vortex shedding dynamics to physical and computational parameters. The ability of the present formulation to accommodate stable, continuous leading-edge
vortex shedding enables uniform comparisons across diverse motions and clarifies the regimes in which inviscid
vortex sheet models can be used reliably for force prediction and physical interpretation.
Read the full abstract ▾