Applied Physics · Cross-listed from nlin.CD
Global continuation as a complement to traditional continuation and bifurcation analysis
George Datseris, Andreas Morr, Muhammed Fadera et al. (+1 more)
Multistable dynamical systems are ever-prevalent, used to model for example ecosystems, power grids,
climate elements,
neurons, and more. When perturbed, such systems may “tip” from one state of operation to another, often with abrupt, irreversible, and high-impact consequences in each context. Traditionally, these systems are analysed via bifurcation diagrams, the result of a process we refer to as local continuation, as it only captures the linear (local) system response to infinitesimal perturbations. Local continuation requires substantial expertise, constant interventions, and may yield inaccurate assessment of the system's response to large perturbations that is crucial for tipping analysis. To address some inherent challenges of local continuation and to provide fundamentally new information during a continuation, this paper introduces global continuation as a complement suitable for the study of multistability, critical transitions and real-world-oriented applications. Global continuation finds and continues in parallel (practically) all system attractors and their response to finite perturbations by synthesising information from the whole state space, while placing a focus on the qualities or observables of a dynamical system that the practitioner cares about in context. Global continuation does not require deep expertise and is effortless to use and troubleshoot, making it attractive to applied scientists from different disciplines. We highlight several unique advantages that allow global continuation to complement the status quo and exemplify them through a plethora of representative examples. Global continuation is also implemented as open source software in DynamicalSystems.jl, enhancing its accessibility.
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All authors George Datseris, Andreas Morr, Muhammed Fadera, Juergen Kurths
Optics
Optical Fourier Surfaces for Free-Space Computer-Generated Holography
Y. M. Glauser, C.-Y. Shen, D. B. Seda et al. (+10 more)
Computer-generated holography can shape electromagnetic fields by encoding wavefront information in nanostructured surfaces. However, despite significant progress, hologram designs for visible and near-infrared wavelengths remain largely limited by fabrication constraints. Most implementations rely on lithographic methods that produce discretized surfaces that do not match the wave nature of light. Further advances would benefit from accurate continuous (grayscale) control of interfacial profiles, which would allow straightforward design principles from
Fourier optics to be applied. In this work, we introduce optical
Fourier surfaces as a versatile, intuitive platform for free-space computer-generated holograms. Exploiting these arbitrarily wavy surfaces, we demonstrate three different design strategies for computer-generated holography. First, we use an analytical linear design approach based on sinusoidal lenses and gratings as fundamental
holographic building blocks. Second, we enhance diffraction efficiencies through an iterative
Fourier-transform
algorithm. Finally, we extend our framework with machine-learning-based inverse design, creating wavelength-multiplexed holograms that reconstruct distinct diffraction responses in a predefined image plane. Our results combine advanced thermal scanning-probe lithography with flexible design strategies to create useful structures for photonic applications, particularly in settings where rapid prototyping is crucial.
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All authors Y. M. Glauser, C.-Y. Shen, D. B. Seda, Ç. Işil, P. Benito Eberhard, H. Niese, J. G. Crimmann, D. Petter, G. Nagamine, S. J. W. Vonk, N. Lassaline, A. Ozcan, D. J. Norris
Optics
Universal Neural Network Based Calibration and Control of Programmable Classical and Quantum Photonic Integrated Processors
José Roberto Rausell-Campo, Daniele Melati, Bhavin Shastri et al. (+2 more)
Efficient calibration and control of programmable photonic integrated
circuits are fundamental for scaling
quantum and classical optical computing processors. While neural network-based models offer an architecture-agnostic solution, existing approaches suffer from limited learning and generalization capabilities due to the many-to-one mapping problem between sets of control signals and optical responses, and biased training
datasets derived from uniform current sampling. In this work, we propose a universal calibration and control framework employing tandem neural networks combined with two novel data generation strategies: architecture-aware sampling based on Haar measure principles, and optimized sampling, a physics-agnostic approach utilizing differential
evolution. We experimentally validate these methods on 3x3 and 4x4 coherent MZI meshes, demonstrating that our approach addresses the sampling bias inherent in previous works. When evaluated using random
unitary matrices, our solution outperforms standard uniform sampling baselines by ~2 bits of precision. Furthermore, we experimentally extend the application of this framework to coherent detection, achieving precise control over both amplitude and phase, and validate its impact on photonic neural network tasks.
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All authors José Roberto Rausell-Campo, Daniele Melati, Bhavin Shastri, Daniel Pérez-López, José Capmany Francoy
Optics
Co-design approach to aperture masking for imaging through atmospheric turbulence
Olivier Herscovici-Schiller, Laurent M. Mugnier, Alice Fontbonne et al. (+5 more)
Aperture masking interferometry is a technique originally designed to alleviate the influence of atmospheric
turbulence on images recorded on ground-based
telescopes. In this communication, we explore the optimization of the aperture mask by an optical/digital co-design approach in order to obtain diffraction-limited images of relatively bright objects imaged through
turbulence. We show that, with a few simplifying assumptions, it is possible to express the Mean Square Error of the restored image as a function of the chosen mask, of the spatial Power Spectral Density of the observed object and of the noise level, without actually computing any image. This allows us to optimize the aperture mask with a reduced computing cost. We also implement a multi-frame myopic
algorithm to estimate jointly the observed object, the piston and the tip-tilt in front of each sub-aperture, and check by simulations that the aperture masks obtained indeed allow a satisfactory image reconstruction.
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All authors Olivier Herscovici-Schiller, Laurent M. Mugnier, Alice Fontbonne, Pauline Trouvé-Peloux, Frédéric Champagnat, Yann Lucas, Yann Lai-Tim, Frédéric Cassaing
Accelerator Physics
Weak-Strong Steady-State Microbunching Accelerator Light Source
Xiujie Deng, Alexander Wu Chao, Wenhui Huang et al. (+3 more)
We propose a phase space manipulation involving one energy modulation sandwiched by two dispersion sections which converts a bunched particle beam or bunch train to ultra-high-harmonic density modulation, while the energy modulation in principle can be arbitrarily weak. The same scheme can also be used for energy bunching, creating energy levels in a bunched beam. We further propose a mechanism invoking three
laser modulators in a storage ring to longitudinally focus the electron beam both weakly and strongly, such that a microbunch train and its high-density-harmonics or energy bunching form and sustain turn-by-turn. We call this mechanism weak-strong steady-state microbunching (Weak-Strong SSMB). The longitudinal beta function can vary by seven orders of magnitude along such a ring, with the minimal value squeezed to 10 nm. An example application of Weak-Strong SSMB for kW coherent EUV radiation is presented. Extension to X-ray can be anticipated. An energy-leveled electron beam enables $\gamma$-ray frequency comb production. The ideas can be scaled to wavelengths like RF and THz, for bunch length and energy spread control, ultrashort X-ray and coherent THz generation. Our work establishes a new paradigm for longitudinal dynamics study, accelerator light source development, and opens great potential for accelerator physics and technology.
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All authors Xiujie Deng, Alexander Wu Chao, Wenhui Huang, Zhilong Pan, Chuanxiang Tang, Jingyuan Zhao
Fluid Dynamics
Coherence does not always imply causality in wall-bounded turbulence
Peng E S Chen and Javier Jimenez
Compact structures of intense tangential Reynolds stress (Q events) are well-known components of wall-bounded
turbulence, and have been shown to be coherent because they approximately govern their own
evolution. It has therefore often been assumed that they also are causally significant, in the sense that they explain the
evolution of the incoherent component of the flow, which could thus be modeled as a superposition of structures. Since strong events typically only fill a small percentage of the total flow volume, this is also cited as a reason for considering structures as targets for efficient engineering flow control. This paper shows that the causality assumption does not hold in general. Only about half of the structures identified in the flow are causally more significant than an equivalent volume of incoherent
turbulence. To explain this variability, feature-based analysis and conditional averaging are performed. For wall-attached Q2 events and wall-detached structures, causally enhanced events are characterized by elevated strain rate and spanwise vorticity. These signatures are traced to intense upstream strain regions generated by the interaction of Q4-like motions impinging on Q2 events. For wall-attached Q4 events, the dominant indicators are instead the wall-normal and streamwise vorticity components; enhanced causal significance is associated with strong wall-normal vorticity. These findings show that quadrant events cannot be treated as a dynamically homogeneous class in causal analyses. Their causal significance depends strongly on the local flow environment, emphasizing the need to interpret coherent structures in terms of their interactions with the surrounding
turbulence.
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Chemical Physics
Serially Improved GTOs for Molecular Applications (SIGMA): basis sets from monovalent ions
Ignacio Ema, Guillermo Ramirez, Rafael Lopez et al. (+1 more)
A new family of ionic basis sets, denoted i{\sigma}XZ1, is presented for molecular calculations on systems containing monovalent ions. The basis sets extend the SIGMA family by explicitly accounting for the different electronic structure of cations and anions. Auxiliary basis sets for resolution-of-the-identity calculations are also developed for the Coulomb term. The performance of the proposed basis sets is assessed for alkali-halide clusters. Compared with conventional basis sets, i{\sigma}XZ1 provides an accurate description of structural, energetic, and electronic properties while showing remarkable robustness against near-linear dependencies, allowing stable calculations on systems containing up to 792 NaCl units. These features make the i{\sigma}XZ1 family a reliable and efficient alternative for large-scale calculations on ionic systems.
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All authors Ignacio Ema, Guillermo Ramirez, Rafael Lopez, Jose Manuel Garcia-de-la-Vega
Plasma Physics
Tens of MeV, collimated, bright fluxes of protons from ordered nano-structured targets in ultra-relativistic laser-matter interaction
Sagar Dam, Stefania Ionescu, Jian Fuh Ong et al. (+20 more)
Laser-driven
proton acceleration from nanostructured solid targets has been extensively studied, yet its performance under realistic temporal contrast conditions at petawatt-class facilities remains an open question. We present an experimental investigation of
proton generation from nanostructured and flat solid targets performed at the ELI-NP facility using femtosecond
laser pulses at peak intensities of $\sim 3\times10^{21}$ \wcm.
Proton spectra are compared for two contrast regimes: $\sim 10^{-10}$ without
plasma mirror and $\sim 10^{-13}$ with single
plasma mirror. Importantly, measurable enhancement in the cutoff energy persists for the nanowire targets at both contrast levels, indicating robustness of nanowire targets against moderate pre-pulse intensities. Alongside, study of energy resolved angular distribution reveals that nanowires promote more directional emission with higher flux of high-energy
protons along the target normal, while flat targets produce broader angular distributions. The results are well supported and explained by 3D particle-in-
cell simulations.
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All authors Sagar Dam, Stefania Ionescu, Jian Fuh Ong, Ameya Parab, Sk Rakeeb, Hideaki Habara, Gabriel Cojocaru, Vojtěch Horný, Dmitrii Nistor, Saidbek Norbaev, Rudrajyoti Palit, Daniel Popa, Deepak Sangwan, Klaus Spohr, Bianca Stan, Antonia Toma, Lucian Tudor, Daniel Ursescu, Adrian Vatcu, Keita Yamanaka, Prashant Kumar Singh, Kazuo A. Tanaka, G. Ravindra Kumar
Instrumentation and Detectors
Energy, time, and position resolution measurements of an array of large tapered LYSO crystals
O. Beesley, J. Carlton, D. Ding et al. (+19 more)
We report on the performance of six custom-made tapered LYSO
crystals of unprecedented volume, which constitute a sector of the 19 radiation length electromagnetic calorimeter planned for the PIONEER experiment. The longitudinal response uniformity of each
crystal was measured using radioactive sources before characterizing the energy and time resolution of the
crystals in an array using a 20 to 80 MeV positron beam at the Paul Scherrer Institute. The array demonstrated an energy resolution better than 2 % for energies above 40 MeV and a time resolution better than 140 ps for energies above 30 MeV. The spatial resolution was measured in the central region of the array to be 5.06 mm in x and 5.20 mm in y at 70 MeV. The measured properties satisfy the key design parameters of the PIONEER calorimeter for the measurement of rare pion decays.
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All authors O. Beesley, J. Carlton, D. Ding, S. Foster, K. Frahm, T. Frank, L. Gibbons, D. Goeldi, T. Gorringe, D. W. Hertzog, S. Hochrein, J. Hui, E. Klemets, J. LaBounty, J. Liu, P. Lopez Maggi, W. Osar, R. Roehnelt, P. Schwendimann, W. Shuai, A. Soter, E. Swanson
Physics and Society
I see you, do you see me? Perception-based crowdedness and behavioral responses in pedestrian dynamics
Igor Hołowacz and Pratik Mullick
Pedestrian traffic is commonly characterized using local density, yet the interactions experienced by individuals depend on the relative positions and perceptual relevance of surrounding pedestrians. This raises the question of whether behavioral relationships inferred from local crowdedness are robust to the representation of perceptual anisotropy, and how interaction geometry shapes pedestrian adaptation over time. We analyze experimental pedestrian crossing flows over angles from 0 to 180 degrees using a distance-weighted measure of local crowdedness. Perceptual anisotropy is varied by reducing the contribution of pedestrians outside the focal pedestrian's field of view. We examine the temporal
evolution of crowdedness and its relationships with velocity, directional deviation, and acceleration. Anisotropy primarily changes the numerical scale of crowdedness, while the qualitative dynamics, temporal progression, and crossing-angle dependence remain largely preserved. Pedestrians deviate appreciably from their expected group directions, but changes between successive walking directions remain small, indicating adaptation through smooth, incremental corrections rather than abrupt turns. Acceleration dynamics reveal an asymmetry between disruption and recovery: initial deceleration varies strongly with crossing geometry, whereas recovery accelerations are more similar across angles. Non-retracing trajectories in the behavioral phase spaces show that similar instantaneous conditions can correspond to different phases of the interaction. Overall, interaction geometry has a stronger influence on the organization of crossing flows than the perceptual weighting used to quantify local crowdedness. More broadly, dynamic fundamental diagrams provide a more complete characterization of transient pedestrian interactions than conventional relationships based on instantaneous state variables alone.
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Instrumentation and Detectors
Laser-Induced Fluorescence for measuring salt mass fraction in evaporating saline solutions
Antoine Dumain, Florine Giraud, Ophélie Caballina et al. (+2 more)
A non-intrusive optical diagnostic based on
Laser-Induced Fluorescence (LIF) is developed for measuring salt mass fraction in highly concentrated aqueous solutions relevant to absorption heat pump applications. The method relies on a systematic
redshift of the fluorescence emission spectra of several dyes, likely induced by an increase of ionic strength with salt mass fraction. A two-color ratiometric approach, based on the ratio of fluorescence intensities in two spectral bands, enables robust mass fraction measurements. This study demonstrates that the techniques is not limited to LiBr but also NaCl, relevant for desalination applications. In parallel, fluorescence lifetime measurements using Time-Correlated Single
Photon Counting (TCSPC) reveals that fluorescence lifetime is also affected by the LiBr mass fraction, allowing an alternative measurement technique. For both techniques, many dyes are tested and are compared in terms of salt mass fraction sensitivity. Both techniques are validated independently through comparison with shadowgraphbased measurements during evaporation of droplets. Good agreement is obtained in
liquid-phase conditions over a wide range of salt mass fractions, confirming the reliability of the proposed diagnostics. Key sources of uncertainty including temperature, reabsorption effects and phase changes has been identified and analyzed. Finally, preliminary results demonstrate the potential extension of the approach toward planar imaging of evaporating droplets and more complex multiphase flows. The methodology provides a basis for future quantitative diagnostics of heat and mass transfer in desorption systems such as falling-films.
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All authors Antoine Dumain, Florine Giraud, Ophélie Caballina, Benoit Stutz, Guillaume Castanet
Plasma Physics
Comparison of DBS measurements of turbulence spectra by vertical-displacement and poloidal-angle scans using the Scotty synthetic diagnostic
Y.T. Tan, V. Hall-Chen and T. Rhodes
Doppler backscattering (DBS) measures electron density fluctuations. The measured wavenumber is typically varied by changing the probe beam poloidal launch angle. As most DBS systems are unable to steer during a shot, the shot is repeated and the poloidal angle is changed intershot. An alternative method is to keep the DBS launch angle fixed and move the
plasma up and down instead, enabling a range of wavenumbers to be measured within a single shot. We call this the bouncing ball method. We use the Scotty synthetic diagnostic (
Hall-Chen, 2022) to evaluate the similarities and differences between these two approaches. Both approaches are capable of measuring a similar range of fluctuation wavenumbers as well as radial locations. However, the vertical-displacement scan has a larger range of measured poloidal locations than the poloidal-angle scan. Using the same synthetic
turbulence spectrum as input, we show that the two approaches are expected to have different backscattered powers due to different instrumentation functions. When mismatch attenuation is accounted for via a synthetic diagnostic, the vertical-displacement scan can provide comparable radial and wavenumber coverage while reducing reliance on shot-to-shot repeatability. These results establish vertical-displacement scan as a practical route to single-shot DBS wavenumber spectra.
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Classical Physics
Mean field homogenization schemes for composites with prolate and oblate spheroids: use of the orientation tensors and computation of the strain second-moments
Antoine Martin
In this document we provide the homogenized stiffnesses from Mori-Tanaka scheme and Ponte-Castañeda and Willis scheme applied to composites with spheroidal inclusions. The inclusions can be prolate spheroids ('fibers') or oblate spheroids ('penny-shapes'). We show how to compute the homogenized stiffnesses for particular distribution of spheroid orientations, using the second-order and fourth-order orientation tensors. We also provide formulas to compute the derivatives of these quantities w.r.t. the material parameters, which is of particular interest for computing the second-moments of the strains.
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Optics · Cross-listed from quant-ph
Quantum Scattering Model of Dual Parallel Mach Zehnder Electro Optic Modulators: General Formalism, Impairments, and Applications to Frequency-Bin Photonic Quantum States
Mar Yuste, Carlos R. Fernández Pousa, Javier Fraile Peláez et al. (+1 more)
We present a
quantum mechanical model of dual parallel Mach Zehnder electro-optic modulators (DPMZMs), derived using the
quantum scattering formalism [1,2]. We obtain the complete, unrestricted transformation of single-
photon and coherent input states through the DPMZM architecture, including independent radiofrequency drive conditions on each internal modulator, and recover the symmetric push pull operating point as an exact special case. We numerically evaluate the resulting frequency comb structure, quantify the device sensitivity to bias error, modulation-index imbalance, and RF noise, and use the model to design a DP-MZM-based frequency-bin
qubit source, reporting its fidelity as a function of these impairments.
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All authors Mar Yuste, Carlos R. Fernández Pousa, Javier Fraile Peláez, José Capmany
Physics and Society
Heterogeneous Network Topology Induces the Widom Line
Cook Hyun Kim and B. Kahng
The Widom line, initially identified as a crossover line between
liquid-like and gas-like behavior in water and supercritical fluids, separates these two types of behavior. Here, we show that an analogous line arises in
spin models on scale-free networks as a consequence of degree heterogeneity, which we analyze using the annealed network approximation. For the Ashkin–Teller and Invisible Potts models, the Widom line exists within a finite range of the degree exponent. It separates two distinct ordered regimes$-$distributed
spin alignment and hub-dominant
alignment$-$while also giving rise to a supercritical-like state where the two
alignments become indistinguishable. These results demonstrate that degree heterogeneity alone can generate mesoscopic crossovers beyond conventional phase-transition theory, opening new directions for understanding and controlling collective dynamics in complex networks.
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Optics
Sequential Multi-Step Nanoimprint Lithography Fabrication of Zero-Mode Waveguide Nanoaperture Arrays to Enhance Single Molecule Fluorescence Detection
Hamza Khelidj, Badre Kerzabi, Igor Ozerov et al. (+3 more)
Zero-mode waveguides (ZMWs) enable single-molecule fluorescence detection at micromolar concentrations by confining light to nanoscale volumes, overcoming the diffraction limit of confocal microscopy. However, their widespread adoption is hindered by high fabrication costs and limited throughput of traditional methods like focused ion beam or electron-beam lithography. Here, we introduce a scalable cost-effective approach using sequential nanoimprint lithography (NIL) combined with hydrofluoric acid etching to fabricate ZMW arrays with tunable diameters from a single initial master. In our sequential nanoimprint approach, each stamped NIL output serves as a master for the next nanoimprint generation. By leveraging the shrinkage of sol-gel nanopatterns during annealing, we achieve a cumulative diameter reduction from 230 nm to 115 nm over four successive imprints, all based on the same initial master. The resulting ZMWs exhibit detection volumes reduced by up to 1000-fold and fluorescence enhancement exceeding 16x, achieving performance comparable to state-of-the-art focused ion beam-fabricated devices. Eliminating the need for multiple master structures significantly expands the scalability of nanoimprint lithography approaches. By lowering the nanofabrication barriers and making ZMW arrays more accessible, the sequential NIL method paves the way towards broader adoption of nanophotonic devices in single-molecule biophysics, biosensing, and surface patterning applications.
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All authors Hamza Khelidj, Badre Kerzabi, Igor Ozerov, Olivier Hector, David Grosso, Jérôme Wenger
Applied Physics
Symmetry-constrained low-energy effective Hamiltonian for topological RuC and OsC monolayers
A. Baradaran and O. Sedaghatfar
We derive a low-energy $\mathbf{k}\cdot\mathbf{p}$ effective
Hamiltonian for monolayer osmium carbide (OsC) and ruthenium carbide (RuC) in a planar hexagonal configuration. First-principles calculations indicate that both monolayers are dynamically stable and exhibit features of a two-dimensional
quantum spin Hall (QSH) phase, characterized by a nontrivial $\mathbb{Z}_2$ topological invariant. Using
symmetry analysis at the $\Gamma$ point, we construct a multiband $\mathbf{k}\cdot\mathbf{p}$
Hamiltonian including
spin-orbit coupling and reduce it to a four-band low-energy model through Löwdin partitioning. The effective
Hamiltonian has a block-diagonal form, with two blocks related by time-reversal
symmetry, analogous to the Bernevig–Hughes–Zhang (BHZ) model. In contrast to the standard BHZ form, the
symmetry-allowed off-diagonal coupling contains quadratic momentum-dependent terms, which modify the low-energy dispersion near the $\Gamma$ point. The fitted parameters reproduce the ab initio band structures in the low-energy region, yielding a compact model for analyzing the electronic and topological properties of monolayer OsC and RuC.
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Plasma Physics · Cross-listed from math-ph
TokaGrad: End-to-end differentiable tokamak simulator for L-to-H full scenario optimization
Jaemin Seo
As fusion energy moves from theoretical feasibility toward commercialization, design of new reactor concepts, autonomous tokamak control, and high-performance scenario optimization are becoming increasingly important. Traditionally, such optimization tasks have relied on costly trial-and-error or brute-force parameter searches, based on black-box experiments or simulations. Recently, advances in differentiable programming are changing the paradigm of numerical simulation. Unlike conventional simulations, which are typically executed as locally connected step-by-step procedures, differentiable simulation represents the entire simulation pipeline as a connected computational graph. In such a framework, machine parameters, actuator waveforms, and
plasma responses are linked through differentiable operations, allowing Jacobians to propagate across the full simulation. This enables direct gradient-based control and optimization using the internal sensitivities of the simulator, rather than treating the simulator as a black box. Here, we present TokaGrad, an end-to-end differentiable tokamak transport simulator for full-scenario modeling, including ramp-up, L-mode operation, and H-mode access. TokaGrad self-consistently integrates differentiable models for
plasma equilibrium, transport, heating, L-H transition, and pedestal formation. To our knowledge, this is the first differentiable tokamak simulator capable of self-consistently modeling dynamic full-discharge scenarios where actuators and
plasma evolve together with
equilibrium, pedestal, and confinement-regime transitions. We demonstrate that, when coupled to gradient-based optimizers, TokaGrad enables reactor-design optimization, actuator control, and full-scenario waveform optimization. This framework provides a pathway toward automated, differentiable optimization of burning-
plasma scenarios and reactor concepts.
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Classical Physics
Chiral switching of elastic spin via dynamic encirclement of exceptional points
Chenwen Yang and Shubo Wang
Dynamically encircling exceptional points (EPs) enables
chiral state conversion in classical wave systems. However, whether this mechanism can be extended to
chiral spin conversion has remained elusive. Here we demonstrate
chiral switching of elastic
spin via dynamic encirclement of EPs in a non-Hermitian micropolar (Cosserat) metamaterial. The interplay between micropolar chirality and anisotropic loss generates EPs with a nontrivial Riemann-sheet
topology. Encircling these EPs converts the elastic
spin, with the final
spin sign dictated solely by the handedness of the encircling trajectory. Our results establish a fundamental route for the selective manipulation of elastic
spin, opening avenues for non-Hermitian
spin phononics and broader applications in other wave systems.
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Fluid Dynamics
Physics informed wavelet Fourier representation for multiscale fluid dynamics
Chao Wang, Shilong Li, Yunpeng Wang et al. (+4 more)
Multiscale fluid flows often contain localized flow structures, such as viscous shock layers, wet-dry fronts, steady viscous wakes, decaying vortical structures, and
vortex-shedding patterns, whose accurate prediction requires the simultaneous preservation of global conservation trends and small-scale gradients. This study examines these flow-physics requirements through a physics-informed wavelet-
Fourier (PIWF) representation for multiscale fluid dynamics. Instead of relying on a single monolithic neural approximator, the formulation separates two complementary components of the flow field within a physics-informed neural representation: long-range coherent modes through a
Fourier-basis branch and localized steep-gradient or vortical features through a compactly supported wavelet branch. The outputs are fused with a residual multilayer perceptron using channel
attention, and the governing equations, initial conditions, and boundary conditions are imposed directly through the physics-informed loss. The model is assessed on five canonical fluid-dynamics problems: Burgers' equation, the shallow water equations, Kovasznay flow, Taylor–Green
vortex flow, and two-dimensional cylinder wake flow. The results show that PIWF improves the resolution of shock-like gradients, wet–dry interfaces, steady wake fields, decaying vortical structures, vorticity extrema, and broadband wake spectra relative to standard physics-informed neural networks and physics-informed Kolmogorov–Arnold networks. These findings indicate that a wavelet-
Fourier physics-informed representation can provide a useful route for analyzing multiscale flow phenomena when high-fidelity interior reference data are limited or unavailable.
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All authors Chao Wang, Shilong Li, Yunpeng Wang, Tianbai Xiao, Zelong Yuan, Chenyue Xie, Chunyu Guo
Plasma Physics
Implicit discretization schemes for full-kinetic ion and drift-kinetic electron simulations
Zilong Li, Yang Chen, Haotian Chen et al. (+3 more)
We present a new electromagnetic
plasma simulation model with full-kinetic ions and drift-kinetic electrons. This model (termed as FIDES) solves the electric field using the implicit perpendicular Ohm's law and a novel implicit parallel Ampere's law, where the latter requires an implicit scheme for the parallel electric field in advancing the electron weights. To suppress unphysical high-frequency instabilities, ion weights are advanced using an implicit scheme for perpendicular electric fields. Simulations of perpendicular and parallel waves validate the model's capability in handling high-frequency physics. Low-frequency wave simulations demonstrate that the implicit parallel Ampere's law can mitigate the cancellation problem more effectively than the conventional schemes using the parallel Ohm's law. To reduce the numerical damping from implicit time-stepping, we develop a second-order scheme for particle pushing. Meanwhile, an integrated strategy combining the first- and second-order schemes is employed to suppress odd-even decoupling while maintaining the accuracy of the second-order formulation.
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All authors Zilong Li, Yang Chen, Haotian Chen, Lei Ye, Zhe Gao, Wei Chen
Accelerator Physics
First Synchrotron Injection Attempt into The SuperKEKB High Energy Ring
N. Iida, Y. Funakoshi, H. Kaji et al. (+17 more)
A synchrotron injection scheme for the SuperKEKB electron high-energy ring (HER) was implemented and experimentally evaluated as the first attempt with a top-up injection during beam collisions. The
lattice at the HER injection point was configured to provide a large horizontal dispersion of -1.6 m, and the injection beam energy was accordingly set to +0.6% above the ring energy. Since the beam extraction system is located near the injection point, the optics design was constrained to ensure compatibility with its requirements. A systematic tuning procedure of the injection parameters has been established with turn-by-turn BPMs(TbT-BPMs) in the ring, by which the betatron amplitude of the injected beam was successfully removed. Using optimized ring optics, synchrotron injection into the HER was successfully demonstrated, followed by the establishment of stable collisions and the production of luminosity.
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All authors N. Iida, Y. Funakoshi, H. Kaji, T. Kamitani, M. Kikuchi, K. Kodama, H. Koiso, T. Mimashi, G. Mitsuka, T. Mori, Y. Ohnishi, Y. Seimiya, K. Shibata, H. Sugimoto, M. Tawada, T. Ueda, R. Ueki, T. Yoshimoto, M. Li, K. Oide
Physics and Society
Topological Signatures of Imperial Collapse and Fragmentation: Administrative Dissolution, Territorial Reorganization and Early-Warning Observables in the Han Dynasty Network (206~BCE\,–\,220~CE)
Jose de Jesus Bernal-Alvarado, David Delepine and Carlos Pinedo Guadarrama
We extend the persistent homology formalism done in references~\cite{paper1,paper2} to the Han Dynasty ($206~\mathrm{BCE}$–$220~\mathrm{CE}$), testing whether the collapse threshold $\Hstar = 0.5241$ and the three-network decomposition methodology established for the Roman–Byzantine case generalize to a mechanistically distinct imperial system. Three complementary networks are constructed from geospatial and historical data: an administrative network ($\Hadm$, 392~prefectures from CHGIS~v6), a geographic network ($\Hgeo$, with node end-dates extended beyond administrative dissolution), and an 81-node Silk Road trade network ($\Htrd$) as a structural control. Edge costs are derived via least-cost path analysis on a $1~\mathrm{km/pixel}$ digital elevation model, modulated by five historical friction channels. $\Hadm$ collapses to zero at 220~CE (phase~G slope $-0.0261~\mathrm{yr}^{-1}$, $R^2 = 0.689$) while $\Hgeo$ simultaneously increases to $3.065$, producing a divergence $\Delta H = 3.065$ – the topological signature of internal fragmentation. The cross-network Wasserstein distance $W_\times(\mathrm{Admin},\mathrm{Geo})$ jumps from exactly zero to $737$ at $d=190$~CE, one decade after the Yellow Turban Rebellion, and three long-lived $\beta_1$ cycles matching the Wei, Shu, and Wu domains emerge under the post-184~CE fragmentation model – thirty years before formal partition. Three independent early-warning indicators (Wasserstein velocity $\dot{W}_2$, correlation length $\xi$, and the Integrated Change Tracker) signal collapse onset 45–50~years before formal dissolution.
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Geophysics
Benchmarking Universal Machine Learning Force Fields for Molecular Dynamics of Lunar Regolith Minerals
Ziyu Huang and Ken-ichi Nomura
Universal machine-learning interatomic potentials provide a promising route for accelerating molecular dynamics simulations of materials, but their transferability to lunar regolith-relevant silicates,
oxides, and hydrogen-bearing surface species remains elucidated. Here, we
benchmark six foundation models, MACE-MH, MatterSim, SevenNet-0, UPET, UMA, and NequIP-OAM-L, using NVT molecular dynamics simulations of four representative lunar minerals: forsterite, fayalite, ilmenite, and anorthite. Structural fidelity is evaluated using temperature stability, bond-distance statistics, bond-angle distributions, and partial radial distribution functions, with comparison to crystallographic reference data. The models reproduce Si–O, Mg–O, Al–O, and Ca–O local environments reasonably well, while Fe–O and Ti–O coordination environments show broader distributions and larger short-timescale fluctuations, highlighting the need for further validation and fine tuning with additional ground truth data for Fe- and Ti-bearing lunar phases. Hydroxylated surface tests show consistent O–H bond-distance distributions across models and minerals, suggesting that these foundation models may provide useful starting points for screening surface hydroxyl stability and volatile-related processes. Performance
benchmarks on a single NVIDIA RTX 4090 show that SevenNet-0, MatterSim, and UPET provide the highest throughput among the six tested models, MACE-MH remains practical at intermediate cost, and UMA and NequIP-OAM-L extend the comparison to newer foundation potentials at higher runtime cost and
memory demand. These results provide an initial
benchmark for applying universal foundation models to lunar mineral simulations and identify key directions for future ab initio validation, model fine-tuning, and applications to lunar volatile
evolution, space weathering, ISRU, and polar sample return studies.
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