Fluid Dynamics
Deforming Vortex Force Mapping for Undulating Swimmers
Xingxin Yang, Matteo Liguori, Vedang Joshi et al. (+1 more)
Undulatory propulsion is commonly interpreted through reactive added-mass loading associated with body kinematics and
vortex-induced loading, but their relative contributions to the streamwise force have not been systematically quantified across swimming kinematics. Moreover, existing
vortex-based descriptions do not resolve the signed spatial contribution of vortical flow to the streamwise force. We extend
vortex force map (VFM) attribution to deforming bodies, demonstrated for prescribed two-dimensional undulating swimmers at $Re=5000$ across a range of Strouhal numbers and dimensionless wavelengths. The deforming-body VFM organises the streamwise force as a positive reactive added-mass scale with a signed
vortex-pressure modification. Across the 80 cases,
vortex pressure opposes the reactive contribution in 76 cases. Reference-configuration maps show that the near-body
vortex-pressure contribution is consistently adverse, whereas the wake contribution changes sign across regimes and becomes favourable at high thrust. Net
vortex-pressure assistance occurs only for the high-thrust anguilliform swimmer. A matched high-thrust pair further shows that the case with the higher peak downstream velocity has the smaller signed wake contribution, demonstrating that wake intensity alone does not determine its force effect.
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All authors Xingxin Yang, Matteo Liguori, Vedang Joshi, Juan Li
Optics
Strong suppression of the photonic density of states in three-dimensional disordered silicon networks
Abraham Aguilar Uribe, Francisco Hernández Alejandre, Mattis Reisner et al. (+4 more)
Photonic bandgaps can open not only in crystalline dielectric materials but also in amorphous structures. Self-uniform amorphous gyroid networks have been proposed as promising disordered photonic architectures. Motivated by numerical studies, we combine direct
laser-writing lithography with advanced materials processing to fabricate these structures from high-refractive-index silicon. Spectroscopic measurements at mid-infrared wavelengths reveal pronounced transmission minima. To investigate the formation of photonic band gaps in amorphous structures, we develop polarization-resolved transmission spectroscopy that separates ballistic and multiply scattered contributions, enabling direct identification of the underlying transport regimes. We observe a strong suppression of diffuse transmission, providing direct experimental evidence for a breakdown of conventional diffuse transport associated with a strongly reduced photonic density of states. Together with large-scale numerical simulations, our results establish the presence of a deep photonic pseudogap in an amorphous three-dimensional dielectric material and open new opportunities for observing disorder-induced localization phenomena, including Anderson localization of light.
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All authors Abraham Aguilar Uribe, Francisco Hernández Alejandre, Mattis Reisner, Geoffroy Aubry, Luis S. Froufe-Pérez, Marian Florescu, Frank Scheffold
Atmospheric and Oceanic Physics
Reconciling the Lack of a Robust Anvil Cloud Amount Response to Warming
Zachary McGraw, Blaž Gasparini, Wouter Mol et al. (+1 more)
The stability-iris hypothesis proposes that tropical anvil cloud amount decreases with warming as anvils rise into environments of greater static stability. Here we show that there is no clear theoretical or simulated link between increasing static stability and anvil amount. We demonstrate analytically that identified sensitivities of static stability and pressure velocity to surface warming arise from decreasing air density aloft, which enters pressure-coordinate formulations but does not represent a process that dynamically constrains anvil formation. An ensemble of RCEMIP simulations verifies that the stability increase is robust yet arises from the air density reduction, and hence is not accompanied by a robust response in anvil amount, convectively driven water convergence into anvil levels, or the efficiency with which this convergence produces cloudiness. Overall, these findings dispel the expectation of a systematic reduction in anvil amount with warming arising from basic physical arguments.
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All authors Zachary McGraw, Blaž Gasparini, Wouter Mol, Aiko Voigt
Computational Physics
Mixture of Polyconvex Neural Potentials for Parametric Hyperelasticity: Towards Foundation Material Models
Steven J. Yang, Govinda Anantha Padmanabha, D. Thomas Seidl et al. (+1 more)
Hyperelastic constitutive models enable modeling large deformations in elastic solids. In common practice, a strain energy density function is prescribed in advance and model-specific parameters are calibrated from experiments. However, many applications require constitutive models for a family of related materials whose mechanical behavior varies with composition. A fixed constitutive model-form may not capture the full range of behavior across the family, while fitting separate forms does not provide a direct way to predict the response of new compositions. Recent work has developed data-driven constitutive models that learn flexible strain energy functions while incorporating key physical constraints. In this work, we propose using mixtures of convex neural potentials based on input convex neural networks as a modular and data efficient approach to modeling material families. Each potential is convex and monotonic with respect to polyconvex strain invariants, while a conditioning network maps material descriptors to mixture weights. We compare the approach with a monolithic partially input-convex neural network using experimental data from PolyJet 3D-printed materials and a synthetic Gent-type
benchmark. Across both
benchmarks, the mixture architecture generalized better to material descriptors not seen during training. In the PolyJet experimental
benchmark, we showed that the mixture architecture is less sensitive to model hyperparameters, while in the Gent-type
benchmark it generalized more reliably with sparse data in the material-descriptor space. These results suggest that representing a material family through a small set of shared convex neural potentials provides a useful structural prior for learning descriptor-dependent constitutive behavior from limited data.
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All authors Steven J. Yang, Govinda Anantha Padmanabha, D. Thomas Seidl, Nikolaos Bouklas
Atomic Physics · Cross-listed from quant-ph
Spatial correlations of photons interacting via transverse Rydberg blockade
Bankim Chandra Das, Daniil Svirskiy, Matthias Metternich et al. (+3 more)
We develop a theory of the transverse spatial dynamics of two interacting
photons in a Rydberg nonlinear medium. Extending the well-studied one-dimensional case, we explore both longitudinal and transverse correlations of
photons propagating as Rydberg polaritons. We identify distinct behaviors and scaling laws for these correlations, arising from fundamentally different mechanisms in the two directions: diffraction for transverse correlations and
diffusion for longitudinal correlations. We develop a model incorporating a Gaussian optical beam and an inhomogeneous atomic density distribution, from which we derive quantitative predictions for correlation functions in both directions. We further show that the propagation equations can be reduced to a single Schrödinger-like equation, allowing approximate solutions that are supported by full numerical results. Our findings indicate that the transverse correlation length is determined primarily by the blockade radius, whereas the longitudinal correlation length is limited by bandwidth. These results establish transverse Rydberg blockade as a distinct and measurable correlation mechanism and show that spatial
photon correlations provide a direct means of measuring the blockade radius.
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All authors Bankim Chandra Das, Daniil Svirskiy, Matthias Metternich, Wolfgang Alt, Sebastian Hofferberth, Ofer Firstenberg
Physics and Society
Modeling of Mobility and Energy Policies in an Agent-Based Framework: Case Studies for Chicago Region in 2050
Md Rakibul Alam, Omer Verbas, Taner Cokyasar et al. (+10 more)
Metropolitan regions are simultaneously pursuing several interventions to improve mobility, accessibility, and energy efficiency, necessitating integrated tools to understand how these policies interact to affect travel behavior, energy use, and infrastructure needs. This paper evaluates the combined impacts of electrification, freight demand management, road pricing, parking reform, and transit expansion on the Chicago metropolitan transportation system in 2050, using a business-as-usual (BAU) scenario as the baseline. We employ POLARIS, a large-scale
agent-based modeling framework calibrated to 2019 conditions, to simulate nine policy scenarios for the seven-county northeastern Illinois region. The framework co-simulates activity-based passenger demand, endogenous freight generation,
multimodal traffic assignment, and transit operations, with charging infrastructure and freight operations optimized for each case. Our findings reveal that under the high electrification scenario, total fuel mass declines by 68% while total charging energy increases by approximately 4-8x from BAU, resulting in a peak power demand near 4 GW concentrated in the urban core. Furthermore, freight management policies reduce freight VMT by increasing trip frequency but shortening distances, smart road pricing most effectively reduces auto VMT, and transit expansion boosts ridership by 18% relative to BAU. By presenting the first integrated,
agent-based scenario framework for Chicago that jointly evaluates these interventions, this study provides actionable insights for regional transportation planning, grid infrastructure investment, and emissions reduction, highlighting the value of targeted charger upgrades and coordinated policy bundles.
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All authors Md Rakibul Alam, Omer Verbas, Taner Cokyasar, Hadi Bhidya, Jesse Altman, Nora Beck, Joshua Auld, Pedro Veiga de Camargo, Jamie Cook, Felipe de Souza, Gopindra Nair, Hyunseop Uhm, Jan Zill
Physics and Society
Modeling microbiome dynamics on social networks: how between-host transmission shapes within-host evolution
Longmei Shu and Feng Fu
A social network perspective on the human microbiome is crucial for understanding how the interplay between within-host microbial dynamics and between-host transmission influences microbial community stability, host metabolism, and population health and nutrition. Here, we provide a mathematical and numerical analysis of human-associated microbial communities in dyadic social ties and within a small network. By utilizing a generalized Lotka-Volterra model, we simulate within-host dynamics while incorporating inter-host microbial sharing driven by social interactions. Furthermore, the study accounts for individual variability in microbial behavior across different hosts. Our work identifies the conditions under which microbial sharing can have long-lasting effects, offering insights into how social networks shape the human microbiome.
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Space Physics · Cross-listed from astro-ph.SR
Direct Measurement of Polar Coronal Hole-like Solar Wind in its Acceleration Phase
Samuel T. Badman, Yeimy J. Rivera, Michael L. Stevens et al. (+38 more)
The early
evolution of fast polar coronal hole (PCH)
solar wind remains largely unconstrained by in situ measurements. In March 2025, Parker
Solar Probe (Parker) at its closest approach of 9.86
Solar Radii ($R_\odot$) measured
outflow from a large equatorial coronal hole (ECH) which was also measured at 1\,au and at intermediate distances by
Solar Orbiter (also near its perihelion). At 1\,au the stream properties are consistent with PCH properties established by Ulysses. The stream was measured by Parker substantially below the Alfvén surface, with
proton temperatures in excess of 2\,MK and a speed at $\sim$10\,$R_\odot$ which was only $\sim$60% of its asymptotic value. The
Solar Orbiter data indicates that the acceleration is largely complete by 60~$R_{\odot}$. Spherically-polarized fluctuations in the stream are observed to develop from near-transverse and small-angle at Parker to full reversal “switchbacks” at
Solar Orbiter. Comparison of the implied acceleration profile to historical doppler-dimming measurements suggests that the stream's low coronal acceleration is similar to that of PCH flows. Consistent with previous work, this acceleration requires significantly more energy than can be provided by the observed thermal pressure gradients, with a significant contribution likely from the abundant Alfvénic fluctuation energy observed at Parker. These observations provide unique constraints on models of the radial
evolution of the fastest
solar wind, and indicate that these wind streams experience gradual, steady acceleration over their first few tens of
solar radii of
evolution.
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All authors Samuel T. Badman, Yeimy J. Rivera, Michael L. Stevens, Mari Paz Miralles, Steven R. Cranmer, Andrea Verdini, Lynn B. Wilson III, Xiangyu Wu, Georgios Nicolaou, Jean-Baptiste Dakeyo, Kai Jaffarove, Tamar Ervin, Dominic S. Payne, Michael Terres, Kristopher G. Klein, Jasper S. Halekas, Sujan Prasad Gautam, William H. Matthaeus, Riddhi Bandyopadhyay, Srijan Bharati Das, Tatiana Niembro, Christopher J. Owen, Rungployphan Kieokaew, Ali Rahmati, Orlando M. Romeo, Federico Fraschetti, Marco Velli, Lorenzo Matteini, Kristoff W. Paulson, Lidiya Ahmed, Stuart D. Bale, Phyllis Whittlesey, Marc Pulupa, Nour E. Raouafi, Timothy S. Horbury, Jean Morris, Helen O'Brien, Roberto Livi, Davin E. Larson, Adam J. Finley, Philippe Louarn
Chemical Physics
Use of Cholesky decomposition in the CFOUR program package
Jürgen Gauss, Simon Blaschke, Sophia Burger et al. (+10 more)
An overview is given about our efforts to speed up high-level computations of molec- ular energies and properties using Cholesky decomposition (CD). We describe the cor- responding developments in the CFOUR
quantum-chemical package with a focus on (a) the use of CD in complete-active space self-consistent-field (CASSCF) and coupled- cluster (CC) computations, (b) the implementation of analytic CC gradients using CD, (c) the efficient calculation of
magnetic properties (NMR shieldings and magnetizabili- ties) using CD when carried out with explicit
magnetic-field dependent basis functions, i.e., the so-called gauge-including atomic orbitals (GIAOs), (d) the efficient computa- tion of CASSCF response properties using CD, (e) the use of CD in relativistic two- and four-component computations, as well as (f) computations for molecules in finite
magnetic fields using GIAOs together with CD. An outlook on future developments concerning the CFOUR package is given.
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All authors Jürgen Gauss, Simon Blaschke, Sophia Burger, Davide Cianchino, Marios-Petros Kitsaras, Luca Melega, Tommaso Nottoli, Jeremias Oswald, Tereza Uhlířová, Chaoqun Zhang, Lan Cheng, Stella Stopkowicz, Filippo Lipparini
Accelerator Physics
A particle-in-cell model of beam dynamics in a dielectric wall accelerator
Christopher M. Lund, Paul M. Jung, Jamiel Nasser et al. (+6 more)
Dielectric wall accelerator (DWA) technology has been proposed as a compact, cost-effective alternative to rf accelerators for
proton therapy, but its beam dynamics and practical feasibility remain relatively unexplored. In this work, we derive a three-dimensional, time-dependent axisymmetric electromagnetic field model from a prescribed on-wall excitation and implement it as stacked external field elements in the particle-in-
cell code Warp. In the absence of experimental DWA beam-transport data, the implementation is cross-checked against a previously developed linear optics model in TRANSOPTR using deliberately idealized beam conditions. Strong agreement is observed between the two models in this regime. The models are then compared for larger transverse and longitudinal emittances, bunch charges up to 1x10^8e, and beam parameters representative of a low-energy
proton source. The PIC simulations remain consistent with the linear predictions over much of the investigated range, while also identifying wall interactions, longitudinal phase-space distortions, and space-charge induced aberrations. The PIC model represents an intermediate step between linear optics and combined, geometry-specific electromagnetic and particle-transport simulations. It resolves particle-level transport and beam self-fields while retaining an analytical field description that can be varied without committing to a particular DWA structure. More detailed effects may be introduced through externally generated field data or empirical corrections, including models of
cell-to-
cell coupling, providing a practical basis for increasingly realistic DWA field and beamline studies.
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All authors Christopher M. Lund, Paul M. Jung, Jamiel Nasser, Morgan J. Maher, Julien Bancheri, Chau Giang Bui, Thomas Planche, Rick Baartman, Jan Seuntjens
Applied Physics
A fully coupled electromagnetic-thermal-mechanical model for metal-insulated HTS high field magnets
Anang Dadhich, Nikola Jerance, Tara Benkel et al. (+2 more)
Ultra high field REBCO magnets operate under strongly coupled electromagnetic, thermal and mechanical conditions, where screening currents, localized heating, thermal expansion and Lorentz forces can modify both the structural state and the critical current density of the conductor. In this work, a coupled electromagnetic, thermal and mechanical model is developed for a metal-insulated nested REBCO insert designed for a 40 T class SuperEMFL magnet. The existing electromagnetic formulation resolves the non-uniform screening currents in the REBCO tapes. The thermal model is extended from an explicit Finite Difference Method (FDM) to an implicit Backward Euler scheme with Picard iteration, while a new axisymmetric mechanical FDM solver based on BiCGSTAB is introduced to calculate displacements, strains and stresses in the coil windings and G10 spacer regions. Thermal expansion and Lorentz force contributions are included, and the calculated longitudinal mechanical strain is coupled back to the electromagnetic model through a strain dependent critical current density, which also depends on temperature,
magnetic field, and its orientation. A literature-informed
Parabolic-Weibull model is used to model reversible and irreversible strain degradation of the REBCO conductor. The numerical methods are benchmarked, and the resulting framework provides a computationally efficient approach for investigating temperature gradients, thermo-mechanical stresses, strain-dependent critical current degradation and quench behaviour in full scale nested high field REBCO magnets.
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All authors Anang Dadhich, Nikola Jerance, Tara Benkel, Philippe Fazilleau, Enric Pardo
Fluid Dynamics
Creeping flows through confined arrays of cylinders
Sean Bohling, Sri Savya Tanikella, J.P. Raimondi et al. (+2 more)
Hair-covered appendages serve a variety of purposes in Nature, from chemical sensing and particle capture on the
antennae of a crustacean to drag generation on bristled wings. At low to intermediate Reynolds numbers, these finite porous media experience three flow regimes. At low Reynolds numbers, the flow goes around the porous structure; this is the paddle or rake regime. As the Reynolds number increases, so does the relative flow rate through the array. If the fluid exits the structure mostly laterally, the flow is in the deflection regime. If the fluid exits downstream, the flow is in the sieve regime. Confining structures, such as the animal body or larger hairs, have been hypothesized to focus the flow on the hair-covered region. We investigate the influence of confinement on the flow through and around an array of cylinders, using a combination of experiments and numerical simulations. Experimentally, we vary the cylinder spacing, channel dimension, and flow rate and measure the velocity field using Particle Image Velocimetry. After comparing the results of finite element analysis with the experimental data, we numerically investigate a broader range of system geometries and flow parameters. Our results show that the confinement focuses the flow in the array and shifts the domains of existence of the three regimes. We present an analytical model that relies on the permeability of rectangular slits to predict the relative flow rate through and around the array. The model is in quantitative agreement with the numerical results, demonstrating that the flow through the array increases with increasing confinement, while the flow angle decreases. These results should provide insight into the morphology of hairy surfaces and have implications in the design of bio-inspired flow sensors and filters.
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All authors Sean Bohling, Sri Savya Tanikella, J.P. Raimondi, Nathan Jones, Emilie Dressaire
Optics
Modeling and Optimization of Cascaded Four-Wave Mixing toward the VUV in Xenon-Filled Negative-Curvature Fibers
Jose Otavio Rosa, Frédéric Gérôme, Fetah Benabid et al. (+2 more)
In this work, we thoroughly characterize third- and fourth-harmonic generation through cascaded four-wave mixing in a xenon-filled negative-
curvature hollow-core fiber operated under a pressure gradient. The experimental results are supported by both a semi-analytical model and numerical simulations, which accurately reproduce the pressure dependence of the harmonic conversion. We identify the optimum pressure conditions for third and fourth-harmonic generation and experimentally observe the cascaded four-wave-mixing process extending into the
vacuum ultraviolet (VUV), up to the sixth harmonic at 172 nm, with the accessible spectral range limited by the available VUV filter.
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All authors Jose Otavio Rosa, Frédéric Gérôme, Fetah Benabid, Jonas H. Osório, Jonathas de Paula Siqueira
Computational Physics · Cross-listed from math.NA
Solving the Incompressible Navier-Stokes Equations on Oriented Curved Surfaces Discretized by Point Clouds
Alejandra Foggia and Ivo F. Sbalzarini
We present a meshfree numerical solver for the incompressible Navier-Stokes equations on oriented curved surfaces that are represented by surface point clouds. On curved surfaces, numerical challenges pertaining to stiffness and pressure-velocity coupling are exacerbated. Moreover, vector calculus on curved surfaces differs from its Euclidean counterpart. The presented method operates on surface point clouds in an Eulerian frame of reference without requiring a computational grid or mesh. It achieves consistent approximation in space and time with high order of accuracy; we demonstrate up to order six. The incompressibility constraint is locally imposed as a weak artificial compressibility approximation, avoiding global
matrix inversion. We show that the method provides consistent and convergent approximations of surface vector fields and differential operators. We study the relationship between error, spatial resolution, and artificial Mach number and characterize the frequency spectrum of the artificial oscillations. We provide numerical solutions of the incompressible Navier-Stokes equations on symmetric surfaces, such as the sphere and
torus, and on parametric and non-parametric asymmetric surfaces. Since the proposed method works directly on unstructured surface point clouds, it provides a promising approach for simulations on image-derived geometries, such as in biological morphogenesis from microscopy
videos.
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Accelerator Physics · Cross-listed from cond-mat.mtrl-sci
Cryogenic Enhancement of Electron Spin Polarization from a Strained GaAs/GaAsP Superlattice Photocathode
Matt Grau, Colin Kirk, Greg Blume et al. (+7 more)
We report electron
spin polarization of 95.0 +/- 0.8 (stat) +/- 2.4 (sys)% from a strained GaAs/GaAsP superlattice photocathode grown by metalorganic chemical vapor deposition (MOCVD) and cooled to dry-ice temperature (195 K). We achieved this polarization with 97.8% circularly polarized excitation light and a
quantum efficiency of 0.7% at the peak polarization wavelength. This measurement exceeds the values of previously reported GaAs-based photocathode polarizations, which have clustered near 92% for two decades. We vary the temperature of the cathode and measure the polarization and
quantum-efficiency spectra at 295 K, 273 K, 195 K, and 77 K. The polarization rises from 91.2(1)% at 295 K to its maximum at 195 K, while the spectral peak shifts from 775 nm to 739 nm (78 meV) over the full temperature range, tracking the widening band gap. The spectra probe two depolarization mechanisms: a thermalized transport channel that is suppressed on cooling, and energy-dependent hot-electron relaxation that persists and sets the low-temperature saturation. The polarization recovers after a full cooling and warmup cycle and is stable while the
quantum efficiency decays, which disfavors surface energy filtering as the origin of the gain. These results indicate that modest cooling to 195 K, for which dry ice suffices, is a practical route to higher-polarization GaAs-based electron sources.
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All authors Matt Grau, Colin Kirk, Greg Blume, John Hill, Sushil Poudel, Alimohammed Kachwala, Marcy Stutzman, Joseph Michael Grames, Sylvain Marsillac, Matt Poelker
Fluid Dynamics
Chordwise micro-jet placement reveals a trade-off between mean hydrodynamic performance and unsteady loading under cloud cavitation
Amirmehran Mahdavi, Soheil Motezakkeri, Yasin Ebrahimi et al. (+1 more)
Prescribed tangential micro-jet injection can modify cloud-cavitation dynamics, but the chordwise location that improves mean hydrodynamic performance may differ from the location that minimizes unsteady loading. This study compares five injection locations (x/c = 0.15, 0.30, 0.45, 0.60, and 0.70) on a Clark-Y hydrofoil at Re = 7 x 10^5 and cavitation number 0.8. Transient large-eddy simulation with a Volume-of-Fluid formulation and the Schnerr-Sauer cavitation model is used in a two-dimensional parametric framework, with one representative three-dimensional case included to illustrate spanwise cavity deformation. The analysis considers vapor
topology, turbulent kinetic energy, velocity and pressure fields, cycle-averaged surface pressure, hydrodynamic forces, force fluctuations, spectra, and cavity-thickness histories. Injection at x/c = 0.15 gives the highest cycle-averaged lift-to-drag ratio among the tested cases: drag decreases from 0.137 to 0.107 and the lift-to-drag ratio increases from 5.693 to 6.261, while lift decreases from 0.78 to 0.67. In contrast, x/c = 0.60 gives the lowest recorded force-fluctuation RMS, with lift- and drag-coefficient RMS values of about 0.112 and 0.0165. The preferred injection location is therefore objective-dependent: the location favored by mean hydrodynamic performance does not coincide with the location favored by unsteady-load reduction under the present conditions.
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All authors Amirmehran Mahdavi, Soheil Motezakkeri, Yasin Ebrahimi, Ali Alavi
Physics and Society
Rock, Paper, Scissors, ... Dynamite - A Model of Disruption from New Technologies
Andrew J. Lohn
We seek to understand the effect of adding disruptive highly-capable new technologies to competitions by assessing the addition of Dynamite to Rock-Paper-Scissors. We find that providing a versatile Dynamite move to only one player provides limited value (win probability increases from 50% to 55.5%) and is played rarely. That value decreases further if the game is expanded beyond just the original three moves. We also observe several mechanisms by which prior moves can become strategically unplayable, or obsolete. We hope that this model illustrates some non-intuitive aspects of developing new versatile technologies. We also hope that it illustrates some pitfalls for developers and integrators to avoid in order to create value rather than merely capability.
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Chemical Physics
Smoothed truncated Coulomb potential for periodic Gaussian-basis Hartree–Fock exchange
Gengzhi Yang, Aamy Bakry and Hong-Zhou Ye
Truncated Coulomb (TC) potentials reduce finite-size errors and accelerate thermodynamic-limit convergence in periodic Hartree–Fock (HF) calculations, but their use with Gaussian basis sets is complicated by the evaluation of electron repulsion integrals (ERIs), particularly for nonspherical truncation domains and all-electron calculations. We introduce the smoothed truncated Coulomb (sTC) potential as a systematically improvable approximation to a parent TC potential. A real-space Gaussian convolution smooths the sharp truncation boundary, and a single dimensionless parameter, $\eta$, controls the width of the smoothing window, which can be tightened to systematically approach the TC reference. The smoothing by sTC enables a dual-space
algorithm for evaluating periodic Gaussian-basis ERIs that requires neither a large plane-wave basis nor new molecular integral kernels and is applicable to both pseudopotential and all-electron calculations, including the important Wigner–Seitz-
cell truncation boundaries.
Benchmarks spanning insulating, semiconducting, layered, metallic, and molecular-
crystal systems show that sTC-based HF closely reproduces TC results in pseudopotential calculations and extends TC-quality calculations to all-electron settings. Across these systems, sTC substantially improves thermodynamic-limit convergence relative to the probe-charge Ewald method while remaining practical for all-electron calculations in which direct TC-based calculations are computationally challenging.
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Fluid Dynamics · Cross-listed from cs.CV
A Lagrangian View of Flow Matching
Peyman Milanfar
Modern explicit-time generative models, such as Flow Matching [Lipman et al., 2023] and Rectified Flow [Liu et al., 2023], are typically derived top-down via Optimal Transport and the continuity equation. This standard Eulerian approach focuses on the macroscopic transport of probability mass. In this paper, we present an alternative, bottom-up mechanical derivation grounded in a Lagrangian (particle-centric) perspective. By analyzing the local Taylor expansion of a continuous denoiser, we motivate a strict invariance condition required for optimal, singlestep generation: the conservation of target identity. Enforcing this condition yields a governing quasi-linear advection Partial Differential Equation (PDE). We demonstrate that solving this PDE via the Method of Characteristics analytically yields the straight-line trajectories of Flow Matching. This
geometric perspective isolates the Jacobian of the denoiser as the primary source of trajectory
curvature, providing a direct mathematical explanation for why straight-line flows enable massive step sizes, and why empirical models require
distillation to flatten intersecting characteristics.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Size-Dependent Growth Rates Amplify Infinitesimal Asymmetry in Nanocrystals
Sam Oaks-Leaf and David T. Limmer
The kinetic Wulff construction predicts symmetric nonequilibrium shapes when crystallographically equivalent facets share a fixed growth rate. However, nanocrystals grow through finite facets whose nucleation barriers and ligand coverages depend on facet size. Here we develop a size-dependent kinetic construction and show that as a consequence infinitesimal seed asymmetries can be amplified into strongly asymmetric nanocrystal morphologies even when all
symmetry-related facets obey the same microscopic growth law. Spatially heterogeneous nucleation rates and boundary limited growth generate facet growth velocities that depend on size, and deterministic shape
evolution translates these local rates into global shape
symmetry breaking. We illustrate the mechanism of persistent anisotropic growth on square and triangular
lattices in two dimensions and on FCC seeds in three dimensions, where cuboctahedra can evolve toward rods or tetrahedra depending on which facet-area perturbations are amplified.
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Atomic Physics
Collective dressed states for inelastic light scattering by atomic ensembles
Sébastien Lucas, David Wilkowski, Christian Miniatura et al. (+1 more)
We develop a general dressed-state framework for computing fluorescence spectra, probe absorption spectra, and
photon-
photon correlations of light scattered by ensembles of $N_\mathrm{at}$ two-level atoms with arbitrary $J_g \to J_e$ transitions driven by intense coherent fields. The approach employs a full vectorial treatment of the electromagnetic field, handles any atomic geometries, illumination directions, and polarizations, and yields optical observables as explicit sums of Lorentzian lines whose positions, widths, and weights are directly tied to the
eigenvalues and eigenvectors of the Lindbladian. The framework is implemented in an open-source Python package and benchmarked against exact single- and two-atom calculations. We identify geometries in which the full vectorial description is essential, and the scalar approximation fails qualitatively. Applying the method to pairs of atoms with a $J_g=0\to J_e=1$ transition, we show that elastic and inelastic scattered intensities collapse onto universal master curves controlled by a single collective saturation parameter built from the dominant superradiant mode, across several orders of magnitude in drive strength and interatomic distance. We identify collective phenomena that require a description beyond this single-mode picture. Extending the analysis to atoms with ground-state degeneracy, we find that most collective features carry over, while two qualitatively new effects emerge: an incoherent spontaneous Raman channel that modifies the scaling of inelastic emission, and a slow timescale in the time-delayed correlations $g^{(2)}(\tau)$ governed by the competition between Raman scattering and subradiant decay, controlled by a single dimensionless parameter. These results provide both physical insight and practical computational tools for engineering collective optical responses in few-atom systems such as optical tweezer arrays.
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All authors Sébastien Lucas, David Wilkowski, Christian Miniatura, Sergey E. Skipetrov
Atmospheric and Oceanic Physics
How well is surface ocean carbon represented in observations and ocean models?
Viviana Acquaviva, Romina Wild, Alessandro Laio et al. (+3 more)
We introduce a general framework for quantifying the information content and representation quality of complex geophysical
datasets based on the intrinsic dimension and differentiable information imbalance of data
manifolds. We use it to derive and compare optimal representations of surface ocean carbon in the SOCAT database of observations and in global ocean biogeochemistry models (GOBMs) and to assess the robustness of the information we can extract from existing data. We find that within the most widely used feature set, the complexity of the data space of SOCAT observations is not fully captured by GOBMs, but the ranking and relative importance of variables learned through GOBMs are substantially correct. We observe that the learned representation of ocean carbon is less accurate in some regions, including the Southern Ocean, but doesn't appear to have evolved significantly over the last two decades. Finally, we show how the optimal representations can be used to improve the skill of distance-based machine learning models and demonstrate it for ocean carbon, and we propose two new metrics to compare models and observations that can be used to build more accurate weighted ensembles of estimates.
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All authors Viviana Acquaviva, Romina Wild, Alessandro Laio, Amanda R. Fay, Thea H. Heimdal, Galen A. McKinley
Data Analysis and Statistics · Cross-listed from hep-ph
Anomaly detection for multijet scenarios
Gregor Kasieczka, Sung Hak Lim, Louis Moureaux et al. (+3 more)
Signals of physics beyond the Standard Model continue to resist discovery at the LHC. Recent years have seen the proliferation of new anomaly detection techniques, promising discovery with significantly fewer model assumptions than traditional approaches. Strategies based on weak supervision have been especially successful, but so far were largely limited in scope by their reliance on a resonance manifesting a decay into a pair of jets. In this work, we demonstrate that a well-established idea from jet substructure physics - recursive soft drop - in combination with the CATHODE technique for anomaly detection can be used to simultaneously perform anomaly detection for signals with an arbitrary number of jets in the final state, greatly increasing the scope of such searches.
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All authors Gregor Kasieczka, Sung Hak Lim, Louis Moureaux, Tore von Schwartz, David Shih, Chitrakshee Yede
Optics · Cross-listed from hep-ph
Searching for Axions on a Higher Note: Third-Harmonic Generation from Colliding High-Intensity Laser Beams
Ashis Paul, Leone di Mauro Villari, Davide Tedeschi et al. (+3 more)
We propose a new laboratory strategy to generate and detect
axion-like particles via third-harmonic generation induced by two non-collinear, polarised high-intensity
laser beams of peak intensity of the order of $10^{24}\,\mathrm{W/cm^2}$, where the third-harmonic signal is generated by the
axion field. Starting from the
axion-modified Maxwell equations, we analytically derive the
axion-induced third-harmonic field, and show that by using state-of-the-art petawatt
laser facilities, a detectable signal can be obtained over a broad range of
axion masses and couplings. A key feature of the setup is that the
axion-
photon conversion rate can be resonantly enhanced by tuning the angle between the two beams through a mechanism that does not depend on the physical volume of the apparatus. The proposed configuration may therefore probe an unexplored region of
axion parameter space and pave the way for next-generation high-power
laser-based
axion searches.
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All authors Ashis Paul, Leone di Mauro Villari, Davide Tedeschi, Carino Ferrante, Luca Di Luzio, Andrea Marini
Accelerator Physics
Modernization and Statistical Validation of a Multilayer TRIM.SP Code for Low-Energy Muon and Ion Implantation
Zaher Salman, Ryan M. L. McFadden and Thomas Prokscha
We describe the staged modernization of a local multilayer TRIM.SP implementation, denoted TRIM.SP-NL. The work included behavior-preserving refactoring, correction of localized bookkeeping and initialization defects, support for more than five elements per layer, reproducible build modes, and a runtime-selectable random-number-generator (RNG) interface. The RANLUX RNG remains the default reference backend, while PCG32 and xoshiro256** provide faster alternatives without changing the input-deck format. The code validation combined exact regression testing with statistical comparisons over 13 representative target multilayer configurations, comprising 143 energy-configuration points per backend and 429 simulations in total. Across the test suite, PCG32 and xoshiro256** reduced runtime by factors of 1.98 and 2.01, respectively. The implanted, backscattered, and transmitted fractions, as well as the mean implantation depths, range straggling, and representative depth profiles showed no systematic RNG dependence. Together with a Node.js-based graphical interface for setup, scans, and result collection, the Fortran engine forms the open-source TRIM.SP-NL Workbench.
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General Physics
Dark Matter Imprints on Black Hole Shadows and Chaotic Dynamics: A Comparative Study of Halo Profiles around Sgr A and M87
Ali Naqi, Mubasher Jamil, Noraiz Tahir et al. (+1 more)
The gravitational influence of dark matter (DM)
halos on the strong-field regime around supermassive black holes (SMBHs) remains largely unexplored. In the present work, we try to make a framework of the
halo-modified space times for four well-known DM profiles including the Navarro Frenk-White (NFW), Moore, Burkert, and Dehnen-(1,4,3/4) profiles, respectively. We derive the corresponding
photon spheres, shadow radii, and innermost stable circular orbits (ISCO) for the Sgr A* and M87*. We then constrain the DM
halo parameters by comparing the theoretical values with the observed Event Horizon
Telescope (EHT) data, and the robustness was checked by comparing the obtained virial mass of the Milky Way and M87 from the parameters with the values already present in the literature. In addition to this we extend the geodesic analysis by formulating the perturbed orbital dynamics using a Painlevé-Gullstrand
Hamiltonian framework, and as a result we compute orbital trajectories, Poincaré sections, and finite-time Lyapunov ex ponents. These chaotic dynamics leave distinct imprints on gravitational waveforms, including phase irregularities and amplitude modulations.
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All authors Ali Naqi, Mubasher Jamil, Noraiz Tahir, Saira Yamsin
History and Philosophy of Physics
Foreknowledge and Free Will Revisited
Eliyahu Zvi Engelberg
The apparent incompatibility between foreknowledge and free will is traditionally formulated in terms of the implication of knowledge of a future event for the freedom of that event. This paper reexamines the problem using the notions of causal order and physical determination provided by modern physics. I consider measurements of two entangled particles at spacelike-separated events, where a measurement outcome is taken to be free if it is not determined by the previous history of the part of the universe accessible to it. Relativity allows the temporal order of the two measurements to be reversed between reference frames while preserving their causal independence.
Quantum correlations nevertheless allow an observer at one measurement event to know the outcome at the other. I show that there is, therefore, a frame in which an observer possesses foreknowledge of a measurement outcome that remains free in this sense. The argument demonstrates that epistemic access to a future event need not be grounded in physical conditions that determine it.
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Popular Physics · Cross-listed from astro-ph.IM
Slysh haloes: the waste heat of cold computing as a submillimetre technosignature
Michael Garrett
Searches for Dysonian waste heat have operated almost exclusively in the mid-infrared and are therefore sensitive primarily to technology radiating at 100-600K. We argue that mature, computation-dominated civilisations may instead dissipate much of their energy at far lower temperatures. The Landauer cost of irreversible computation scales linearly with temperature, while ambient temperatures at large circumstellar radii approach the 2.7K
cosmic microwave background floor. Cold computation is therefore thermodynamically attractive and, because the required radiating area scales as T**-4, potentially conspicuous. These considerations predict a new object class, which we term the SLYSH
HALO after the first advocate of cold Dysonian searches. A Slysh
halo is a physically motivated partial Dyson swarm producing grey, line-free thermal emission from the cold outer regions of planetary systems. We show that such structures are energetically and materially plausible, and that M
dwarfs provide especially favourable search targets. Archival far-infrared and submillimetre surveys of nearby
stars (DEBRIS, DUNES and SONS) can in principle be reinterpreted to constrain cold circumstellar dissipation at approximately the 10**20 Watt level, several orders of magnitude below the waste-heat luminosities targeted by previous infrared searches. Additional opportunities are provided by archival observations from Planck and the JCMT, together with the reprocessing of interferometric data from facilities such as ALMA and NOEMA. We assemble six observational discriminants that separate engineered radiators from natural cold sources and outline a three-tier search programme. Even a null result would provide the first temperature-complete assessment of Dysonian technosignatures.
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Optics
Integrated Microwave Photonics: From Material Platforms to Systems-on-Chip
Jiejun Zhang and Jianping Yao
In this paper, recent advances in integrated microwave photonics (IMWP) are reviewed, including material platforms, integration technologies, and system functionalities. Emerging opportunities and future perspectives are discussed. Silicon (Si) and silicon nitride (SiN) provide dense routing, programmable filtering, and low-loss delay; indium phosphide (InP) supplies optical gain, light generation, and high-speed photodetection; thin-film lithium niobate (TFLN) offers linear and broadband electro-optic conversion; and photonic integration is emerging as a practical path to synergize complementary capabilities. Recent work shows a marked shift from isolated modulators, filters, and delay lines toward chip- and module-level systems, ranging from signal processing engines, real-time spectrum sensing, to full-spectrum wireless links, fiber-wireless conversion, silicon beamforming, integrated radar, programmable processors, and photonic convolution engines with on-chip sources and detectors. As these demonstrations become more mature and complete, the key questions move beyond bandwidth and efficiency toward system integration, microwave packaging, calibration stability, analog link performance, and application-level validation.
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Fluid Dynamics
Numerical simulation of a two-frequency-driven superlattice Faraday-wave pattern
Debashis Panda, Nicolas Périnet, Abdullah M. Abdal et al. (+6 more)
The formation of a superlattice pattern in two-frequency-driven Faraday waves discovered and named SSS-I by Arbell & Fineberg (1998, 2002) is investigated by means of Direct Numerical Simulations (DNS) of the full three-dimensional Navier–Stokes equations with a free surface. Two simulations with distinct quasi-hexagonal initial conditions run at a forcing amplitude $25\%$ above the Faraday-wave onset followed quite different routes, but both led eventually to the same superlattice pattern after around 250 forcing periods. This regime is inaccessible to the approximations of weak nonlinearity or viscosity. The standing-wave pattern contain rows of patches, alternating in time between hills and lakes that are connected by a long skeleton resembing the backbone of DNA strands. The patches and skeleton of the pattern can be related to its spatial
Fourier decomposition, which combines hexagonal modes with a spatially and temporally subharmonic mode. One of the transition routes passes through several fairly long-lived transients including different hexagonal patterns and another superlattice pattern; the other passes only through erratic and disordered states. After another 100 periods, the pattern became unstable and was succeeded by a dynamic version of SSS-I in which the superlattice is modulated and drifts in the direction of the backbone, while preserving its basic shape. Convergence to SSS-I states both experimentally in a large geometry and numerically from two different initial conditions and in a minimal geometry demonstrates the robustness of the SSS-I pattern.
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All authors Debashis Panda, Nicolas Périnet, Abdullah M. Abdal, Lyes Kahouadji, Seungwon Shin, Jalel Chergui, Damir Juric, Omar K. Matar, Laurette S. Tuckerman