Computational Physics · Cross-listed from cond-mat.mtrl-sci
High-pressure single-crystal X-ray diffraction study of ErVO4
Josu Sanchez-Martin, Gaston Garbarino, Samuel Gallego-Parra et al. (+5 more)
We present an investigation into the
crystal structure of ErVO4 under variable pressure conditions. The high-pressure single
crystal X-ray diffraction experiments performed employing helium as the pressure medium facilitated structure refinements up to 24.1(2) GPa. The transition from zircon to scheelite was observed at a pressure of 7.9(1) GPa. In contrast to previous reports, we did not detect any sign of phase coexistence. We also did not observe the second phase transitions previously predicted by density-functional theory to occur below 20 GPa. The determination of the pressure dependence of unit-
cell parameters and volume yields precise values for linear compressibility of each axis and the pressure-volume equation of state for both the zircon and scheelite phases. Additional information on the mechanical properties of ErVO4, obtained from density-functional theory calculations, is also reported.
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All authors Josu Sanchez-Martin, Gaston Garbarino, Samuel Gallego-Parra, Alfonso Munoz, Sushree Sarita Sahoo, Kanchana Venkatakrishnan, Ganapathy Vaitheeswaran, Daniel Errandonea
Plasma Physics · Cross-listed from astro-ph.HE
Whistler-Alfvén turbulence in a non-neutral ultrarelativistic pair plasma
Stanislav Boldyrev and Mikhail Medvedev
The large-scale dynamics of most conventional space and astrophysical
plasmas are predominantly governed by Alfvén modes, which are low-frequency magnetohydrodynamic modes existing in magnetized media. At scales smaller than the ion gyroscale or frequencies exceeding the ion cyclotron frequency, the Alfvén modes transform into kinetic-Alfvén or whistler modes that significantly contribute to
plasma dynamics. However, this scenario reverses in non-neutral pair
plasmas, such as those found in the magnetospheres of
pulsars and magnetars, around rotating black holes and in their relativistic jets, as well as in certain laboratory
plasmas. In these systems, the large-scale dynamics is governed by hybrid whistler-Alfvén modes, which transform into pure Alfvén modes at smaller scales. We derive the nonlinear equations that describe the dynamics of whistler-Alfvén modes in ultrarelativistic non-neutral magnetically dominated pair
plasma and discuss the spectrum of
turbulence governed by these equations.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
High-Pressure X-Ray Diffraction Study of Scheelite-type Perrhenates
Neha Bura, Pablo Botella, Catalin Popescu et al. (+7 more)
The effects of pressure on the
crystal structure of scheelite-type perrhenates were studied using synchrotron powder X-ray diffraction and density-functional theory. At ambient conditions, the studied materials AgReO4, KReO4, and RbReO4, exhibit a tetragonal scheelite-type
crystal structure described by space group I41/a. Under compression, a transition from scheelite-to-M${\prime}$-fergusonite (space group P21/c) was observed at 1.6 and 7.4 GPa for RbReO4 and KReO4, respectively. The transition involves a relative volume decrease. On the other hand, AgReO4 underwent a phase transition to the M-fergusonite structure (space group I2/a) at 13.6 GPa. In this case there is no appreciable volume discontinuity. The room-temperature pressure-volume equation of state for the three studied perrhenates was estimated using a second-order Birch-Murnaghan equation of state. The results for the low-pressure phase are confirmed by density-functional theory calculations. The analysis of the bulk modulus shows that the compressibility of the compounds decreases following the sequence RbReO4 > KReO4 > AgReO4, which is related to the compressibility of the RbO8, KO8, and AgO8 bidisphenoid units. Density-functional theory also offers valuable insights into the elastic constants. Despite giving a good description for the low-pressure phase in the three compounds, density-functional theory cannot catch the structural phase transition observed in experiments. Reasons for it are discussed in the manuscript.
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All authors Neha Bura, Pablo Botella, Catalin Popescu, Frederico Alabarse, Ganapathy Vaitheeswaran, Alfonso Munoz, Brendan J. Kennedy, Jose Luis Rodrigo Ramon, Josu Sanchez-Martin, Daniel Errandonea
Applied Physics · Cross-listed from cond-mat.soft
Spatiotemporal Thermal Modulation and Patterning using a Programmable 1024 Element Microheater Array
Rahul Goyal, Jang-Hwan Han, Sadaf Pashapour et al. (+1 more)
Programmable microheater arrays are essential for a variety of applications including gas sensing, microfluidic lab on a chip devices, 3D printers, and biosensors that rely on DNA amplification. Increasing the density and number of heating elements directly correlates with the precision with which spatiotemporal heat profiles can be delivered. However, large arrays have thus far not been realized. One challenge is that as the number of elements in an array increases, the complexity of connecting them grows. Here, we show that row-column addressing provides a promising architecture for the efficient operation of a large micro-heater array. We introduce a programmable 32 x 32 microheater array consisting of individually addressable robust platinum (Pt)-based Joule heating elements- each smaller than 300 micrometer. We show that combining high-voltage multiplexed electronics and sequential addressing controlled by a high frequency clock, allows the independent operation of the 1024 microheater elements. We demonstrate the generation of heat images and the patterning of metallic structures formed from the
liquid metal Gallium. Our work demonstrates new capabilities for on-chip thermal devices, and opens the possibility to realize novel heat-controlled microactuation systems.
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All authors Rahul Goyal, Jang-Hwan Han, Sadaf Pashapour, Peer Fischer
Atomic Physics
Spectral Phase Pulse Shaping Alters Photoionization Time
J. Aygun, D. Yaacoub and A. L. Harris
Photoionization is a key step in many attosecond processes. Accurately determining the photoionization time delay is critical to understanding electron dynamics during and after ionization and can guide future efforts to manipulate electron motion. Prior studies have shown that the photoionization time delay is non-zero and that pulse shaping through alteration of the spectral phase may change the number and timing of ionization events. In order to more quantitatively assess whether and how the spectral phase modifies the photoionization time delay, we use attosecond streaking simulations to extract the streaking time delay for ionizing pulses with identical power spectra, but different spectral phases. We compare streaking time delays for Gaussian, Airy, and fifth order phase extreme ultraviolet (XUV) pulses. We find that the streaking delay depends on the XUV spectral phase and that the sign of the delay is determined by the sign of the phase for large phases. Pulses with non-zero spectral phase show an asymmetry in the streaking spectrogram that is associated with phase-dependent spectral compression or broadening. Comparison of the streaking delays for short- and long-range potentials indicates that Coulomb-
laser coupling contributions to the streaking shift are independent of spectral phase, confirming that the observed phase dependence arises from intrinsic photoionization dynamics. Overall, our work suggests that the spectral phase may open the door to new opportunities for controlling ionization timing and provide new avenues for coherent control of ultrafast electron
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Computational Physics
Phase-Dependent Excitonic Light Harvesting and Photovoltaic Limits in Monolayer Y2TeO2 MOenes
Bill D. A. Huacarpuma, Jose A. dos S. Laranjeira, Nicolas F. Martins et al. (+5 more)
We investigate phase-dependent electronic and excitonic phenomena in monolayer Y2TeO2 MOenes in the 1T and 2H polymorphs using first-principles theory and an effective many-body framework.
Phonon spectra and elastic stability criteria establish both phases as dynamically and mechanically stable. Quasiparticle band structures reveal direct gaps in the near-infrared to visible range, with gap values increasing systematically from semilocal to hybrid exchange treatments. Optical spectra computed using a tight-binding Bethe-Salpeter approach demonstrate pronounced excitonic resonances arising from reduced dimensionality and weak dielectric screening. The
exciton binding energies reach 152 meV in the 1T phase and 126 meV in the 2H phase, reflecting enhanced
quantum confinement in the structurally denser phase. Our results identify Y2TeO2monolayers as a rare class of stable, direct-gap MOenes with strong excitonic effects, providing a platform for exploring many-body physics in low-dimensional oxychalcogenide systems especially for photovoltaic applications.
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All authors Bill D. A. Huacarpuma, Jose A. dos S. Laranjeira, Nicolas F. Martins, Julio R. Sambrano, Kleuton A. L. Lima, Santosh K. Tiwari, Alexandre C. Dias, Luiz A. Ribeiro Jr
Optics
Purcell-enhanced Bright and Dark Exciton Emission from Perovskite Quantum Dots in Micro-ring Resonators
Lanyin Luo, Mohit Khurana, Ian M. Murray et al. (+5 more)
Colloidal
quantum dots (QDs) integrated with waveguide-coupled dielectric resonators are promising building blocks for compact on-chip light sources. However, deterministic placement of QDs with strong mode overlap at the desired location remains a challenge. Here, we demonstrate a simple and scalable strategy for integrating colloidal QDs with a waveguide-coupled Si3N4 micro-ring resonator platform and for controlling the radiative dynamics of both bright and dark
excitons via Purcell enhancement. We use strongly
quantum-confined CsPbBr3 QDs, which exhibit bright-
exciton emission at room-temperature, while emission at cryogenic temperatures originates from both bright and dark
excitons. The CsPbBr3 QDs are selectively retained on the Si3N4 micro-ring cavities through a
spin-coating/rinsing process, enabling efficient overlap with whispering-gallery modes and routing of the emission through integrated waveguides. We confirm accelerated decay of emission from both bright and dark
excitons for CsPbBr3 QDs coupled to the micro-ring cavities. These results demonstrate an effective route to integrate colloidal QDs with Si3N4 micro-ring cavities and to leverage cavity-enhanced emission in scalable integrated photonic devices.
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All authors Lanyin Luo, Mohit Khurana, Ian M. Murray, Sina Baghbani Kordmahale, Akanksha Pandey, Xiaohan Liu, Alexei V. Sokolov, Dong Hee Son
Optics
Through-bottle spectroscopy as a tool for quality control and anti-counterfeiting of Brandy and Cognac
George O. Dwapanyin, Edward I. Appleton, Stella Corsetti et al. (+4 more)
Counterfeiting of premium spirits poses significant economic and health risks, that could be tackled by robust, accurate, portable and non-destructive through-bottle measurements. Here, we demonstrate the capability of focus-matched inverse spatially offset spectroscopy, combining fluorescence and Raman signals, for authenticating Cognac and Brandy. The technique accurately identifies age classification, bottling year, spoilage due to elevated storage temperatures, and distinguishes between Cognac brands. Critically, our method effectively differentiates genuine Cognacs from counterfeit products, correctly identifying 98% of counterfeit samples. This shows the promise of through-bottle spectroscopy as a powerful tool for supply chain integrity and consumer protection in the high-value spirits
market.
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All authors George O. Dwapanyin, Edward I. Appleton, Stella Corsetti, Charles Descoins, Xavier Poitou, Kishan Dholakia, Graham D. Bruce
Chemical Physics
MBD-ML: Many-body dispersion from machine learning for molecules and materials
Evgeny Moerman, Adil Kabylda, Almaz Khabibrakhmanov et al. (+1 more)
Van der Waals (vdW) interactions are essential for describing molecules and materials, from drug design and catalysis to battery applications. These omnipresent interactions must also be accurately included in machine-learned force fields. The many-body dispersion (MBD) method stands out as one of the most accurate and transferable approaches to capture vdW interactions, requiring only atomic $C_6$ coefficients and polarizabilities as input. We present MBD-ML, a pretrained message passing neural network that predicts these atomic properties directly from atomic structures. Through seamless integration with libMBD, our method enables the immediate calculation of MBD-inclusive total energies, forces, and stress tensors. By eliminating the need for intermediate electronic structure calculations, MBD-ML offers a practical and streamlined tool that simplifies the incorporation of state-of-the-art vdW interactions into any electronic structure code, as well as empirical and machine-learned force fields.
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All authors Evgeny Moerman, Adil Kabylda, Almaz Khabibrakhmanov, Alexandre Tkatchenko
Plasma Physics
Effects of Screening and Pressure Ionization on the Electron Broadening of Spectral Lines in Dense Plasmas
Julian P. Kinney, Stephanie B. Hansen, Thomas A. Gomez et al. (+1 more)
Collisions between electrons and radiating atoms broaden spectral absorption and emission lines in dense
plasmas. High densities also introduce screening and pressure ionization effects that distort the wavefunctions of both bound and free electrons. In order to study how dense
plasma effects influence the electron broadening of spectral lines, this paper incorporates electron wavefunctions from an average-atom (AA) model to calculate the line width of the B III $2p-2s$ transition at $T = 10$ eV for mass densities ranging from $\rho=10^{-4}-0.4$ g/cc. The calculation method uses the impact approximation, allowing the line width to be written in terms of electron-collision cross sections and an interference term. Compared to an otherwise identical calculation that uses Coulomb free wavefunctions, the AA method is found to modify both the cross sections and the resulting line width at sufficiently high density by introducing screening and pressure ionized bound states. Screening lowers the cross sections at low energies and near electron excitation thresholds, while pressure ionized bound states introduce resonances into the continuum. Thus, as the density increases, the relative line width between the AA and Coulomb calculations follows a general decrease because of screening, with sharp increases at various intervals due to pressure ionization. The AA results are also compared with a common approach to introduce screening through the interaction potential and reduced models that use the Bethe formula for the inelastic electron-collision cross sections.
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All authors Julian P. Kinney, Stephanie B. Hansen, Thomas A. Gomez, Scott D. Baalrud
Optics
Nanosecond-scale discrete wavelength switching in feedback-controlled single-gain-section multi-wavelength lasers
Mathieu Ladouce, Pablo Marin-Palomo and Martin Virte
We investigate discrete wavelength switching in single-gain-section multi-wavelength
lasers monolithically integrated on InP with phase-controlled optical-feedback. By modulating the feedback phase, nanosecond-scale wavelength switching is experimentally demonstrated with transition times below 2.5 ns. Measurements consistently show that the switching time decreases with stronger optical feedback and larger phase-modulation amplitudes. Transitions from lower to higher modal gain are faster. We support the experimental observations with a multi-mode extension of the Lang-Kobayashi rate-equation model. We analyze the influence of
laser, feedback-cavity, and modulation parameters on the switching dynamics, and highlight the role of mode coupling. These results highlight the potential of integrated multi-wavelength
lasers for compact and high-speed all-optical networking systems.
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Biological Physics · Cross-listed from cond-mat.soft
Hydrodynamics of Dense Active Fluids: Turbulence-Like States and the Role of Advected Activity
Sandip Sahoo, Siddhartha Mukherjee and Samriddhi Sankar Ray
Dense suspensions of self-propelled bacteria and related active fluids exhibit spontaneous flow generation,
vortex formation, and spatiotemporally chaotic dynamics despite operating at vanishingly small Reynolds numbers. These phenomena, commonly referred to as active
turbulence, display striking visual and statistical similarities to classical inertial
turbulence while arising from fundamentally different nonequilibrium mechanisms. In this article, we present a combined review and theoretical study of hydrodynamic models for dense active fluids, with particular emphasis on bacterial suspensions described by the Toner–Tu–Swift–Hohenberg (TTSH) framework. We review key experimental and theoretical developments underlying the analogy between active and inertial
turbulence, highlighting the emergence of multiple dynamical regimes and the conditions under which universal spectral and intermittent behavior arises in homogeneous systems. Moving beyond the conventional assumption of spatially uniform activity, we introduce a minimal model in which the activity field is heterogeneous and dynamically advected by the flow it generates. Thus treating activity as a spatiotemporally evolving field coupled to the TTSH dynamics, we investigate how advection and
diffusion lead to sharp activity fronts, confinement of turbulent motion, and complex interfacial morphologies. Our numerical results demonstrate that spatial variations in activity can induce transient coexistence of distinct spectral regimes and that universality in active
turbulence is inherently local and time-dependent in heterogeneous systems. These findings underscore the importance of treating activity as a dynamical field in its own right and provide a framework for studying active
turbulence in more realistic, spatially structured biological and synthetic active matter systems.
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Fluid Dynamics
A minimal wake-vortex model explains formation flight of flapping birds
Olivia Pomerenk and Kenneth S. Breuer
Collective patterns of motion emerge across biological taxa: insects swarm, fish school, and birds flock. In particular, many large migratory bird species form distinctly ordered V-shaped formations, which experiments and direct numerical simulations have demonstrated provide substantial energetic benefits during long-distance flight. However, the precise aerodynamic and morphological mechanisms which underlie these benefits remain unclear. In this work, we develop a reduced-order model of the wake-
vortex interactions between two flapping birds flying in tandem. The model retains essential unsteady flapping dynamics while remaining computationally tractable. By optimizing over a six-dimensional state space, which comprises the follower's three-dimensional relative position as well as three independent flapping parameters, we identify the energetically optimal leader-follower configuration of northern bald ibises (Geronticus eremita). The predicted optimum agrees quantitatively with live-bird measurements. Because of its simplicity, the model allows for direct interrogation of the physical mechanisms responsible for this optimum. In particular, it isolates precisely how the follower's wing kinematics interact with the leader's wake to enhance aerodynamic efficiency. The model predicts an 11% reduction in total mechanical power for a follower in formation flight – consistent with experimental estimates – and shows that this saving arises from reductions in both induced and profile power, dominated by decreased profile power enabled primarily through reduced flapping amplitude and, secondarily, reduced upstroke flexion. These results provide a mechanistic explanation for the structure of V-formations and offer new insight into the aerodynamic principles governing collective flight.
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Optics
Chirped Pulse Analysis and Control in Non-Hermitian Scattering Systems using Complex Time Delay
Isabella L. Giovannelli, Steven M. Anlage and Thomas M. Antonsen
We theoretically and experimentally establish a connection between linearly chirped pulse propagation properties and the complex generalization of Wigner-Smith time delay for both transmitted and reflected pulses in linear and dispersive reverberant non-Hermitian scattering systems. We demonstrate that the time shift of the chirped pulse depends on both the real and imaginary parts of the complex time delay of the scattering system. We also show that the chirped pulse experiences a center frequency shift that is directly proportional to the imaginary component of complex time delay, similar to that found in Giovannelli and Anlage (2025). Using these insights, we then demonstrate how complex time delay can be harnessed to systematically tune the propagation properties of a chirped pulse such that a near-zero time shift can be achieved for a wide range of pulse center frequencies in a resonant scattering system. Overall, this work broadens the utility and establishes the physical significance of complex time delays in non-Hermitian settings.
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Physics and Society
Academic collaborations and movements towards successful careers in physics
Mingrong She, Jan Bachmann, Fariba Karimi et al. (+1 more)
Collaboration networks evolve throughout academic careers, yet few studies systematically examine how these network dynamics relate to long-term career success and mobility. Analysing 35,708 physicists' careers spanning at least 15 years, we use time series clustering to identify ten distinct
evolution patterns of network size and clustering coefficient across career years 5 to 15. We report three key results. First, authors who begin with loosely connected networks and progressively tighten their networks while expanding network size during mid-career achieve the highest PI attainment rates, publication output, and citation impact. Second, despite different starting points, network
evolution patterns associated with better outcomes converge toward moderate clustering by career year 15, suggesting an optimal balance between core team cohesion and diverse external connections. Third, mobility is positively associated with these successful network
evolution patterns and remains positively associated with scientific outcomes even after controlling for network
evolution patterns.
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All authors Mingrong She, Jan Bachmann, Fariba Karimi, Leto Peel
Physics and Society
Capacity drop accounting for microscopic vehicle interaction effects: analytical model and validation with high-resolution trajectories
Yu Han, Pan Liu, Zhiyuan Liu et al. (+1 more)
Capacity drop is a traffic phenomenon in which the discharge flow from a queue is lower than the theoretical infrastructure capacity. This paper proposes a generic analytical method to estimate the queue discharge flow of freeway traffic. Capacity drop is primarily attributed to hesitant vehicles, defined as vehicles that stochastically and temporarily enter an acceleration delay state and generate voids (i.e., extra gaps) in front of them. The proposed method estimates the expected total void length generated by all hesitant vehicles, based on the distributions of their spatial and temporal locations as well as the associated delays. It also accounts for interactions between the waves triggered by downstream hesitant vehicles and the voids generated by upstream ones. Our analysis reveals that this interaction is the key mechanism behind the differing extents of capacity drop observed between standing queues and jam waves in previous studies. The accuracy of the model is validated through both numerical simulations and real-world trajectories. Overall, the proposed method offers a deeper understanding of capacity drop, which can be leveraged in traffic flow modeling and control.
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All authors Yu Han, Pan Liu, Zhiyuan Liu, Ludovic Leclercq
Fluid Dynamics
Experimental study of turbulent thermal diffusion of inertial particles in a convective turbulence forced by oscillating grids
E. Elmakies, O. Shildkrot, N. Kleeorin et al. (+2 more)
We investigate the phenomenon of turbulent thermal
diffusion of inertial solid particles in laboratory experiments with convective
turbulence forced by one or two oscillating grids in the air. Turbulent thermal
diffusion causes a non-diffusive contribution to turbulent flux of particles described in terms of an effective drift velocity directed opposite to the gradient of the mean fluid temperature. For inertial particles, this effective drift velocity depends on the Stokes and Reynolds numbers. In the experiments, fluid velocity and spatial distribution of inertial particles are measured using a Particle Image Velocimetry (PIV) system, and the temperature field is measured in many locations by a temperature probe equipped with 12 thermocouples. Measurements of temperature and particle number density spatial distributions have demonstrated the formation of large-scale clusters of inertial particles in the vicinity of the mean temperature minimum due to turbulent thermal
diffusion. In the experiments, the effective drift velocity caused by turbulent thermal
diffusion that results in the formation of large-scale clusters of inertial particles (having the diameter $10 \mu m$) is in 1.5 – 2.5 times larger than that for noninertial particles (having the diameter $0.7 \mu m$) depending on the level of
turbulence. This is in agreement with the theoretical predictions.
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All authors E. Elmakies, O. Shildkrot, N. Kleeorin, A. Levy, I. Rogachevskii
Optics
Geometric representation of higher-order optical modes
Claire Cisowski
An octant representation of higher-order optical modes that includes Laguerre-Gaussian and Hermite-Gaussian modes is presented. The octant picture captures the high-dimensional nature of three-state optical systems and beyond, with standard Poincaré spheres for orbital angular momentum forming subspaces of the entire state space. This representation enables intuitive manipulation of both classical modes and optical qudits and provides a framework for extending Berry phases and topological invariants to high dimensions.
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Accelerator Physics
Proof-of-principle experiment of a novel beam extraction over millions of turns using stable resonance islands and bent crystal
D. E. Veres, P. Arrutia, S. Cettour Cave et al. (+6 more)
A recent study [1] has introduced an advanced method aimed at extracting from a circular particle accelerator over millions of turns using stable islands and a bent
crystal. This technique leverages the strength of non-linear beam dynamics along with adiabatic trapping and transport within stable islands, in combination with a bent silicon
crystal, to provide an efficient extraction of
hadron beams over millions of turns. The positive and encouraging results of the comprehensive numerical simulations were validated through a successful proof-of-principle experiment at the CERN Super
Proton Synchrotron, which demonstrated the feasibility of the technique. This paper presents a detailed discussion and analysis of the experimental results.
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All authors D. E. Veres, P. Arrutia, S. Cettour Cave, B. H. F. Lindström, M. Giovannozzi, L. E. Pauwels, F. F. Van der Veken, F. M. Velotti, G. Franchetti
Optics
Polarization Dynamics in VCSELs Under Sinusoidal Signal Modulation around the Polarization Switching point
Salah Guessoum, Tushar Malica, Athanasios Kyriazis et al. (+3 more)
Vertical-Cavity Surface-Emitting
Lasers (VCSELs) combine compact geometry, low threshold current, and ease of integration, making them central to modern photonic systems. However, their polarization behavior remains a critical factor affecting performance, as the emission state can switch between orthogonally polarized modes around the so-called polarization switching point. This regime exhibits high sensitivity, where small perturbations induce abrupt polarization changes and nonlinear responses. In this work, the polarization dynamics of VCSELs under sinusoidal current modulation around the switching point are numerically investigated using the
Spin-Flip Model. The study examines the influence of modulation frequency, amplitude, and bias current, revealing distinct dynamical regimes including polarization locking, periodic and irregular switching. The observed transitions between regimes elucidate the interplay between modulation and polarization stability, providing insight into the control of VCSEL dynamics for high-speed optical communication and sensing applications.
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All authors Salah Guessoum, Tushar Malica, Athanasios Kyriazis, Jürgen Van Erps, Geert Van Steenberge, Martin Virte
Atmospheric and Oceanic Physics
A consistent phase-averaged model of the interactions between surface gravity waves and currents
Jacques Vanneste and William R. Young
We formulate a model of the two-way interactions between surface
gravity waves and ocean currents. The model couples the transport of wave action in the four-dimensional (horizontal) position–wavevector phase space with the Craik–Leibovich system for the currents. Coupling is via the Doppler shift in the dispersion relation governing action transport, and wave pseudomomentum in the Craik–Leibovich system. The velocity in the Doppler shift is a vertical integral of the Lagrangian mean velocity of the currents, with a weight that is consistent with the vertical structure of the pseudomomentum. This consistency ensures conservation of momentum and energy in the coupled wave–current system. The conservation properties of the wave–current model stem from an underlying variational structure. We derive this structure from that of the rotating Euler equations for an incompressible fluid with free surface by introducing a Lagrangian wave–mean decomposition, making simplifying approximations, and Whitham averaging. The wave–mean decomposition is constructed such that the Lagrangian mean velocity is non-divergent and satisfies a rigid-lid boundary condition. We apply the wave–current model to the problem of generation of inertial oscillations by surface waves originally considered by Hasselmann.
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Atmospheric and Oceanic Physics · Cross-listed from math-ph
Particle, kinetic and hydrodynamic models for sea ice floes. Part II: Rotating floes with environmental forces
Quanling Deng, Seung-Yeal Ha, Jaemoon Lee et al. (+2 more)
This paper builds on the multiscale modeling framework introduced in Part I (Deng and Ha, Physica D: Nonlinear Phenomena 483 (2025) 134951) for sea-ice floe dynamics with non-rotating floes to the case with rotational floes, nonlinear contact interactions, Coriolis force and ocean tilt. Building on the particle-kinetic-hydrodynamic hierarchy developed for non-rotating floes, we generalize the particle model to describe ice floes as rigid bodies characterized by position, linear velocity, angular velocity, size, and moment of inertia. The interaction rules now include nonlinear contact forces and torques arising from short-range compression, restitution, and tangential friction laws, together with both oceanic and atmospheric drags that couple translational and rotational motions. These particle descriptions lead to an enriched Vlasov-type kinetic equation posed on an extended phase space, whose moments yield a hydrodynamic system for mass, momentum, and angular-momentum balances. Compared with Part I, the resulting macroscopic equations feature additional hydrodynamic and stress contributions, rotational transport, and dissipative mechanisms stemming from nonlinear collisions. The proposed framework provides a more accurate description of sea-ice floe dynamics and offers a systematic pathway toward multiscale modeling of sea-ice rheology under complex environmental forcing.
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All authors Quanling Deng, Seung-Yeal Ha, Jaemoon Lee, Alberto Alberello, Luke G. Bennetts
Physics and Society · Cross-listed from cs.LG
Robustness in sparse artificial neural networks trained with adaptive topology
Bendegúz Sulyok, Gergely Palla, Filippo Radicchi et al. (+1 more)
We investigate the robustness of sparse artificial neural networks trained with adaptive
topology. We focus on a simple yet effective architecture consisting of three sparse layers with 99% sparsity followed by a dense layer, applied to image classification tasks such as MNIST and Fashion MNIST. By updating the
topology of the sparse layers between each epoch, we achieve competitive accuracy despite the significantly reduced number of weights. Our primary contribution is a detailed analysis of the robustness of these networks, exploring their performance under various perturbations including random link removal,
adversarial attack, and link weight shuffling. Through extensive experiments, we demonstrate that adaptive
topology not only enhances efficiency but also maintains robustness. This work highlights the potential of adaptive sparse networks as a promising direction for developing efficient and reliable deep learning models.
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All authors Bendegúz Sulyok, Gergely Palla, Filippo Radicchi, Santo Fortunato
Physics and Society
The Swarm Intelligence Freeway-Urban Trajectories (SWIFTraj) Dataset – Part II: A Graph-Based Approach for Trajectory Connection
Xinkai Ji, Pan Liu, Ying Yang et al. (+1 more)
In Part I of this companion paper series, we introduced SWIFTraj, a new open-source vehicle trajectory
dataset collected using a unmanned aerial vehicle (
UAV) swarm. The
dataset has two distinctive features. First, by connecting trajectories across consecutive
UAV videos, it provides long-distance continuous trajectories, with the longest exceeding 4.5 km. Second, it covers an integrated traffic network consisting of both freeways and their connected urban roads. Obtaining such long-distance continuous trajectories from a
UAV swarm is challenging, due to the need for accurate time
alignment across multiple
videos and the irregular spatial distribution of
UAVs. To address these challenges, this paper proposes a novel graph-based approach for connecting vehicle trajectories captured by a
UAV swarm. An undirected graph is constructed to represent flexible
UAV layouts, and an automatic time
alignment method based on trajectory matching cost minimization is developed to estimate optimal time offsets across
videos. To associate trajectories of the same vehicle observed in different
videos, a vehicle matching table is established using the Hungarian
algorithm. The proposed approach is evaluated using both simulated and real-world data. Results from real-world experiments show that the time
alignment error is within three
video frames, corresponding to approximately 0.1 s, and that the vehicle matching achieves an F1-score of about 0.99. These results demonstrate the effectiveness of the proposed method in addressing key challenges in
UAV-based trajectory connection and highlight its potential for large-scale vehicle trajectory collection.
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All authors Xinkai Ji, Pan Liu, Ying Yang, Yu Han
Optics
Symmetry-Broken Cavity Solitons and Collective Polarization Conformity in Fabry-Perot Kerr Resonators
Yohann G. Sanvert, Abdullah Alabbadi, Lewis Hill et al. (+7 more)
We report on the experimental generation of polarization
symmetry-broken cavity
solitons (CSs) in a passive, fiber-based, coherently-driven, Fabry-Perot (FP) Kerr resonator. Polarization resolved measurements reveal the spontaneous transition of initially symmetric CSs into asymmetrical vectorial states, triggered by a cross-phase modulation-induced polarization bifurcation. Most notably, due to counter-propagation of light occurring in FP resonators, we unveil a collective polarization conformity effect, whereby multiple CSs circulating in the cavity converge to the same asymmetric polarization state once their number exceeds a certain threshold. These results demonstrate that Fabry-Perot resonators support novel collective
soliton dynamics that are absent in ring architectures.
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All authors Yohann G. Sanvert, Abdullah Alabbadi, Lewis Hill, Yuandi Xu, Gang Xu, Gian-Luca Oppo, Stephane Coen, Erwan Lucas, Pascal Del'Haye, Julien Fatome
Fluid Dynamics
Large eddy simulation of turbulent swirl-stabilized flames using the front propagation formulation: impact of the resolved flame thickness
Ruochen Guo, Yunde Su and Yuewen Jiang
This work extends the front propagation formulation (FPF) combustion model to large eddy simulation (LES) of swirl-stabilized turbulent premixed flames and investigates the effects of resolved flame thickness on the predicted flame dynamics. The FPF method is designed to mitigate the spurious propagation of under-resolved flames while preserving the reaction characteristics of filtered flame fronts. In this study, the model is extended to account for non-adiabatic effects and is coupled with an improved sub-filter flame speed estimation that resolves the inconsistency arising from heat-release effects on local sub-filter
turbulence. The performance of the extended FPF method is validated by LES of the TECFLAM swirl-stabilized burner, where the results agree well with experimental measurements. The simulations reveal that the stretching of vortical structures in the outer shear layer leads to the formation of trapped flame pockets, which are identified as the physical mechanism responsible for the secondary temperature peaks observed in the experiment. The prediction of this phenomenon is shown to be strongly dependent on the resolved flame thickness, when the filter size is used for modeling sub-filter flame wrinklings. Without proper modeling of the chemical steepening effects, the thickness of the resolved flame brush is over-predicted, causing the flame consumption rate to be under-estimated. Consequently, the flame brush detaches from the outer shear layer, resulting in a failure to capture the flame pockets and the associated secondary temperature peaks.
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Biological Physics
From quantitative modeling of fluorescence experiments on biomolecules to the prediction of spectroscopic dye properties
Thomas-Otavio Peulen, Daria Maksutova and Thorben Cordes
Fluorescence spectroscopy and modeling provide powerful means to characterize biomacromolecular structures, dynamics, and interactions. Förster resonance energy transfer serves as a key technique for this due to its nanometer-scale distance sensitivity. Quantitative interpretation of fluorescence data relies on models that link molecular structure to observable spectroscopic quantities and vice versa. Integrative modelling frameworks combine fluorescence observables with complementary structural information to infer molecular structures and conformational ensembles. This review outlines conceptual components of fluorescence-based modeling, discusses dye representations, and highlights advances toward refined models enabling quantitative structural analysis. Finally, we discuss the prediction of spectroscopic properties of dyes based on biomolecular structures and fluorescence assay design beyond traditional FRET applications.
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Physics and Society · Cross-listed from cs.SI
Bridging Through Absence: How Comeback Researchers Bridge Knowledge Gaps Through Structural Re-emergence
Somyajit Chakraborty, Angshuman Jana and Avijit Gayen
Understanding the role of researchers who return to academia after prolonged inactivity, termed "comeback researchers", is crucial for developing inclusive models of scientific careers. This study investigates the structural and semantic behaviors of comeback researchers, focusing on their role in cross-disciplinary knowledge transfer and network reintegration. Using the AMiner citation
dataset, we analyze 113,637 early-career researchers and identify 1,425 comeback cases based on a three-year-or-longer publication gap followed by renewed activity. We find that comeback researchers cite 126% more distinct communities and exhibit 7.6% higher bridging scores compared to dropouts. They also demonstrate 74% higher gap
entropy, reflecting more irregular yet strategically impactful publication trajectories. Predictive models trained on these bridging- and
entropy-based features achieve a 97% ROC-AUC, far outperforming the 54% ROC-AUC of baseline models using traditional metrics like publication count and h-index. Finally, we substantiate these results via a multi-lens validation. These findings highlight the unique contributions of comeback researchers and offer data-driven tools for their early identification and institutional support.
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Biological Physics
Universal Persistent Brownian Motions in Confluent Tissues
Alessandro Rizzi and Sangwoo Kim
Biological tissues are active materials whose non-
equilibrium dynamics emerge from distinct cellular force-generating mechanisms. Using a two-dimensional active foam model, we compare the effects of traction forces and junctional tension fluctuations on confluent tissue dynamics. While these two modes of activity produce qualitatively different
cell shapes, rearrangement statistics, and spatiotemporal correlations in fluid states, we find that the long-time cellular motion universally converges to persistent Brownian dynamics. This universal feature contrasts with the non-universal correlations between
cell geometry, rearrangement rate, and fluidity, which depend sensitively on the underlying modes of active force. Our results demonstrate that persistent Brownian motion provides a minimal framework for describing tissue dynamics, while distinct active forces leave identifiable structural and dynamical signatures, thereby enabling inference of the dominant active force in fluid state tissues.
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Medical Physics · Cross-listed from eess.SP
Modeling of Human Body-coupled Electric Field Interference in Unshielded Ultra-Low Field MRI
Jiali He, Yamei Dai, Sheng Shen et al. (+2 more)
Portable ultra-low field MRI (ULF-MRI) systems operated in unshielded environments are susceptible to electromagnetic interference (EMI). Subject presence in the imaging region will lead to substantial noise increases, yet the dominant coupling mechanism remains insufficiently characterized. We develop a lumped-parameter
circuit model of the coupled environment-body-receiver system. The model indicates that ambient time-varying electric fields induce a body common-mode potential, which is converted into differential-mode noise through capacitive imbalance between the head and the receive-coil terminals, yielding strong dependence on subject position and geometry.
Circuit analysis, simulations, and controlled experiments support the model, with predicted imbalance consistent with measured noise variations. Guided by this mechanism, we implement a capacitive low-impedance bypass to clamp the body potential, achieving an approximately 3.5-fold SNR improvement on a 50 mT prototype. The proposed model offers a compact
circuit-based tool for analyzing and mitigating human body-coupled electric-field interference in portable ULF-MRI.
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All authors Jiali He, Yamei Dai, Sheng Shen, Jiamin Wu, Zheng Xu