Physics and Society
Generating consensus and dissent on massive discussion platforms with a semantic-vector model
A. Ferrer, D. Muñoz-Jordán, A. Rivero et al. (+3 more)
Reaching consensus on massive discussion networks is critical for reducing noise and achieving optimal collective outcomes. However, the natural tendency of humans to preserve their initial ideas constrains the emergence of global solutions. To address this, Collective Intelligence (CI) platforms facilitate the discovery of globally superior solutions. We introduce a dynamical system based on the standard $O(N)$ model to drive the aggregation of semantically similar ideas. The system consists of users represented as nodes in a $d=2$
lattice with nearest-neighbor interactions, where their ideas are represented by semantic vectors computed with a pretrained
embedding model. We analyze the system's
equilibrium states as a function of the coupling parameter $\beta$. Our results show that $\beta > 0$ drives the system toward a
ferromagnetic-like phase (global consensus), while $\beta < 0$ induces an
antiferromagnetic-like state (maximum dissent), where users maximize semantic distance from their neighbors. This framework offers a controllable method for managing the tradeoff between cohesion and diversity in CI platforms.
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All authors A. Ferrer, D. Muñoz-Jordán, A. Rivero, A. Tarancón, C. Tarancón, D. Yllanes
Biological Physics
Supercontraction-Induced Twist in Spider Silk Is a Dual Poynting Effect
V. Fazio, G. Puglisi and G. Saccomandi
Spider dragline silk supercontracts as humidity increases, displaying large axial shortening together with a reproducible macroscopic twist. The physical origin of this torsion remains debated and is often attributed to helically arranged load-bearing elements, despite the lack of direct evidence for helicity in the native fiber. Here we show that torsion can arise generically from nonlinear anisotropic elasticity: humidity-driven shortening of the amorphous
matrix, mechanically constrained by stiff, axially aligned $\beta$-sheet–rich load-bearing segments and their experimentally induced prestretch, drives the system into a dual Poynting regime in which axial shortening couples to spontaneous twist. Coupling a
diffusion-based water-uptake law to irreversible
matrix remodeling and fiber plasticity, the model quantitatively reproduces monotonic and cyclic torsional measurements using parameter values consistent with available experimental material parameters. These results identify supercontraction-induced torsion in spider silk as a manifestation of a dual Poynting effect and provide a minimal, physically grounded framework for humidity-driven torsional actuation in
matrix–fiber architectures.
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Atomic Physics · Cross-listed from quant-ph
Universal composite phase gates with tunable target phase
Peter Chernev, Mouhamad Al-Mahmoud and Andon A. Rangelov
We present a systematic method for constructing universal composite phase gates with a continuously tunable target phase. Using a general Cayley–Klein parametrization of the single-pulse propagator, we design gates from an even number of nominal $\pi$ pulses and derive analytic phase families by canceling, order by order in a small deviation parameter, the leading contributions to the undesired off-diagonal element of the composite propagator, independently of the dynamical phase. The resulting sequences provide intrinsic robustness against generic control imperfections and parameter fluctuations and remain valid for arbitrary pulse shapes. Numerical simulations in a standard two-level model confirm high-order error suppression and demonstrate broad, flat high-fidelity plateaus over wide ranges of simultaneous pulse-area and detuning errors, highlighting the efficiency of the proposed universal composite phase gates for resilient phase control in
quantum information processing.
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Atomic Physics · Cross-listed from quant-ph
Superradiance of entangled photon pairs from a high-density chip-scale Cs vapor cell
Heewoo Kim, Bojeong Seo and Han Seb Moon
Superradiance is one of the most fundamental collective
quantum phenomena in light-matter interactions and has been studied extensively since Dicke's seminal work. However, its practical implementation remains challenging because superradiant enhancement requires strict experiment conditions for strong collective coupling among emitters. Can superradiance emerge in a simple platform, such as an atomic vapor
cell composed of thermally moving atoms? To address this question, we identify the key signatures of superradiance in a hot atomic ensemble and find a use case of superradiance using an atomic vapor
cell. Here, the
Photon-Pair SuperRadiance (PPSR) process in an atomic vapor
cell provides a novel approach to generating superradiant
quantum light from a practical atomic platform. We experimentally demonstrate a superradiant entangled
photon-pair generation via PPSR process in a high-density, 1-mm-long chip-scale Cs vapor
cell. The hot, dense atomic vapor
cell allows the mean interatomic distance in the Doppler-broadened atomic ensemble to be reduced to 0.29 times the idler-
photon wavelength, satisfying the condition for cooperative emission. The thin chip-scale geometry enables high atomic densities while mitigating the reabsorption of emitted
photons and maintaining moderate optical depth. In this subwavelength regime, we clearly observe the temporal narrowing of the biphoton wavefunction from 0.60 ns to 0.17 ns due to a superradiant decay. This pronounced temporal compression provides strong evidence of collective superradiant emission in the chip-scale Cs vapor
cell. Our PPSR source delivers a detected
photon-pair rate exceeding 10^6 pairs/s while maintaining a high coincidence-to-accidental ratio of 280.
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Applied Physics · Cross-listed from math.NA
Improving the local solution of the DG predictor of the ADER-DG method for solving systems of ordinary differential equations and its applicability to systems of differential-algebraic equations
I.S. Popov
Improved local numerical solution for the ADER-DG numerical method with a local DG predictor for solving the initial value problem for a first-order ODE system is proposed. The improved local numerical solution demonstrates convergence orders of one higher than the convergence order of the local numerical solution of the original ADER-DG numerical method and has the property of continuity at grid nodes. Rigorous proofs of the approximation orders of the local numerical solution and the improved local numerical solution are presented. Obtaining the proposed improved local numerical solution does not require significant changes to the structure of the ADER-DG numerical method. Therefore, all conclusions regarding the convergence orders of the numerical solution at grid nodes, the resulting superconvergence, and the high stability of the ADER-DG numerical method remain unchanged. A wide range of applications of the ADER-DG numerical method is presented for solving specific initial value problems for ODE systems for a wide range of
polynomial degrees. The obtained results provide strong confirmation for the developed rigorous theory. The improved local numerical solution is shown to exhibit both higher accuracy and improved smoothness and point-wise comparability. Empirical convergence orders of all individual numerical solutions were calculated for a wide range of error norms, which well agree with the expected convergence orders. The rigorous proof, based on the $\epsilon$-
embedding method, of the applicability of the ADER-DG numerical method with a local DG predictor to solving DAE systems is presents.
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Plasma Physics
Reduction of SAXS Signal due to Doppler Broadening Induced Loss of Coherence
Thomas Kluge, Uwe Hernandez Acosta, Klaus Steiniger et al. (+2 more)
We present an analytical and numerical study of how Doppler-induced spectral broadening in
laser-heated
plasmas degrades the coherence of small-angle X-ray scattering (SAXS) signals, and show that the resulting loss of temporal coherence reduces the SAXS intensity. Applying this formalism to two
benchmark geometries - single density steps (wires) and periodic gratings – we obtain analytic estimates. For gratings, finite coherence simultaneously lowers Bragg-peak heights and broadens their widths, whereas for isolated steps only the overall scaling with q affected. We map the parameter space relevant to current SASE and self-seeded XFELs, revealing that Doppler effects remain managable for the trieval of geometry parameters (less than few 10 % error) for SASE bandwidths but become the dominant error source in seeded configurations or above-keV temperatures. Practical consequences for density-gradient
retrieval and interface-sharpness measurements are quantified. The results supply clear criteria for when Doppler broadening must be included in SAXS data analysis and offer a route to infer electron temperature directly from coherence-loss signatures.
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All authors Thomas Kluge, Uwe Hernandez Acosta, Klaus Steiniger, Ulrich Schramm, Thomas E. Cowan
Optics
Intelligent Distributed Optical Fiber Sensing in Transportation Infrastructures: Research Progress, Applications, and Challenges
Xin Gui, Fanhao Zeng, Yunchuan Zhang et al. (+9 more)
Distributed optical fiber sensing (DOFS), along with its capabilities of long-range coverage, multi-parameter monitoring, and completely passive detection, emerges as one of the most promising non-destructive detection techniques for structural health monitoring (SHM) and operational assessment of linear transportation infrastructures. In this paper, we provide a state-of-the-art review on DOFS applications across typical linear infrastructure systems, encompassing highways, long-span bridges, rail transit networks, airport runways, and analogous linear structures. The comprehensive discussion consists of four critical research dimensions: 1) optical fiber selection for multi-parameter sensing and robust cable packaging techniques, 2) distributed sensing principles and signal processing
algorithms, 3) diverse application scenarios in SHM and related fields, and 4) anomaly detection and event classification methodologies. Building upon the foundational introduction of DOFS technical principles and monitoring solutions for intelligent transportation infrastructure, this paper elaborates on system design approaches, sensing data analytics
algorithms, and future research directions.
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All authors Xin Gui, Fanhao Zeng, Yunchuan Zhang, Yiming Wang, Jiaqi Wang, Changjia Wang, Xuelei Fu, Sheng Li, Fang Liu, Lina Yue, Jinpeng Jiang, Zhengying Li
Plasma Physics
Quasi-linear approach of bi-Kappa distributed electrons with dynamic $\kappa$ parameter. EMEC instability
Pablo S Moya, Roberto E Navarro, Marian Lazar et al. (+3 more)
In recent years, significant progress has been made in the velocity-moment-based quasi-linear (QL) theory of waves and instabilities in
plasmas with nonequilibrium velocity distributions (VDs) of the Kappa (or $\kappa$) type. However, the temporal variation of the parameter $\kappa$, which quantifies the presence of suprathermal particles, is not fully captured by such a QL analysis, and typically $\kappa$ remains constant during
plasma dynamics. We propose a new QL modeling that goes beyond the limits of a previous approach, realistically assuming that the quasithermal core cannot evolve independently of energetic suprathermals. The case study is done on the electron-cyclotron (EMEC) instability generated by anisotropic bi-Kappa electrons with $A=T_\perp/T_\parallel > 1$ ($\parallel, \perp$ denoting directions with respect to the background
magnetic field). The parameter $\kappa$ self-consistently varies through the QL equation of kurtosis (fourth-order moment) coupled with temporal variations of the temperature components, relaxing the constraint on the independence of the low-energy (core) electrons and suprathermal high-energy tails of VDs. The results refine and extend previous approaches. A clear distinction is made between regimes that lead to a decrease or an increase in the $\kappa$ parameter with saturation of the instability. What predominates is a decrease in $\kappa$, i.e., an excess of suprathermalization, which energizes suprathermal electrons due to self-generated wave fluctuations. Additionally, we found that VDs can evolve toward a quasi-Maxwellian shape (as $\kappa$ increases) primarily in regimes with low beta and initial kappa values greater than five. Instability-driven relaxation only partially resolves temperature anisotropy in bi-Kappa electron VDs, as wave fluctuations generally act to further energize suprathermal electrons.
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All authors Pablo S Moya, Roberto E Navarro, Marian Lazar, Peter H Yoon, Rodrigo A López, Stefaan Poedts
Optics
Ethernet-over-OWC Using VCSELs: Transparent Gigabit Links with Low Latency and Robust Alignment Tolerance
Hossein Safi, Isaac N. O. Osahon, Iman Tavakkolnia et al. (+1 more)
We demonstrate a fully bidirectional 1 Gbs Ethernet over OWC link over a 1m free space path using a VCSEL-PIN pair and only commercially available components. The unamplified, transparent system achieves error-free operation, with a latency of less than 25 ns, and a centimetre-scale
alignment tolerance.
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All authors Hossein Safi, Isaac N. O. Osahon, Iman Tavakkolnia, Harald Haas
Computational Physics
An efficient treatment of heat-flux boundary conditions in GSIS for rarefied gas flows
Yanbing Zhang, Ruifeng Yuan, Liyan Luo et al. (+1 more)
Heat-flux boundary conditions are challenging to implement efficiently in rarefied gas flow simulations because the wall-reflected gas temperature and density must be determined dynamically during the computation. This paper aims to tackle this problem within the general synthetic iterative scheme (GSIS), where the Boltzmann kinetic equation is solved deterministically in an outer loop and macroscopic synthetic equations are solved in an inner loop. To avoid kinetic-macroscopic boundary-flux mismatch and the resulting convergence bottlenecks, for the macroscopic boundary flux at every inner iteration, the incident increment is estimated using a Maxwellian distribution, and then the reflected contribution is obtained by boundary conditions consistent with those in the kinetic solver. In addition to retaining the fast-converging and asymptotic-preserving properties of GSIS, the proposed method significantly reduces the iterations required to determine the wall-reflected gas parameters. Numerical simulations of rarefied gas flows in and around a 3D nozzle, a 2D adiabatic cylinder, and a 2D annular heat-transfer configuration show good agreement with the direct simulation Monte Carlo method, while achieving substantial efficiency gains over conventional iterative schemes.
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All authors Yanbing Zhang, Ruifeng Yuan, Liyan Luo, Lei Wu
Physics and Society
Block-Fitness Modeling of the Global Air Mobility Network
Giulia Fischetti, Anna Mancini, Giulio Cimini et al. (+4 more)
Accurate representations of the World Air Transportation Network (WAN) are fundamental inputs to models of global mobility, epidemic risk, and infrastructure planning. However, high-resolution, real-time data on the WAN are largely commercial and proprietary, therefore often inaccessible to the research community. Here we introduce a generative model of the WAN that treats air travel as a
stochastic process within a maximum-
entropy framework. The model uses airport-level passenger flows to probabilistically generate connections while preserving traffic volumes across geographic regions. The resulting reconstructed networks reproduce key structural properties of the WAN and enable simulations of dynamic spreading that closely match those obtained using the real network. Our approach provides a scalable, interpretable, and computationally efficient framework for
forecasting and policy design in global mobility systems.
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All authors Giulia Fischetti, Anna Mancini, Giulio Cimini, Jessica T. Davis, Abby Leung, Alessandro Vespignani, Guido Caldarelli
Physics and Society
The mechanistic origin of branching-driven nucleation in abrupt phase transitions
Leyang Xue, Shengling Gao, Bnaya Gross et al. (+5 more)
Phase transitions are the macroscopic manifestation of microscopic processes that drive a system towards a new state. The detailed
evolution of these processes, particularly in abrupt phase transitions, are currently not fully understood. Here, we introduce a theoretical framework based on internal node dependencies within a single-layer
lattice. Crucially, we demonstrate that the fundamental mechanism underlying abrupt transitions is nucleation propagation preceded by a slow cascading process which scales with the range of dependencies. Our findings show that the synergy between these two distinct stages is essential for the occurrence of an abrupt transition. The first stage of a slow cascading mechanism was recently observed experimentally in superconducting layered materials, where heat acts as the dependency links, for the limit of infinite dependency range. Our model thus generalizes the framework to include finite dependency ranges, revealing previously unobserved mechanisms that could be experimentally verified through controlling the range of thermal
diffusion in the material. As a universal mechanism, our model provides a robust method to test nucleation-controlled phase transitions in multiple systems, providing a path to discover and understand microscopic mechanisms in phase transitions.
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All authors Leyang Xue, Shengling Gao, Bnaya Gross, Orr Levy, Daqing Li, Zengru Di, Lazaros K. Gallos, Shlomo Havlin
Atomic and Molecular Clusters
Interpretable, Physics-Informed Learning Reveals Sulfur Adsorption and Poisoning Mechanisms in 13-Atom Icosahedra Nanoclusters
Raiane Ferreira Monteiro, João Marcos T. Palheta, Tulio Gnoatto Grison et al. (+7 more)
Transition-metal nanoclusters exhibit structural and electronic properties that depend on their size, often making them superior to bulk materials for heterogeneous catalysis. However, their performance can be limited by sulfur poisoning. Here, we use dispersion-corrected density functional theory (DFT) and physics-informed machine learning to map how atomic sulfur adsorbs and causes poisoning on 13-atom icosahedral clusters from 30 different transition metals (3$d$ to 5$d$). We measure which sites sulfur prefers to adsorb to, the thermodynamics and energy breakdown, changes in structure, such as bond lengths and coordination, and electronic properties, such as $\varepsilon_d$, the HOMO-LUMO gap, and charge transfer. Vibrational analysis reveals true energy minima and provides ZPE-based descriptors that reflect the
lattice stiffening upon sulfur adsorption. For most metals, the metal-sulfur interaction mainly determines adsorption energy. At the same time, distortion penalties are usually moderate but can be significant for a few metals, suggesting these are more likely to restructure when sulfur is adsorbed. Using unsupervised k-means clustering, we identify periodic trends and group metals based on their adsorption responses. Supervised regression models with leave-one-feature-out analysis identify the descriptors that best predict adsorption for new samples. Our results highlight the isoelectronic triad \ce{Ti}, \ce{Zr}, and \ce{Hf} as a balanced group that combines strong sulfur binding with minimal structural change. Additional DFT calculations for \ce{SO2} adsorption reveal strong binding and a clear tendency toward dissociation on these clusters, linking electronic states,
lattice response, and poisoning strength. These findings offer data-driven guidelines for designing sulfur-tolerant nanocatalysts at the subnanometer scale.
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All authors Raiane Ferreira Monteiro, João Marcos T. Palheta, Tulio Gnoatto Grison, Octávio Rodrigues Filho, Renato Luis Tame Parreira, Diego Guedes-Sobrinho, Celso R. C. Rêgo, Alexandre C. Dias, Krys Elly de Araújo Batista, Maurício J. Piotrowski
Optics
Modulating Retroreflectors for CubeSat Optical Inter Satellite Links: Modeling, Optimization, and Benchmarking
Makafui Avevor, Hossein Safi, Harald Haas et al. (+1 more)
Modulating retroreflectors (MRRs) offer a promising pathway to low-complexity and energy efficient asymmetric optical inter-satellite link (OISL) for small spacecrafts, such as CubeSats. In this paper, we develop a unified statistical channel model for an on off keying modulated, retroreflector-enabled OISL. The model captures both
stochastic and deterministic pointing losses, as well as signal-dependent noise.
Stochastic channel distributions are approximated via Monte Carlo simulation, and system optimization is carried out under CubeSat constraints using the achievable information rate as the primary metric. In addition, we derive bit-error ratio and outage probability to evaluate communication reliability. The proposed architecture is benchmarked against three state-of-the-art CubeSat
laser terminals, i.e., NASA's Optical Communications and Sensors Demonstration (OCSD), DLR's OSIRIS4CubeSat, and NASA's CLICK BC. Results indicate that an optimized MRR-based transmitter can outperform OCSD and achieve performance comparable to OSIRIS4CubeSat at ranges below 500 km, while consuming only 2.5 W of power during transmission, significantly less than conventional CubeSat optical terminals.
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All authors Makafui Avevor, Hossein Safi, Harald Haas, Iman Tavakkolnia
Atomic Physics · Cross-listed from nucl-th
Comparative study of quartet superfluid state: Quartet Bardeen-Cooper-Schrieffer theory and generalized Nambu-Gor'kov formalism
Yixin Guo, Hiroyuki Tajima and Haozhao Liang
We theoretically investigate a quartet superfluid state in fermionic matter by using the quartet Bardeen-Cooper-Schrieffer (BCS) variational theory and the Green's function method. We demonstrate that the quartet BCS theory with the multiple-infinite-product ansatz successfully reproduces an exact four-body result in a one-dimensional four-component
Fermi gas at the dilute limit, in contrast to the single-infinite-product ansatz. To see the validity of the quartet BCS state, we derive the self-consistent equation for the quartet superfluid order parameter within the generalized imaginary-time Nambu-Gor'kov formalism, which is found to be consistent with the quartet BCS variational equation. Moreover, by numerically computing the momentum-resolved single-particle spectral function in a one-dimensional system, we discuss how the single-particle spectra evolve with increasing the strength of the four-body cluster formation. We show that a coherent BCS-like quasiparticle branch on the weak-coupling side evolves into a strongly damped, continuum-dominated spectrum in the strong-coupling side, while nonzero quartet superfluid order parameter persists throughout the crossover regime. Our results would be useful for understanding beyond-BCS pairing effects and four-body cluster formations in fermionic systems in an interdisciplinary way.
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Optics
Carrier-Envelope-Offset Frequency Stabilization of a High Peak and Average Power Thin-Disk Oscillator
Yasmin Kopp, Gregor Hehl, Johann Gabriel Meyer et al. (+2 more)
In this work, we demonstrate carrier-envelope-offset (CEO) frequency stabilization of a Kerr-lens mode-locked thin-disk oscillator delivering 180 W average power, 80 MW output peak power, and >500 MW intra-cavity peak power, the highest peak power achieved in any stabilized thin-disk oscillator system. The CEO frequency detection is performed with an f-2f interferometer based on supercontinuum generation in a YAG
crystal. Intra-cavity loss modulation using an acousto-optic modulator, that simultaneously provides the Kerr lens, yields 50 mrad of residual phase noise with a 250 kHz control bandwidth. After pulse compression to 0.9 GW peak power in a dual-stage multipass
cell, the system directly enables high harmonic generation in noble gases. These results represent a significant step in realizing a compact and robust high-repetition-rate driver system suitable for
vacuum ultraviolet and extreme ultraviolet frequency comb generation.
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All authors Yasmin Kopp, Gregor Hehl, Johann Gabriel Meyer, Simon Goncharov, Oleg Pronin
Applied Physics
Two-dimensional FrBD friction models for rolling contact: extension to linear viscoelasticity
Luigi Romano
This paper extends the distributed rolling contact FrBD framework to linear viscoelasticity by considering classic derivative Generalised Maxwell and Kelvin-Voigt rheological representations of the bristle element. With this modelling approach, the dynamics of the bristle, generated friction forces, and internal deformation states are described by a system of 2(n+1)
hyperbolic partial differential equations (PDEs), which can capture complex relaxation phenomena originating from viscoelastic behaviours. By appropriately specifying the analytical expressions for the transport and rigid relative velocity, three distributed formulations of increasing complexity are introduced, which account for different levels of
spin excitation. For the linear variants, well-posedness and passivity are analysed rigorously, showing that these properties hold for any physically meaningful parametrisation. Numerical experiments complement the theoretical results by illustrating steady-state characteristics and transient relaxation effects. The findings of this paper substantially advance the FrBD paradigm by enabling a unified and systematic treatment of linear viscoelasticity.
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Physics Education
It's Not the Tool, It's the Task: A Framework for Cognitively Activated AI Augmentation in Physics Instruction
Jochen Kuhn, Stefan Küchemann, Dave Rakestraw et al. (+1 more)
Generative artificial intelligence (AI) systems can now reliably solve many standard tasks used in introductory physics courses, producing correct equations, graphs, and explanations. While this capability is often framed as an opportunity for efficiency or personalization, it also poses a subtle ethical and educational risk: students may increasingly submit correct results without engaging in the epistemic practices that define learning physics. This challenge has recently been described as the "boiling frog problem" because we may not fully recognize how rapidly AI capabilities are advancing and fail to respond with commensurate urgency. In this article, we argue that the central challenge of AI in physics education is not cheating or tool selection, but instructional design. Drawing on research on self-regulated learning, cognitive load, multiple representations, and hybrid intelligence, we propose a practical framework for cognitively activated learning activities that structures student activities before, during, and after AI use. Using an example from an introductory kinematics laboratory, we show how AI can be integrated in ways that preserve prediction, interpretation, and evaluation as core learning activities. Rather than treating AI as an answer-generating tool, the framework positions AI as an epistemic partner whose contributions are deliberately bounded and reflected upon.
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All authors Jochen Kuhn, Stefan Küchemann, Dave Rakestraw, Patrik Vogt
Instrumentation and Detectors
Projected sensitivity to light WIMP-like particles of the BULLKID-DM experiment
Matteo Folcarelli, A. Acevedo-Rentería, L. E. Ardila-Perez et al. (+39 more)
BULLKID-DM is an experiment designed for the direct searches of particle dark matter candidates with mass around 1 GeV, or below, and cross-section with nucleons smaller than $10^{-40}$ cm$^2$. The detector consists of a stack of diced silicon wafers, acting as arrays of particle absorbers, sensed by multiplexed Kinetic Inductance Detectors. The target will amount to 800 g subdivided in more than 2000 silicon dice, with the aim of controlling the background from natural radioactivity by creating a fully active structure and by applying fiducialization techniques. In this work we present the projected sensitivity of BULLKID-DM to light WIMP-like particles considering also the other future experiments in the field.
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All authors Matteo Folcarelli, A. Acevedo-Rentería, L. E. Ardila-Perez, L. Bandiera, M. Calvo, M. Cappelli, R. Caravita, F. Carillo, U. Chowdhury, D. Crovo, A. Cruciani, A. D'Addabbo, D. Delicato, M. De Lucia, G. Del Castello, M. del Gallo Roccagiovine, F. Ferraro, S. Fu, R. Gartmann, M. Grassi, V. Guidi, D. Helis, T. Lari, L. Malagutti, A. Mazzolari, A. Monfardini, T. Muscheid, D. Nicolò, F. Paolucci, D. Pasciuto, L. Pesce, C. Puglia, D. Quaranta, C. M. A. Roda, S. Roddaro, M. Romagnoni, G. Signorelli, F. Simon, A. Tartari, E. Vázquez-Jáuregui, M. Vignati, K. Zhao
Plasma Physics · Cross-listed from math-ph
Hamiltonian hydrodynamic reductions of one-dimensional Vlasov equations
Rayan Oufar and Cristel Chandre
We investigate
Hamiltonian fluid reductions of the one-dimensional Vlasov-Poisson equation. Our approach utilizes the hydrodynamic Poisson bracket framework, which allows us to systematically identify fundamental normal variables derived from the analysis of the Casimir invariants of the resulting Poisson bracket. This framework is then applied to analyze several well-established
Hamiltonian closures of the onedimensional Vlasov equation, including the multi-delta distribution and the waterbag models. Our key finding is that all of these seemingly distinct closures consistently lead to the formulation of a unified form of parametric closures: When expressed in terms of the identified normal variables, the parameterization across all these closures is revealed to be
polynomial and of the same degree. All these parametric closures are uniquely generated from one of the moments, called $\mu$2, a cubic
polynomial in the normal variables. This result establishes a structural connection between these different physical models, offering a path toward a more unified and simplified description of the one-dimensional Vlasov-Poisson dynamics through its reduced hydrodynamic forms with an arbitrary number of fluid variables.
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Accelerator Physics
The Hamilton-Jacobi Equation and its Application to Nonlinear Beam Dynamics: Comparison of Approaches
Stephan I. Tzenov
The rarely used Hamilton-Jacobi equation has been utilized as an elegant way to find the trajectories of mechanical systems and to derive
symplectic maps. Further, the exact solution in kick approximation of Hamilton's equations of motion in interaction representation is written as a generalized one-turn twist map. One can imagine that the nonlinear kick comes first, followed by the one-period rotation along the machine circumference, or a second alternative in which the one-period rotation occurs before the kick. There is a difference in the result of solving Hamilton's equations between the two cases, which is expressed in obtaining a standard forward twist map in the first case, or alternatively a backward map in the second one. This nontrivial and intuitively unclear peculiarity is usually ignored/overlooked in practically all specialized references on the topic. Finally, the statistical properties and the behavior of the density distribution of a particle beam in configuration space under the influence of an isolated sextupole have been studied.
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Fluid Dynamics
Flash Freeze–Thaw Phenomenon in Sprayed Evaporating Micrometer Droplets
Junshi Wang, Zehao Pan, Howard A. Stone et al. (+1 more)
Two-fluid spray nozzles are widely used in combustion, chemical processing, pharmaceutical coating, environmental control, and spray drying to atomize
liquids with pressurized gas. However, the adiabatic cooling and resulting flash freeze–thaw exposure of atomized droplets remain underexplored. Using high-fidelity computational fluid dynamics coupled with droplet-scale nucleation modeling, we show that the atomizing gas temperature at the nozzle exit can fall from $22\,^{\circ}\mathrm{C}$ to below $-130\,^{\circ}\mathrm{C}$, initiating rapid ice nucleation and freezing in micro-scale droplets. For atomizing gas at $5\,\mathrm{bar}$ (gauge) and $22\,^{\circ}\mathrm{C}$, all droplets smaller than $1.5\,\mu\mathrm{m}$ freeze, whereas droplets larger than $3\,\mu\mathrm{m}$ remain
liquid. These frozen droplets thaw within $O(10)\,\mu\mathrm{s}$ upon leaving the cold zone, subjecting sensitive actives to intense freeze–thaw thermomechanical stresses near the nozzle even when the bulk drying gas is warm. Parametric studies show that ice formation is eliminated at atomizing gas temperatures above $110\,^{\circ}\mathrm{C}$ for all gas-to-
liquid mass ratios (GLRs) between 8 and 25, or at $\mathrm{GLR}<12$ for all atomizing gas temperatures; the chamber drying gas does not influence near-nozzle freezing. Additionally, we demonstrate that swirling flow intensifies flash freeze–thaw by deepening gas cooling, whereas non-swirling flow extends cold-zone residence time, yet both designs produce similar iced-droplet fractions. We construct an operating map delineating conditions that avoid flash freeze–thaw and show that the no-ice boundary provides a conservative criterion for both swirl and non-swirl nozzles. These findings identify a previously unrecognized freeze–thaw stress mechanism that can compromise spray-dried pharmaceutical product stability.
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All authors Junshi Wang, Zehao Pan, Howard A. Stone, Maksim Mezhericher
Optics
Multi-mode Coherent Detection Ghost Imaging Lidar and Vibration-Mode Imaging
Jinquan Qi, Shuang Liu, Chenjin Deng et al. (+4 more)
Coherent detection ghost imaging
lidar (CD-GI
lidar) integrates ghost imaging with coherent detection, thereby achieving enhanced anti-interference and phase-resolved imaging capability. Here, we propose a bucket-detector-based multi-mode coherent detection scheme for CD-GI
lidar, where the reflected multi-mode light fields are coherently mixed with a single-mode local oscillator (LO) at the bucket detector photosensitive plane. The bucket-detector-based multi-mode CD-GI
lidar system breaks the constraints of Siegman
antenna theorem by utilizing field correlation to decouple the reflected multi-mode light fields and reconstructs the spatial distribution of targets' vibration modes. Theoretical analysis of the bucket-detector-based multi-mode CD-GI
lidar system is presented in this work, and its feasibility is verified through a series of experiments.
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All authors Jinquan Qi, Shuang Liu, Chenjin Deng, Chaoran Wang, Zunwang Bo, Youzhen Gui, Shensheng Han
Optics
Electrical detection of high-order optical orbital angular momentum
Guanyu Zhang, Xianghan Meng, Zini Cao et al. (+6 more)
The orbital angular momentum (OAM) of light provides an unbounded set of orthogonal modes for ultrahigh-capacity optical information processing. However, current OAM detection schemes typically rely on light interference or diffraction, which require bulky optical components and pose a major obstacle to on-chip integration. Here, we demonstrate a fully integrated silicon-based photodetector that enables direct electrical detection of light OAM. This photodetector can resolve
vortex beams with topological charges from m = -9 to 9, achieving a record-high mode number resolution among on-chip devices. By integrating plasmonic gratings onto the device electrodes, incident
vortex beams can be converted into surface plasmon polaritons with OAM-dependent splitting angles, which in turn produce photocurrents that vary monotonically with the OAM order. Further incorporation of a surface dielectric lens can enhance mode resolution, and a split-electrode architecture enables OAM chirality discrimination. Owing to its CMOS-compatibility and spectral scalability, this platform provides a compact and robust solution for integrated OAM detection, opening new opportunities for on-chip optical communication and computing systems based on structured light.
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All authors Guanyu Zhang, Xianghan Meng, Zini Cao, Hai Lin, Shuxin Huang, Minghao Deng, Jiaqi Li, Qihuang Gong, Guowei Lyu
Atmospheric and Oceanic Physics
A stable hothouse triggered by a tipping mechanism
Erik Chavez, Jan Rombouts and Michael Ghil
The
climate system's nonlinear dynamics is influenced by various external forcings and internal feedbacks that can give rise to regional and even global tipping points that may lead to significant and potentially irreversible changes. Paleoclimatic records reveal that Earth's
climate has shifted between distinct equlibria, including a "hothouse Earth" state with temperatures about 10 K higher than present. However, a specific mechanism for a sudden tipping to an alternate stable state, several degrees warmer than the present
climate, has yet to be presented. We introduce a temperature-carbon-vegetation (TCV) model comprising an energy balance model of global temperature, coupled with global terrestrial and ocean CO2 dynamics, and with vegetation ecosystem change. Our model exhibits a new tipping mechanism that leads to a hothouse Earth under a high-emissions scenario. Its simulations align with both observations and IPCC-class global
climate models prior to tipping. The two processes that produce global tipping are: (i) temperature-albedo feedback due to darkening of the terrestrial cryosphere by glacial microalgae; and (ii) limits to vegetation adaptation that lead to reduced carbon absorption.
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Fluid Dynamics
Manifold Learning with Implicit Physics Embedding for Reduced-Order Flow-Field Modeling
Weiji Wang, Chunlin Gong, Xuyi Jia et al. (+1 more)
Nonlinear
manifold learning (ML) based reduced-order models (ROMs) can substantially improve the quality of nonlinear flow-field modeling. However, noise and the lack of physical information often distort the dimensionality-reduction process, reducing the robustness and accuracy of flow-field prediction. To address this problem, we propose a novel
manifold learning ROM with implicit physics
embedding (IPE-ML). Starting from data-driven
manifold coordinates, we incorporate physical parameters (e.g., angle of attack, Mach number) into
manifold coordinates system by minimizing the prediction error of Gaussian process regression (GPR) model, thereby fine-tuning the
manifold structure. These adjusted coordinates are then used to construct a flow-fields prediction model that predict nonlinear flow-field more accurately. The method is validated on two test cases: transonic flow-field modeling of the RAE2822 and supersonic flow-field modeling of the hexagon airfoil. The results indicate that the proposed IPE-ML can significantly improve the overall prediction accuracy of nonlinear flow fields. In transonic case, shock-related errors have been notably reduced, while in supersonic case the method can confine errors to small local regions. This study offers a new perspective on
embedding physical information into nonlinear ROMs.
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All authors Weiji Wang, Chunlin Gong, Xuyi Jia, Chunna Li
Chemical Physics · Cross-listed from quant-ph
Theory for Entangled-Photons Stimulated Raman Scattering versus Nonlinear Absorption for Polyatomic Molecules
Mingran Zhang, Jiahao Joel Fan, Frank Schlawin et al. (+1 more)
Quantum entanglement offers an incredible resource for enhancing the sensing and spectroscopic probes. Here we develop a microscopic theory for the stimulated Raman scattering (SRS) using entangled
photons. We demonstrate that the time-energy correlation of the
photon pairs can optimize the signal for polyatomic molecules. Our results show that the spectral-line intensity of the entangled-
photon SRS (ESRS) is of the same order of magnitude as the one for the entangled two-
photon absorption (ETPA); the parameter window is thus identified to do so. Moreover, the vibrational coherence is found to play an important role for enhancing the ESRS against the ETPA intensity. Our work paves a firm road for extending the schemes of molecular spectroscopy with
quantum light, based on the observation of the ETPA in experiments.
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All authors Mingran Zhang, Jiahao Joel Fan, Frank Schlawin, Zhedong Zhang
Applied Physics
Steady-State Exceptional Point Degeneracy and Sensitivity of Nonlinear Saturable Coupled Oscillators
Benjamin Bradshaw, Amin Hakimi and Filippo Capolino
A coupled oscillator system displays enhanced sensitivity of its saturated steady-state (SS) oscillation frequency to small parameter perturbations near an exceptional point degeneracy (EPD), a property that can be used to realize EPD-based sensors. Linear $\mathcal{PT}$-symmetric systems, consisting of two coupled resonators, exhibit EPDs around which square-root sensitivity is observed. However, linear models are insufficient for realistic systems that rely on nonlinear, saturable gain elements, particularly when $\mathcal{PT}$-
symmetry is broken. Thus, we study the SS of a general system of two coupled oscillators featuring EPDs and saturable nonlinear gain, using coupled-mode theory. We do this by synthesizing and extending prior SS analyses of the system's stability, and its square-root and cubic-root oscillation frequency sensitivity at a unique third-order SS-EPD. We include an SS analysis of the saturated gain values, energy, and the oscillation frequency's sensitivity in the vicinity of the third-order SS-EPD, providing a comprehensive analysis of the system's various SS regimes. We determine that the stable and bistable regions in parameter space directly depend on the saturated gain values; that the dynamic range of high sensitivity around degenerate conditions is extended by increasing losses, consequently reducing the system's stored energy; and that, to exploit the cubic-root-like sensitivity associated to the third-order SS-EPD, the suggested working regime is best confined to operation within the weakly coupled regime and not exactly at the third order SS-EPD. Finally, we apply the model to two electronic
circuits that exhibit cubic-root sensitivity, demonstrating the application and limitations of this analysis.
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Optics
Programmable branched flow of light
Shan-shan Chang, Daxing Xiong, Ze-huan Zheng et al. (+5 more)
We demonstrate deterministic control of branched flow of light using anisotropic nematic
liquid crystals. By sculpting the director field via photoalignment, we create spatially programmable optical potentials that govern light scattering and propagation. This platform enables configurable, anisotropic branched flow of light and reveals a universal scaling law for its characteristic features, directly connecting disordered photonics with mesoscopic wave transport. Under extreme anisotropy, we observe a pronounced directional channeling effect, driven by anomalous
symmetry-breaking velocity
diffusion, which concentrates light propagation along preferential directions while suppressing transverse spreading. These findings establish a tunable material platform for harnessing branched flow of light, opening pathways toward on-chip photonic
circuits that exploit disorder-guided transport, scattering-resilient endoscopic imaging, and adaptive optical interfaces in complex media.
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All authors Shan-shan Chang, Daxing Xiong, Ze-huan Zheng, Li-Wei Wang, Yan-qing Lu, Lu-Jian Chen, Jian-Hua Jiang, Jin-hui Chen
Computational Physics
Efficient local classification of parity-based material topology
Stephan Wong, Ichitaro Yamazaki, Chris Siefert et al. (+3 more)
Although the classification of crystalline materials can be generally handled by momentum-space-based approaches, topological classification of aperiodic materials remains an outstanding challenge, as the absence of translational
symmetry renders such conventional approaches inapplicable. Here, we present a numerically efficient real-space framework for classifying parity-based $\mathbb{Z}_2$
topology in aperiodic systems based on the spectral localizer framework and the direct computation of the sign of a Pfaffian associated with a large sparse skew-symmetric
matrix. Unlike projector-based or momentum-space-based approaches, our method does not rely on translational
symmetry, spectral gaps in the
Hamiltonian's bulk, or gapped auxiliary operators such as
spin projections, and instead provides a local, energy-resolved topological invariant accompanied by an intrinsic measure of topological protection. A central contribution of this work is the development of a scalable sparse factorization
algorithm that enables the reliable determination of the Pfaffian's sign for large sparse
matrices, making the approach practical to realistic physical materials. We apply this framework to identify the
quantum spin Hall effect in quasicrystalline class AII systems, including gapless
heterostructures, and to diagnose fragile
topology in a large $C_2 \mathcal{T}$-symmetric photonic quasicrystal. Overall, our results demonstrate that the spectral localizer, combined with efficient sparse numerical methods, provides a unified and robust tool for diagnosing parity-based topological phases in aperiodic electronic, photonic, and acoustic materials where conventional band-theoretic indexes are inapplicable.
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All authors Stephan Wong, Ichitaro Yamazaki, Chris Siefert, Iain Duff, Terry A. Loring, Alexander Cerjan