Optics
Millimeter-scale wide-field mid-infrared photothermal imaging enabled by a broadly tunable picosecond optical parametric oscillator
Anooj Thayyil Raveendran, Supatcharee Cael, Anju Jose et al. (+2 more)
Wide-field mid-infrared photothermal (MIP) imaging enables chemically specific microscopy with submicron spatial resolution but remains fundamentally limited by the trade-off between field of view, mid-infrared pulse energy, and spectral tunability. As a result, current wide-field implementations are typically restricted to fields of view below 200 {\mu}m and to either the fingerprint or high-wavenumber spectral regions. Here, we overcome these limitations by developing a wide-field fluorescence-detected mid-infrared photothermal (F-MIP) imaging platform driven by a commercial picosecond optical parametric oscillator (OPO). The system provides pulse energies of up to 360 {\mu}J together with a broad tuning range from 625 to 4327 cm-1, enabling millimeter-scale wide-field imaging in the high-wavenumber regions. We demonstrate a field of view of approximately 1 mm in diameter for fluorescently labeled polystyrene beads while preserving spectral fidelity. Furthermore, the platform enables, to our knowledge, the first wide-field MIP imaging below 900 cm-1. To demonstrate its applicability to biomedical imaging, we performed large-area mosaic imaging of fluorescent tuberculosis-infected tissue sections, providing chemically resolved maps over millimeter-sized sample areas. These results establish broadly tunable OPO-driven F-MIP as a scalable platform for high-throughput vibrational imaging of large biological specimens and advanced materials.
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All authors Anooj Thayyil Raveendran, Supatcharee Cael, Anju Jose, Jürgen Popp, Christoph Krafft
Computational Physics · Cross-listed from cond-mat.stat-mech
Thermodynamic phase transitions in lattice spin systems with severe kinetic constraints: Numerical simulation results
Ruifeng Liu, Jianwen Zhou, Yejia Chen et al. (+2 more)
The Fredrickson-Andersen model with hyperparameter $K=1$ is a severely constrained kinetic
lattice spin system, such that any site is temporarily blocked from changing its packing state (empty or occupied) if there is one or more occupied nearest neighbors. Starting from a completely random initial configuration with a fraction $\rho$ of sites being occupied, some of the sites may be permanently frozen to their initial state under this severe kinetic constraint. The remaining sites can switch states at least occasionally, and they form the unfrozen subsystem associated with the given initial configuration. In the present work we investigate thermodynamic phase transitions in such unfrozen subsystems of the two-dimensional square
lattice and the three-dimensional cubic
lattice by extensive numerical simulations. We demonstrate that the
giant connected component of the unfrozen subsystem collapses at certain critical value $\rho_{c}$ of initial packing density, with $\rho_c = 0.2475$ for the square
lattice and $\rho_c = 0.2809$ for the cubic
lattice. This phase transition belongs to the same universality class of the conventional site percolation. We also observe that the ground states (densest packing configurations) experience a continuous
crystal-to-glass phase transition at the critical value $\rho^* = 0.1423$ of initial packing density for the cubic
lattice. For the two-dimensional square
lattice we argue that long-range crystalline order is destroyed in the ground states as long as the initial packing density $\rho$ is positive.
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All authors Ruifeng Liu, Jianwen Zhou, Yejia Chen, Jiahang Chen, Hai-Jun Zhou
Fluid Dynamics
A systematic evaluation of the Richards equation for predicting soil moisture in Irish grasslands
S Kumar, S Mathias, E Ruelle et al. (+5 more)
The Richards equation (RE) is widely used to model water flow in unsaturated soils, but its performance in persistently wet grassland systems remains uncertain. This is particularly relevant in Irish grasslands, where soils often remain close to saturation for extended periods and seasonal waterlogging is common. Here, we evaluate the RE against three soil moisture
datasets from County Wexford, Ireland, spanning different locations, soil types, and observation periods. We show that the standard RE formulation systematically over-predicts soil moisture under prolonged near-saturated conditions. We find that this arises from the commonly used Feddes plant water uptake function, which suppresses water losses under anaerobic conditions, despite continued evaporation from near-saturated soils. To address this limitation, we introduce a simple modification that retains a small non-zero water loss rate in the anaerobic regime. The modified model produces substantially improved agreement with observations across all three
datasets. These results provide a systematic evaluation of RE-based soil moisture modelling in Irish grasslands. More broadly, they identify an important limitation of conventional RE implementations in waterlogged environments and demonstrate a practical approach for improving soil moisture predictions in persistently wet soils.
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All authors S Kumar, S Mathias, E Ruelle, H Khan, O Fenton, K Shishkin, L O'Naraigh, GP Benham
Optics
Transmissive extreme ultraviolet metagrating
Anna Kulter, Tiago Regio Crispim, Lorenz Weiss et al. (+11 more)
Extreme ultraviolet (EUV) radiation is a key tool for attosecond physics and lithography. However, strong material absorption limits the availability of transmissive optical elements at these wavelengths. Metaoptics exploit geometry to control the wavefront of transmitted light on the nanoscale and, due to their minimal thickness, promise to fill this gap. Here, we demonstrate the first EUV metaoptics for broadband applications: we design, fabricate, and experimentally investigate a blazed transmissive EUV metagrating and compare it with a focused-ion-beam-milled sawtooth-blazed grating serving as an in-situ reference. The metagrating achieves an angular dispersion of 0.04{\deg}/nm with a directionality (the ratio of the +1st and -1st diffraction order efficiency) of up to 5.8. The device shows phase-based operation up to 50 eV
photon energy (down to 25 nm
vacuum wavelength) and an octave-spanning bandwidth of 25 eV, doubling the previous spectral window addressable by metasurfaces. Comparing both gratings' performance reveals that, when accounting for fabrication constraints, EUV metasurfaces are competitive with free-form optics while offering scalability to large apertures and arbitrary phase profiles. Broadband transmissive operation removes the need for grazing incidence optics, defeating a major source of aberrations, and allows polarization-insensitive spectral analysis, enabling energy-resolved ultrafast spectroscopy in compact experimental configurations.
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All authors Anna Kulter, Tiago Regio Crispim, Lorenz Weiss, Alexander Sagar Grossek, David J. Grafinger, Zsuzsanna Pápa, Judit Budai, Lázár Tóth, Péter Dombi, Rodolfo Previdi, Harald Plank, Andreas Hohenau, Martin Schultze, Marcus Ossiander
Physics and Society
From Gravity to Confinement: Wealth Redistribution as Optimal Drift Design in the Fokker-Planck Framework
Anders G Frøseth
A proportional wealth tax acts as a uniform gravitational field on the wealth distribution: it shifts the drift of the Fokker-Planck equation without altering the
diffusion, preserving the Gini coefficient at all finite times. The same drift-shift
symmetry that makes the tax non-distortionary also makes it non-redistributive through the
market channel. Redistribution requires breaking this
symmetry. A progressive tax (confining potential) replaces the Pareto steady state with a thinner-tailed distribution whose Gini is a closed-form function of the progressivity parameter; source-sink terms (tax-funded transfers) reshape the density directly. We formulate optimal redistribution as a control problem for the Fokker-Planck equation, penalising intervention costs including migration, evasion, and portfolio distortion. In general
equilibrium the tax design feeds back through aggregate capital and the production function, yielding a self-consistent McKean-Vlasov equation with diminishing returns to progressivity. The spectral gap of the Fokker-Planck operator determines convergence speed: progressive taxes redistribute within policy-relevant timescales, whereas proportional taxes rely on slow demographic turnover.
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Medical Physics · Cross-listed from cs.LG
Self-Supervised Implicit CEST Reconstruction via Physics-Informed Lorentz Encoding
Dexuan Li, Yupeng Wu, Chenglong Wang et al. (+4 more)
Multi-Pool Chemical Exchange Saturation Transfer (CEST) MRI provides valuable metabolic information but is clinically limited by long acquisition times. Although sparse sampling reduces scanning time, reconstructing high-resolution Z-spectra from limited data remains an ill-posed inverse problem. Conventional interpolation and generic Implicit Neural Rep-resentations (INRs) often lack physical constraints, leading to spectral artifacts and physically invalid signals. To address this, we propose Lorentz Encoding (LE), a physics-informed framework that formulates CEST reconstruction as a self-supervised reconstruction task via implicit continuous coordinate learning. Unlike generic positional encodings, LE regularizes the continuous spectral mapping by projecting sparse coordinates into a physically constrained space governed by a combination of parametric Lorentzian profiles with learnable basis functions. This mechanism effectively reduces noise and enforces consistency with physical models. Experiments on in vivo human
brain data demonstrate that LE significantly outperforms state-of-the-art methods. Specifically, under a 39-point sampling strategy, LE achieves a PSNR of 57.58 dB and an SSIM of 0.9994. Furthermore, the learned physics-informed encodings form a continuous, geometrically ordered trajectory in the latent space, ensuring accurate quantitative metabo-lite mapping (APT, NOE, MT).
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All authors Dexuan Li, Yupeng Wu, Chenglong Wang, Hanlin Liu, Hui Zhen, Jianqi Li, Guang Yang
Computational Physics
Mass-Conserving Physics-Informed Neural Networks For The One-Dimensional Advection-Diffusion Equation
Eszra Forenita Sigalingging, Liu Kin Men, Setianto Setianto et al. (+1 more)
The advection-
diffusion equation is a fundamental model of transport phenomena in which mass conservation is an essential physical constraint. While classical schemes such as Crank-Nicolson preserve this property by construction, Physics-Informed Neural Networks (PINNs) enforce only the local residual of the governing PDE and are therefore not guaranteed to conserve global quantities such as mass over long integration horizons. In this work, we examine the extent of this limitation for the periodic one-dimensional advection-
diffusion equation and evaluate a Mass-Penalty PINN that augments the standard PINN loss with a soft mass-conservation constraint. We compare the performance of Vanilla PINN, Mass-Penalty PINN, and the Crank-Nicolson scheme across a range of Peclet numbers spanning
diffusion-dominated to advection-dominated regimes, and over two simulation horizons representing short-term and long-term dynamics. The results show that, for short-term simulations, the Mass-Penalty PINN does not always provide a consistent improvement in accuracy. However, for long-term simulations, the Mass-Penalty PINN reduces the relative L2 error and mass conservation error by factors of approximately 9-67 and 15-215, respectively, compared with the Vanilla PINN, across the tested Peclet numbers. Further analysis reveals that the accuracy degradation observed in Vanilla PINN is predominantly caused by the accumulation of mass drift over time. These results demonstrate that incorporating a soft mass-conservation constraint substantially improves the long-term reliability of PINN for conservative transport problems, particularly in mitigating mass drift over extended simulation horizons.
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All authors Eszra Forenita Sigalingging, Liu Kin Men, Setianto Setianto, Ferry Faizal
Optics
Breathing k-Gap Events and Instability on Instability in Nonlinear Photonic Time Crystals
Liang Zhang, Chenhao Pan and Yiming Pan
Photonic time
crystals (PTCs) host momentum bandgaps, or k gaps, that enable parametric amplification and lasing of seeded fields. In nonlinear PTCs, Kerr saturation dynamically suppresses the exponential growth, reshaping k-gap amplification into an active, spatially homogeneous k gap
soliton train. Here, we show that a localized perturbation on this unstable background then nucleates a transient spatiotemporal excitation: the breathing k gap event. Unlike Peregrine breathers emerging from modulational instability on a planewave background, this event extracts energy from competing host k gap
solitons and remains sustained by their interaction. We identify this process as an instability on instability mechanism intrinsic to nonlinear k gap dynamics. The event is robust against noise and disorder, and can be deterministically reshaped into collective breathing patterns by periodic and phase engineered seeding. These results establish k gap engineering as a route to generating and controlling extreme spatiotemporal waves in photonic time varying media.
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Physics and Society
Long-range social pressure and the evolution of cooperation in multiplex networks
María Pereda and Gabrielle Muller
Social pressure—the awareness of being observed by others—is a fundamental driver of prosocial behavior in human societies. Yet it is typically assumed that only direct neighbors exert vigilance pressure on an individual, despite empirical evidence that social influence persists to at least three degrees of separation. Here we show that extending the reach of social vigilance beyond direct neighbors substantially promotes cooperation. We couple a Prisoner's Dilemma on one layer of a multiplex network to a vigilance cascade on the other, with influence decaying geometrically with network distance. Extending vigilance to just the second circle of influence ($L=2$) shifts the critical temptation for defection by roughly 36% in sparse Erdős–Rényi networks. Extending to four circles ($L=4$) raises this threshold by over 50% in the same networks. Both shifts are
topology dependent: the $L=1\to2$ step alone already accounts for most of the gain in these sparse networks, whereas the pattern is more gradual in denser, hub-dominated Barabási–Albert networks, consistent with the decay coefficients of social influence reported in controlled experiments. The effect is strongest in sparse networks, requires that the vigilance and game layers be aligned, and reproduces directly on a real social network of physicians; in dense, hub-dominated networks the gain instead depends sharply on how fast influence decays with distance, switching between weak and strong cooperation as the decay rate crosses a threshold. Our results strongly suggest that even modest expansions of social awareness—such as those enabled by online social platforms—can substantially reshape the landscape of cooperative behavior in human populations.
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Optics
Single-photon polarization tomography with an integrated metal-superconductor nanowire array
Pierre Brosseau, Jiawei Wang, Giorgio Adamo et al. (+2 more)
Light polarization is a primary degree of freedom for encoding
quantum information. The scaling up of photonic
quantum networks and computer architecture depends crucially on its precise characterization. This is typically achieved by placing external waveplates, polarizers, moving mounts, and recently metasurfaces, on top of the detectors. All these solutions complicate integration and scaling. Here we break convention with traditional architecture and present a monolithic, self-aligned metal-
superconductor nanowire single
photon detector (M-SNSPD) possessing intrinsic full polarization selectivity. Gold nanowires, co-fabricated atop NbTiN superconducting nanowires within the same lithographic footprint, act as polarization-selective plasmonic metamaterials inducing resonant absorption in the NbTiN. U-shaped wires provide linear polarization selectivity, while S-shaped meanders distinguish circular polarization, while retaining the high-count rates and low dark count rates of conventional SNSPDs. By arranging them into a four-pixel array we realize simultaneous projection onto four polarizations and demonstrate continuous polarization state
tomography with an ensemble average fidelity exceeding 98%. Our approach opens new avenues towards scalable detector arrays with integrated plasmonic functionalities, for single
photon polarimetry, imaging and spectroscopy.
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All authors Pierre Brosseau, Jiawei Wang, Giorgio Adamo, Anton N. Vetlugin, Cesare Soci
Physics Education
Associations Between Event-Based (Mis)Recognition by STEM Authorities with STEM Identity and STEM Career Aspirations
Amdad Ahmed Awsaf, Remy Dou, Gerhard Sonnert et al. (+1 more)
Several programs for marginalized young people have been intentionally designed to increase the diversity in STEM careers; however, the participation of racially and ethnically minoritized individuals continued to be underrepresented in STEM disciplines. Using discipline-based STEM identity theories and drawing data from an NSF-funded survey of 1,134 participants, these regression analyses examine the impact of prior educational experiences on STEM identity (i.e., seeing oneself as a STEM person) and career aspirations among individuals attending Minority Serving Institutions (MSIs). The study's findings indicate that although positive reinforcement positively correlates with the STEM identity construct, the efforts are not always supportive enough to predict STEM career aspirations for minoritized individuals. It underscores the importance of explicitly designing appropriate interventions to support STEM identity formation and STEM career pursuit.
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All authors Amdad Ahmed Awsaf, Remy Dou, Gerhard Sonnert, Philip Sadler
Physics Education
Concurrent Phenomenological Analysis of STEM Career Aspirations in Underrepresented Youth: Role of Experiences and Identity
Amdad Ahmed Awsaf, Nicole Giansanti, Susan Sunbury et al. (+1 more)
Despite numerous initiatives aimed at enhancing diversity and achieving equity in the STEM workforce, racially and ethnically minoritized individuals remain underrepresented in STEM disciplines and the STEM workforce. While many factors influence STEM identity (i.e., seeing oneself as a STEM person), it strongly correlates with individuals' future STEM career choices. This phenomenological qualitative study explores the impact of formal or informal STEM-related recognition that influences minority youths' aspirations to pursue a STEM career. Results indicate that though misrecognition negatively impacts one's motivation to study STEM areas, lack of recognition in formal schooling contexts was sometimes mitigated by recognition and support from family. The study suggests providing targeted interventions to facilitate underrepresented youths' achievements in STEM to foster a strong STEM identity and STEM career aspirations.
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All authors Amdad Ahmed Awsaf, Nicole Giansanti, Susan Sunbury, Remy Dou
Optics
Engineering Disordered Many-particle Plasmonic Nanoclusters for Wafer-scale Uniform and Giant Electromagnetic Field Enhancement
Minjun Kim, Vasanthan Devaraj, Hyeon-Seok Seo et al. (+6 more)
Scalable plasmonic technologies face a critical trade-off: few-body architectures offer high enhancement but are sensitive to fabrication flaws, while scalable methods like solid-state dewetting yield large, low-enhancement gaps. We introduce a paradigm shift using a many-body plasmonic architecture inspired by statistical mechanics. By moving toward the continuum limit (N>>1), local
geometric variations are statistically averaged out, effectively decoupling optical performance from microscopic disorder. We implement this concept via a lithography- and etching-free, multi-step dewetting strategy, creating wafer-scale nanoclusters. This process strategically forms a robust many-body system by introducing numerous small satellite nanoparticles between larger particles. Crucially, this design achieves a high collective enhancement that surpasses even optimized few-body systems, despite having larger individual gaps. Under optimized conditions, these substrates exhibit a surface-enhanced Raman scattering enhancement factor approaching 4 x 108 with unprecedented reproducibility (RSD of ~10%). This scalable, low-cost concept establishes a practical route toward reproducible wafer-scale nanophotonic platforms for sensing, spectroscopy, and
quantum technologies.
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All authors Minjun Kim, Vasanthan Devaraj, Hyeon-Seok Seo, Seongjae Eom, Jeong-Su Lee, Donghan Lee, Min Yong Jeon, Thomas Zentgraf, Jong-Min Lee
Physics and Society · Cross-listed from cond-mat.stat-mech
The Ramsey community number as a renormalization-group crossing
Alexei Vazquez
The Ramsey community number $r_k$ is the smallest size at which a network is better described by communities than by none, under a
Bayesian detection rule. On the diamond hierarchical
lattice we show that $r_k$ is an exact renormalization-group crossing: the block-model sufficient statistics obey a linear map with
eigenvalues $\{bs,b\}$, the degree-corrected evidence density flows to $\ln K$ at a community fixed point, and $r_k$ is the generation at which the running evidence clears the detection threshold. Degree correction advances detection by two generations. We derive $r_k(b,s;q)$ in closed form for the whole family. Finally, placing on the
lattice the Reichardt–Bornholdt community
Hamiltonian – whose ground state is the partition itself – we find an exact community-ordered phase: below the
ferromagnetic critical temperature the two hubs lock into opposite communities for any resolution $\gamma>0$, a staggered order that persists as $n\to\infty$. Allowing each nested sub-community its own label, the optimal partition is a hierarchy of $q_{\rm opt}\sim\sqrt{n}$ communities, so the number of Potts states that best describes the network grows with the network. This hierarchy orders thermally level by level, through a cascade of first-order transitions whose temperatures fall as $1/\ln q$, so every stable level persists as $n\to\infty$: the emergent partition is detectable, optimal, and thermodynamically ordered.
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Optics
Exact flat bands in a 3D photonic crystal
Kin Hung Fung, Yan-Long Chen, C. T. Chan et al. (+1 more)
Photonic flat bands are hard to engineer because Maxwell's equations are vectorial: transversality obstructs the localized scalar-like bases that generate destructive-interference flat bands in tight-binding models. We show that a three-dimensional metallic network of dipolar cavities joined by waveguide channels–a fully vectorial photonic
crystal belonging to space group No. 224–hosts an exact scalar sector, carrying exact flat bands. The twelve-band vector problem contains one self-adaptive radial dipole axis per site whose projection is exactly the scalar four-band
Hamiltonian of the same network. A microwave-scale coupled-dipole calculation confirms this scalar-vectorial duality. The result is a
symmetry-based design rule for scalar-like flat bands in reciprocal vector media.
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All authors Kin Hung Fung, Yan-Long Chen, C. T. Chan, Qinghua Guo
Chemical Physics
Direct Analytical Evaluation of Electron-Impact Excitation Cross Sections via Multiconfigurational Binary Encounter Approach: Applications to Benzene and Naphthalene
Kaoru Yamazaki
We present a multiconfigurational binary-encounter (MC-BE) framework for direct analytical evaluation of electron-impact electronic-excitation cross sections for dipole-allowed transitions from ab initio excited-state data. The method combines the threshold-modified Mott-Massey (TMMM) approximation with binary-encounter (BE/BE$f$) scaling. The effective binding energy in the BE/BE$f$ prefactor is obtained from amplitude-weighted occupied-orbital contributions computed by linear-response time-dependent density functional theory (LR-TDDFT), without system-specific fitting parameters. For benzene, MC-BE/TMMM cross sections for the dominant $1{}^{1}\!E_{\mathrm{1u}}$ ($\pi\!\to\!\pi^{\ast}$) band agree well with experiment at incident energies $T=10$-$20$ eV and improve on the Schwinger multichannel/truncated configuration-interaction singles results of Falkowski et al. [J. Chem. Phys. 159, 194301 (2023)] for this band and energy range. For naphthalene, the calculated total excitation cross section reproduces the onset and principal maximum of the gas-phase apparent fluorescence cross section, used as an emission-based proxy under dipole-dominated conditions, without empirical energy shifts or intensity scaling. Analytic peak-position and peak-height expressions, parameterized by $r=\langle B\rangle/\Delta E$, show that typical valence excitations peak at incident energies $T\simeq 1.5$-$1.6\Delta E$ with substantial BE attenuation, providing a diagnostic for relating measured cross-section profiles to excitation energies. Although demonstrated with LR-TDDFT, the framework is transferable to other excited-state theories that provide compatible amplitudes and well-defined orbital energies. These results support MC-BE/TMMM as a practical, inexpensive route for modeling electron-impact excitation of polyatomic molecules with finite oscillator strength.
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Optics
Refractive-index tomography of opaque tissue from its own backscattered light
Tran Dinh Hoang, Jaecheol Cho, Thi Van Anh Nguyen et al. (+9 more)
The refractive index (RI) is an intrinsic, label-free marker of a living
cell's dry mass and subcellular morphology, and hence of its physiological state. Its three-dimensional (3D) reconstruction has become a powerful way to study
cells and tissues in their native state, spanning
cell growth, drug response and disease diagnosis. Yet this capability rests on a fundamental constraint: the RI can be recovered only from light transmitted through the specimen, which demands optical access to both sides. The
cells that matter most – those within thick tissues, intact organs and living animals – are therefore out of reach. A tissue, however, can illuminate its own
cells from behind: light backscattered by intrinsic tissue structures beneath a
cell carries the same transmission information a microscope would collect from the far side. Here we develop a divide-and-conquer inverse-scattering framework that recovers this transmission from the backscattering and reconstructs a
cell's 3D RI. We demonstrate label-free, quantitative imaging of
cells within an engineered tissue, and a living mouse through its intact skull, where we further quantify the dry mass of individual osteocytes in vivo. By removing the need for two-sided access, this reflection-only approach extends RI
tomography into living tissue, enabling non-destructive, longitudinal imaging of
cells in their native environment.
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All authors Tran Dinh Hoang, Jaecheol Cho, Thi Van Anh Nguyen, Eunyoung Seong, Joowon Lim, Jin Hee Hong, Yongwoo Kwon, Jun Wan Kim, Juhee Yang, Seokchan Yoon, Sungsam Kang, Wonshik Choi
Atomic Physics
Constraints on Yukawa-type New Forces from the Lamb Shift in Muonic Hydrogen and Deuterium
Chung-Chien Huang and Li-Bang Wang
We develop an analytical framework to constrain Yukawa-type fifth-force interactions using the Lamb shift in hydrogen and deuterium. The sixfold coordinate-space integral for the energy shift is transformed into a one-dimensional momentum-space convolution of the atomic form factor and the Yukawa potential, eliminating the need for approximations. This formulation directly incorporates empirical
nuclear charge distributions through their form factors, making the implementation of experimental results straightforward. Applying this method to the latest hydrogen and deuterium spectroscopy data, we derive constraints on the coupling constant $\alpha$ in the interaction range $\lambda \in [10^{-4}, 10^{6}]$~fm. A resonance-like cancellation between the $2s$ and $2p$ orbital shifts is identified at a critical range $\lambda \sim 10^{5}$~fm, where the energy shift vanishes and the constraint on $\alpha$ diverges, marking a transition between attractive and repulsive regimes. The constraints are shown to be independent of the
nuclear charge distribution model. Our results indicate that the transition frequency shifts induced by such new forces lie well below current spectroscopic resolution, establishing spectroscopic precision as the primary bottleneck for probing these interactions.
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Fluid Dynamics · Cross-listed from math.AP
Hopf Obstruction and Transported Forced Brakke Motion in Ordered Viscoelastic Cores
Sai Peng
We study topological relaxation in ordered viscoelastic conformation flows at finite epsilon. In an ordered region, a positive spectral gap selects an oriented principal axis and hence an S^2-valued director with a
Hopf class. We show that a change of this class must be accompanied, before the sharp-interface limit, by one of a finite list of costs: exterior gap concentration, ordered-core mass, boundary flux, FENE/collar loss, or a
topology exit. The result is proved for a concrete Landau-de Gennes ordered-core closure coupled to an Oldroyd/FENE-type transport law. The structural hypotheses used in the argument are verified up to the first typed exit time: the Morse-Bott ordered well, tubular soft coordinates, massive-mode coercivity, a projected transported Ginzburg-Landau equation, exterior gap control, and tame FENE/collar coefficients. The projected Ginzburg-Landau equation separates translation modes from the remaining residuals. The translation modes give the normal line force, while the orthogonal soft, massive,
geometric, and collar terms are absorbed by coercivity or charged to the corresponding exit. A modulated-energy argument propagates a nonempty class of
vortex-tube data on regular intervals. On each such interval, the normalized core measures converge to an integral one-varifold satisfying a transported forced Brakke inequality with the computed force. The
theorem therefore derives the force projection, open-basin propagation, and Brakke compactness estimates before invoking any limiting Brakke flow, and it records the finite-epsilon cost when the regular ordered-core description breaks down.
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Biological Physics · Cross-listed from cond-mat.soft
Spatially heterogeneous noise restructures flocking into geometry-locked and vortex states
Ankush Semwal, Mahak Poonia and Pintu Patra
Spatially heterogeneous environments continually challenge the ability of active matter to sustain coherent collective motion. Understanding how collective motion remains robust under changing environments is central to both the functioning of biological systems and the design of smart active matter. Here, we extend the Vicsek model to include a circular non-noisy region surrounded by a noisy environment - a configuration in which the noise difference sets up a contrast in local directional order between the two regions. We find that, as the surrounding noise is increased, the system passes through three distinct dynamical regimes: (i) conventional global flocking at low noise; (ii) geometry-locked motion, aligned with simulation boundaries, at intermediate noise; and (iii) vortical motion within the non-noisy region at high noise. Extending the environment to multiple non-noisy regions, we find that the geometry-locked regime can develop a directional coupling, while the
vortex mode leads to
antiferromagnetic order between the regions. Taken together, our results demonstrate that the spatial modulation of order and disorder offers a powerful and generic strategy for steering active matter, aligning with recent experimental observations of active particles in patterned landscapes.
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Applied Physics
Shape Ultrasound with Dynamic Microfluidic Lenses
Dajun Zhang, Hyunji Shim, Michael Ferolito et al. (+3 more)
Dynamic shaping of ultrasound into prescribed spatial patterns underlies a broad range of biomedical and engineering applications. However, existing modulation strategies face fundamental limitations: single element transducers paired with acoustic lenses lack reconfigurability, whereas phased arrays require large numbers of independently driven elements, leading to substantial hardware complexity, cost, and
rigidity. Here we introduce a microfluidic ultrasound lens system that enables reconfigurable spatial modulation of ultrasonic fields using two orthogonal layers of soft microfluidic channels. Each channel is selectively filled with one of two
liquids with distinct sound speeds via an FPGA controlled array of micropumps, generating programmable binary phase patterns. Integrating a 20-row-by-20-column microfluidic lens with a single element transducer, we demonstrate three-dimensional ultrasound focusing with approximately one second reconfiguration time and spatial resolution comparable to that of a 400-element transducer array. The system provides 400 addressable pixels through parallel control of 80 pumps, allowing hardware complexity to scale with the square root of the pixel count. Building on this platform, we demonstrate dynamic ultrasound heating, as well as remote particle manipulation. Furthermore, we demonstrate a cylindrical lens that manipulates ultrasound propagation in the azimuthal direction. Owing to its
liquid based, soft architecture, the microfluidic lens offers design flexibility, scalable operation across ultrasound frequencies, low acoustic transmission loss, and stable performance under high acoustic power. Together, these results establish microfluidic phase modulation as a compact, scalable, and flexible approach for dynamic ultrasound field control.
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All authors Dajun Zhang, Hyunji Shim, Michael Ferolito, Feng Ye, Hongrui Jiang, Chu Ma
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Efficient Bethe-Salpeter Equation Calculations Based on Numerical Atomic Orbitals and Norm-Conserving Pseudopotentials: Dual-${\boldsymbol k}$-Mesh Strategy
Ziqing Guan, Yu Cao, Min-Ye Zhang et al. (+3 more)
We present an efficient implementation of the Bethe–Salpeter equation (BSE) based on numerical atomic orbitals (NAOs) and norm-conserving pseudopotentials within the ABACUS+LibRPA framework. By exploiting the localized resolution-of-identity (LRI) technique, the screened Coulomb interaction is cast into a real-space, unit-
cell-indexed form $W_{\mu\nu}(\boldsymbol R)$ that is inherently short-ranged and well localized. This spatial locality enables an efficient
Fourier interpolation of the BSE kernel from the coarse $\boldsymbol k$-mesh used in the preceding $GW$ calculation to an arbitrarily dense $\boldsymbol k$-mesh on which the BSE
Hamiltonian is assembled and diagonalized, thereby giving rise naturally to a dual-$\boldsymbol k$-mesh workflow. Building on this scheme, we systematically examine the convergence of the absorption spectra with respect to the NAO basis set, the auxiliary basis set, and the $\boldsymbol k$-point sampling.
Benchmark calculations for both molecular and periodic systems collectively validate the accuracy of the present implementation and establish the dual-$\boldsymbol k$-mesh strategy as a practical and reliable approach for $GW$+BSE calculations.
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All authors Ziqing Guan, Yu Cao, Min-Ye Zhang, Peize Lin, Ruiyi Zhou, Xinguo Ren
Optics
Broadband microwave time-frequency analysis via stabilized period-one oscillation and recirculating frequency shifting with shared fiber loop
Xianxin Zhang, Chi Jiang, Taixia Shi et al. (+1 more)
To address the need for time-frequency analysis (TFA) of broadband microwave signals and to overcome the reliance of existing schemes on large-bandwidth swept microwave sources, we propose a broadband microwave signal TFA approach based on stabilized period-one (P1) oscillation and recirculating frequency shifting (RFS). By employing a feedback loop, a stable swept optical signal is generated from the stabilized P1 oscillation of a
semiconductor laser, and its sweep bandwidth is further extended by an RFS loop to achieve multi-fold bandwidth expansion. For system compactness, the feedback loop and RFS loop share a common long fiber. The combined operation produces a broadband swept optical signal, which, through stimulated Brillouin scattering-based frequency-to-time mapping, enables TFA and frequency measurement of broadband microwave signals. Experimental results demonstrate an instantaneous analysis bandwidth of up to 57 GHz, a frequency resolution of 60 MHz, and a maximum mean absolute frequency measurement error of 38.16 MHz.
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All authors Xianxin Zhang, Chi Jiang, Taixia Shi, Yang Chen
Physics and Society
A behavioral principle underlying attacker-defender interactions in soccer
Issei Yamazaki, Hirotaka Goto, Kojiro Otoguro et al. (+3 more)
Soccer is widely popular for its simple rules and complex yet coordinated play that unfolds on the pitch. Nevertheless, the fundamental mechanisms governing such play are not well understood: what shapes player interactions on the pitch? What short-term goals guide players' decisions about their movements over the next few seconds? We address these questions by focusing on one-on-one settings in open play, in which the attacker, in possession of the ball and typically dribbling, faces a defender aiming to stop or delay the attacker's actions over a short period. Here we develop a mathematical model of attacker-defender interactions and analyze 306 professional soccer games. Synthesizing the large-scale
dataset with an analysis of the model reveals a simple behavioral principle that may underlie these interactions: the defender seeks to minimize their future relative speed to the attacker, whereas the attacker initiates their movements to preempt the defender's objective. This principle, relative-speed minimization, provides a consistent and unified account of the empirical data. Since our framework depends little on soccer-specific details, this principle may govern diverse pursuit-evasion scenarios as well as other invasion team sports.
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All authors Issei Yamazaki, Hirotaka Goto, Kojiro Otoguro, Hiraku Nishimori, Masashi Shiraishi, Takuma Narizuka
Optics
Numerical-aperture transfer in holotomography with a deterministic diffusion prior
Dong-min Ryu, Jeong-hyun Roh, Woon-soo Lee et al. (+3 more)
High-throughput holotomography often relies on long-working-distance, multiwell-compatible optics that reduce illumination numerical aperture (NA) and limit access to high spatial frequencies. Here we present ResShift-ODE, a deterministic
diffusion-prior framework that transfers low-NA refractive-index (RI) tomograms to high-NA-equivalent volumes without modifying the acquisition hardware. We formulate low-NA-to-high-NA transfer as a
diffusion-prior inverse problem under an explicit NA-limited
Fourier-domain forward operator, distinct from suppressing artifacts within an already measured passband. The method extends residual-shifting
diffusion to volumetric RI data and reformulates the reverse process as a probability-flow ordinary differential equation, enabling reproducible inference in five denoiser evaluations. On held-out emulated-pair test volumes, inferred volumes matched high-NA references with RI errors of 0.002-0.003 for >99% of voxels, while
Fourier analysis confirmed measurement-anchored lateral-band recovery without filling the axial missing cone. 3D ResShift-ODE required five denoiser evaluations per volume, incurring ~5.8x the cost of a 3D U-Net while remaining ~166x faster than a 1000-step 3D denoising
diffusion probabilistic model.
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All authors Dong-min Ryu, Jeong-hyun Roh, Woon-soo Lee, Hansol Yoon, Hyun-seok Min, Yongkeun Park
Fluid Dynamics
Continuum modeling of fluidic and elastic flow during growth-driven wound closure in partial-EMT cell monolayers
Chaozhen Wei, Han Jiang, Yifan Gu et al. (+5 more)
Large-scale circular gap closure occurs over a time scale on which
cell growth and proliferation become important. Growth is the main driver of the closing process, while
cell dynamics such as elongation and intercalation reflect elastic and fluidic contributions to tissue deformation. We develop a novel fluidized growth-elasticity framework as a nonlinear analogue of a Maxwell fluid with growth. The framework decomposes the experimentally observable strain rate into the additive sum of the growth, elastic, and fluidic strain rates, thus enabling the separate quantification of these contributions from tissue kinematics and allowing the roles of tissue elasticity and fluidity (the inverse of viscosity) to be characterized. We apply the model to large circular gaps ($\sim$1.7 mm in diameter) in confluent monolayers of mouse embryonic epicardial
cells (MEC1) under two conditions, without and with TGF-$\beta$ treatment. We show that both tissue fluidity and the elastic properties associated with fiber reinforcement are critical for reproducing the closure kinematics. Specifically, we predict that the treated condition has lower fluidity, associated with a lower fluidic deformation rate and a higher elastic deformation rate than the untreated condition, in agreement with the experimental observations.
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All authors Chaozhen Wei, Han Jiang, Yifan Gu, Nonthakorn Olaranont, Pengbo Wang, Qi Wen, Yubing Sun, Min Wu
Chemical Physics · Cross-listed from quant-ph
A Quantum-HPC Hybrid Workflow for Reaction-Center Electronic Dynamics: Application to a Cytochrome P450-Inspired Iron-Complex Model
Shintaro Maekawa, Takao Otsuka, Riku Masui et al. (+4 more)
We introduce population-transfer dynamics as a practical validation observable for active-space-derived reduced
Hamiltonians in multistate reaction-center chemistry. Using a cytochrome P450-inspired Fe-complex model, we construct a reaction-coordinate-dependent effective
Hamiltonian from state-averaged complete active-space self-consistent field (SA-CASSCF) calculations, map it to a
quantum-
circuit representation suitable for current hardware, and propagate dynamics from the reactant-side ground state. The reduced
Hamiltonian reproduces the SA-CASSCF reference with an RMS deviation of 0.030 eV and a maximum absolute deviation of 0.143 eV. As a dynamics-based diagnostic, the product-
manifold population p_P(t) identifies a pronounced near-degeneracy region around x = 0.3, where state mixing is strongest. Classical exact time
evolution yields a product population of 0.488 at x = 0.3 after 10 fs, compared with 7.26 x 10^-2 at x = 0.2 and 5.90 x 10^-3 at x = 0.0. To enable execution on current trapped-ion hardware, we examine the trade-off between dynamical fidelity and
circuit resources through coupling
pruning and first-order Trotterization. A coupling cutoff of 0.02 eV reduces the non-zero coupling set from 32 to 7 while preserving the dominant transfer pathways, and M = 30 provides the best practical operating point. Finally, we demonstrate the workflow on Quantinuum's trapped-ion
quantum computer Reimei. The hardware reproduces the key reaction-coordinate trend identified by the classical model, including the maximum at x = 0.3, where the measured product population is 0.42 on hardware and 0.43 on the matched emulator. This work establishes a dynamics-based framework for assessing active-space-derived reduced
Hamiltonians and demonstrates chemically interpretable multistate electronic dynamics on current trapped-ion hardware.
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All authors Shintaro Maekawa, Takao Otsuka, Riku Masui, Juan W. Pedersen, David Muñoz Ramo, Yasushi Okuno, Kentaro Yamamoto
Computational Physics · Cross-listed from math.NA
Design Principle for Mode-Consistent Galerkin Closure under a Physical Energy Metric for Hyperbolic Systems
Hirofumi Tomita
This paper derives a design principle for structure-preserving Galerkin formulations of energy-conserving
hyperbolic systems. The aim is to reproduce the modal-energy-exchange structure of the continuous system within a resolved finite-mode space. Total energy conservation follows from this structure. We introduce a state-dependent physical-energy metric H and derive the corresponding energy-compatibility identity. In the infinite-mode exact-integration model, the volume contribution has an antisymmetric representation after H-orthogonalization, yielding pairwise modal energy exchange. Interface contributions take the same exchange form. To reproduce this structure in the practical finite-mode system, we combine two constructions: a Galerkin projection coupled with the physical-energy metric that guarantees the H-metric summation-by-parts identity, and an energy-compatibility closure that removes the component of the compatibility action contributing to the scalar energy residual. With a shared numerical energy flux at interfaces, they close the total-energy balance of the finite-mode system while preserving pairwise modal energy exchange. We also compare the practical operator construction with the finite-mode exact-integration reference and obtain an O(h^p+1) defect estimate. Finally, we derive an equivalent form of the resulting equation in the fixed Galerkin basis for direct implementation.
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Plasma Physics · Cross-listed from astro-ph.HE
Dependence of Particle Acceleration Efficiency on Shock Velocity in Weakly Magnetized Electron-Ion Shocks
Taiki Jikei, Daniel Groselj and Lorenzo Sironi
Using unprecedentedly long 2D particle-in-
cell simulations, we study electron and ion acceleration in weakly magnetized quasi-parallel shocks, propagating at velocities ranging from transrelativistic to subrelativistic. At a fixed upstream
magnetic field strength, low-velocity quasi-parallel shocks are dominated by the Bell instability, whereas high-velocity shocks are dominated by the Weibel instability. Both regimes accelerate ions with similar efficiency, with the Bell-dominated regime exhibiting faster growth in the maximum particle energy. The electron acceleration efficiency is strongly dependent on shock velocity. Weibel-dominated shocks have $\sim15\,\%$ of shock energy in nonthermal electrons, whereas in the Bell-dominated regime we attribute less than $\sim2\,\%$ of shock energy to nonthermal electrons. We discuss applications of our results to the bright X-ray emission from the late-stage afterglows of gamma-ray bursts, the
radio emission from fast blue optical transients, and the X-ray variability in microquasars.
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Instrumentation and Detectors
The Cryogenic System of DMRadio-50L
V. Ankel, C. Bartram, J. Begin et al. (+36 more)
The DMRadio-50L experiment is designed to search for
axion dark matter in the 5 kHz - 5 MHz frequency range using a lumped-element LC resonator and a toroidal magnet and to serve as a testbed for
quantum sensors. This paper describes the custom cryogenic system developed to meet the stringent requirements of the experiment within a standard laboratory environment. The system is designed to cool a 200 kg detector assembly to temperatures as low as 50 mK while providing sufficient cooling power at multiple temperature stages. We present the conceptual design, technical implementation, and measured performance of the hybrid cryogenic system, which combines a horizontal dilution refrigerator with a large vertical payload cryostat.
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All authors V. Ankel, C. Bartram, J. Begin, C. Bell, S. Chaudhuri, H.-M. Cho, J. Corbin, W. Craddock, S. Cuadra, A. Droster, J. Echevers, E. Engelhardt, J. T. Fry, J. Fu, K. D. Irwin, A. Keller, R. Kolevatov, A. Kunder, D. Li, M. Marangola, N. Otto, K. M. W. Pappas, E. Pariset, S. Puranam, P. Quassolo, N. M. Rapidis, C. P. Salemi, M. Simanovskaia, J. Singh, P. Stark, E. C. van Assendelft, K. van Bibber, K. J. Vetter, K. Wells, J. Wiedemann, L. Winslow, D. Wright, A. K. Yi, B. F. Zemenu