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Physics Physics

physics Watch Physics

Monday 20 July

Applied Physics · Cross-listed from math-ph

On the use of equilibrium models to describe dynamic adsorption regimes

M. Calvo-Schwarzwalder, A. Valverde, A. Cuesta López et al. (+3 more)

We present a column adsorption model that couples a Pseudo-First-Order (PFO) kinetic formulation with the Sips isotherm framework. Using a traveling wave approximation, we derive analytical solutions for specific operating conditions. Qualitatively, these solutions deviate significantly from their pure Sips counterparts: instead of a smooth, continuous increase in concentration at the column outlet, the PFO-Sips model predicts an abrupt, sudden breakthrough. We validate these analytical solutions against diverse experimental datasets from the literature. The results reveal that the PFO-based model consistently underperforms compared to the original Sips formulation. Furthermore, this validation exposes fundamental inconsistencies within the PFO framework. We demonstrate that despite its widespread use in the literature for almost a century, the PFO model is inherently flawed and structurally unfit for describing column adsorption dynamics.
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All authors M. Calvo-Schwarzwalder, A. Valverde, A. Cuesta López, A. Cabrera-Codony, U. Thorat, T.G. Myers

Optics

Femtosecond-to-millisecond holographic imaging of laser ablation dynamics

Shotaro Kawano, Keiichiro Toda, Miu Tamamitsu et al. (+3 more)

Femtosecond laser ablation redistributes optically deposited energy across electronic, structural, mechanical, and thermal degrees of freedom over timescales from femtoseconds to milliseconds. However, these coupled processes are usually measured in separate temporal ranges and through different observables, limiting quantitative comparison between early transient dynamics, residual heating, and final morphology. Here we introduce pump-probe holographic imaging that reconstructs amplitude- and phase-resolved optical fields across this full temporal range under matched imaging conditions. Applied to deep-ultraviolet femtosecond ablation of BK7 glass, the method captures the transition from early excitation and removal-stage dynamics to residual substrate heating and permanent modification. Differential phase analysis isolates sub-nanosecond evolution of the transient ablating layer and microsecond residual heating after material removal. Above the ablation threshold, crater depth increases with fluence, whereas the residual thermal signal saturates, indicating that additional absorbed energy is preferentially partitioned into material removal and ablation-related processes rather than retained as substrate heat. These results identify fluence-dependent energy partitioning as a dynamical basis of low-heat-affected femtosecond processing and establish holographic imaging as a route to tracking laser-driven nonequilibrium material transformations.
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All authors Shotaro Kawano, Keiichiro Toda, Miu Tamamitsu, Haruyuki Sakurai, Kuniaki Konishi, Takuro Ideguchi

Fluid Dynamics

Transition to chaos in two-dimensional Rayleigh-Bénard convection: the role of the magnetic field

Francis F. Franco, Gabriel de T. Paula, Roman Chertovskih et al. (+2 more)

The impact of an externally imposed magnetic field on numerical simulations of two-dimensional Rayleigh-Bénard convection (RBC) is investigated. Initially, the RBC model is examined in the absence of a magnetic field to establish a baseline. Then, a background magnetic field is introduced, and its influence on the transition to chaos is explored. For the purely hydrodynamic case and a range of the reduced Rayleigh number, the system exhibits traveling rolls which, after an attractor-merging crisis, give way to chaotic traveling rolls. Upon imposing a background magnetic field, there is a notable increase in the occurrence of traveling roll dynamics. Furthermore, the presence of the magnetic field favors the splitting/breaking of convective rolls, indicating a possible mechanism for transition to two-dimensional turbulence, with the structure of the convection cell being disrupted. A detailed analysis of the velocity field reveals that the collision between a saddle point and the center of a convective roll restores the system's original topology, with two symmetric kinetic vortices. During this collision, a magnetic vortex splits in two as a result of a magnetic reconnection. This behavior occurs intermittently in time.
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All authors Francis F. Franco, Gabriel de T. Paula, Roman Chertovskih, Dalton N. Oliveira, Erico L. Rempel

Fluid Dynamics · Cross-listed from cond-mat.stat-mech

Large scale behavior in the Kuramoto-Sivashinsky equation: The Schwinger-Dyson route

Olivier Coquand

The present paper is a study of the large scale properties of the Kuramoto-Sivashinsky equation. By using a Schwinger-Dyson framework, we aim to provide a proof that the only solutions that can sustain a stable scaling in the infrared limit have a negative effective viscosity (in the Kuramoto-Sivashinsky sense) with a minimal set of hypotheses, thereby showing that this constitutes a general property of the wave equation that does not depend on a specific set of truncations of a renormalisation group flow, or limitations of a given numerical scheme for example.
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Medical Physics

Portable surrogate-free 4D MRI from standard fast multi-slice 2D MRI via implicit neural representations

Muheng Li, Xinyang Wu, Xia Li et al. (+5 more)

Four-dimensional MRI (4D MRI) characterizes respiratory organ motion, yet existing reconstruction pipelines are tightly coupled to specific acquisition platforms (e.g., non-Cartesian trajectories with self-gating, vendor-specific navigators, or external respiratory hardware), limiting broad adoption across diverse clinical and research settings, including low-field, open-bore, and non-supine imaging. We present SIMPLE-4D (Surrogate-free, IMplicit, PortabLE 4D MRI), a software-first portable workflow that operates entirely on reconstructed slices from standard fast multi-slice 2D MRI and requires no pulse-sequence modification, no non-Cartesian trajectory, no navigator, and no external hardware. SIMPLE-4D combines an acquisition-agnostic front end consuming standard 2D protocols, a surrogate-free variational motion encoder that extracts a compact motion code directly from each 2D slice, and a physics-aware continuous spatio-temporal reconstruction based on a hash-encoded implicit neural representation (INR) with a SIREN deformation network producing bidirectional cycle-consistent DVFs and motion-dependent Gauss-Legendre thick-slice quadrature. Bidirectionality yields a complete inter-frame motion model by composition, supporting downstream tasks such as dose accumulation without retraining. We validate the identical pipeline on two contrasting datasets: a 1.5 T clinical bSSFP dataset (5 volunteers, 3 sessions each) and a 0.5 T open-bore HASTE dataset (5 volunteers, supine and upright). To our knowledge, this is the first per-frame 4D volumetric respiratory MRI reconstruction on a weight-bearing upright open-bore low-field scanner from reconstructed 2D Cartesian slices alone. On low-field data the INR template additionally acts as an implicit denoiser, yielding +132% SNR. Systematic ablations isolate each component's contribution.
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All authors Muheng Li, Xinyang Wu, Xia Li, Orso Pusterla, Philippe C. Cattin, Sairos Safai, Antony J. Lomax, Ye Zhang

Optics · Cross-listed from cond-mat.mtrl-sci

Localized crystallization of Ce:YIG thin films on Si using CO2 laser annealing for integrated nonreciprocal photonic device applications

Xinran Ji, Junxian Wang, Tianchi Zhang et al. (+6 more)

Laser annealing (LA) technique has emerged as an effective method for localized crystallization of magneto-optical (MO) garnet thin films on semiconductor substrates. However, no studies have explored the crystallization and magneto-optical (MO) properties of cerium-substituted yttrium iron garnet (Ce:YIG, Ce1Y2Fe5O12) thin films for integrated photonic device applications using LA technique. In this study, we provide a comprehensive investigation into the laser annealing of Ce:YIG films deposited on SiO2 substrates and silicon nitride photonic waveguides for integrated nonreciprocal photonic device applications. Garnet phase was successfully observed in films grown on SiO2 substrates, and SiN waveguides with laser annealing of sputtered Ce:YIG films on top of a laser annealed Y3Fe5O12 seed layer. The magneto-optical (MO) properties of Ce:YIG films on oxidized Si substrates were found to be comparable to those prepared by rapid thermal annealing (RTA). A Mach-Zehnder Interferometer (MZI) type optical isolator based on Ce:YIG film on SiN was fabricated, exhibiting a saturation Faraday rotation of -2317.7 deg/cm and propagation loss of 188.2 dB/cm. Isolation ratio of 27.1 dB and insertion loss of 10.1 dB were achieved at 1552.7 nm wavelength.
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All authors Xinran Ji, Junxian Wang, Tianchi Zhang, Xuan Zhao, Di Wu, Zixuan Wei, Yizhi Chen, Jialong Wang, Lei Bi

Plasma Physics

Nonlinear Dynamics of Current-Carrying ELM Filaments: Spiral Vorticity, Rotation, and Velocity Suppression

Souvik Mondal, N Bisai, Abhijit Sen et al. (+1 more)

In this work, we investigate the nonlinear dynamics of isolated current-carrying edge-localized mode (ELM) filaments using a reduced electromagnetic fluid model in slab geometry. Numerical simulations show that unidirectional parallel current significantly suppresses radial filament velocity and reduces the outward propagation velocity by weakening the curvature-driven interchange force. The reduction in radial velocity is found to follow a modified scaling relation, demonstrating that increasing current progressively weakens outward filament propagation. Analysis of the vorticity equation shows that the electromagnetic current source changes from a dipolar structure to a remarkable spiral pattern, and overcomes the conventional curvature drive in the nonlinear phase. This current-driven source directly imprints its topology on the vorticity field, resulting in spiral vorticity, enhanced angular momentum, increased rotational energy, and localized shear layers. The filament therefore undergoes a transition from a conventional propagating state to a rotationally self-organized electromagnetic structure. These findings demonstrate that parallel current acts as an effective electromagnetic vorticity source and provides new insight into the nonlinear dynamics of ELM filaments in tokamak edge plasmas.
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All authors Souvik Mondal, N Bisai, Abhijit Sen, Indranil Bandyopadhyay

Fluid Dynamics

Physically Consistent Outflow Boundary Conditions for Global Stability Analysis of Bluff Body Wakes

Guangyao Cui, Amit Sigawi and Michael Karp

Global linear stability analysis of bluff body wake flows is performed using the matrix-forming method based on finite-difference discretization. Particular emphasis is placed on the influence of outflow boundary conditions, with the aim of minimizing the required computational domain size without degrading accuracy or inducing spurious oscillations near the outlet. This study focuses on incompressible wakes behind bluff bodies such as cylinders and airfoils at high angle of attack, especially in regimes where global modes exhibit downstream spatial amplification. It is shown that below the critical Reynolds number – where the global mode remains linearly stable – significant spatial growth can persist far downstream, even when the wake is nearly absent. This behavior underscores the importance of imposing a physical boundary condition at the outlet. Several commonly used outflow boundary conditions are evaluated, including Dirichlet, Neumann, extrapolation, stress-free, sponge layer, and the Robin condition that incorporates predictions from local linear stability analysis at the outlet. The results demonstrate that, for different $Re$ cases, the Robin condition enables robust convergence of global modes within substantially truncated domains, thereby improving the efficiency of global stability analysis. These findings highlight the broader applicability of the matrix-forming approach for complex stability analyses, including Floquet analysis of time-periodic flows and extensions to compressible configurations.
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Fluid Dynamics

A coupled Eulerian Lagrangian approach for fluid and particle dynamics

Snehanshu Maiti and Rajaraman Ganesh

We present a one-way coupled Eulerian-Lagrangian computational framework for simulating fluid and particle dynamics in two-dimensional incompressible flows. The framework extends the GPU-accelerated GHD2D Fourier pseudospectral Navier-Stokes solver \cite{Mukherjee2018,Biswas2024} by incorporating passive tracer and finite-inertia particle modules. The Eulerian fluid equations are integrated using a second-order Adams-Bashforth scheme, while particle trajectories are advanced with a classical fourth-order Runge-Kutta method. Coupling between the Eulerian and Lagrangian descriptions is achieved through spatial and temporal interpolation of the fluid fields using bilinear, bicubic Catmull-Rom, and bicubic B-spline schemes. The framework is verified using analytical solutions and benchmark problems for the fluid solver, tracer transport, and inertial-particle dynamics. Bilinear interpolation produces transport statistics nearly identical to higher-order schemes while providing greater computational efficiency, and particle-number convergence demonstrates statistical robustness. Simulations of tracer and inertial particles in decaying two-dimensional turbulence capture long-time transport, turbulent dispersion, vortex trapping, coherent-structure interactions, preferential concentration, and inertia-dependent transport. The solver exhibits stable scaling with grid resolution and particle number while maintaining efficient single-GPU performance. The modular architecture and computational efficiency make the framework suitable for Eulerian-Lagrangian studies of turbulent transport and particle-laden incompressible flows.
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Optics

Photonic Memory as a Dynamical Phase for Neuromorphic Computing: A Unified Framework with Experimental Realization

Isaac Yorke

Photonic memory underpins optical information processing, neuromorphic photonics, and photonic computing. Existing studies typically treat dispersive, nonlinear, and driven-dissipative memory as distinct physical phenomena, despite all being governed by the evolution of the optical field. This work proposes a unified phase-based framework in which photonic memory is interpreted as a dynamical phase, with transitions between memory regimes governed by optical phase evolution, Kerr nonlinearity, and the balance between delayed feedback and dissipation. Within this framework, dispersive memory arises from frequency-dependent phase accumulation, nonlinear memory emerges through intensity-dependent phase evolution leading to bistability and hysteresis, and driven-dissipative memory is established through attractor convergence and memory stabilization. The proposed framework is validated through theoretical analysis and numerical simulations, demonstrating a continuous progression from linear dispersive memory to nonlinear and ultimately driven-dissipative memory. Experimental validation is performed using a silicon photonic waveguide incorporating chirped Bragg gratings. Group delay measurements reveal distinct linear and nonlinear memory responses, while the reconstructed memory distribution demonstrates the coexistence of dispersive, nonlinear, and driven-dissipative memory within a single integrated photonic device. To the best of the author's knowledge, this constitutes the first experimental demonstration supporting the coexistence of all three photonic memory regimes in a single photonic platform. These results establish optical phase as the unifying physical quantity underlying photonic memory and provide a common framework for designing future neuromorphic photonic systems, reservoir computers, and integrated photonic processors.
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Optics

Real-time THz ptychography using an optically modulated aperture

Diksha Garg, Anil Kumar, Ian R. Hooper et al. (+6 more)

Ptychography allows ordinary cameras to perform both quantitative phase and intensity imaging. However, the requirement for relative object to probe motion and high measurement count significantly limits imaging speed and application scope. In this work, we introduce optically modulated aperture ptychography, using a silicon photomodulator as a rapidly reconfigurable aperture, deployable across the microwave, millimeter wave and terahertz bands. We demonstrate experimentally at ~ 0.1 THz real-time ptychographic image capture, without moving parts. Furthermore, a reconfigurable aperture facilitates diverse and spatially multiplexed probes. We use a multiplexed known-probe reconstruction strategy that improves signal-to-noise ratio and increases the information content per measurement, enabling the capture of fluid dynamics at 16 fps. Our optical modulation approach enables high-throughput ptychographic imaging of dynamic samples, for applications such as non-destructive evaluation and in-vivo biomedical imaging.
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All authors Diksha Garg, Anil Kumar, Ian R. Hooper, Nicholas E. Grant, John D. Murphy, John E. Cunningham, Nick Stone, Euan Hendry, Harry Penketh

Biological Physics

Feedback-mediated circulation and persistence of stochastic fluctuations in gene regulatory circuits

Nashita Rahman, Mintu Nandi, Sudip Chattopadhyay et al. (+1 more)

Feedback plays a significant role in biochemical networks that govern a multitude of cellular functions, including development, adaptation, and homeostasis. Yet, how feedback topology controls stochastic fluctuations remains incompletely understood. Here, we develop a theoretical framework for two-node feedback motifs composed of activating and repressive regulatory interactions between two transcription factors. Under the linear noise approximation, we identify a feedback-driven contribution to node-wise fluctuations, termed cyclic noise, that arises specifically from loop closure. Cyclic noise is the component of fluctuations that circulates through the regulatory circuit. Its sign and magnitude distinguish whether feedback amplifies or attenuates node-wise fluctuations. We further show that feedback-mediated noise circulation leaves a temporal signature in the decay of steady-state autocorrelation, revealing how loop closure modifies the persistence of fluctuations. We thus provide a minimal framework for understanding how feedback architecture regulates both the magnitude and the temporal persistence of noise in gene regulatory circuits.
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All authors Nashita Rahman, Mintu Nandi, Sudip Chattopadhyay, Suman K Banik

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Efficient Quantum-Mechanical Modeling of Nonradiative Charge Transfer Processes

Alexander Karl, Dominic Waldhoer, Theresia Knobloch et al. (+2 more)

Nonradiative charge transfer processes play a central role in a wide range of physical phenomena, including reliability phenomena in semiconductor devices such as bias temperature instability, hysteresis, random telegraph noise, and trap-assisted tunneling. nonradiative multiphonon (NMP) theory provides a physically rigorous framework for describing such charge transitions, but its full quantum-mechanical formulation is computationally too demanding for large-scale simulations. In this work, we present a systematic and implementation-oriented treatment of NMP-based models for practical large-scale simulations. Starting from the quantum-mechanical foundations of coupled electron–phonon dynamics, we derive computationally efficient approximations for charge capture and emission rates and clearly identify the underlying assumptions and validity regimes. In particular, we introduce an effective crossing-preserving approximation that yields fully analytic, numerically stable, and computationally inexpensive transition rates while retaining the essential quantum-mechanical physics. The resulting expressions are therefore well suited for large-scale device simulations, where capture coefficients must be evaluated repeatedly over broad multidimensional parameter spaces. Furthermore, we derive continuum formulations for transitions between localized defect states and extended electronic bands, enabling direct incorporation into semiconductor-device simulations. The resulting framework bridges microscopic defect physics and practical large-scale simulations of charge transfer processes in complex semiconductor devices. At the same time this work serves as a practical guide for implementing physically grounded NMP-based models, providing both a systematic derivation of the underlying theory and a clear guidance on the validity limits.
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All authors Alexander Karl, Dominic Waldhoer, Theresia Knobloch, Christoph Wilhelmer, Tibor Grasser

Fluid Dynamics · Cross-listed from cond-mat.soft

Emergent odd response in active chiral films

Seema Chahal, Naveen Kumar D and Brato Chakrabarti

Active chiral fluids can support a nondissipative transport coefficient known as odd (or Hall) viscosity. Hydrodynamic descriptions of such fluids typically introduce odd viscosity phenomenologically. How such a response emerges from specific microscopic interactions remains incompletely understood. Here, building on classical shear rheology, we microscopically derive an odd rheological response in active chiral films: thin layers of torque-exerting, elongated particles anchored to a no-slip surface. A canonical realization of such a film is the bacterial carpet, in which flagellated bacteria are tethered head-down to a solid surface while their flagella remain free to spin and inject angular momentum into the surrounding fluid. Using a kinetic theory for the orientational dynamics of these anchored particles, we derive their stress response to an imposed shear flow. We reveal that shear-induced reorientation leads to a flow-aligned polarization and a transverse surface traction from which the odd-viscosity tensor follows in closed form. Numerical solutions of the nonlinear kinetic theory further highlight saturation of the transverse traction at strong shear, driven by shear-induced orientation dynamics – signaling departure from linear response. Our results demonstrate how odd viscosity can emerge self-consistently as a coarse-grained rheological signature of active fluid-structure interaction and establish active chiral films as a new controllable setting for odd hydrodynamics.
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Physics and Society

Ant swarm functional control via stigmergic Reinforcement Learning agents

Alessio Pitteri, Andrea Guizzo, Laura Ferrarotti et al. (+2 more)

In this work, we propose a novel framework for the functional controllability of the ant swarm model, a well-known and relevant model of collective behaviour. Our approach introduces a population of controlling stigmergic agents, trained via Reinforcement Learning (RL), that act on the environment to influence the system dynamics and promote the emergence of ordered behaviour. Stigmergic agents are optimized in a centralized-training decentralized-execution setting, interacting with ants only through the shared pheromone field. The reward design promotes trail pheromone structures and alignment of ant positions with high-pheromone paths, without requiring control of specific microscopic configurations. Our results demonstrate that the learned policies effectively shift the phase transition line that characterizes the global behaviour of the system, enabling the emergence of trails scenarios in regimes that are typically dominated by randomness. This study provides insights into the potential of RL based control strategies for complex systems, contributing to the general understanding of functional controllability in this field.
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All authors Alessio Pitteri, Andrea Guizzo, Laura Ferrarotti, Bruno Lepri, Riccardo Gallotti

Optics

Multiple soliton regimes enabled by parametric down-conversion in $\chi^{(2)}+\chi^{(3)}$ microresonators

Francesco Rinaldo Talenti, Tommi Isoniemi, Jonathan Silver et al. (+1 more)

Half-harmonic generation in microresonators with mixed $\chi^{(2)}$ and $\chi^{(3)}$ nonlinearities provides access to a rich landscape of two-colour soliton states and frequency combs. We numerically demonstrate the formation of both bright and topological two-colour solitons at relatively modest pump powers and phase-mismatch parameters. At higher powers and larger phase mismatches, we identify a regime where parametric down-conversion assists the formation of dark solitons in the normally dispersive pump field. While the dark-soliton core is primarily shaped by the Kerr nonlinearity, nonlinear coupling between the pump and its half-harmonic modes enables soliton excitation using a standard laser-frequency scanning technique, a capability not normally associated with dark solitons. The simulations are performed using parameters representative of lithium-niobate microresonators pumped near 775 nm and generating a half-harmonic near 1550 nm. These results reveal how the interplay of $\chi^{(2)}$ and $\chi^{(3)}$ nonlinearities can substantially expand the range and types of experimentally accessible soliton states in a single integrated frequency-comb platform.
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All authors Francesco Rinaldo Talenti, Tommi Isoniemi, Jonathan Silver, Dmitry Skryabin

Fluid Dynamics

Generalized Reynolds Analogy for Compressible Wall Turbulence: Unified Velocity–Temperature Relations from Mean to Fluctuating Field

You-sheng Zhang

The Reynolds analogy between velocity and temperature fields is a central problem in the statistical theory of compressible wall turbulence. The generalized Reynolds analogy (GRA) established by the author describes the mean velocity–temperature relation accurately, but a self-consistent closure for the fluctuating field has remained elusive. Here, the instantaneous similarity relation that the generalized total enthalpy (minus its wall value) is proportional to the local velocity is shown to close both fields at once. The mean field reproduces the GRA solution, while the fluctuating field yields the closed relation $T'_{rms}/u'_{rms} = f(Re_\tau,\Pr)\,\Pr_m^{-1/2}\,|\partial\bar{T}/\partial\bar{u}|$, where the prefactor $f$ is derived from the universal cascade dynamics of turbulence and the Obukhov–Corrsin theory, without adjustable parameters. The relation recovers the refined strong Reynolds analogy (RSRA) of Huang et al.~(2025), the most accurate benchmark to date, recasting it from an empirical relation into a consequence of universality principles and explaining the origin of its fitted prefactor $f=1.09$; and its ratio to boundary-layer and channel direct numerical simulation (DNS) data collapses onto unity across Mach numbers ($2.25$–$14$), Prandtl numbers ($0.025$–$1$) and wall thermal conditions, with an overall accuracy of about $5\%$.
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Optics

Numerical Investigation of a 3D End-Firing Antenna Array Based on Two-Photon Polymerization on Thin-Film Lithium Niobate for Optical Beam Steering

David Trop and Boris Desiatov

Optical phased arrays (OPAs) are key components for solid-state beam steering in emerging photonic technologies such as LiDAR, optical communication, and adaptive optics. However, conventional integrated OPA designs face trade-offs between bandwidth, steering range, and fabrication complexity. Here we designed and numerically analyzed a novel three-dimensional end-firing antenna array compatible with fabrication using two-photon polymerization (2PP) directly on a thin-film lithium niobate (TFLN) platform. By elevating the polymer antennas above the chip surface, the design enables two-dimensional beam steering while maintaining the broadband advantages of end-fire emission. Full-wave electromagnetic simulations demonstrate transmission efficiencies up to 89.5% over the \SIrange{1.4}{1.6}{\micro\meter} wavelength range, achieving a field of view of \ang{24.9} $\times$ \ang{22.8} with beamwidths of approximately \ang{1.7}. The architecture's compatibility with electro-optic phase control and advanced array configurations suggests significant potential for high-speed, low-loss beam steering systems. This work establishes a foundation for scalable 3D photonic phased arrays that bridge integrated optics with free-space beam manipulation.
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Biological Physics · Cross-listed from q-bio.PE

How genome redundancy can promote evolutionary innovation

Domenico Caudo, Mattia Miotto, Giancarlo Ruocco et al. (+1 more)

Polyploidy is defined as the existence of more than two complete sets of homologous chromosomes. Despite it being a widespread phenomenon across the tree of life, its role as either an evolutionary innovation or a dead end is still debated. Here, we investigate how under varying selective pressures the degree of ploidy interacts with two key biological factors: the mode of inheritance and the genotype-phenotype mapping. Through a minimal evolutionary model we find that polyploidy is especially advantageous during abrupt environmental changes, confirming that polyploidization is often associated with ecological upheavals. We observe that stochastic inheritance combined with a nonlinear (maximum-based) genotype-phenotype mapping maximizes both phenotypic exploitation and landscape exploration across all environments. By contrast, structured inheritance with an additive phenotype mapping systematically underperforms, yet displays a pronounced optimum at low-to-intermediate ploidy level that mirrors the distribution observed in natural plant and bacterial populations. When individuals are free to carry different chromosome numbers, selection drives the population toward values that reflect an interplay between exploitation, exploration, and convergence speed rather than any single evolutionary objective. The relative weight of these three factors depends on the fitness landscape, providing a unifying framework for understanding when and why polyploidy is favored by natural selection.
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All authors Domenico Caudo, Mattia Miotto, Giancarlo Ruocco, Greta Grassmann

Fluid Dynamics · Cross-listed from cond-mat.soft

History-dependent discharge of compressed particle rafts

Mario Nabernik, Gregor Plohl, Kathrin Schulte et al. (+1 more)

While particle-laden interfaces play a central role in many natural and industrial processes, predicting their mechanical properties remains a major challenge. These systems combine granular characteristics conferred by particle-particle contacts with elastic behavior originating from capillary interactions, making them very sensitive to their history. Using the relaxation of uniaxially compressed particle rafts through a local constriction as a model experiment, we demonstrate the existence of a reproducible and continuous aging process. Aging is observed for both front- and back-compressed rafts and is characterized by a progressive increase in particle mobility and raft deformability. Macroscopic changes are seen, for example, in the extent of relaxation and are correlated with flow modifications observed at the mesoscopic level among which are increased particle fluxes, broader shear zones and enhanced particle rearrangements. While aging can be attributed unambiguously to the constrained passage of the particles through a constriction, its microscopic origin remains hypothetical, the results suggesting that contact lines around the particles may evolve. Beyond providing new insight into the effects of raft history, the proposed constriction flow experiment offers a simple method to control and compare aging in different particulate assemblies.
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All authors Mario Nabernik, Gregor Plohl, Kathrin Schulte, Carole Planchette

Computational Physics · Cross-listed from quant-ph

Variance-Reduced Trajectory Unravelings for GPU Noisy Quantum-Circuit Simulation: Characterization and a Qiskit-Aer Integration Gap

Chun-Yeol You

Monte-Carlo trajectory (quantum-jump) methods are the practical route to simulating noisy quantum circuits once the exact density-matrix method is precluded by its $4^n$ memory cost. Their bottleneck is estimator variance: resolving one expectation value can demand thousands of trajectories. Recent tensor-network work shows that variance-reduced unravelings – projector and analog sampling – sharply cut this variance, but only on CPU matrix-product-state backends, with no path into production tooling. We implement both unravelings on a GPU dense-statevector trajectory engine and validate them against the exact density matrix (ideal-circuit fidelity $1-2.2\times10^{-16}$; $1/\sqrt{N}$ convergence; all unravelings unbiased to trace distance $<0.01$). On a single consumer GPU, projector unraveling reaches a target standard error with $20.8\times$ fewer trajectories than Qiskit-Aer's batched\_shots\_gpu at $n=10$, a factor that holds at $19$–$26\times$ across $n=8$–$20$. A regime map places analog sampling optimal at weak noise and projector at strong noise, crossing near $\gamma t\approx0.35$. We further report a systems finding: Qiskit-Aer applies noise at the channel level and reconstructs a canonical Kraus decomposition at apply time, discarding any user-supplied unraveling, so variance-reduced unravelings cannot be delivered through its public API. Because Aer's Born-rule collapse machinery already exists, we specify a minimal change that would unlock the technique in production.
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Chemical Physics

Vibrational Circular Dichroism enhancement in conformationally flexible transition metal complexes

Mariia Sapova, Menno de Boer, Wybren Jan Buma et al. (+1 more)

We extend our previously developed approach for calculating enhanced vibrational circular dichroism (VCD) spectra of transition-metal complexes to systems for which conformational flexibility is key to reproduce and elucidate experimental spectra. Treating both the Gibbs free energies and electronic excitation energies as fitting parameters, we show for Co(II)bis[N-(1-arylethyl)- salicylaldiminato] Schiff base complexes that these calculations can excellently reproduce the experiment. An important conclusion is that the DFT-optimized conformer set is spectrally redundant and that the model can be reduced from 18 conformers to only two conformers with opposite chirality at the metal center ($\Lambda$/$\Delta$) without affecting the agreement between theory and experiment, both with respect to the VCD spectrum as well population distribution over the $\Lambda$ and $\Delta$ conformers. Finally, we numerically confirm the symmetry-selective nature of the enhancement and formulate the corresponding selection rules within the framework of the pertaining Sum-Over-States expressions.
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All authors Mariia Sapova, Menno de Boer, Wybren Jan Buma, Lucas Visscher

Optics · Cross-listed from quant-ph

Active Optical Frequency Measurements with Superradiance Prolonged by a Modulated Magnetic Field

Huihui Yu, Shi-Lei Su, Chongxin Shan et al. (+2 more)

Superradiant emission from long-lived excited states of an atomic ensemble confined in an optical cavity constitutes a practical source of light with narrow linewidth. In the pulsed regime, however, superradiance implies rapid emission and a broadening of the spectrum. Recent experiments have demonstrated constructive and destructive interference of superradiant emission by different strontium atomic transitions. In this article, we show that by modulating the atomic transition frequencies with a magnetic field, it is possible to control the release of the atomic excitation energy as a prolonged pulse or a train of superradiant pulses. By simulations, we show that heterodyne detection of the prolonged superradiance shows extremely sharp spectral features, which leads to significantly reduced frequency uncertainty and fluctuation.
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All authors Huihui Yu, Shi-Lei Su, Chongxin Shan, Klaus Mølmer, Yuan Zhang

Optics

Ghost-wave momentum bandgaps in anisotropic Floquet lattices

Junhua Dong, Huan He and Huanan Li

Momentum bandgaps, characterized by complex frequencies and non-resonant amplification effects, provide a powerful route for wave manipulation beyond conventional band theory. Here, we introduce a distinct mechanism for momentum-gap engineering in higher-dimensional Schrödinger-type Floquet lattices by exploiting the intrinsically complex wave vectors of ghost waves, with complex-frequency excitation providing an additional degree of freedom for continuously tailoring the ghost-wave branch and the associated Floquet spectrum. Furthermore, we show that the higher-dimensional Floquet band structure supports momentum bandgaps extending across the entire Brillouin zone along the propagation direction and enables amplification over a broad frequency range under arbitrarily weak modulation. When the lattice is truncated along the ghost-wave decay direction, the resulting Floquet waveguide exhibits broadband reflectionless pulse amplification. Our results establish a higher-dimensional framework for ghost-wave momentum-gap physics and reveal new opportunities for non-Bloch wave engineering in time-varying photonic systems.
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Applied Physics

Biodegradable, Millimeter-Scale Light-Emitting Sensors for Distributed Environmental Monitoring-Functional Pixie Dust

Zhiming Hu, Danzhen Zhang, Janghun Ko et al. (+24 more)

Methods for large-area, precise monitoring across natural environments are of growing interest due to pressing needs for sustainable management of rapidly increasing anthropogenic activities. Established approaches involve sparse spatial sampling and/or sequential measurements, while emerging techniques exploit miniaturized electronics or passive optical methods. Various constraints in scalability, costs, robustness, operational range and other factors create a need for alternatives. Here, we introduce a concept that overcomes many of these limitations through the combined use of chemically induced light emission and chemically responsive optical filter elements in millimeter-scale systems that we refer to as functional pixie dust (fPD) sensors, designed specifically for monitoring natural water systems during nighttime to eliminate background optical interference and to enhance remote analysis. These floating devices act as Lagrangian tracers to follow surface flows and to simultaneously measure the concentrations of key chemical species along their trajectories. Optimized designs exploit environmentally compatible constituent materials that are also degradable through natural processes to benign end products, thereby eliminating the need for recovery. Spatially and spectrally resolved ratiometric measurement schemes ensure robust operation and ability to address practical requirements in range, operational lifetime, time response and sensitivity. Demonstrations include distributed measurements of pH, Hg2+, and NO2-, each of relevance to industrial discharge, toxic metal contamination, and nitrogen-rich runoff, adapted for static concentration gradients, flow-driven transport conditions, and outdoor aquatic settings. The results establish a framework for environmental sensing using degradable, self-powered microsystems capable of scalable deployment and remote readout.
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All authors Zhiming Hu, Danzhen Zhang, Janghun Ko, Haohui Zhang, Jiale Chen, Chanho Park, Jiatong Zhang, Qiuna Zhuang, Shiwei Xu, Xiaoran Yang, Dain Son, Taehoon Kim, Uikang Joo, Zhaojian Xu, Hyunsoo Kim, Richard Chai, Gwangmin Bae, Wooyoul Maeng, Qiong Wang, Sangmin Lim, Liangsong Zeng, Un-Seong Baik, Kaiqing Zhang, Liming Yuan, Yonggang Huang, Jin-Tae Kim, John A. Rogers

Optics · Cross-listed from quant-ph

Spatial nonlocality imaging via metasurface

Jian Li, Zi-Mu Fan, Qing-Yuan Wu et al. (+7 more)

Bell nonlocality is both a defining signature of entanglement and a key quantum information resource. However, visualizing and certifying nonlocal correlations across a spatially multimode photonic field remains challenging due to the rapidly growing measurement cost of spatially resolved projective tests. To address this issue, we build a spatial nonlocality imaging scheme that directly reveals the spatial distribution of quantum nonlocality by integrating a metasurface that performs parallel polarization projections with a quantum-adaptive neural network. Spatially resolved Clauser–Horne–Shimony–Holt (CHSH) tests are realized over a 400-pixel biphoton field using an average of only 1.7 detected coincidence pairs per pixel per basis. This approach yields a nonlocality image that maps the two-dimensional spatial distribution of Bell violations across the optical field and reveals the target-state-dependent spatial evolution of Bell violations. It provides a highly resource-efficient route to large-scale Bell certification and opens new possibilities for exploiting spatially multimode entanglement in quantum imaging, quantum networking, and scalable photonic quantum technologies.
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All authors Jian Li, Zi-Mu Fan, Qing-Yuan Wu, Wen-Kai Yu, Zhe Meng, Xing-Yan Fan, Wen-Hao Wang, Jie Ma, Xia Guo, An-Ning Zhang

Optics

Crystal orientation enables near-unity nonlinear circular dichroism in resonant metasurfaces

Chi Wang, Dmitrii Gromyko, Polina Pantiukhina et al. (+2 more)

Achieving near-unity nonlinear circular dichroism (CD) typically requires geometric symmetry breaking, making it challenging to combine helicity selectivity, resonant enhancement, and structural simplicity. We show that crystal orientation enables near-unity third-harmonic (TH) CD in highly symmetric resonant metasurfaces formed by a square lattice of circular holes in a cubic nonlinear material. Under circularly polarized excitation, strong near-field components of both helicities enabled by the rotational symmetry of the metasurface open two symmetry-allowed in-plane TH generation pathways. Crystal orientation controls their nonlinear coupling, selectively enabling destructive interference for one incident helicity. Our nonlinear temporal coupled-mode theory identifies the conditions for near-unity CD, reveals the distinct roles of pump and TH resonances, and explains the fourfold and eightfold crystal-orientation dependence. Across silicon, germanium, and diamond, we obtain resonantly enhanced TH CD exceeding 99% in the near-infrared, establishing crystal orientation as a design degree of freedom for nonlinear CD in highly symmetric metasurfaces.
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All authors Chi Wang, Dmitrii Gromyko, Polina Pantiukhina, Lin Wu, Kirill Koshelev

Plasma Physics · Cross-listed from cond-mat.mtrl-sci

CuCrZr heat-sink irradiation performance reveals new challenges for thermonuclear fusion reactors

Thomas Barzic, Anna-Carina Seitlinger, Christoph Frühwirth et al. (+10 more)

Commercial fusion energy requires materials that survive intense neutron bombardment whilst extracting extreme heat loads for conversion to electricity. The CuCrZr alloy, the leading heat-sink material for fusion reactors, derives its strength from a fine dispersion of nano-precipitates formed during prime-ageing heat-treatment. Whether this precipitation-hardening strategy can withstand fusion-relevant irradiation remains untested. Here we show, combining in situ transmission electron microscopy under heavy-ion irradiation and He implantation with thermodynamic and transmutation modelling, that the hardening precipitates dissolve under two opposing kinetic regimes: ballistic dissolution dominates at low temperatures, whilst dissolution and re-precipitation dominate at high temperatures. Although the accelerated dose rates inherent to ion irradiation shift the balance between ballistic mixing and thermal back-diffusion relative to reactor conditions, precipitate degradation at both kinetic extremes indicates that the prime-aged microstructure is unlikely to remain unaltered under prolonged neutron exposure. He bubbles and Kr-rich voids nucleate once vacancies become mobile, and transmutation over five service years irreversibly redirects the alloy chemistry towards Ni-Zr intermetallics. These three independent mechanisms converge to challenge the strategy on which CuCrZr performance depends, suggesting that the long-term performance of age-hardenable Cu-based heat-sink alloys in fusion reactors warrants further assessment. Our findings reveal a new materials challenge for fusion reactor design and commercialisation: the need for new Cu-based heat-sink alloys able to retain engineered strength whilst their chemistry is irreversibly rewritten - thermodynamically and ballistically - by the fusion neutron spectrum.
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All authors Thomas Barzic, Anna-Carina Seitlinger, Christoph Frühwirth, Edward McDonald, Jing Tang, Jonathan A. Hinks, Alexandr Zinovev, Dmitry Terentyev, Stefan Luidold, Cláudio G. Schön, Enrique Jimenez-Melero, Stefan Pogatscher, Matheus A. Tunes

Chemical Physics

Disorder-induced Dark States Line Shape in Pump-Probe Spectroscopy of Polaritons

Luca Nils Philipp, Julian Lüttig and Roland Mitrić

The formation of hybrid light–matter states called polaritons provides a route to shape the photophysics and photochemistry of molecules. Accordingly, the dynamics of polaritons following photoexcitation is extensively studied. In particular, the role of the dark state manifold in such processes remains unclear. Here, we investigate the line shape of pump-probe spectra of polaritons emerging at the dark states energy under the influence of disorder. Previously, we already investigated the pump-probe line shapes of polaritons in a disorder-free model and identified distinct signatures of relaxation into dark states, thus providing an indirect probe of this relaxation. Since the transition dipole moment of dark states vanishes in a disorder-free model, they cannot be directly probed. However, dark states acquire small transition dipole moments as soon as disorder is explicitly included in the model enabling them to be directly probed. In this work, we demonstrate that the inclusion of the relaxation to dark states and disorder leads to the evolution of the spectral shape at the DS energy from a derivative-like into an absorptive line shape. Furthermore, we investigate the dependence of the line shape on the disorder strength and its asymptotic scaling for a large number of coupled molecules. Our results demonstrate that probing dark states can help to single out the polaritonic response from the total signal.
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Applied Physics · Cross-listed from quant-ph

Single-atom sensor for low-frequency electric field

Quan Yuan, Shuang-Qing Dai, Tai-Hao Cui et al. (+8 more)

Precision measurement of low-frequency electric field (LFEF) signals with frequency from 30 kHz to 300 kHz is crucial for advancing both fundamental science and practical applications, owing to their unique frequency regime. For conventional electromagnetic antennas, the long wavelength (i.e., several kilometers) of the LFEF leads to a severe size constraint that efficient radiation becomes challenging to achieve when the antenna size is much smaller than the long wavelength of the LFEF signals, which in turn results in a reduction of measurement sensitivity and compromises antenna's performance. By exploiting the high intrinsic sensitivity of cold trapped ions to weak alternating electric signals via Coulomb interaction, we demonstrate a single-ion phonon laser sensor acted by an injection-locked 40Ca+ ion confined in a surface-electrode trap. Combining the beat frequency technique with the injection-locked phonon laser oscillation, we demonstrate a practical and efficient approach for simultaneous extraction of the frequency, phase, and amplitude from a single measurement, without the need for sideband cooling. This approach achieves precision detection for LFEF signals with the sensitivity of 404 uV/(m * Hz1/2) and the detection limit of 61.5 uV/m. Besides, this approach also shows remarkable robustness against noise. Our study helps realizing practical single-atom sensors in the low-frequency regime, opening avenues for applications in subsurface communication, precision metrology, mass spectrometry, and biomedical monitoring.
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All authors Quan Yuan, Shuang-Qing Dai, Tai-Hao Cui, Pei-Dong Li, Yuan-Zhang Dong, Zhuo-Zhu Wu, Ji Li, Fei Zhou, Jian-Qi Zhang, Liang Chen, Mang Feng