Optics
Electro-Optical Metalens for Near-Surface Cooling of a Levitated Particle
Pedro Rosso Gomez, Bruno Melo, Adeel Afridi et al. (+3 more)
Advanced levitation optomechanics in the
quantum regime requires sophisticated quantumengineered protocols operating at shorter length and time scales, demanding an increasing control over both optical and electrical potentials. Integrated chip-scale platforms offer a natural route toward such control. Here, we demonstrate optical levitation in
vacuum using a miniaturized hybrid electro-optical metalens. Motion control is achieved using a high numerical aperture metalens combined with electrical active feedback using planar electrodes, enabling cooling to low
phonon occupations. Reheating measurements enable us to rule out any significant influence from electric field noise; an encouraging result for the future development of on-chip levitation platforms operating close to surfaces. This compact integrated platform facilitates the precise manipulation and control of levitated nanoparticles while laying the ground toward exploiting the full capacity of metaoptics to engineer complex optical potentials, marking a significant step forward in technologies for
quantum levitation optomechanics.
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All authors Pedro Rosso Gomez, Bruno Melo, Adeel Afridi, Mohamed Sabry Mohamed, Nadine Meyer, Romain Quidant
Biological Physics · Cross-listed from cond-mat.soft
Hydrodynamics of perceptual matter: from neural representations to collective motion
Mohammad Salahshour
How do neural representations of neighbors become collective material behavior? Harmonic Theory (HT) reduces bearing representations to signed perceptual channels traceable to sensory acuity, decision dynamics, and interaction distance. Here we derive a nonlocal kinetic and hydrodynamic theory from the HT particle law without introducing heading
alignment. The resulting fields retain HT's order-resolved perceptual spectrum and keep the neural and sensory origin of each coefficient visible. The theory predicts a torque-driven density instability: HT's direct-approach channel turns
agents toward density excesses, while self-propulsion carries them inward. For isotropic spatial interactions and positive rotational
diffusion, perceptual channel $n$ generically first affects conserved density at spatial order $k^{2n}$, and the full radial transforms select finite pattern wavelengths. Two populations can share the same long-wave instability threshold yet select different initial pattern spacings because their higher perceptual channels differ. Beyond onset, the one-particle continuum sustains a bidirectional nematic column; a prescribed,
symmetry-allowed two-stream response amplifies a directional imbalance into sustained polar flow. In a distinct pure-repulsion regime, one-particle calculations show polar transport and translating transverse bands, with late pattern selection sensitive to numerical transport. The framework connects neural and sensory mechanisms to continuum coefficients, instabilities, and
alignment-free collective motion.
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Atomic Physics
The influence of the binding energy on Compton-scattering-driven ionization
N. Melzer, M. Kircher, G. Kastirke et al. (+31 more)
We present a comprehensive study of Compton scattering of 20 keV
photons by bound electrons over a wide range of binding energies (Ne 2p, Ne 2s, C 1s, O 1s, and Ne 1s orbitals). In particular, we have measured fully differential cross sections, i.e., electron angular distributions with respect to the direction of the
photon momentum transfer for fixed electron energy. Our data show strong deviations from the predictions of the ”quasi-free” electron approximation. The binding energy and the shape of the Coulomb potential from which the electron escapes both play a significant role in its kinematics. We find that Compton electrons are scattered and even back-reflected by the ionic potential. The strength of this effect depends on the orbital from which the electron is ejected.
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All authors N. Melzer, M. Kircher, G. Kastirke, J. Rist, D. Tsitsonis, A. Pier, L. Kaiser, J. Kruse, N. Anders, J. Stindl, L. Sommerlad, O. D. McGinnis, M. Schmidt, L. Nowak, A. Kügler, I. Dwojak, P. Daum, P. Roth, M. Astaschov, J. Drnec, K. Lin, N. Wong, F. Trinter, M. S. Schöffler, L. Ph. H. Schmidt, D. M. Haubenreißer, N. M. Novikovskiy, N. Diehl, Ph. V. Demekhin, S. Brennecke, M. Lein, S. Eckart, T. Jahnke, R. Dörner
Fluid Dynamics
A Semi-Implicit All-Mach Numerical Method for Implicit Large Eddy Simulations
Simon D. Wilkinson
Implicit Large Eddy Simulation (ILES) is a well established approach for modeling high-Reynolds-number turbulent flows by numerical solution of the inviscid Euler equations in 3D. These turbulent flows cover a wide range of Mach numbers, including within individual simulations. For example, Richtmyer-Meshkov instability simulations transition from a high-Mach compressible regime to a low-Mach quasi-incompressible regime during the late-time
evolution. These flows motivate the development of a semi-implicit all-Mach numerical method, which is subject to a CFL stability constraint corresponding to the fluid velocity, but independent of the speed of sound, and can be applied efficiently and accurately across the whole spectrum of Mach numbers. Furthermore, finite-volume discretization is chosen to maintain strict conservation and ensure robust and accurate capturing of strong shocks. The method is validated in both high- and low-Mach regimes. Validation is also presented for stratified atmospheres in the presence of
gravity, and the method is thus shown to be applicable to buoyancy driven flows. We present favorable comparison against previously published ILES simulations of multimode Richtmyer-Meshkov instability from the $\Theta$-group collaboration, Thornber et al., (arXiv:1706.09991).
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Optics
Spatial delocalization of cold oscillators in hollow-core fibers
Soumya Chakraborty, Pardeep Kumar, Gordon K. L. Wong et al. (+2 more)
Trapped particles in hollow-core fibers enable long-range sensing, though advanced control of their in-fiber motion, such as
multimodal cooling and squeezing, remains challenging. Here, we present optical interference-based adaptive techniques for controlling the motion of a fringe-trapped silica nanoparticle inside a fiber. After feedback-cooling its axial and radial motion, we induce axial delocalization (position anti-squeezing) via two complementary approaches. First, non-adiabatic fringe suppression expands the position variance by 11.83 ($\pm$0.7) dB to that of the initial cold-state while retaining Gaussian statistics. Second, multi-pass particle positioning at dark fringes increases the delocalization to 13.23 ($\pm$0.5) dB relative to the cold-state's variance via dark inverted optical potentials, in agreement with our Wiener
stochastic model. Stronger delocalization produces non-Gaussian states of motion. Unlike prior inverted-trap implementations, our method requires neither auxiliary optical traps nor charged particles in Paul traps. Our results demonstrate fringe-trapped particles in hollow-core fibers as a versatile platform for long-range sensing and macroscopic
quantum physics.
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All authors Soumya Chakraborty, Pardeep Kumar, Gordon K. L. Wong, Claudiu Genes, Nicolas Y. Joly
Optics · Cross-listed from quant-ph
A robust framework for the comprehensive characterisation of parametric down-conversion sources
Denis A. Kopylov, Michael Stefszky and Christine Silberhorn
Reliable verification of squeezed-light sources is essential for photonic
quantum technologies. High-dimensional
quantum optical networks demand single-mode, pure squeezed states which, in principle, can be generated through careful engineering of parametric down-conversion-based (PDC) sources. However, due to the imperfections of optical components, the generated state is never pure and commonly contains internal mode structure. Existing characterisation techniques, based on either joint spectral intensity or normalized second-order correlation functions, work under the assumption that the probed state is pure, and therefore can result in incomplete or misleading assessment of the source quality. Here, we develop a device-agnostic characterisation framework for PDC-based sources with distinguishable signal and idler fields. Treating the source as a black box producing a mixed multimode Gaussian state, we find a lower bound for the state purity, which can be experimentally determined via mode-unresolved measurements. Our approach enables a holistic assessment of realistic squeezed-light source quality without requiring a detailed model of the nonlinear device and its surrounding optical network, providing practical
benchmarks for optimizing sources for state-of-the-art
quantum applications.
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Plasma Physics
Eliminating Tokamak Disruptions with Feedback
H. R. Strauss
Tokamak disruptions caused by tearing modes can be prevented with
magnetic feedback. A database of DIII-D locked mode disruptions provides criteria for major disruptions. The main criterion is that the q = 2 rational surface must be sufficiently close to the resistive wall surrounding the
plasma to interact with it. This is shown in simulations of a sequence of model
equilibria derived from the database. If the wall is ideally conducting, major disruptions do not occur.
Magnetic feedback emulates a conducting wall, and can prevent major disruptions. Feedback coils must be designed appropriately, otherwise they are not effective in disruption prevention. Simulations of a model of MST also show the q = 2 criterion for major disruptions, as well as feedback stabilization. Feedback offers an attractive alternative to disruption mitigation by impurity injection.
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Instrumentation and Detectors
Expanding Neutron Capacity at the ESS through Symbiotic Instruments: SLEIPNIR & Remora
Nicolai Lindaa Amin, Mohamed Aouane, Peter Kjær Willendrup et al. (+6 more)
The long pulse of the European Spallation Source (ESS) offers unique opportunities to host more than one
neutron instrument on a single beam-port. Here, we present two symbiotic instrument concepts designed for previously unexploited
neutrons, without imposing significant perturbation on existing or planned beamlines. The first concept employs a doubly focusing dual-monochromator system to vertically translate the
neutron beam, enabling compact instruments to be stacked within spatially constrained beam ports inaccessible to conventional instruments. The second extracts excess spectral bandwidth from an existing guide via Bragg reflection upstream of the flagship instrument's chopper system, feeding a second instrument. Both concepts are optimized using gradient-descent Monte Carlo ray-tracing simulations in McStas and benchmarked against existing productive instruments at other sources. Despite operating under significant
geometric and flux constraints, the resulting instruments demonstrate performance comparable to well-established reference instruments at the ILL. The two concepts together illustrate a modular and cost-effective route to expanding ESS scientific capacity, using the facility's resources that would otherwise go unused.
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All authors Nicolai Lindaa Amin, Mohamed Aouane, Peter Kjær Willendrup, Jörg Voigt, Gregory S. Tucker, Robert Georgii, Ellen Fogh, Niels Bech Christensen, Rasmus Toft-Petersen
Optics
Time frequency distributions of Optical sources (II): externally modulated semiconductor lasers
José Capmany
We extend a time frequency framework previously developed for directly modulated
lasers to external modulation of the continuous wave output of a 1550 nm DFB
laser described by Langevin rate equations. Four modulators are considered an InP electro absorption modulator, a LiNbO3 dual drive Mach Zehnder modulator, a dual parallel Mach Zehnder modulator and a silicon carrier depletion modulator
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Plasma Physics
Turbulent Origin of the Edge Radial Electric Field Asymmetry between Favourable and Unfavourable Drift Configurations
B. J. Frei, R. Bilato, W. Zholobenko et al. (+9 more)
We study the influence of the ion
magnetic-drift direction relative to the active X-point (favourable and unfavourable configurations) on edge
turbulence, transport, and the radial electric field $E_r$ in ASDEX Upgrade and TCV. First-principles gyrokinetic simulations of the edge and scrape-off layer are performed in diverted X-point geometry using the spectral full-$f$ GENE-X code. Two matched pairs of L-mode discharges are simulated and validated against the available measurements in all four cases, showing good agreement, in particular for the $E_r$ profiles. A radial force-balance analysis shows that the deeper $E_r$ well in the favourable configuration is determined by the larger poloidal ion flow near the separatrix, which cannot be reproduced by neoclassical solvers and is identified in axisymmetric simulations as
turbulence-driven. We then derive an exact
evolution equation for the mean poloidal-flow acceleration from the full-$f$ gyrokinetic vorticity equation, which identifies the radial gradient of the total velocity stress as its nonlinear drive. The observed asymmetry is found to arise from stronger nonlinear energy transfer into the mean flow in the favourable configuration, associated with enhanced nonlinear $E\times B$ advection of vorticity near the separatrix and X-point. Flux-driven TCV simulations further show that the asymmetry persists at matched power more than six times the L-mode value. Assuming a critical $E_r$ at the L-H transition, this yields an estimated ratio of approximately 1.7 between the unfavourable and favourable L-H power thresholds, close to the experimental factor of two. Overall, the unfavourable configuration exhibits larger fluctuation amplitudes, a weaker $E_r$ well, stronger geodesic acoustic modes, and shorter energy confinement times for the same profiles, which may explain the observed difference in access to high-confinement regimes.
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All authors B. J. Frei, R. Bilato, W. Zholobenko, O. Grover, C. Angioni, M. Bergmann, P. Ulbl, F. Jenko, S. Rienäcker, L. Vermare, P. Hennequin, B. Labit
Optics
Time frequency distributions of optical sources (I): directly modulated semiconductor lasers
Jose Capmany
We develop a time frequency framework for the dynamics of directly modulated
semiconductor lasers in which the optical field obtained from the singlemode rate equations is represented by distributions of Cohen class. Closed form small signal solutions are derived for RC filtered square current pulses and for sinusoidal modulation, including the exact chirp to power ratio with gain compression and spontaneous emission and a line expansion of the Wigner distribution of the sinusoidally modulated field. Kernels satisfying two known conditions return the
laser chirp as the first conditional moment.
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Chemical Physics · Cross-listed from math.DS
Classification of strongly non-hyperbolic critical points of planar second-order chemical reaction systems
Norm Yeung and Radek Erban
The dynamics of chemical reaction systems with two chemical species can be described (under mass-action kinetics) by planar autonomous systems of ordinary differential equations (ODEs) with right-hand sides containing
polynomials. While their behaviour close to
hyperbolic critical points is well understood, their dynamics has not been fully characterized for strongly non-
hyperbolic critical points, where the linearization close to the
equilibrium is given by the zero
matrix. In this paper, the behaviour of such chemical reaction systems is investigated. Considering second-order chemical reaction networks with a positive
equilibrium point, we show that only nine
geometric equivalence classes are possible out of the sixteen classes for general ODE systems. Examples of chemical reaction networks in each class are presented. All sixteen
geometric equivalence classes can be realized by chemical systems if the non-
hyperbolic equilibrium point is located at the origin.
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Physics and Society
Preferential centrality with a density penalty: formulation and an open-source implementation
Alexander Hellervik
Preferential centrality (Hellervik, Nilsson and Andersson, 2019) models spatial activity through feedback between activity and attraction. We extend it with a density penalty. The local response depends on activity per unit of capacity and scales with capacity. A correction that is uniform per unit of capacity preserves total activity, and for a chosen response function and penalty strength, conservation determines this correction. We provide prefcent, an open-source reference implementation with convergence and feasibility checks and records of each run's inputs and settings. It reproduces the 200-iteration outputs of a companion Porto Alegre study across all 65,357 network segments, with median relative differences of order $10^{-14}$. In a strong-feedback example, the penalty reduces concentration and reaches the stopping tolerance in fewer iterations. Other synthetic examples show how penalty strength changes the relative prominence of centers and how their number varies with transport costs. A further example reaches different numerical
equilibria from different initial states on the same network and capacity landscape. In multi-start sweeps on three synthetic two-dimensional landscapes, distinct converged states occur over a range of parameter values: at 172 of 420 points of a grid in feedback strength and transport cost, including 75 where the states differ in their number of centers. The note provides a model specification and a reproducible computational basis for further theoretical and empirical work.
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Computational Physics · Cross-listed from nlin.CD
A Renormalization-Group Hierarchy of Stochastic Effective Dynamics Learned through Path Integrals
Yuki Yasuda and Tobias Bischoff
This study combines a
stochastic renormalization group (RG) in space with a path-integral description of the time
evolution, giving a spatial hierarchy of coarse-grained dynamics together with the distribution over spatiotemporal paths. The RG is defined as a
diffusion process that applies scale-dependent
Laplacian damping together with additive Gaussian noise. The time
evolution at each spatial scale is formulated as an Onsager–Machlup action, with a drift (i.e., the predictor) and white noise whose amplitude is fixed by the RG. The predictor of these dynamics is optimized by minimizing the Kullback–Leibler divergence between the path distributions from the RG and from the path-integral description. The optimal predictor contains the score function that connects the spatial scales, so the predictor and the score are two aspects of the same multiscale path formulation. The formulation unifies simulation using the predictor, unconditional generation using the score, and super-resolution using both. The predictor has no closed form, so it is computed by a neural network in two realizations that differ only in how the score is computed. The first realization obtains the score by automatic differentiation of the path distribution, remaining faithful to that formulation. The second obtains the score as an additional network output trained by denoising, at a lower computational cost. These two realizations are validated through numerical experiments on two representative multiscale systems, the Kolmogorov flow and the two-timescale Lorenz-96 model.
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Medical Physics
A Differentiable Brain Tumor Mass Effect Solver
Marco L. Wittrich, Michal Balcerak, Lucas Zimmer et al. (+6 more)
A growing
brain tumor mechanically deforms the surrounding healthy
brain through mass effect. This compression and displacement of tissue affects both patient prognosis and treatment planning, so biophysical models of tumor growth must account for this deformation. Established mass-effect models are partial differential equation (PDE) solvers that couple growth to elasticity and calibrate parameters per patient, at substantial implementation, runtime, and calibration cost. We ask how much of this deformation a fully differentiable energy-based model can recover, and introduce a potential-spring model: a regular grid over the
brain is driven outward by a tumor-concentration potential and held by an elastic spring
lattice with tissue-specific stiffness. It shares the tumor-gradient driving force of continuum elasticity but uses a single global parameter and no per-patient inversion, minimized end-to-end by gradient descent. We
benchmark it against established solvers by applying each displacement field to a healthy atlas and measuring tissue overlap with the patient's own segmentation on 134 BraTS patients. Our model yields the largest overall local overlap improvement at up to 100$\times$ shorter computation time, establishing a lightweight, differentiable solver for tumor mass effect. Because our model obeys mechanical laws and reflects the tumor-induced tissue loading, it remains physically plausible, a prerequisite for clinical use.
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All authors Marco L. Wittrich, Michal Balcerak, Lucas Zimmer, Ivan Ezhov, Björn Menze, Marie-Christin Metz, Nicole Tueni, Benedikt Wiestler, Jonas Weidner
Medical Physics
The FetalSenseM V2: a wearable and wireless, multi-wavelength NIRS device for continuous monitoring of placental oxygenation and metabolism
Luca Giannoni, Frederic Lange, Musa Talati et al. (+9 more)
We present here the FetalSenseM V2 (FSM V2), a wireless and wearable, multi-wavelength, NIRS device, based on LED illumination at six NIR wavelengths (782, 800, 818, 830, 848 and 888 nm). It utilises two sources located on the flexible wings of the sensor body, and three photodiodes placed symmetrically in its centre at 1 cm from each other. The configuration provides two sets of three source-to-detector distances (SDS) at 3, 4 and 5 cm. FSM V2 allows estimation of dynamic, relative changes in placental concentrations of HbO2, HHb and oxCCO. At the same time, the dual set of SDS also enables the use of multi-distance
algorithms, such as spatially-resolved spectroscopy (SRS) and Dual Slope (DS), for estimating placental oxygen saturation (PlO2). FSM V2 is the first example of a new generation of wearable NIRS devices, paving the way for smart and advanced monitoring of placental health at bedside. The FSM V2 was successfully validated on a bench-testing, metrological platform based on optical phantoms, as well as against a gold-standard, time-domain (TD) NIRS system, before moving to preliminary examples of clinical application and usability on pregnancy monitoring trials at University College Lon-don Hospital (UCLH), conducted as part of an in vivo proof-of-concept study.
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All authors Luca Giannoni, Frederic Lange, Musa Talati, Uzair Hakim, Darshana Gopal, Angelos Artemiou, Niccole Ranaei-Zamani, Olivia Newth, Sarah Johnson, Maeve McGaughey, Subhabrata Mitra, Ilias Tachtsidis
Plasma Physics
Stellarators Linking Axisymmetric Mirrors Part 1: Coil Design, MHD Equilibrium, and Physics Metrics
Rahul Gaur, Djin Patch, Robert Babin et al. (+3 more)
We present a computational design study of a stellarator-mirror hybrid concept, Stellarators Linking Axisymmetric Mirrors (SLAMs), in which an optimized poloidally omnigenous (OP or QI) stellarator serves as the rotational-transform-generating element that links long, axisymmetric (circular cross-section)
magnetic mirrors. Starting from an OP precursor configuration obtained from the DESC omnigenity database, we construct hybrid coil sets for field period nFP = 2 SLAMs by separating the OP modular coils along the device midplane and inserting axisymmetric planar mirror coils into the resulting gap. Field-line tracing shows that nested
vacuum flux surfaces survive this extrusion across a range of mirror-section lengths, with the cross-section qualitatively preserved at the point where the mirror is inserted. We use the field-line tracing data to map the shape of a surface and use the GVEC fixed-boundary solver to calculate an ideal magnetohydrodynamic (MHD)
equilibrium and evaluate physics metrics such as the neoclassical transport proxy (eps_eff), the
vacuum magnetic well (W), and the gyrokinetic heat fluxes (Q), providing a first-principles analysis of such concepts using modern stellarator analysis tools.
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All authors Rahul Gaur, Djin Patch, Robert Babin, Florian Hindenlang, Xu Chu, Tony Qian
Computational Physics · Cross-listed from quant-ph
Quantum data loading from the learned shared structure of real signals
Pablo Herrero Gómez, Antonio Jimeno Morenilla, David Muñoz-Hernández et al. (+1 more)
Preparing
quantum states from classical data can cost more than the computation they serve; most loaders tailor a
circuit to each input. Here we show that the signals of a real
dataset share structure that can be learned once and reused. Our
quantum-native loader learns a low-dimensional description of a
dataset and prepares every signal with one fixed
circuit set by a few numbers. Across seven views of five public
datasets it meets the targets of the strongest structured loader at equal gate cost with several times fewer numbers per signal. These numbers can be inferred from a random subset: in a preregistered blind replication the subset needed to come within ten per cent of full-signal accuracy stayed constant within a prespecified margin as signals grew sixteenfold, whereas the structured loader needed ever more. It declines what it cannot represent, covering fewer cases than that baseline and no electrocardiogram.
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All authors Pablo Herrero Gómez, Antonio Jimeno Morenilla, David Muñoz-Hernández, Higinio Mora Mora
Optics
Advances in the Vacuum Magnetic Birefringence measurement using a pulsed Foil Coil
Enzo Rodriguez Alvarez, Jonathan Agil, Julien Billette et al. (+3 more)
In this paper, in the framework of the Biréfringence Magnétique du Vide (BMV) experiment, we present our current apparatus in detail and we discuss its critical points. We also report the results obtained using specially designed pulsed coils called Foil Coils. Our novel measurement of the
vacuum linear
magnetic birefringence constant is $K_{VMB} < 1.7 \cdot 10^{-21}~\text{T}^{-2}$ at a confidence level of 68$\%$, which is an improvement with respect to our previous 2014 measurement.
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All authors Enzo Rodriguez Alvarez, Jonathan Agil, Julien Billette, Jérôme Béard, Rémy Battesti, Carlo Rizzo
Instrumentation and Detectors
Investigating Optical Coupling Material Candidates in NaI(Tl) Detectors for the SABRE-North Dark Matter Experiment
Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo et al. (+21 more)
Direct dark matter detection with NaI(Tl) scintillators requires ultra-low-background materials. Silicone optical pads can couple NaI(Tl)
crystals to photomultiplier tubes (PMTs) if they provide adequate optical transmission and radiopurity. We characterize four candidate materials for the SABRE-North experiment: commercial EJ-560, used as a reference, and three materials produced at the University of Salento (SYLGARD 184, EGel 3002 A/B, and a hybrid formulation) using different catalyst ratios and curing conditions, yielding ten samples in total. Optical transmittance was measured from 310 to 850 nm by UV/Vis/NIR spectrophotometry. Radiopurity was assessed at the STELLA facility at LNGS using high-purity germanium (HPGe) $\gamma$-ray spectrometry and, for EJ-560, high-resolution ICP-MS. At the 410 nm NaI(Tl) emission peak, EJ-560 shows an absorbance coefficient of $0.064\pm0.017$ mm$^{-1}$. The best locally produced samples reach $0.097\pm0.015$ and $0.093\pm0.014$ mm$^{-1}$ for SYLGARD 184 with a 10:2 base-to-catalyst ratio cured at room temperature and at $40^\circ$C, respectively, $0.125\pm0.015$ mm$^{-1}$ for EGel 3002 with a 2B:A ratio cured at $40^\circ$C, and $0.106\pm0.014$ mm$^{-1}$ for the hybrid 10:1 EGel A:CataSYL formulation cured at room temperature. EJ-560 exhibits detectable $^{232}$Th-chain activity at about 1.8 mBq/kg and the highest $^{40}$K activity, $(120\pm20)$ mBq/kg. The locally produced materials show no detectable Th-chain contamination but exhibit $^{226}$Ra activities of about 2.3 mBq/kg and lower $^{40}$K levels. No single material is optimal across all criteria. Additional ICP-MS screening, HPGe measurements of cured pads, and direct NaI(Tl)-PMT light-yield tests are required for a conclusive SABRE-North material selection.
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All authors Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo, Giulia D'Imperio, Maria Luisa De Giorgi, Giuseppe Di Carlo, Attilio Di Giacinto, Marcella Diemoz, Aldo Ianni, Sana Gul Khattak, Edoardo Martinenghi, Alessandro Miccoli, Marcin Misiaszek, Daniele Montanino, Valerio Pettinacci, Lidio Pietrofaccia, Shahram Rahatlou, Krzysztof Szczepaniec, Claudia Tomei, Valerio Toso, Chiara Vignoli, Samina Zuhra, Francesco Ferella, Stefano Nisi
Biological Physics
Unraveling phenotypic variation in multiscale behavioral dynamics
Gautam Sridhar, Claire Wyart and Antonio Carlos Costa
Behavioral variability reflects differences in internal and external parameters and provides a substrate for natural selection. However, uncovering its structure is challenging because behavior evolves nonlinearly across multiple timescales. Our goal is to reconstruct phenotypic variation from finite behavioral observations without prescribing the scales at which individuals should be compared. To achieve this, we introduce a multiscale dissimilarity that compares dynamics across all statistically resolvable resolutions by constructing reduced transfer operators at progressively finer scales and weighting their differences by finite-sampling uncertainty. This dissimilarity defines a geometry of dynamical phenotypes, which we reconstruct using
diffusion maps. We show that the resulting phenotypic coordinates locally follow the parameter directions to which dynamics are most sensitive. We validate our approach in a
stochastic model and apply it to bacterial and larval zebrafish behavior. In bacteria, we identify run speed as a major component of inter-individual variability, associated with the chemotaxis
protein CheB. In zebrafish, we find that prior prey experience reshapes behavioral dynamics and phenotypic variability, with paramecia experience concentrating fish in a prey-capture-associated region of phenotypic space. Together, these results provide a framework for identifying internal and environmental variables that structure dynamical phenotypes across scales.
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Atomic Physics
Sub-Doppler cooling in a compact conical hollow mirror integrated with anti-Helmholtz coils
Shintaro Nagase, Naoya Ozawa, Teruhito Nakashita et al. (+7 more)
We demonstrate sub-Doppler cooling of rubidium ($^{87}$Rb) atoms using a compact, single-beam configuration based on a conical hollow mirror integrated with anti-Helmholtz coils. The conical geometry converts a single incident beam into an effective six-beam magneto-optical trap (MOT) configuration while focusing the light towards the cone axis, thereby reducing the required
laser power. The number of atoms in the conical MOT is maximized at an incident intensity of 6.5 $\mathrm{mW/cm^2}$ in our conical MOT, several times lower than in conventional six-beam MOTs. Under optimal conditions, we trap $\sim 1 \times 10^7$ $^{87}$Rb atoms. We obtain sub-Doppler temperature of $T_r=13.4\pm 1.2\ \mathrm{\mu K}$ and $T_z=106\pm 11\ \mathrm{\mu K}$ by polarization gradient cooling (PGC), revealing a strong anisotropy that we attribute to the polarization pattern created by the conical mirror. In addition, a modified release-and-recapture measurement in the MOT yields a radial temperature $T_r = 1.20\pm 0.02$ mK, approximately five times higher than that expected for comparable light-shift parameters in a six-beam MOT, in agreement with previous simulations. Our results establish conical hollow mirrors as a practical and power-efficient platform for compact cold-atom sources and integrated
quantum sensors.
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All authors Shintaro Nagase, Naoya Ozawa, Teruhito Nakashita, Masaki Nakazawa, Kota Abe, Yu Nezu, Ryosuke Tsutsui, Hideki Ueno, Hiromitsu Haba, Yasuhiro Sakemi
Plasma Physics · Cross-listed from astro-ph.SR
Coherent radio bursts, polarity reversal, and quiescent emission from the M4V dwarf WW PsA
Jackson Mitchell-Bolton, Laura Driessen, Tara Murphy et al. (+6 more)
Coherent
radio emission from magnetically active M dwarfs is largely observed in two varieties:
stochastic solar-like bursts and beamed, rotationally modulated emission including auroral pulses. Detailed monitoring of these
stars is critical for probing the
plasmas and
magnetic fields driving the emission. We conducted a search for polarised
radio emission from
stars within 85 pc, covering $2.2\times10^4$ h of stellar dynamic spectra from the ASKAP Deep Investigation of Neutral Gas Origins (DINGO) survey. We report the discovery of coherent
radio bursts from the M4V dwarf WW PsA. In addition to quiescent emission, we detect three long-duration ($\gtrsim$30 min) bursts, each ~100% circularly polarised, in 283.3 h of data. We also report a fourth burst in an epoch not covered by our search, detected using the VASTER pipeline. One of the bursts features a polarity reversal midway through, based on which we favour the electron cyclotron maser (ECM) mechanism over
plasma emission. We tentatively propose the bursts are due to rotationally modulated ECM pulses of variable intensity. We infer the required physical properties of WW PsA, including a high obliquity $\beta = 74^{+6}_{-22}$ deg under an oblique rotator model.
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All authors Jackson Mitchell-Bolton, Laura Driessen, Tara Murphy, Joshua Pritchard, Barnali Das, Richard Dodson, Martin Meyer, Jonghwan Rhee, Yuanming Wang
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Out-of-Plane Oscillating Electric Fields Unlock Low-Temperature Nonequilibrium Superionicity in Quasi-Two-Dimensional AgCrSe2
Jia-Wen Li, Kun Yang, Sheng Meng et al. (+3 more)
Superionic conductors enable exceptionally fast ion transport in solids and offer broad technological potential. However, their highly conductive states are typically accessed only above the order-disorder transition of the mobile-ion sublattice, which limits low-temperature operation. Here, electric-field-responsive machine-learning molecular dynamics reveals a nonequilibrium route to superionic transport in quasi-two-dimensional AgCrSe2 driven by an out-of-plane oscillating electric field. At 300 K, far below the transition temperature near 475 K, the field activates fast in-plane Ag+ transport with an ionic conductivity reaching ~1.7 S/cm. This originates from field-driven dynamic disorder of Ag+ across two equivalent sublattices rather than thermally induced disordering. With increasing frequency, the Ag occupation evolves from complete switching to a highly conductive dynamically disordered state and finally to an ordered state with weak field response. These regimes shift to higher frequencies with increasing temperature or field amplitude, consistent with competition between the driving period and Ag-sublattice response time. At strong fields, this timescale is consistent with field-assisted thermal activation, while weak-field deviations suggest additional dynamics beyond single-ion activation. These results suggest timescale-matched periodic driving as a route to transport-active ionic disorder far below an
equilibrium superionic transition.
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All authors Jia-Wen Li, Kun Yang, Sheng Meng, Xinghua Shi, Wei-Hai Fang, Jin Zhang
Optics
Tunable low-phase-noise terahertz synthesis using a fiber-interferometer-referenced optical frequency comb and an EDFA-integrated Vernier cavity
Masayuki Higaki, Yoshiaki Nakajima, Yu Tokizane et al. (+4 more)
demonstrate a frequency-tunable, low-phase-noise terahertz (THz) synthesizer based on a fiber-interferometer-referenced optical frequency comb (OFC), an erbium-doped fiber amplifier (EDFA)-integrated Vernier cavity, and dual optical injection locking (OIL). The Vernier cavity converts the densely spaced modes of a fiber OFC with a repetition frequency of approximately 100 MHz into a filtered comb with gigahertz-scale effective mode spacing, facilitating selective single-mode OIL. Intracavity and extracavity EDFAs in the Vernier cavity enable a side-mode suppression ratio exceeding 70 dB. Independent control of the Vernier-cavity free spectral range and the OFC repetition frequency provides flexible Vernier filtering conditions for selecting master modes for dual OIL. Two selected comb modes are transferred to injection-locked optical carriers and photomixed in a uni-traveling-carrier photodiode to generate continuous-wave THz signals. Frequency-tunable THz generation is demonstrated at 230, 267, and 320 GHz. At 267 GHz, a signal-to-noise ratio exceeding 70 dB and a measured phase noise of -95.7 dBc/Hz at a 10-kHz offset are obtained; the phase-noise measurement is limited by the local-oscillator system. The proposed architecture provides a fiber-based approach to frequency-tunable, low-phase-noise THz synthesis by combining an optical-reference-based OFC with flexible Vernier-assisted comb-mode selection.
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All authors Masayuki Higaki, Yoshiaki Nakajima, Yu Tokizane, Kwangyun Jung, Ryosuke Nakamura, Naoya Kuse, Takeshi Yasui
Fluid Dynamics
A simple Lagrangian for shallow water equations with constant potential vorticity
Anton Galajinsky
Inspired by a recent gauge field description of shallow water equations [SciPost Phys. 14 (2023) 102], in this work we build a simple Lagrangian formulation for the case of constant potential vorticity. An attractive feature of the construction is that it does not appeal to a Clebsch-like parametrization or the use of auxiliary fields. It is also emphasized that on the equator, where the Coriolis parameter vanishes, the shallow water equations exhibit extra SO(2,1) conformal invariance. Using the group-theoretic method, a new exact solution is found, which is associated with the scaling
symmetry transformation entering the conformal group.
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Atomic Physics
Bifurcation of laser-dressed band extrema in solids under intense low-frequency fields
Alexander Flegel, Liang-Wen Pi, Liang-You Peng et al. (+1 more)
We show that an intense low-frequency
laser field can qualitatively modify the local extremal structure of an interband energy gap in a
crystal. Using an instantaneous
laser-dressed basis obtained from the nonperturbative diagonalization of the multiband
crystal Hamiltonian, we derive a quartic normal form for the dressed gap near a high-
symmetry point. At a critical field, the quadratic part of this normal form changes sign, and the gap experiences a bifurcation: a single symmetric minimum splits into two
symmetry-related minima separated by a local maximum. We identify the microscopic origin of this bifurcation by decomposing the quadratic part into a homogeneous Stark contribution and a field-modified band-
curvature contribution. The latter originates from the multiband redistribution of interband polarizations and provides the mechanism for the field-induced change of the gap extrema. A realization for the Kronig–Penney model demonstrates the same bifurcation at multiple high-
symmetry points and for different interband gaps. As an illustration of its spectral consequences, we show that the bifurcation gives rise to an additional van Hove feature in the instantaneous interband susceptibility above the absorption edge. Our results establish a general mechanism by which strong-field dressing modifies the local geometry of the electronic spectrum.
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All authors Alexander Flegel, Liang-Wen Pi, Liang-You Peng, Mikhail Frolov
Applied Physics · Cross-listed from cond-mat.mes-hall
Giant Conductance Enhancement in Graphene Nanoscrolls via Interlayer-Coupled States
Jia-Cheng Li, Ying-Je Lee, Yu An Cheng et al. (+6 more)
Graphene nanoscrolls form a unique radial superlattice whose geometry enables transport behaviors distinct from their flat counterparts. We theoretically demonstrate that rolling a
graphene nanoribbon into a few-turn nanoscroll (1.0-1.2 turns) triggers a giant enhancement in longitudinal conductance by an order of magnitude (nearly twentyfold). We show that this effect stems from interlayer hopping between open boundaries, which not only transforms localized edge states into one-dimensional-like conducting channels and also induces a significant Fermi energy shift. Our results reveal an inverse scaling of conductance with turn number, establishing GNSs as a platform for geometry-driven
quantum transport and offering a tunable approach to engineering nanoarchitectural electronic states.
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All authors Jia-Cheng Li, Ying-Je Lee, Yu An Cheng, Yu-Hsiang Fu, Xuan-Fu Huang, Yu-Jie Zhong, Ion Cosma Fulga, Carmine Ortix, Ching-Hao Chang
Optics
Scatter-free perfect reflection in multichannel monolithic high-contrast gratings: direct–indirect Fourier-harmonic interference and dimensionality of the solution set
Sun-Goo Lee and Wook-Jae Lee
Monolithic high-contrast gratings (MHCGs) can exhibit scatter-free perfect reflection despite open higher-order substrate diffraction channels, but the underlying mechanism has not been fully clarified. Using a
Fourier-harmonic description, we show that all open higher-order channels in the high-index substrate can be simultaneously extinguished through destructive interference between the radiation fields generated by the direct and indirect source contributions. By contrast, the zeroth-order transmission vanishes when the modulation-induced zeroth-order field interferes destructively with the background transmitted field of the incident wave. Together, these cancellations yield unit zeroth-order reflectance in lossless MHCGs. The near invariance of the internal field harmonics accounts for the remarkable stability of these conditions against changes in the substrate refractive index. We further show that the number of
symmetry-compatible open channels determines the generic codimension of the perfect-reflection solution set. Depending on the number of independent design parameters relative to this codimension, the solutions form continuous curves, appear as isolated points, or are generically absent. Introducing an additional geometrical parameter restores isolated perfect-reflection solutions when an additional diffraction channel opens. The same cancellation mechanisms and channel counting apply to both TE and TM polarizations.
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Physics and Society · Cross-listed from q-bio.PE
Stochastic evolutionary dynamics in structured populations: Network degree governs evolutionary stability
Vikash Kumar Dubey and Sagar Chakraborty
Stochasticity shapes evolutionary dynamics in finite populations beyond the reach of infinite-population theories. Using a
stochastic birth–death framework on random regular networks, we establish evolutionary stability criteria for finite structured populations playing three-strategy games and identify critical degree thresholds governing invasion dynamics. Our framework goes beyond two-strategy evolutionary games to reveal that the initial composition of multi-type mutants, together with population structure and stochasticity, shapes the evolutionary fate of the resident population.
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