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Physics Physics

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Sunday 29 March

Optics

Partial parabolic amplification in rare-earth-doped optical fiber

Wenchao Wang, Yi-Hao Chen and Frank Wise

Nonlinear amplification is a powerful technique for generating ultrashort laser pulses with high peak power in fiber systems. However, the diversity of nonlinear amplification approaches and their inherent complexities present significant challenges to achieving a unified understanding and further scaling of peak power and pulse energy while preserving ultrashort durations. Here, we report the results of a systematic optimization with respect to seed pulse duration that elucidates the dynamics of nonlinear amplification and allows identification of distinct propagation regimes. As part of this analysis, we identify a new regime, termed partial parabolic amplification, which achieves 50-fs pulse duration and yields higher peak power than any other nonlinear amplification regime known to date. An initial experimental demonstration of partial parabolic amplification produces 50-fs and 2.2-uJ pulses with a 25-um-core Yb fiber amplifier, corresponding to a 30-MW peak power. In contrast to other nonlinear amplification techniques, practical energy scaling beyond 10 uJ and 200 MW should be achievable with available gain fibers with larger mode areas, which would fill a gap in existing fiber laser capabilities that would directly impact material processing, nonlinear bio-imaging, and other applications.
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Atomic Physics

High performance imaging of $^{171}$Yb atom in shallow clock-magic tweezer by alternating dual-tone narrowline cooling

Yunheung Song, Kangheun Kim, Jeong Ho Han et al. (+2 more)

We demonstrate imaging $^{171}$Yb single atoms in clock-magic tweezers of 759.4 nm wavelength, with above 99.9% fidelity and survival. We use alternating dual-tone narrowline imaging for more efficient three-dimensional cooling in tweezers, allowing several-millisecond imaging in 200 $\mu$K trap depth, which is half of typical depth used for imaging in clock-magic tweezers. Accordingly, even without repumping, imaging survival is still close to 99.9% with the high fidelity, which can enable high performance nondestructive qubit measurements based on metastable shelving. Moreover, our simulation predicts that more optimal configuration could further reduce the trap depth, as improving the imaging performance. This imaging capability in shallow traps opens high performance imaging for more general trap wavelength, and lays the foundation for large scale systems over 1,000 qubits, and highly repeatable tweezer clocks.
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All authors Yunheung Song, Kangheun Kim, Jeong Ho Han, Seungtaek Oh, Jongchul Mun

Fluid Dynamics

Learnable Viscosity Modulation in Physics-Informed Neural Networks for Incompressible Flow Reconstruction

Ke Xu, Ze Tao and Fujun Liu

Accurately and stably solving the incompressible Navier–Stokes equations with physics-informed neural networks (PINNs) remains challenging, particularly for sparse or noisy observations and for flow regimes in which the local balance among convection, diffusion, and pressure is difficult to capture. To address this issue, we propose a framework, denoted as LVM-PINN, which incorporates a learnable viscosity modulation (LVM) mechanism into the PINN residual. Specifically, the model predicts a spatiotemporal scalar field that is embedded directly into the viscous diffusion term of the momentum equations, thereby enabling adaptive modulation of the local dissipation strength during training. This modification improves optimization stability while enhancing the representation of complex flow structures. The effect of the proposed mechanism is further examined through a controlled ablation setting with an otherwise unchanged network architecture, as well as through comparisons with GRU- and residual-attention-based backbone baselines. Numerical experiments on two-dimensional benchmark problems, including the Kovasznay flow and two manufactured forcing flows, show that the proposed framework yields more stable training behavior and more accurate flow reconstruction under sparse and noisy data conditions.
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Biological Physics · Cross-listed from q-bio.QM

Quantitative mapping of dynamic 3D transport in growing cells via volumetric spatio-temporal image correlation spectroscopy (vSTICS)

Ahmad Mahmood and Paul W. Wiseman

Quantitatively mapping three-dimensional (3D) flow, diffusion, and particle density in crowded living cells remains challenging because most dynamic optical microscopy measurements are effectively planar and existing analysis methods struggle with dense, noisy volumetric data. We introduce volumetric spatio-temporal image correlation spectroscopy (vSTICS), a framework that recovers voxel-resolved flow, diffusion coefficients, and particle densities from 3D fluorescence time series. Growing Camellia japonica pollen tubes were imaged with field-synthesis lattice light-sheet microscopy, and localized 3D spatio-temporal correlation analysis was applied to overlapping volumetric samples to generate maps of velocity, diffusion, and density. Validation with synthetic flow-diffusion simulations showed accurate recovery of seeded transport parameters, including velocities near $3$ $\mu$m s$^{-1}$ and diffusion near $10^{-3}$ $\mu$m$^2$ s$^{-1}$. Fluorescent microsphere experiments verified particle number and point spread function readouts and measured diffusion coefficients of $0.3 \pm 0.1$ $\mu$m$^2$ s$^{-1}$ in gel, consistent with imaging-FCS measurements of $0.5 \pm 0.2$ $\mu$m$^2$ s$^{-1}$. Applied to mitochondria in pollen tubes, vSTICS resolved a bidirectional reverse-fountain pattern with slower anterograde transport ($0.1$-$1$ $\mu$m s$^{-1}$) and faster retrograde motion peaking near $3$ $\mu$m s$^{-1}$, plus a retrograde corridor about $2$ $\mu$m wide. Density and diffusion maps indicated a denser, more advective core and higher peripheral diffusion. High-density sub-diffraction vesicle mapping produced similar velocity landscapes with about ten-fold higher particle densities. These results establish vSTICS as a practical method for quantitative 3D mapping of intracellular transport and refines the reverse-fountain model by revealing asymmetric, predominantly transverse circulation.
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Instrumentation and Detectors

Construction and characterization of a muon trigger detector for the PSI muEDM experiment

Guan Ming Wong, Tianqi Hu, Samip Basnet et al. (+15 more)

We present the upgraded design, construction, and beam test results for the Muon Trigger Detector (MTD) developed for the muon Electric Dipole Moment (muEDM) experiment at the Paul Scherrer Institute (PSI) in Switzerland. This experiment aims to improve the sensitivity of the muon EDM measurement by more than three orders of magnitude beyond the current limit established by the BNL Muon $g-2$ experiment. Precise identification of storable incoming muons at the entrance of the storage solenoid is essential, as the MTD must rapidly trigger a pulsed magnetic kicker to confine muons in the central region of the solenoid, where a weakly focusing magnetic field is maintained. The MTD comprises two subsystems: a \SI{0.1}{mm}-thick plastic scintillator “gate detector” read out by four silicon photomultipliers (SiPMs), and a \SI{5}{mm}-thick CNC-machined plastic scintillator “active aperture detector” read out by six SiPMs. The geometry of the active aperture detector was optimized through acceptance studies to maximize both storage efficiency and background veto efficiency. Integrated fast electronics generate an LVTTL trigger signal under an anti-coincidence condition – a muon detected in the gate but not in the aperture – ensuring selective triggering of storable muon events for the EDM measurement. The system was tested at the PSI $\pi$E1 beamline using \SI{22.5}{MeV/c} muons under scaled-down conditions to characterize detector response and trigger performance. A Geant4 simulation incorporating detailed optical photon transport and SiPM response modeling was developed and reproduces the measured event topologies with ${\sim}97\%$ agreement. These results validate the detector design and demonstrate the MTD's readiness for deployment in the full muEDM Phase-1 setup.
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All authors Guan Ming Wong, Tianqi Hu, Samip Basnet, Chavdar Dutsov, Siew Yan Hoh, David Höhl, Xingyun Huang, Timothy David Hume, Alexander Johannes Jäger, Kim Siang Khaw, Meng Lyu, Ljiljana Morvaj, Jun Kai Ng, Angela Papa, Diego Alejandro Sanz Becerra, Philipp Schmidt-Wellenburg, Yusuke Takeuchi, Yonghao Zeng

Optics

A Dual-Sideband Attosecond Interferometry Setup

Muhammad Jahanzeb, Marvin Schmoll, Paul Weizel et al. (+5 more)

We present the development and implementation of an experimental setup designed to investigate attosecond photoionization delays using a dual-sideband RABBITT (Reconstruction of Attosecond Beating By Interference of Two-Photon Transitions) technique. The setup utilizes an attosecond extreme ultraviolet source from high-harmonic generation driven by a carrier-envelope-phase-stabilized Ti:sapphire laser centered at 800 nm. The extreme ultraviolet radiation is synchronized with a 1200 nm infrared probe pulse generated via a non-collinear optical parametric amplifier. Active delay stabilization by means of a spectrally resolved interferometer signal achieves 45 as root-mean-square timing precision and enables the observation of sideband oscillations. Taking advantage of the dependence of the sideband signal on the carrier-envelope phase of the driving field, we report sideband-yield oscillations as a function of this parameter.
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All authors Muhammad Jahanzeb, Marvin Schmoll, Paul Weizel, Simon Majoni, Ronak Narendra Shah, Mario Niebuhr, Cristian Manzoni, Giuseppe Sansone

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

Unidirectional flow from continuous broken symmetries

Aaron Winn, Justine Parmentier, Eleni Katifori et al. (+1 more)

Locally broken symmetries are used across fields to transport matter, particles and information in preferential directions. Beyond local mechanisms, spatially distributed nonlinearities in crystalline media have enabled non-reciprocal transport, a rectification mechanism that operates continuously across scales and frequencies. Here, we show that this concept applies beyond condensed matter, to fluid transport in living organisms and artificial systems. We take the example of the lymphatic vascular system, which transports interstitial fluid in mammals, and demonstrate that distributed leaflets act as continuous broken symmetries. We build an artificial model of a collecting lymphatic and investigate the naturally richer dynamics of unidirectional transport that arises from spatiotemporal excitations. We observe robust and scalable transport for any waveshape and external pressure gradients. We show experimentally and theoretically that the contraction wavelength, directionality, and pulsatility control the flow rate. In particular, we counterintuitively find waveshapes that maximize transport when propagating against the direction of the flow. Overall, our findings advance the understanding of unidirectional fluid transport in living systems and beyond, and reveal how coupling nonlinearities with spatiotemporal excitations can tune such transport across fields.
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All authors Aaron Winn, Justine Parmentier, Eleni Katifori, Martin Brandenbourger

Applied Physics · Cross-listed from cond-mat.other

Characterizing the Linearity of Magnonic Devices for Radio-Frequency Applications

Robert Erdelyi, Adam Papp Levente Maucha, Philipp Pirro et al. (+5 more)

Magnonic devices exhibit strong amplitude-dependent nonlinearities, which are detrimental to signal integrity in radio-frequency (RF) signal processing applications. They also limit the power that such magnonic devices may process. In this paper we use micromagnetic simulations to characterize the nonlinearity of magnonic RF devices by investigating their intermodulation distortion (specifically third-order intermodulation products, IP$_3$ ). The IP$_3$ is a commonly used metric for RF components in communication systems and allows direct comparison with state-of-the-art electrical counterparts.
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All authors Robert Erdelyi, Adam Papp Levente Maucha, Philipp Pirro, Matthias Wagner, Dieter Ferling, Johannes Greil, Markus Becherer, Gyorgy Csaba

Saturday 28 March

Geophysics

Olivine annealed up to 1500 C: changes traced by polarised IR reflectance and magnetization

Daniel Smith, Donatas Narbutis, Hsin-Hui Huang et al. (+14 more)

Spectral analysis at the infrared (IR) spectral range is introduced with assignment of synthetic red-green-blue (RGB) colours defined by adjustable wavelength and bandwidth. The RGB bands were selected at the phase-specific absorbance A or reflectance R bands of olivine and related materials, which can be formed via high temperature annealing (HTA) of natural minerals up to 1500 C. Natural olivines were collected from quarry at volcanic site in Mortlake, Victoria, Australia and spectrally characterised during IR-THz spectroscopy beamtime experiments at Australian Synchrotron. Phase changes in HTA natural olivines were traced by correlation of optical IR 4-polarisation spectroscopy, X-ray energy dispersive spectroscopy and magnetisation. After HTA, olivine samples were magnetized via precipitation of Fe-rich oxides.
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All authors Daniel Smith, Donatas Narbutis, Hsin-Hui Huang, Philipp Zanon, Michael Boschen, Jitraporn Vongsvivut, Dominique Appadoo, Soon Hock Ng, Haoran Mu, Tomas Katkus, Nguyen Hoai An Le, Dan Kapsaskis, Andy I.R. Herries, Vijayakumar Anand, Meguya Ryu, Junko Morikawa, Saulius Juodkazis

Computational Physics · Cross-listed from cs.CE

Sparse Autoencoders as a Steering Basis for Phase Synchronization in Graph-Based CFD Surrogates

Yeping Hu, Ruben Glatt and Shusen Liu

Graph-based surrogate models provide fast alternatives to high-fidelity CFD solvers, but their opaque latent spaces and limited controllability restrict use in safety-critical settings. A key failure mode in oscillatory flows is phase drift, where predictions remain qualitatively correct but gradually lose temporal alignment with observations, limiting use in digital twins and closed-loop control. Correcting this through retraining is expensive and impractical during deployment. We ask whether phase drift can instead be corrected post hoc by manipulating the latent space of a frozen surrogate. We propose a phase-steering framework for pretrained graph-based CFD models that combines the right representation with the right intervention mechanism. To obtain disentangled representation for effective steering, we use sparse autoencoders (SAEs) on frozen MeshGraphNet embeddings. To steer dynamics, we move beyond static per-feature interventions such as scaling or clamping, and introduce a temporally coherent, phase-aware method. Specifically, we identify oscillatory feature pairs with Hilbert analysis, project spatial fields into low-rank temporal coefficients via SVD, and apply smooth time-varying rotations to advance or delay periodic modes while preserving amplitude-phase structure. Using a representation-agnostic setup, we compare SAE-based steering with PCA and raw embedding spaces under the same intervention pipeline. Results show that sparse, disentangled representations outperform dense or entangled ones, while static interventions fail in this dynamical setting. Overall, this work shows that latent-space steering can be extended from semantic domains to time-dependent physical systems when interventions respect the underlying dynamics, and that the same sparse features used for interpretability can also serve as physically meaningful control axes.
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Classical Physics

Induced-current magnetophoresis

V. Kumaran

When an electrically conducting non-magnetic particle is subjected to a spatially varying and oscillating applied magnetic field of amplitude $\mathcal{H} + \mathcal{G} \cdot x$ and frequency $\omega$, an oscillating eddy current is induced. The Lorentz force density, the cross product of the current density and the magnetic field, consists of a steady component and a component with frequency $2 \omega$. If there is a spatial variation in the applied field, there is a steady force on a sphere of radius $R$ proportional to $- \mu_0 R^3 \mathcal{G} \cdot \mathcal{H} $, and a steady force on a thin rod of radius $R$ and length $L$ proportional to $- \mu_0 R^2 L (\mathcal{G} \cdot \mathcal{H} - \tfrac{1}{2} (\mathcal{G} \cdot \hat o)(\mathcal{H} \cdot \hat o))$, where $\mu_0$ is the magnetic permeability. There is torque proportional to $\mu_0 R^2 L (\hat o \times \mathcal{H} ) (\hat o \cdot \mathcal{H} )$ on a thin rod which tends to align the rod direction of the magnetic field. The coefficients in the force and torque expressions are functions of the dimensionless ratio of the radius and the penetration depth of the magnetic field, $\beta R = \sqrt{\mu_0 \omega \kappa R^2}$, where $\kappa$ is the electrical conductivity. It is shown that the effect of particle interactions can be expressed as an anisotropic diffusion term in the equation for the particle number density. The diffusion coefficient is negative, and concentration fluctuations are amplified, in the plane perpendicular to the magnetic field.
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Classical Physics

Analytic solutions for the longitudinal and the transverse components of the vector potential in the Lorenz gauge

Kuo-Ho Yang and Robert D. Nevels

We derive analytic solutions for the longitudinal and the transverse components of the vector potential in the Lorenz gauge for an arbitrary time-dependent charge-current distribution.

Physics and Society

Complementarity in Social Measurement: A Partition-Logic Approach

Karl Svozil

Partition logics – non-Boolean event structures obtained by pasting Boolean algebras – provide a natural language for situations in which a system has a definite latent state but can be accessed and resolved only through mutually incompatible coarse-grained modes of observation. We show that this structure arises in a range of social-science settings by constructing six explicit examples from personnel assessment, survey framing, clinical diagnosis, espionage coordination, legal pluralism, and organizational auditing. For each case we identify the latent state space, the observational contexts as partitions, and the shared atoms that intertwine contexts, yielding instances of the $L_{12}$ bowtie, triangle, pentagon, and automaton partition logics. These examples make precise a notion of social complementarity: different modes of inquiry can be incompatible even though the underlying system remains fully value-definite. Complementarity in this sense does not entail contextuality or ontic indeterminacy. We further compare the classical probabilities generated by convex mixtures of dispersion-free states with the quantum-like Born probabilities available when the same exclusivity graph admits a faithful orthogonal representation. The framework thus separates logical structure from probabilistic realization and suggests empirically testable benchmarks for quantum-cognition models.
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Fluid Dynamics

Interplay between Temperature Oscillations and Melt Pool Dynamics in 3D Manufacturing Techniques

Stepan L. Lomaev, Georgii A. Gordeev, Marat A. Timirgazin et al. (+2 more)

The aim of this paper is coupling of temperature oscillations and melt pool dynamics experimentally observed in laser melting. The literature survey has shown that the developed explanations are mainly focused on the capillary and hydrodynamic aspects of the problem. As shown, complete analysis is only possible if the temperature oscillations are properly accounted for. Specifically, this effect is a governing mechanism that controls the melt pool dynamics via feedback coupling of heating, evaporation, capillarity and free-surface contraction. The present study suggests a physically consistent model validated on the detailed data of the time-resolved absorptance measured in [Phys. Rev. Appl. 10, 044061 (2018)]. An analytical equation is derived for oscillation spectra within this approach. It has been proved that the surface oscillations can be initiated without the keyhole effect. However, keyhole formation can cause additional modes to appear in the oscillation spectrum. The practical results include the formulas that are convenient for real-time monitoring of the surface temperature and characteristic flow velocity in the molten pool using the measured absorptance spectra. The impact of the temperature coefficient of surface tension on the maximal temperature, pool length, natural frequency of the free surface oscillations, and attenuation coefficient is thoroughly studied. All results are presented as closed-form formulas suitable for design of industrial laser systems.
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All authors Stepan L. Lomaev, Georgii A. Gordeev, Marat A. Timirgazin, Dinara R. Fattalova, Mikhail D. Krivilyov

Optics · Cross-listed from hep-ph

Determining G with Laser Spectroscopy to 38 ppb

Noah Bray-Ali

A precision measurement is proposed to determine, in a couple hours of integration time, the axion Compton frequency using a modest power (3 mW) tunable external cavity diode laser at 2458 nm as input to drive a free space tabletop Mach Zehnder interferometer whose sensing arm passes the expanded beam waist (3 mm) light beam through a 1 T strong, 40 cm long dipole magnetic field created by a custom built permanent magnet assembly with a large but achievable (6 mm) gap between poles. As the laser frequency is slowly modulated at 1 kHz through a 600 MHz wide window that is well within the 30 GHz fine tuning range of the laser, a small but readily observable modulation appears in the dark port optical power of the dark fringe phase locked interferometer due to photons converting into axions within the light beam as it passes through the magnetic field. Measuring the axion Compton frequency, around 122 THz, where the dark port power modulation peaks, to within the linewidth of the laser, about 1 MHz, then determines G to 38 parts per billion (ppb), a roughly 600 fold improvement, through a relation between the axion Compton frequency and G, involving h, c, and nucleon masses.
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Fluid Dynamics

Simulating the swimming motion of a flagellated bacterium in a microstructured bio-fluid

Arjun Sharma, Sabarish V. Narayanan, Sarah Hormozi et al. (+1 more)

We develop a numerical framework to simulate the locomotion of a flagellated bacterium with a spheroidal head (such as Escherichia coli) in biological fluids like mucus, which are entangled polymer solutions exhibiting elasto-viscoplastic (EVP) rheology and porous microstructure. To account for the scale disparity between the large bacterial head and the slender flagellar bundle, whose thickness is comparable to the pore size, we employ a two-fluid model in which the bundle directly drives the solvent and exchanges momentum with the polymer phase via drag proportional to their relative velocity. The numerical implementation combines a finite-difference discretization of the two-fluid equations with a slender-body theory (SBT) to model flagellar forcing. A key observation is that the coupled mass and momentum equations for these inertialess flows, together with SBT, are linear in the pressure and velocity fields and in the force distribution along the flagellar bundle. By treating the polymer stress as a body force, we decompose the flow field and hydrodynamic moments into three additive contributions: kinematic (motion), flagellar forcing, and polymer stress. This decomposition allows several components of the flow to be precomputed and enables the determination of swimming velocity via a resistivity formulation driven by polymer-induced forces, which greatly improves computational efficiency during transient calculations of the polymer stress and the resulting flow. We validate the method and use it to analyze how polymer microstructure and its interactions with the bacterial head and tail affect motility in complex biofluids.
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All authors Arjun Sharma, Sabarish V. Narayanan, Sarah Hormozi, Donald L. Koch

Chemical Physics · Cross-listed from cond-mat.soft

The effects of ionic valency and size asymmetry on counterion adsorption

Or Ben Yaakov, Haim Diamant, Rudolf Podgornik et al. (+1 more)

We study the effect of asymmetry in solvent and ionic size on the equilibrium properties of multivalent ionic solutions near a charged surface. For a single ionic species in solution, we derive a generalized Grahame equation at the charged surface. For general size ratio between the ions and the solvent, we obtain analytical results for the concentration profiles as a function of the distance from the surface. For weak surface charge and small ion-to-solvent size ratio, the profile follows the classical Poisson-Boltzmann equation in dilute solution conditions. However, for high surface charge and large ionic size, the concentration profile saturates near the surface, leading to distinctive dependencies of the solution properties on the surface charge density and size asymmetry. Furthermore, the crossover between dilute and saturated regimes depends on the surface charge and ionic size asymmetry. We suggest that a solution containing multiple ionic species of different valencies and sizes stratifies close to the surface in the saturation regime. This leads to the formation of layers that are ordered according to the ions' valency-to-size ratio.
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All authors Or Ben Yaakov, Haim Diamant, Rudolf Podgornik, David Andelman

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

Neural operator accelerated atomistic to continuum concurrent multiscale simulations of viscoelasticity

Tanvir Sohail, Burigede Liu and Swarnava Ghosh

We present a neural-operator-accelerated concurrent multiscale framework that couples atomistic simulations with continuum finite-element analysis for history-dependent materials, thereby making atomistic-continuum multiscale simulations of viscoelastic materials tractable. The approach replaces direct molecular dynamics (MD) evaluation of the constitutive response with a Recurrent Neural Operator (RNO) surrogate trained on atomistic simulations. The surrogate learns the strain-history-to-stress operator from molecular dynamics simulations and provides a discretization-independent approximation of the atomistic constitutive mapping, enabling efficient evaluation of stresses and latent internal variables at each quadrature point. The framework is implemented within an explicit finite-element solver, where the constitutive update reduces to inexpensive operator evaluations rather than repeated MD solves. Memory effects are represented through learned internal states, and transfer learning across temperature enables the surrogate to capture thermally dependent viscoelastic behavior. The method is assessed using polyurea through cyclic loading, Taylor impact, and plate impact simulations and compared with an experimentally calibrated viscoelastic polyurea model and a Johnson-Cook model. The neural-operator surrogate reproduces correct viscoelastic response while enabling atomistically informed dynamic simulations at scales that are not tractable with direct MD-FEM coupling.
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Space Physics

Turbulent dynamo in the terrestrial magnetosheath

Zoltán Vörös, Owen Wyn Roberts, Yasuhito Narita et al. (+10 more)

Dynamo action refers to energy exchange processes through which magnetic fields are generated at the expense of kinetic energy of the plasma flows. Dynamos can generate magnetic fields across scales larger or smaller than the flows themselves. Multi-scale dynamo processes underpin magnetic phenomena from planetary cores to stellar and galactic environments, while also shaping turbulent magnetic fields at smaller scales. Yet, experimental validation of dynamo action has remained largely confined to laboratories. Here we report evidence for a turbulent dynamo in the terrestrial magnetosheath. Observations reveal the predicted spatial topology of stretched and folded magnetic fields, compressive effects, and pressure anisotropy instabilities essential for magnetic field amplification. Our findings also highlight the central role of turbulent dynamos in energy conversion and structure formation within collisionless plasma turbulence. The observed energy exchange signatures indicate that the magnetosheath may serve as a natural testbed for validating dynamo theories and simulations.
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All authors Zoltán Vörös, Owen Wyn Roberts, Yasuhito Narita, Emiliya Yordanova, Rumi Nakamura, Adriana Settino, Daniel Schmid, Martin Volwerk, Cyril L. Simon Wedlund, Ali Varsani, Luca Sorriso-Valvo, Philippe-A. Bourdin, Árpád Kis

Optics

Differential source-basis encoding for superresolved parameter estimation in a time-reversed Young interferometer

Jianming Wen

We develop a differential source-encoding protocol for local parameter estimation in a time-reversed Young interferometer, where the source plane is used not merely as a scan coordinate but as a programmable measurement basis. Two sequential positive-only source patterns implement an antisymmetric differential probe about a chosen operating point, converting the deterministicc source-coordinate response into a derivative-gradient sensing channel. In the local regime, the differential signal separates naturally into an envelope-gradient term, which is also present in noninterferometric differential sensing, and an interference-gradient term, which is specific to the time-reversed Young fringe law. This decomposition identifies the physical origin of the interferometric advantage and clarifies why it is regime dependent rather than universal. Using a shot-noise-limited Poisson model, we derive the corresponding Fisher information and Cramér–Rao bounds and compare the protocol with raster sampling in the same geometry and with a matched noninterferometric differential baseline. Representative numerical examples show a strong and robust gain over raster sampling, while the additional improvement from the time-reversed Young interference is parameter dependent but can be substantial in favorable regimes. The results establish the time-reversed Young geometry as a practically simple platform for programmable differential interferometric metrology.
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Fluid Dynamics · Cross-listed from cond-mat.soft

Shear-induced self-diffusivity in dilute suspensions with repulsive interactions

Anu V S Nath, Pijush Patra and Anubhab Roy

In a dilute non-Brownian suspension undergoing simple shear, pairwise hydrodynamic interactions are fore-aft symmetric at zero Reynolds number and produce no net cross-streamline displacement. A weak central repulsive force between particles breaks this symmetry, deflecting trajectories and generating irreversible transverse displacements that cumulatively yield a shear-induced self-diffusivity. We derive, via matched asymptotic expansions in the limit of weak repulsion, closed-form scaling laws for the gradient and vorticity components of this diffusivity. The gradient component exhibits a logarithmic enhancement relative to the vorticity component, a structural anisotropy that persists for all monotonically decaying repulsive potentials. The specific interaction enters only through integral functionals of the force profile weighted by hydrodynamic mobility functions, establishing that the scaling is universal across physically distinct mechanisms, such as electrical double-layer repulsion, steric interactions, or any other short-range central force. We validate the asymptotic predictions against full numerical trajectory integration for the representative case of electrostatic repulsion, modelled using the Gouy-Chapman description of the electrical double layer, and find excellent agreement in the expected regime.
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Atmospheric and Oceanic Physics

Omega-blocks with spatially compounding extremes over Europe are highly sensitive to remote atmospheric drivers

Magdalena Mittermeier, Christian M. Grams, Urs Beyerle et al. (+5 more)

Omega-blocks can trigger spatially compounding heat-precipitation extremes with severe societal impacts, as seen in September 2023 when a heatwave over France coincided with devastating floods in the Iberian Peninsula and Greece. Although blocking in general has been linked to moist processes in upstream warm conveyor belts (WCBs), it has remained unexplored whether and how upstream WCB activity influences the evolution of omega-blocks and downstream flood-heat-flood impacts. Here, we show that already five days ahead, small differences in the upstream evolution - particularly in WCB outflow regions - distinguish cases that later produce extreme compound events over Europe from weaker ones, even though their large-scale anomalies initially appear similar. We illustrate the distinct evolution in remote locations by analyzing storylines simulated in a fully coupled climate model. Using ensemble boosting, we generate hundreds of physically plausible simulations of omega-prone situations. Lagrangian air parcel tracking reveals that variations in WCB outflow areas can explain differences in upstream precursors and downstream effects over Europe. Our results highlight ensemble boosting as a powerful approach to systematically track dynamical differences along model-based event storylines, important for understanding and anticipating compound extremes striking multiple regions simultaneously.
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All authors Magdalena Mittermeier, Christian M. Grams, Urs Beyerle, Laura Suarez-Gutierrez, Emanuele Bevacqua, Yixuan Guo, Jakob Zscheischler, Erich M. Fischer

Applied Physics

Magnetic field induced modification of a first-order ferromagnetic transition in Eu2In

Ajay Kumar, Anis Biswas, Trevor A. Tyson et al. (+3 more)

We present a comprehensive study of the temperature- and magnetic-field-dependent magnetization, specific heat, and local crystal structure across the first-order ferromagnetic-paramagnetic transition in Eu$_2$In. Anomalies in the magnetocaloric response are observed near $H \approx 25$~kOe, including changes in field scaling of magnetic entropy, local entropy exponent, and universal master curve, which suggest an apparent weakening of the first-order character of the transition. However, quantitative analysis of the magnetocaloric parameters together with modified Arrott plots demonstrates that the transition remains first order up to at least 70~kOe. Specific-heat measurements reveal a field-induced splitting of the sharp zero-field anomaly into a doublet, providing a natural explanation for the change in the magnetocaloric response. Magnetic field dependent extended x-ray absorption fine structure (EXAFS) measurements show no detectable field-induced changes in the local coordination environment of Eu. We therefore attribute these observations to a magnetic field induced two-step transition process in Eu$_2$In.
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All authors Ajay Kumar, Anis Biswas, Trevor A. Tyson, Daniel Haskel, Christopher J. Pollock, Yaroslav Mudryk

Computational Physics

Characterizing Atomistic Transitions Using Cross-scale Graph-pooled Chebyshev Signatures

Rostyslav Hnatyshyn and Danny Perez

Large-scale atomistic simulations can produce extreme volumes of information in the form of long trajectories. Reliably and automatically extracting key information from such datasets remains a formidable challenge, especially as it pertains to the analysis of the structural transitions affecting the system. We present a novel approach to characterize and compare atomistic transitions using cross-scale graph-pooled Chebyshev signatures. These signatures are permutation invariants of an operator that transform a Coulomb matrix representation of the initial state of the system into that corresponding to the final state. Using a long-time trajectory of a small metallic nanoparticle, we show that these signatures can be used to define a natural distance metric between transitions that allows for classification and clustering into physically meaningful families. This approach is shown to capture complex patterns and hierarchies of transition types that are inaccessible to traditional techniques, dramatically facilitating the analysis of large-scale simulations.
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Applied Physics · Cross-listed from quant-ph

Non-Unitary Quantum Machine Learning: Fisher Efficiency Transitions from Distributed Quantum Expressivity

Apoorv Kumar Masta, Srinjoy Ganguly, Shalini Devendrababu et al. (+3 more)

Quantum machine learning has faced growing scrutiny over its practical advantages compared to classical approaches, particularly following dequantization results and large scale benchmarking studies that have challenged earlier optimistic claims. This work presents a systematic empirical evaluation of non unitary quantum machine learning implemented via the Linear Combination of Unitaries framework within hybrid quantum classical neural networks. Across more than 570 experiments spanning four domains digit classification MNIST, agricultural disease detection PlantVillage, molecular property regression QM9, and medical histopathology PathMNIST non unitary quantum layers are benchmarked against structurally identical unitary baselines. Consistent performance improvements are observed across all domains, with gains ranging from +0.2 percentage to +5.8 percentage depending on dataset complexity and qubit count. A particularly notable finding is a Fisher efficiency transition in medical imaging tasks, where parameter efficiency shifts from negative to positive as qubit count increases from 10 to 12, indicating a threshold dependent efficiency regime. Additionally, non unitary IQP circuit variants reach or exceed classical baselines at 10 qubits on CIFAR 10, demonstrating that circuits with established complexity theoretic hardness guarantees remain compatible with competitive learning performance under the LCU framework. These results offer a large scale, evidence based characterisation of the conditions under which non unitary QML yields measurable empirical benefits in near term settings.
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All authors Apoorv Kumar Masta, Srinjoy Ganguly, Shalini Devendrababu, Farina Riaz, Rajib Rana, Björn Schuller

Applied Physics

Zero-waste manufacturing of ophthalmic lenses by direct Fluidic Shaping in arbitrary domains

Yotam Katzman, Mor Elgarisi, Amos A. Hari et al. (+4 more)

The conventional manufacturing of ophthalmic lenses is an inefficient subtractive process where up to 97% of the material is discarded through grinding, polishing, and edging. Fluidic Shaping has emerged as a powerful alternative, utilizing surface tension to form optical-quality surfaces. While the approach enabled the creation of ophthalmic lenses without grinding or polishing, it was limited to lenses with a circular or elliptical footprint and still required the wasteful edging process to fit the lenses into the eyewear rims. Here, the Cookie Cutter algorithm is introduced, generalizing the Fluidic Shaping approach to be applicable to arbitrary domains, thus eliminating all subtractive processes. This mathematical framework calculates the unique varying edge-height required for a boundary frame, allowing a liquid polymer to naturally settle into a target spherocylindrical prescription within an arbitrary rim footprint. By utilizing neutral buoyancy to negate gravity, the liquid polymer is shaped solely by surface tension and subsequently cured, resulting in a lens that fits directly into commercial eyewear rims without any mechanical post-processing. The method is validated experimentally, demonstrating the fabrication of lenses compatible with standard eyewear rims. This approach represents a complete additive manufacturing solution, enabling end-to-end zero-waste production of prescription eyeglasses.
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All authors Yotam Katzman, Mor Elgarisi, Amos A. Hari, Jonathan Ericson, Omer Luria, Valeri Frumkin, Moran Bercovici

Fluid Dynamics

Retreat to advance: self-blocking enables efficient mineral replacement

Agnieszka Budek, Tomasz Szawełło, Vaughan Voller et al. (+1 more)

Mineral replacement reactions under advective flow often suffer from severe spatial inefficiency: dissolution causes the flow to self-focus into a few dominant wormholes that bypass the surrounding matrix, leaving most of the rock unreplaced. Here we show – through two-dimensional pore-network simulations – that replacement can be effective in two regimes. The first arises when the precipitation rate significantly exceeds the dissolution rate, leading to in situ replacement in which a uniform front of the secondary mineral advances through the matrix. The second, exploratory mode, occurs when the system repeatedly self-blocks and re-routes. In this regime, each channel lives only long enough to deliver reactant a short distance ahead of the front before its tip is cemented by the product phase; pressure re-routes through an adjacent corridor, and the cycle begins anew. Over time the replacement front advances as a mosaic of overlapping micro-fronts, distributing the secondary mineral almost uniformly. We derive design criteria for achieving exploratory-mode behaviour and discuss implications for both natural and engineered reactive-infiltration systems.
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All authors Agnieszka Budek, Tomasz Szawełło, Vaughan Voller, Piotr Szymczak

Fluid Dynamics

The role of thermal buoyancy in stabilizing the axial dipole field in rotating two-component convective dynamos

Debarshi Majumder and Binod Sreenivasan

Two-component convection driven by both compositional and thermal buoyancy within the fluid core of a rapidly rotating planet produces a predominantly axial dipole field. In a dynamo driven by strong compositional buoyancy that by itself destabilizes the axial dipole, the addition of relatively weak thermal buoyancy establishes the dipole field through the spontaneous generation of slow magnetostrophic waves produced by balances between the magnetic, buoyancy and Coriolis (MAC) forces at several locations within the core. A substantially higher compositional buoyancy is then required to trigger polarity transitions, since the dipolar regime is extended in two-component convection, as predicted by a linear magnetoconvection model that analyses the long-time evolution of a density disturbance. The existence of the axial dipole also prescribes a lower bound for the fraction of the total power contributed by thermal buoyancy, $\approx$ 10%, above which the two-component dynamo with homogeneous boundary heat flux lies deep within the dipolar regime. Two-component convection has implications for Earth's core dynamo: dominant compositional buoyancy ensures the observed polar circulation speed, and a large heterogeneity in the lower-mantle heat flux induces magnetic field excursions and occasional polarity reversals.
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Medical Physics

Deep brain microelectrode signal: $q$-statistical approach

Ana Luiza Souza Tavares, Henrique Santos Lima, Artur Pedro Martins Neto et al. (+2 more)

We characterize the amplitude statistics of intraoperative microelectrode recordings (MERs) obtained during deep brain stimulation (DBS) surgery in 46 patients with Parkinson's disease, using 184 recordings equally balanced between inside and outside the subthalamic nucleus (STN). The probability density of every recording is quantitatively well described by a $q$-Gaussian (grounded on a nonadditive entropic functional), $\rho(x) \propto [1 + \beta(q-1) x^2]^{-1/(q-1)}$, with $q > 1$ in all cases, reflecting persistent long-range temporal correlations inconsistent with Gaussian dynamics. Within the superstatistics framework, the slowly fluctuating local variance visible in the raw MER signals is a physical mechanism that directly generates the $q > 1$ form. Beyond individual fits, $q$ and $\beta$ collapse across all 184 recordings onto the single functional constraint $q = 3 - 1.85\,\beta^{-0.33}$ ($R \approx -0.91$), a reduction to one effective degree of freedom that is the quantitative hallmark of near-critical dynamics, previously identified in scale-free network growth and in acoustic precursors of material fracture. The index $q$ is statistically indistinguishable across the STN boundary ($\langle\bar{q}_\text{out}/\bar{q}_\text{in} \rangle = 1.03$), while the inverse-widthparameter shows a modest systematic difference ($\langle\bar{\beta}_\text{out}/\bar{\beta}_\text{in} \rangle = 1.18$). Since $q > 1$ is expected for any brain structure exhibiting long-range correlations, healthy or pathological, it is the tight $q(\beta)$ coupling, not $q > 1$ per se, that constitutes the candidate near-criticality signature of the parkinsonian cortico-basal-ganglia-thalamocortical loop.
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All authors Ana Luiza Souza Tavares, Henrique Santos Lima, Artur Pedro Martins Neto, Bruno Duarte Gomes, Constantino Tsallis

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

Alloying Controlled Tuning of Interfacial Spin Orbit Interaction and Magnetic Damping in Crystalline FeCo Alloys

Hongrui Lao, Matthias Kronseder, Zhe Yuan et al. (+5 more)

The discovery of intrinsic spin orbit fields in noncentrosymmetric ferromagnets has attracted considerable interest for both fundamental studies and technological applications. However, once such materials are synthesized, the strength of the spin orbit fields is difficult to tune because it is primarily a bulk property. Here, we demonstrate that the interfacial spin orbit interaction (SOI) in single crystalline FeCo thin films grown on GaAs(001) can be continuously tuned via alloying. Using spin orbit ferromagnetic resonance, we find that the Lande g factor, the Gilbert damping (alpha), and the interfacial spin orbit fields exhibit a common nonmonotonic dependence on Co concentration. A pronounced minimum occurs near x ~ 0.2 where an ultra low damping alpha ~ 0.0015 is achieved. Furthermore, we observe linear scaling between alpha and (g-2)^2, establishing a direct correlation between interfacial SOI and magnetic relaxation. These results identify alloying as an effective knob to engineer interfacial SOI and damping in single crystalline ferromagnet semiconductor heterostructures.
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All authors Hongrui Lao, Matthias Kronseder, Zhe Yuan, Thomas Narr, Thomas N. G. Meier, Nadine Mundigl, Christian H. Back, Lin Chen