Atomic Physics
Molecular effects in low-energy muon transfer from muonic hydrogen to oxygen
I. Boradjiev, A. Adamczak, D. Bakalov et al. (+24 more)
In the present study we determine from the available experimental data the cross section of
muon transfer to molecular oxygen at low energies with account of the oxygen molecule structure. Building on an earlier work, the results highlight the role of the molecular structure effects and signifcantly improve the agreement with theoretical calculations of the
muon transfer rate. An effcient computational model of the kinetics of processes involving muonic hydrogen atoms in gaseous mixture of H2 and O2 is developed and analyzed. The model is applied in the description of the FAMU experiment for the measurement of the hyperfine splitting in muonic hydrogen and the Zemach radius of the
proton.
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All authors I. Boradjiev, A. Adamczak, D. Bakalov, M. Baruzzo, R. Benocci, M. Bonesini, S. Capra, E. Christova, M. Clemenza, M. Danailov, P. Danev, E. Fasci, L. Gianfrani, A.D. Hillier, K. Ishida, A. Menegolli, E. Mocchiutti, S. Monzani, L. Moretti, C. Pizzolotto, R. Rossini, A. Sbrizzi, M. Stoilov, H.S. Tonchev, A. Vacchi, E. Vallazza, K. Yokoyama
Chemical Physics
Reconstruction of missing low-angle scattering in two-dimensional diffraction signal
Yanwei Xiong and Martin Centurion
Anisotropic two-dimensional diffraction signals encode additional structural information, including atom-pair angular distributions, beyond conventional isotropic scattering. However, experimental constraints such as beam stops result in missing low-angle scattering data, which limits accurate real-space reconstruction. We develop an iterative
algorithm to recover the missing low-angle signal in two-dimensional diffraction patterns. The method transforms between momentum-transfer and real-space domains using coupled
Fourier and Abel transforms, while enforcing real-space support constraints to suppress reconstruction artifacts. Importantly, the
algorithm requires only minimal a priori knowledge of the molecular structure, namely the approximate shortest and longest internuclear distances. We demonstrate accurate reconstruction of the missing signal using both simulated data and experimental diffraction patterns from
laser-aligned trifluoroiodomethane (CF3I) molecules, enabling improved real-space structural
retrieval from incomplete diffraction data. Our results remove a fundamental experimental limitation in ultrafast diffraction and establish a general route toward complete structural
retrieval from incomplete scattering data.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Automated Spin-Assisted Layer-by-Layer Epitaxy Produces Highly Oriented Mixed-Linker MOF Thin Films
Eleonora Afanasenko, Benedetta Marmiroli, Behnaz Abbasgholi-NA et al. (+11 more)
Control over crystallographic orientation in metal-organic framework (MOF) thin films is crucial for exploiting their anisotropic properties in sensing, catalysis, and separation. Achieving reproducible, highly oriented films remains challenging, especially for mixed-linker, pillared-layered frameworks. Here we present an automated,
spin-assisted layer-by-layer
liquid-phase epitaxy (LbL-LPE) strategy that enables rapid, ambient-condition fabrication of highly oriented, mixed-linker MOF thin films, demonstrated for Zn2BDC2DABCO (BDC = terephthalate, DABCO = 1,4-diazabicyclo[2.2.2]octane). Correlative process monitoring by grazing-incidence wide-angle X-ray scattering (GIWAXS), grazing-angle infrared (GI-IR) and UV-Vis spectroscopy, contact-angle measurements, scanning electron microscopy (SEM), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) ensure formation of uniform films with exceptional out-of-plane (001) orientation (degree of orientation >85%, Hermans parameter ~0.95) and excellent reproducibility. This strategy enables highly reproducible, high-throughput fabrication of orientation-controlled MOF thin films, providing a generalizable alternative to conventional LbL approaches. By enabling reproducible and entirely automated fabrication of highly anisotropic architectures, this work establishes a platform for integrating oriented MOFs into next-generation optoelectronic, sensing, and membrane devices where directional transport and ordered pore
alignment are essential.
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All authors Eleonora Afanasenko, Benedetta Marmiroli, Behnaz Abbasgholi-NA, Barbara Sartori, Giovanni Birarda, Chiaramaria Stani, Matjaž Finšgar, Peter E. Hartmann, Mark Bieber, Emma Walitsch, Rolf Breinbauer, Simone Dal Zilio, Sumea Klokic, Heinz Amenitsch
Optics
Reconfigurable topological valley-Hall interfaces: Asymptotics of arrays of Dirichlet and Neumann inclusions for multiple scattering in metamaterials
Richard Wiltshaw, Henry J. Putley, Christelle Bou Dagher et al. (+1 more)
We study two-dimensional periodic metamaterials in which idealised cylindrical inclusions are modelled by boundary conditions. In the scalar time-harmonic setting, the background field satisfies the Helmholtz equation, and high-contrast inclusion limits reduce to Dirichlet or Neumann conditions, with direct analogues in dielectric and acoustic media. By switching the condition assigned to selected inclusions, we break point-group
symmetries of the primitive
cell and thereby lift
symmetry-induced degeneracies in the Floquet–Bloch spectrum of hexagonal and square
lattices, opening valley-type band gaps with Berry
curvature localised near opposite valleys. To analyse infinite and finite structures within a unified framework, we derive matched-asymptotic point-scatterer approximations for mixed Dirichlet–Neumann arrays. For doubly periodic systems, this yields a finite-dimensional generalised
eigenvalue problem for the Floquet–Bloch spectrum; for finite arrays, it yields a generalised Foldy multiple-scattering system. In both hexagonal and square
lattices, geometrically identical
crystals can realise distinct valley-
Hall phases solely through boundary-condition assignment while retaining an overlapping bulk gap. Spatially varying this assignment therefore creates and relocates internal interfaces without altering the underlying geometry, enabling the associated valley-
Hall interfacial modes to be repositioned within the same
crystal.
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All authors Richard Wiltshaw, Henry J. Putley, Christelle Bou Dagher, Mehul P. Makwana
Fluid Dynamics
Characterisation of rough-wall drag in compressible turbulent boundary layers
Dea Daniella Wangsawijaya, Rio Baidya, Sven Scharnowski et al. (+2 more)
In compressible turbulent boundary layers (TBLs), roughness drag is typically characterised by first applying a velocity transformation to account for compressibility, after which the momentum deficit $\Delta U^+$ (Hama, 1954) and the equivalent sand-grain roughness $k_s$ are inferred. In practice, $k_s$ is often obtained from measurements at a single Mach number $M$ and Reynolds number $Re$, effectively forcing the roughness into the $\Delta U^+$–$\log(k_s)$ relation of Nikuradse (1933). This raises a key question: if a rough surface has a known $k_s$ in incompressible flow, under what conditions can this value be used in compressible flows? This question is explored using data obtained through a series of experiments of TBLs on rough walls (P60- and P24-grit sandpapers) over $0.3 \leq M \leq 2.9$ and $7427 \leq Re_{\tau} \leq 30292$, including independent variation of $Re_{\tau}$ at $M=2$. Results show that $\Delta U^+$ is largely insensitive to the velocity transformation, but the fully rough regime exhibits a Mach-number-dependent shift in the logarithmic relation. Three empirical scalings are examined: an equivalent incompressible $k_s$, a viscosity-scaled roughness $k_{*} = k/\nu_\infty^+$ with $\nu_\infty^+ = \nu_\infty/\nu_w$, and a correction factor $\sqrt{1/F_c}$ where $F_c$ depends on $T_\infty/T_w$. The last provides the most consistent improvement across
datasets, although all corrections remain empirical and rely on smooth-wall compressibility transformations. This paves the way for future work to develop custom transformation for a rough-wall TBL that can account for roughness properties and other parameters including wall conditions.
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All authors Dea Daniella Wangsawijaya, Rio Baidya, Sven Scharnowski, Bharath Ganapathisubramani, Christian Kähler
Optics
Colloidal Nanocrystals Regrowth-Assisted Synthesis of Perovskite Microwire Lasers for Integrated Optoelectronics
Elizaveta V. Sapozhnikova, Ivan A. Matchenya, Dmitry A. Tatarinov et al. (+10 more)
Colloidal perovskite nanocrystals (NCs) are a well-proven platform for growing anisotropic structures. Nanowires (NWs) exhibiting a
quantum confinement phenomenon and microwires (MWs), which enable lasing, are of particular interest for optoelectronic devices. Synthesis of the latter is challenging. Herein, we report a straightforward access to high-quality CsPbBr3 MW
lasers. We utilize a diphenyl ether (DPE) solvent for the hot-injection synthesis. DPE coordinates strongly to Pb2+ and allows to reduce an excess of oleic acid/oleylamine ligand pair well established for PbBr2 dissolution and inhibition of as-formed NCs regrowth. Therefore, a rapid injection of Cs-oleate into the PbBr2-containing solution yields lead-depleted Cs4PbBr6 NCs which slowly release perovskite precursors and produce CsPbBr3 counterparts. The latter transform into NWs through an oriented-attachment mechanism, which in turn evolve into
laser MWs. To demonstrate spectrally tunable lasing in MWs we employ YCl3 for ion exchange in perovskite
lattice. Resultant CsPb(Cl,Br)3 MWs show high-Q coherent emission in the 485-540 nm range. To highlight the potential of synthesized MWs for integrated optoelectronics, we assemble a device comprising a CsPb(Cl,Br)3 MW
laser coupled to MoO3 lossless nanowaveguide, which delivers coherent light to a CsPbBr3 MW photodetector. The device exhibits a nonlinear optoelectronic response applicable for on-chip neuromorphic computing.
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All authors Elizaveta V. Sapozhnikova, Ivan A. Matchenya, Dmitry A. Tatarinov, Grigorii A. Verkhogliadov, Dmitry A. Semyonov, Maria A. Kirsanova, Natalia K. Kuzmenko, Julia S. Mironova, Arina O. Kalganova, Valeriya M. Levkovskaya, Stepan A. Baryshev, Yuxi Tian, Anatoly P. Pushkarev
Optics
Cordierite-based optical resonators with extremely low thermal expansion
Nico Wagner, Thomas Legero and Stefanie Kroker
Applications for ultra-stable
lasers outside controlled laboratory environments require compact and robust optical resonators with reduced sensitivity to temperature fluctuations. The low thermal expansion coefficient (CTE) and the high stiffness make cordierite-based ceramics, such as NEXCERA, attractive for vibration insensitive room-temperature resonators. We revisit the effective CTE of resonators with spacers and mirrors made of different materials and use finite element simulations to analyze the impact of a CTE mismatch in a cordierite-based resonator with mirrors made of ultra-low expansion (ULE) glass or fused silica (FS). This enabled us to determine the CTE of a cordierite spacer from the measured effective CTE of a resonator. We confirm a six-fold larger CTE slope of cordierite around the zero-crossing temperature than in ULE glass. The steep CTE slope, in combination with the large stiffness, makes cordierite-based resonators far less sensitive to CTE mismatch with FS mirrors, thereby eliminating the need for additional compensation rings. We further consider the so far neglected case, where the CTE of the spacer is larger than that of the mirror, and propose resonator designs in which the thermal length change of the spacer is fully or partially compensated by the deflection of the mirrors. This results in a cordierite-based resonator with ULE mirrors whose effective CTE can be close to zero over a temperature range of several tens of Kelvin. We are extending our concept to resonators based on crystalline materials with high stiffness and low isothermal length change, such as silicon, enabling compact and robust room-temperature resonators for terrestrial and space-born applications.
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Physics and Society
Heatwave-Related Mortality Across Indian Cities Under Future Climate Scenarios
Ingita Dey Munshi, Abbinav Sankar Kailasam, Sudeep Shukla et al. (+2 more)
Heatwaves are intensifying as a major
climate extreme and have emerged as a growing public health threat in rapidly urbanizing regions such as India. In this study, we integrate long-term heat-related mortality records (1970-2023) with bias-corrected CMIP6
climate projections to quantify future heatwave-related mortality across 67 Indian cities under intermediate (SSP2-4.5) and high-emission (SSP5-8.5) scenarios. A time-series
forecasting framework was applied using summer mean temperature as the primary
climate driver to project mortality trajectories through the end of the 21st century. Results indicate a strong and sustained increase in heat-related mortality under both scenarios, with multi-fold amplification under SSP5-8.5 relative to SSP2-4.5, reflecting the high sensitivity of health outcomes to emission pathways. Spatial analysis reveals increasing regional divergence under high-emission conditions, with urban regions in the Deccan Plateau, western India, and parts of eastern and northeastern India exhibiting disproportionately higher mortality growth. Multidimensional scaling further highlights emerging clustering of state-level mortality behavior under extreme warming, indicating structurally different regional responses to future heat stress. In contrast, the intermediate mitigation pathway produces more moderate and spatially uniform mortality trends. These findings demonstrate that
climate mitigation can substantially reduce both the magnitude and inequality of future urban heat-health burdens. By linking updated
climate projections with long-term mortality data at national and sub-national scales, this study provides policy-relevant evidence to support heat adaptation planning and
climate-resilient urban development in one of the world's most heat-vulnerable regions.
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All authors Ingita Dey Munshi, Abbinav Sankar Kailasam, Sudeep Shukla, K. Shuvo Bakar, Anirban Chakraborti
Atmospheric and Oceanic Physics
Can hot water discharged from industrial processes enhance the likelihood of waterspouts?
Valerio Capecchi, Bernardo Gozzini and Mario Marcello Miglietta
Italy and the surrounding seas are recognised as one of the European hotspots for tornadoes and waterspouts. In recent years, the town of Rosignano Solvay (on the Northern Tyrrhenian coast) experienced repeated waterspouts affecting the same areas, raising local concern about the possible influence of heated wastewater discharged into the sea by a nearby industrial site. We reconstruct the mesoscale meteorological conditions of four intense waterspouts near Rosignano Solvay using a limited-area weather model at high-to-very-high resolution (inner domain grid spacing 500 m; sensitivity tests at 100 m). At the reported event times, the intensity of key mesoscale precursors (low-level wind shear, 1 km storm-relative helicity, maximum updraft intensity, and lifting condensation level) is consistent with the values typically associated with EF1 (or stronger) tornadoes and waterspouts. The model systematically predicts the peak of instability indices 2-3 hours earlier than the reported event times. For one case study, we conduct two sea surface temperature sensitivity experiments to assess the potential atmospheric impact of heated wastewater discharge (temperature increases of +1.5 K and +5 K over a 10 km$^2$ area). The resulting changes in instability indices are marginal, with differences of at most 3% relative to the control run. A simple mass-balance estimate for the modified sea patch suggests that, given the reported discharge rates, a plausible impact of the warm water released from the industrial site could lead to an increase in the local sea surface temperature of approximately +0.7 {\deg}C over two months. We conclude that synoptic and mesoscale conditions primarily govern waterspout initiation in this region, while the direct effect of the small, warm coastal plume from the industrial discharge appears to be minor.
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Computational Physics · Cross-listed from quant-ph
Quantum Neural Physics: Solving Partial Differential Equations on Quantum Simulators using Quantum Convolutional Neural Networks
Jucai Zhai, Muhammad Abdullah, Boyang Chen et al. (+6 more)
Neural Physics recasts local discretisations of partial differential equations (PDEs) as fixed convolutional operators, providing a physics-preserving alternative to data-driven surrogate modelling in scientific machine learning. However, existing realizations remain largely confined to classical AI hardware and do not directly connect to
quantum structured operator design. To bridge this gap, we introduce a
Quantum Neural Physics framework and develop a Hybrid
Quantum-Classical CNN Multigrid Solver (HQC-CNNMG). The proposed method maps analytically prescribed stencil operators to local
quantum convolutional primitives and embeds them within a classical multilevel W-cycle architecture, combining the operator-centric view of scientific ML with the numerical rigor of multigrid solvers. Using amplitude encoding together with the Linear Combination of
Unitaries (LCU) and the
Quantum Fourier Transform (QFT), the resulting local
quantum operators admit logarithmic-depth implementation, with
circuit depth scaling as $\mathcal{O}(\log K)$ for an encoded block of size $K$ under the idealized parallel
circuit model considered here. Numerical experiments on Poisson, transient
diffusion, convection–
diffusion, and incompressible Navier–Stokes problems demonstrate numerical consistency, stable multilevel behaviour, and workflow-level feasibility on noiseless simulators. Comparisons with representative
quantum linear solver paradigms further show that the main strength of HQC-CNNMG lies in its balanced trade-off among local
circuit depth, numerical robustness, and compatibility with PDE structure, rather than in fully
quantum global inversion.
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All authors Jucai Zhai, Muhammad Abdullah, Boyang Chen, Fazal Chaudry, Paul N. Smith, Claire E. Heaney, Yanghua Wang, Jiansheng Xiang, Christopher C. Pain
Physics and Society · Cross-listed from cond-mat.stat-mech
Dynamical thermalization and turbulence in social stratification models
Klaus M. Frahm and Dima L. Shepelyansky
We study the nonlinear chaotic dynamics in a system of linear oscillators coupled by social network links with an additional stratification of oscillator energies, or frequencies, and supplementary nonlinear interactions. It is argued that this system can be viewed as a model of social stratification in a society with nonlinear interacting
agents with energies playing a role of wealth states of society. The
Hamiltonian evolution is characterized by two integrals of motion being energy and probability norm. Above a certain chaos border the chaotic dynamics leads to dynamical thermalization with the Rayleigh-Jeans (RJ) distribution over states with given energy or wealth. At low energies, this distribution has RJ condensation of norm at low energy modes. We point out a similarity of this condensation with the wealth inequality in the world countries where about a half of population owns only a couple of percent of the total wealth. In the presence of energy pumping and absorption, the system reveals features of the Kolmogorov-Zakharov
turbulence of nonlinear waves.
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Computational Physics · Cross-listed from cond-mat.stat-mech
Digitally Optimized Initializations for Fast Thermodynamic Computing
Mattia Moroder, Felix C. Binder and John Goold
Thermodynamic computing harnesses the relaxation dynamics of physical systems to perform
matrix operations. A key limitation of such approaches is the often long thermalization time required for the system to approach
equilibrium with sufficient accuracy. Here, we introduce a hybrid digital-thermodynamic
algorithm that substantially accelerates relaxation through optimized initializations inspired by the Mpemba effect. In the proposed scheme, a classical digital processor efficiently computes an initialization that suppresses slow relaxation modes, after which the physical system performs the remaining computation through its intrinsic relaxation dynamics. We focus on overdamped Langevin dynamics for quadratic energy landscapes, analyzing the spectral structure of the associated Fokker-Planck operator and identifying the corresponding optimal initial covariances. This yields a predictable reduction in thermalization time, determined by the spectrum of the encoded
matrix. We derive analytic expressions for the resulting speedups and numerically analyze thermodynamic implementations of
matrix inversion and determinant computation as concrete examples. Our results show that optimized initialization protocols provide a simple and broadly applicable route to accelerating thermodynamic computations.
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Optics · Cross-listed from astro-ph.IM
Refractive multi-conjugate adaptive optics for wide-field atmospheric turbulence correction
Tommaso Furieri and Stefano Bonora
Multi-Conjugate Adaptive Optics (MCAO) is essential for increasing the corrected Field-of-View (FoV) in astronomical imaging and potentially for free-space optical communications, particularly for small-aperture, transportable systems. We demonstrate the viability and performance of a Refractive-MCAO system utilizing a novel multi-actuator Deformable Lens (DL) as the wavefront correction element. Unlike conventional Deformable Mirrors (DMs), the transmissive nature of the DL simplifies the optical train, making it ideal for compact setups. Using a Shack-Hartmann Wavefront Sensor (SH-WFS) in conjunction with two DLs conjugated to different atmospheric layers, we achieved an extension of the isoplanatic patch up to three times the uncorrected atmospheric isoplanatic angle under moderate
turbulence D/r0 = 2. We tested the MCAO system in a setup that emulates a free space optical communication for compact transportable system. In a double-channel, single-mode fiber coupling experiment we demonstrated the efficiency of this method.
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Chemical Physics
Collective Electronic Polarization Drives Charge Asymmetry at Oil-Water Interfaces
Gabriele Amante, Klaudia Mrazikova, Gabriele Centi et al. (+3 more)
Why kinetically stable oil droplets in water spontaneously acquire a negative charge remains one of the most vigorously debated questions in interfacial science. Here, we combine neural-network based deep potential molecular dynamics with a data-driven and information theory approach to probe the real-space electron density at an extended decane-water interface. While decane-water clusters show nearly symmetric forward and backward charge transfer (CT) and thus negligible net CT, the extended interface displays a systematic electronic asymmetry, yielding a net CT from water to the hydrocarbon phase producing an average surface charge density of $\sim0.006~e^{-}\,\mathrm{nm}^{-2}$ on the oil phase. This imbalance is accompanied by much larger intra-phase self-polarization, particularly within the hydrocarbon phase, demonstrating that collective many-body polarization dominates the interfacial electronic response. Structural analysis reveals an asymmetry between forward C–H$\cdots$O and backward O–H$\cdots$C motifs, providing a microscopic origin for a net CT from one phase to the other. Curiously, both the water O–H and decane C–H covalent bonds incur subtle contractions which originate from a response to the charge-separation layers at the interface. These features are fully consistent with the weak improper hydrogen-bonds forming at the oil-water interface that results in blue-shifts of the C-H modes.
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All authors Gabriele Amante, Klaudia Mrazikova, Gabriele Centi, Sylvie Roke, Ali Hassanali, Giuseppe Cassone
Fluid Dynamics
Jet-edge interaction: linear and non-linear frequency-selection mechanisms
Michael N. Stavropoulos, André V. G. Cavalieri, Lutz Lesshafft et al. (+1 more)
We consider a round turbulent jet grazing a rectangular plate angled at $45^\circ$. Through sound pressure measurements, the tonal dynamics associated with jet-edge interaction are explored in a parameter space comprising jet Mach number, $M_j$, and plate radial position, $R/D$. A variety of spectral signatures are observed and classified. The classification - based on analysis of power-spectral density and bicoherence, and on the resonance model proposed by Jordan et al. (2018) - comprises: broadband spectra; tonal spectra associated with purely linear frequency-selection mechanisms; tonal spectra associated with both linear and non-linear frequency selection. The classification identifies regions in the parameter space ($M_j$, $R/D$); and clarifies mechanisms underpinning regime changes. The linear frequency selection (LFS) regime comprises multiple tones, with no evidence of triad interaction. A regime involving non-linear frequency selection emerges from this state, with the strong amplification of one LFS tone, which then generates multiple harmonics. Intermediate regimes are identified involving weaker, non-harmonic triadic interactions where two LFS tones interact to generate a third tone. In addition to these mechanisms a mode-switching mechanism is identified at $M_j$ = 0.84 and shown to result from the cut-on of a new upstream-travelling wave at that Mach number. The mode-switch is found to be remarkably robust, occurring in a repeatable manner over a Mach-number increment of 0.01 regardless of whether the Mach number is increased or decreased (no hysteresis is observed).
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All authors Michael N. Stavropoulos, André V. G. Cavalieri, Lutz Lesshafft, Peter Jordan
Optics
Free-electron laser-based extended wide-field mid-infrared photothermal imaging for biomedical and microplastic analysis
Anooj Thayyil Raveendran, Subham Adak, Artem Shydliukh et al. (+8 more)
Wide-field mid-infrared photothermal (MIP) imaging offers rapid labelfree chemical contrast for biomedical and
polymer analysis. However, its field of view (FOV) is limited by the pulse intensity of conventional infrared
lasers. Here, we present a wide-field MIP microscope that uses a high-power free-electron
laser (FEL) rather than a
quantum cascade
laser (QCL) as the pump source to achieve a substantially larger FOV. Both implementations use counter-propagating beam paths with a 450 nm LED as the probe source and a CMOS camera that records images using a virtual lock-in detection scheme. QCL nanojoule pulse energies enables FOV of around 45 micrometers for widefield MIP imaging with a sub-micrometer resolution for polystyrene beads, Mycobacterium tuberculosis infected fixed tissues, and laryngeal cancer cryosections. IR spectra in the range of 1000-1800 wavenumbers can be reconstructed by tuning the QCL. FEL pulse energies of up to microjoules expand the FOV by a factor of nearly 20 as demonstrated by wide-field MIP imaging of polystyrene beads, single
cells, and murine
brain tissue. We discuss current challenges and further improvements to implement high-power IR
lasers for wide-field MIP imaging with even larger FOVs in the context of biomedical research and diagnostics.
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All authors Anooj Thayyil Raveendran, Subham Adak, Artem Shydliukh, Natalja Redinger, Matthias Hauptmann, Ulrich E. Schaible, Anna Muehlig, J. Michael Klopf, Orlando Guntinas-Lichius, Juergen Popp, Christoph Krafft
Optics · Cross-listed from cond-mat.mtrl-sci
Unified ab initio quantum-electrodynamical density-functional theory for cavity-modified electron-phonon-photon coupling in solids
Benshu Fan, I-Te Lu, Michael Ruggenthaler et al. (+1 more)
Quantum-electrodynamical density-functional theory (QEDFT) provides a first-principles framework for describing materials coupled to quantized electromagnetic fields. While QEDFT has successfully captured cavity-induced modifications of electronic structures in atoms and molecules, a fully self-consistent and accurate framework to simulate and predict the structural,
phonon-related, polarization and optical response of periodic solids in optical cavities has remained elusive. Here, we introduce a unified QEDFT approach that combines collective light-matter coupling parameter in the electronic ground state, density functional perturbation theory for
phonons, and real-time time-dependent QEDFT for optical excitations. This framework enables ab initio calculations of cavity-modified electronic and phononic dispersions, Born effective charges, dielectric tensors, and both resonant and non-resonant optical absorption spectra. Using wurtzite gallium nitride (GaN) in an optical cavity as a case study, we demonstrate that the quantized
vacuum field reshapes electronic, phononic and polarization properties, producing experimentally accessible signatures in the dielectric function and absorption spectra. These results establish QEDFT as a general first-principles platform for predicting and exploring cavity-modified
quantum materials.
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All authors Benshu Fan, I-Te Lu, Michael Ruggenthaler, Angel Rubio
Optics
The Spectral Domain Snell Law in Diffusion-Wave Fields
Pengfei Zhu, Julien Lecompagnon, Philipp Daniel Hirsch et al. (+2 more)
Snell law is traditionally regarded as a hallmark of phase-propagating phenomena such as optical, acoustic, elastic, electromagnetic, and
quantum waves. In contrast, purely diffusive processes, such as
Fourier heat conduction and chemical
diffusion, are generally considered incapable of exhibiting refractive/reflective behavior. In this letter, we demonstrate that although
diffusion waves including thermal
diffusion, mass
diffusion, Lindblad
quantum diffusion, and electromagnetic
diffusion do not follow Snell law in either time or frequency-domain, nevertheless they obey a spectral form of Snell law which reveals a hidden analog of wave refraction/reflection within the mathematical structure of
diffusion dynamics. Remarkably, the spectral refraction ratio is governed not by the
diffusion coefficient itself but by the constitutive relations of the media across the interface, establishing a new physical paradigm for
diffusion-wave fields. Importantly, while each spectral eigenmode satisfies a rigorous Snell-type refraction relation, the inverse
Fourier-Laplace transformation mixes these modes and suppresses any persistent real-space refraction angle, thereby reconciling the modal-level directionality with the long-standing absence of
geometric refraction in diffusive systems.
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All authors Pengfei Zhu, Julien Lecompagnon, Philipp Daniel Hirsch, Mathias Ziegler, Andreas Mandelis
Geophysics
Primary creep encodes time to failure across laboratory and natural systems
Qinghua Lei and Didier Sornette
Geomaterials often exhibit progressive creep characterized by an initial decelerating phase, frequently followed by an extended period of approximately constant deformation rate, and ultimately an accelerating regime leading to catastrophic failure. Despite extensive research, the timing of rupture and its relationship to the different creep phases, particularly in natural systems, remain poorly constrained. Here, we compile creep data from laboratory experiments on rocks, composites, papers, and glasses, together with observations from field systems including landslides, rockfalls, and glaciers. We find that the duration of the early-stage creep, marked by the transition to the minimum (or quasi-stationary) deformation rate, correlates nearly linearly with the time to rupture over five orders of magnitude. This unified scaling highlights that the early-time dynamics reflect the full
evolution toward failure, providing a simple and robust framework for
forecasting rupture across laboratory and natural systems.
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Data Analysis and Statistics · Cross-listed from astro-ph.IM
Ising noise filter: physics-informed filtering for particle detectors
I. Kharuk
We present the Ising noise filter, a highly portable, graph-based pre-filtering
algorithm for early-stage background suppression in particle accelerators and astrophysical detectors. Standard noise rejection methods relying on track fitting suffer from severe combinatorial explosion. Our method bypasses this by mapping individual detector hits to a network of binary
spins and minimizing an energy functional. The interaction kernels are physics-informed, tailored to the underlying physics and geometry of the experiment. We demonstrate the efficacy of this approach in two distinct experimental regimes. Applied to the Baikal-GVD
neutrino telescope the filter yields fast, standard-quality noise rejection with 96.8% recall for astrophysical
neutrinos. For the SPD detector at the NICA
collider the filter attains recall of 97% on a toy Monte Carlo sample. Furthermore, when combined with a Peterson–Hopfield network for track finding, our physics-informed coupling improves the TrackML score from 0.5 to 0.95.
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Instrumentation and Detectors · Cross-listed from cond-mat.mtrl-sci
Photoelectron angular distribution as a linear polarization analyzer for soft and tender X-rays
Yoshiyuki Ohtsubo and Hiroaki Kimura
Although the polarization of soft and tender X-rays is widely used to investigate the diverse physical properties of materials, experimental methods to determine the polarization of tender X-rays (1.5-3.0 keV) remain limited. To address this issue, we propose a method based on the photoelectron angular distribution to detect the polarization of X-rays in this energy range. The angular distribution of photoelectrons emitted from carbon targets was measured using linearly polarized 0.2 to 3.0 keV synchrotron radiation. The photoelectron intensity depends on the angle between the
photon's electric field vector and the direction at which the photoelectron is emitted from the target. This result indicates that the photoelectron angular distribution can be used to reliably determine the linear polarization of soft and tender X-rays over a wide range of energy.
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Fluid Dynamics
Early warning signals for primary and secondary bifurcation to oscillatory instabilities
Rohit Radhakrishnan, Prasana Kumar, Induja Pavithran et al. (+1 more)
In several natural and engineering systems, changes in control parameters can trigger bifurcations that lead to sustained or growing periodic oscillations, indicating the onset of oscillatory instabilities. Such emergent behaviour often results from positive feedback between interacting subsystems, resulting in large-amplitude oscillations that can be detrimental. Several precursors are available to provide early warning of an impending oscillatory instability. In reality, practical systems may exhibit different sequences of bifurcations, including a primary bifurcation to an oscillatory state that may be either continuous or abrupt, followed by an abrupt secondary bifurcation, and further transitions beyond the secondary bifurcation. Existing precursors for oscillatory instabilities typically forewarn the onset of the primary bifurcation to an oscillatory state and tend to saturate once the system enters the oscillatory regime. Notably, primary bifurcations often involve lower amplitudes compared to the more severe states after secondary bifurcation. In this study, we propose a methodology based on spectral visibility graphs to get forewarning for both primary and secondary bifurcations. The method inherently captures the
evolution of the harmonic content of the signal relative to other frequency components. The approach employs tuning of a single sensitivity parameter to detect different sequences of bifurcation. We demonstrate the usefulness of our method for thermo-acoustic and aero-acoustic instabilities in multiple engineering systems involving turbulent flow and reactions. Our methodology can help systems prepare in advance or even avoid undesirable transitions. Tuning the sensitivity parameter allows adaptive, risk-based warnings, ensuring high performance without tipping into undesirable regimes.
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All authors Rohit Radhakrishnan, Prasana Kumar, Induja Pavithran, R. I. Sujith
Optics · Cross-listed from quant-ph
Towards Schrödinger Cat States in the Second Harmonic Generation
Ranjit Singh, Leonid A. Barinov, Grigori G. Amosov et al. (+1 more)
We investigate the
quantum evolution of the pump field in second-harmonic generation under strong pump depletion. Starting from a coherent state, the pump develops a nonclassical phase-space structure resembling a Schrödinger cat state. This behavior originates from phase instability induced by
vacuum fluctuations of the harmonic mode. A rigorous
quantum analysis has been performed for mean
photon numbers up to $\langle \hat n \rangle = 100$ in pump mode. For larger
photon numbers, up to $\langle \hat n \rangle = 10^{7}$, the dynamics have been analyzed using a classical trajectory method with sampled initial conditions that reproduces the main features of the
quantum evolution. The results indicate that nonlinear frequency conversion can generate macroscopic superposition-like states of the pump field. Although the resulting state is not pure due to correlations with the second-harmonic wave, it remains non-classical with negative zones of Wigner function. These results indicate that strongly nonlinear frequency conversion can provide a scalable route toward macroscopic nonclassical states of light.
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All authors Ranjit Singh, Leonid A. Barinov, Grigori G. Amosov, Anatoly V. Masalov
Computational Physics
Conserved quantities and ensemble measure for Martyna–Tobias–Klein barostats with restricted cell degrees of freedom
Kohei Shinohara
We derive the conserved energy-like quantity and ensemble measure for Martyna–Tobias–Klein (MTK) barostats in which only a restricted subset of the
cell degrees of freedom are active. In the standard fully anisotropic MTK formulation, the number of barostat degrees of freedom is $d^{2}$, where $d$ is the spatial dimension. When only $n_c$ axes of the
cell matrix are allowed to fluctuate, the conserved energy-like quantity retains the same functional form but with $d^{2}$ replaced by $n_c$ in every term that counts barostat degrees of freedom. The derivation builds on the generalized Liouville framework for non-
Hamiltonian systems and the existing MTK integration machinery. We verify that this quantity is exactly conserved, show that the resulting dynamics samples the isothermal–isobaric ensemble restricted to the submanifold of
cell shapes in which inactive components are held fixed, and provide a complete Liouville-operator-based integration scheme for the masked MTK variant.
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Biological Physics · Cross-listed from cond-mat.soft
Multi-filament coordination rescues active transport from inertia-induced spinning arrest
Anuradha Rajput, Arnab Bhattacharjee and Annwesha Dutta
Active filaments driven by tangential forces can become trapped in a spinning state when attached to a heavy head, where activity and inertia drive persistent rotation rather than directed transport. Using three-dimensional Langevin dynamics of tangentially driven bead-spring chains anchored to a common heavy head, we demonstrate that increasing the filament number $\Nf$ systematically rescues directed transport by sterically preventing the coiled conformations that underlie spinning. The rescue is established through three independent diagnostics: (i)~the mean-square displacement recovers monotonic growth (transport rescue), (ii)~the spatial tangent autocorrelation loses its negative dip signaling helical coiling (conformational rescue), and (iii)~the tangent time autocorrelation ceases crossing zero (orientational rescue). At high bending stiffness ($\kb = 1000$), coiling is fully eliminated at a critical filament number $\Nf^* \approx 3$. At moderate stiffness ($\kb = 100$), residual coiling persists ($\min C_s \approx -0.13$) yet transport is still rescued – demonstrating that the destruction of spinning coherence, not coiling elimination, is the essential mechanism. The multi-filament architecture achieves up to five orders of magnitude transport enhancement. Two physically distinct rescue pathways emerge: at high stiffness, steric constraints force filaments into a coordinated bundle sustaining directed propulsion; at low stiffness, steric interactions destroy orientational coherence, producing enhanced active
diffusion. These results demonstrate a purely mechanical, density-independent route to overcome inertia-induced motility arrest, with implications for synthetic microswimmer design, motor-driven filament assays, and multi-filament organization in biological systems.
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Instrumentation and Detectors
Data-driven synthesis of high-fidelity triaxial magnetic waveforms for quantum control
Giuseppe Bevilacqua, Valerio Biancalana and Roberto Cecchi
We present a system for generating arbitrary, triaxial
magnetic waveforms with a spectral content spanning from DC to tens of kHz, a critical capability for
quantum control and
spin manipulation. To compensate for amplifier-coil dynamics, we implement a data-driven approach to identify a numerical compensation model. The method parametrizes the system response using a Finite Impulse Response (FIR) filter calibrated on the specific waveform to be generated. The application of a driving signal designed via frequency-domain inversion of the identified model enables the synthesis of complex field sequences with sharp transitions between static and single- or multi-frequency temporal segments. The work is validated with experimental results demonstrating waveform fidelity and transient performance, thereby showcasing the precision and feasibility of the method.
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Instrumentation and Detectors
A Simulation Framework for Ramsey Interferometry
Linus B. Persson, Peter Fierlinger, Matthias Holl et al. (+1 more)
The sensitivity of Ramsey interferometry experiments is governed by the interplay between the beam phase-space distribution and the
magnetic field environment through which the
spins propagate. Quantitative optimisation thus requires a consistent treatment of optics, magnetics and
spin dynamics. We present a simulation framework that enables such an analysis by combining
neutron optics simulations in McStas,
magnetic field modelling in COMSOL and
spin-dynamics simulation in the new RamseyProp program. We describe how important experimental parameters such as adiabaticity, flip angle distributions and Ramsey fringe contrast can be studied. The code is being applied to design an experiment to search for
axion-like particles at the European Spallation Source (ESS). We examine how the pulsed time structure of the ESS can be exploited to perform Ramsey interferometry on a broad
neutron velocity spectrum. In the absence of velocity or timing restrictions, the standard deviation of the
spin flip angle at zero detuning can be reduced from 0.67 to 0.17 radians using time-dependent amplitude modulation. Similarly, the phase sensitivity can be improved by a factor of 4 for a 10 m long setup starting 15 m from the ESS moderator.
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All authors Linus B. Persson, Peter Fierlinger, Matthias Holl, Valentina Santoro
Optics · Cross-listed from quant-ph
Efficient Many-Body Shadow Metrology via Clifford Lensing
Sooryansh Asthana, Conan Alexander, Anubhav Kumar Srivastava et al. (+2 more)
Quantum probes that enable enhanced exploration and characterization of complex systems are central to modern science, spanning applications from biology to astrophysics and chemical design. In large many-body
quantum systems, interactions delocalize phase information across many degrees of freedom, dispersing it away from accessible measurements and limiting the scalability of
quantum metrology. Here we show that experimentally accessible Clifford operations acting jointly on
quantum states and observables can refocus this distributed information. These operations implement what we term Clifford
lensing–transformations that coherently localize phase information onto a reduced set of degrees of freedom, mapping optimal measurements onto observables of reduced Pauli weight. We establish a correspondence between
quantum error-correcting codes and interferometric constructions that enforce deterministic phase kickback, and generalize this to
circuits that concentrate many-body phase information onto a controllable subset of
qubits. We further develop partial shadow
tomography protocols for estimating subsystem-supported phases. We experimentally demonstrate these principles in
liquid-state
nuclear magnetic resonance systems of up to fifteen
qubits, achieving optimal sensing with constrained resources. Our results establish a scalable route to coherent control of information flow in interacting
quantum systems, enabling many-body
quantum sensing and multimode interferometry across complex architectures.
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All authors Sooryansh Asthana, Conan Alexander, Anubhav Kumar Srivastava, T. S. Mahesh, Sai Vinjanampathy
Computational Physics
Numerical field optimization for enhanced efficiency in time-reversible gradient computation of open-source GPU-accelerated FDTD simulations
Yannik Mahlau, Lukas Berg and Bodo Rosenhahn
Finite-difference time-domain (FDTD) simulations often involve physical quantities spanning multiple orders of magnitude, such as the speed of light or electromagnetic field amplitudes. The standard practice for maintaining numerical accuracy in many FDTD implementations is to use 32-bit or 64-bit floating-point values to represent the electric and
magnetic fields. However, this approach is not always optimal when recording field values, particularly during time-reversible gradient computation where electric and
magnetic field values need to be saved at the boundary of the simulation domain. Since this
memory bottleneck is often the limiting factor in time-reversible inverse design for nanophotonics, we present two field optimizations for enhancing
memory efficiency in FDTD simulations. Using a smaller bit-width representation of field values as well as interpolation, we achieve similar accuracy at lower
memory cost. This approach is particularly beneficial for GPU-accelerated computing, where reduced-precision data types are increasingly preferred due to their computational efficiency and prevalence in machine learning frameworks. We integrate our approach into FDTDX, an open-source, differentiable FDTD solver that natively supports time-reversible gradient computation. Our approach is especially important for future developments towards large-scale open-source simulations, which are critical for advancing computational nanophotonic applications.
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Plasma Physics
Self-Consistent Numerical Framework for Multiscale Circuit-Plasma Coupling with Secondary Electron Emission
Hongbin Kim, Soung Yong Yun, Jaeguk Lee et al. (+1 more)
Voltage breakdown in high-voltage pulsed
vacuum systems arises from nonlinear multiscale interactions among
circuit dynamics, kinetic
plasma evolution, and ion-induced secondary electron emission (SEE) at electrode surfaces. Although
circuit-
plasma co-simulation frameworks couple lumped
circuits with particle-in-
cell (PIC) solvers, most neglect energy-resolved SEE and its feedback to both
plasma and
circuit, limiting predictive capability. We present a self-consistent framework for multiscale
circuit-
plasma coupling that incorporates ion-energy-dependent SEE into the electrode boundary of an electrostatic PIC solver. The emitted electron flux is included in the surface charge update, leading to a modified Poisson boundary condition that couples
plasma and
circuit within a unified formulation. Two integration strategies are developed: (i) a fully implicit strict coupling scheme solving the
plasma-
circuit system monolithically, and (ii) a weak coupling scheme based on operator splitting, compatible with SPICE solvers and enabling partitioned time integration with one-step lag. The framework is applied to a Tesla-
transformer-driven
vacuum capacitor with ion injection. Results show that SEE alters surface charge
evolution, triggering rapid voltage collapse and sustaining a near-zero-voltage plateau, while SEE-free models fail. Agreement between strict and weak coupling confirms robustness. The method provides a unified framework for predictive simulation of multiscale
circuit-
plasma interactions.
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All authors Hongbin Kim, Soung Yong Yun, Jaeguk Lee, Dong-Yeop Na