Applied Physics · Cross-listed from quant-ph
Orthogonality Edges in Strong-Coupling Quantum Work Statistics
Atta ur Rahman, Muhammad Noman, S. M. Zangi et al. (+1 more)
Strong coupling to a reservoir can do more than shift, broaden, or dress the work peaks of a driven
quantum system. When the reservoir is infrared singular, a sudden change of a local control parameter can alter the boundary condition seen by infinitely many low-energy modes, converting a quasiparticle-like threshold line into a many-body edge. We demonstrate this mechanism for the inclusive work distribution of the biased
spin-
boson model under a sudden bias inversion. In the independent-
boson limit, the problem is exactly solvable and gives a sharp infrared classification: a super-Ohmic bath can retain a finite elastic threshold weight, whereas Ohmic and sub-Ohmic baths extinguish the elastic line through boundary orthogonality. At the Ohmic fixed point, the same exponent controls both the vanishing elastic residue and the low-work continuum. We then ask how this edge is resolved away from the static-boundary limit. Using displaced-basis exact diagonalization of logarithmically discretized baths, we find that finite tunnelling leaves an edge-like continuum over the accessible energy window, while separating two operational diagnostics of the threshold: the cumulative-continuum exponent extracted from $z$-interleaved spectra lies above the elastic-overlap exponent extracted from $z$-averaged overlaps, $\theta_C>\theta_Z$. We interpret this separation as a finite-energy crossover away from the static-boundary fixed point, not as evidence for a new asymptotic fixed point. The separation survives fitting-window variation, oscillator-cutoff checks, spectrum-size checks, and leave-one-$z$-out tests, while time-domain characteristic functions provide a compatible but non-decisive diagnostic. Finally, the same threshold edge controls the sampling cost of Jarzynski-type exponential averages, making rare low-work events increasingly important at low temperature.
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All authors Atta ur Rahman, Muhammad Noman, S. M. Zangi, Saeed Haddadi
Medical Physics
Beam monitoring for radiotherapy from conventional to FLASH dose rates using Low Gain Avalanche Silicon detectors
Cristhian Cadena, Antonio Cota Rodriguez, Tonatiuh García Chávez et al. (+10 more)
We report the performance of low gain avalanche Silicon detectors (LGADs) for instantaneous electron and
proton beam monitoring across dose rates ranging from conventional radiotherapy to the FLASH regime, benefiting from the fast response of these detectors of a few nanoseconds. The beam sources provide a dose rate greater than 40~Gy/s through pulses of widths 0.5, 1, 2 and 3~$\mu$s for electron beams and 3, 5, 10 $\mu$s for
proton beams. Two different LGAD devices and silicon diodes are tested, yielding a linear dose response for electron beams up to $\sim$450~Gy/s and for
proton beams up to $\sim$12~Gy/s. Beyond the linear regime the response continues to increase with a reduced slope and no true signal plateau is observed, at least up to 1800 Gy/s for electrons and 150 Gy/s for
protons. This study contributes towards the instantaneous monitoring of increasingly intense flash beams for radiotherapy using fast detectors such as LGADs since measurements can be performed every fraction of $\mu$s.
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All authors Cristhian Cadena, Antonio Cota Rodriguez, Tonatiuh García Chávez, Yao Hao, Rachel Kovach-Fuentes, Harold Li, Wei Li, Javier A. Murillo Quijada, Saul Anibal Rodríguez Ramírez, Christophe Royon, Emil Schueler, Brett D. Velasquez, Pablo Yepes
Medical Physics · Cross-listed from eess.IV
GLOW-FDG: Generalized cancer LesiOn Whole-body segmentation model for $^{18}$F-FDG-PET/CT
Maksym Fritsak, Maximilian Rokuss, Hubert S. Gabryś et al. (+10 more)
Whole-body fluorodeoxyglucose positron emission
tomography combined with computed
tomography is widely used in cancer care, but manual lesion delineation is slow, subjective, and difficult to scale. We present GLOW-FDG, an open-source artificial intelligence model for whole-body cancer lesion
segmentation in fluorodeoxyglucose positron emission
tomography and computed
tomography. The model was trained on 1,563 scans spanning multiple cancer types and evaluated on 185 external scans from independent institutions. Across breast cancer, nonmetastatic and oligometastatic lung cancer, head and neck cancer, and metastatic melanoma, GLOW-FDG consistently outperformed publicly available
benchmark models in lesion detection, while reducing false positives and maintaining strong
segmentation accuracy. Quantification of total tumor burden and total lesion glycolysis was robust across cohorts, and performance approached the variability observed between expert radiation oncologists. These results support GLOW-FDG as a generalizable tool for automated cancer
segmentation and quantitative imaging biomarker extraction in whole-body imaging.
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All authors Maksym Fritsak, Maximilian Rokuss, Hubert S. Gabryś, Yannick Kirchhoff, Benjamin Hamm, Sebastian M. Christ, Nicolas Martz, Isabelle Opitz, Rolf Stahel, Martin Hüllner, Matthias Guckenberger, Klaus Maier-Hein, Stephanie Tanadini-Lang
Plasma Physics
Runaway electron induced explosions of graphite; modeling versus controlled DIII-D experiments
T. Rizzi, A. Kavroulakis, S. Ratynskaia et al. (+10 more)
The state-of-the-art concerning the modeling of the thermomechanical response of graphite to runaway electron (RE) impact is based on one-way coupled linear thermoelasticity combined with Rankine's strength-based failure criterion and limited to the onset of material failure. Here, the predictive capabilities are extended to the nonlinear damage phase characterized by material fragmentation and debris expulsion. This is achieved by introducing plasticity via the Johnson-Holmquist constitutive model, adopting an effective plastic strain-based failure criterion and coupling finite element analysis with smoothed-particle hydrodynamics. The extended thermomechanical model is successfully benchmarked against the results of two controlled RE-induced damage experiments recently carried out in DIII-D. This constitutes an important step towards the final objective of quantitatively describing the thermomechanical response of tungsten to REs.
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All authors T. Rizzi, A. Kavroulakis, S. Ratynskaia, P. Tolias, M. Tatarakis, E. Kaselouris, V. Dimitriou, E. Hollmann, F. Brochard, A. Kulachenko, M. Beidler, C. Lasnier, R. A. Pitts
Computational Physics · Cross-listed from math.NA
Accelerated iterative method for solving the steady-state Boltzmann equation
Pei Zhang, Zhenning Cai and Yanli Wang
The efficient simulation of steady-state rarefied gas flows remains a significant computational challenge due to the high dimensionality of the collision integral and the severe numerical stiffness in the near-continuum regime. In this work, we propose a modified Newton method equipped with a macroscopic synthetic system (Newton-MS) for the steady-state Boltzmann equation with the quadratic collision operator. In Newton-MS, the modified Newton iteration is utilized as the outer nonlinear solver, while each Newton correction equation is solved by an inner source iteration, where the linearized collision operator is utilized to approximate the quadratic collision model, and it is reduced into a linear iteration. Moreover, a macroscopic synthetic system based on Chapman-Enskog closure is derived to accelerate the convergence of the linear inner iteration in the continuum limit. Besides, the fully discrete macroscopic synthetic system is deduced under the framework of the discontinuous Galerkin method to reduce computational cost compared to directly discretizing the continuous macroscopic synthetic system. Several numerical examples, including the 1D
Fourier, Couette flow problem, and the 2D cavity flow and thermal-driven cavity flow, are studied to validate the high efficiency of Newton-MS.
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Accelerator Physics
Beam-Level Nonlinear Compton Spectra via a Neural Network Surrogate Model
Antonina Timoshenko, Maxim Malakhov, Alexander Fedotov et al. (+1 more)
Nonlinear Compton scattering enables sources of intense high-energy radiation. However, predicting source-level spectra for realistic electron beams typically requires computationally expensive trajectory-based calculations, whereas existing analytical models for spectral envelopes are limited to a restricted range of
laser pulse parameters. Here, we demonstrate that, for electron beams with sufficiently broad phase-space distributions, beam-level nonlinear Compton spectra can be predicted without lengthy numerical calculations. Our approach combines a fast neural-network surrogate for single-electron spectral envelopes with particle-wise Lorentz transformations. Benchmarked against trajectory-based numerical calculations with thousands of macroparticles, the surrogate reproduces the macroscopic spectral-angular structure while reducing the computational cost by orders of magnitude.
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All authors Antonina Timoshenko, Maxim Malakhov, Alexander Fedotov, Sergey Rykovanov
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Morphology-Property Interplay in Chemo-Mechanics of Ion-Intercalation Active Particles
Rongyue Lin, Royal C. Ihuaenyi, Juner Zhu et al. (+1 more)
Morphology, material property, and mechanical constraint jointly govern the chemo-mechanical behavior of ion-intercalation particles, yet their coupled effects remain insufficiently understood. Here we establish a thermodynamically consistent single-particle framework and combine analytical solutions with multiphysics simulations to determine how these factors regulate lithiation and stress generation. We study hollow spherical, cylindrical, and ellipsoidal particles with isotropic or transversely isotropic material properties under fully constrained, inner-free, or unconstrained boundary conditions. We show that the transient lithiation pathway and the associated stress and strain fields are governed not by morphology, property, or constraint alone, but by their coupled interaction: isotropic particles are sensitive to the mechanical constraint, whereas transversely isotropic particles exhibit persistent heterogeneous lithiation dominated by anisotropic diffusivity. Flux decomposition analysis reveals that the mechanical contribution to Li flux is negligible in spheres but dominant in ellipsoids. Correlation analysis further shows that Li concentration and volumetric strain exhibit strong anti-correlation in unconstrained particles but weak correlation under full constraints.
Bayesian optimization of hollow ellipsoids identifies Pareto-optimal morphologies that balance lithiation capacity against peak tensile stress. These results provide a unified framework for the morphology-property interplay in intercalation particles and offer morphology design principles for chemo-mechanical stability.
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All authors Rongyue Lin, Royal C. Ihuaenyi, Juner Zhu, Ruobing Bai
Fluid Dynamics
Mechanisms of lift generation and drag invariance by asymmetric surface roughness on a sphere
Putu Brahmanda Sudarsana, Jagmohan Singh and Anchal Sareen
The mechanisms governing transverse force generation on a sphere with asymmetric dimpled roughness are investigated using wall-resolved large eddy simulation at $Re=U_\infty d/\nu=100{,}000$ for $k/d=0.004$, $0.006$, and $0.008$. Previous experiments by Sudarsana et al. (2024) showed that asymmetric roughness can generate lift comparable to the peak Magnus force on a rotating sphere while leaving the mean drag nearly unchanged. The present simulations reproduce this behavior and reveal the coupled mechanisms responsible for lift generation and drag invariance. Pressure-force decomposition shows that asymmetric dimples redistribute the streamwise pressure contribution between the upstream and downstream hemispheres with little change in net drag, while producing a finite transverse pressure imbalance that generates lift. A
Fourier decomposition further shows that pressure drag is governed primarily by the axisymmetric pressure component, whereas lift is governed by the non-axisymmetric component. The dimples also produce distinct transition pathways on the two hemispheres: the dimpled side undergoes near-wall transition before separation, delaying separation non-uniformly to $\phi_s\sim105^\circ - 125^\circ$, while the smooth side separates in a laminar state at $\phi_s\sim80^\circ$. The resulting pressure asymmetry drives sidewash from the smooth to the dimpled side, which rolls up into a counter-rotating streamwise
vortex pair that amplifies wake deflection beyond that expected from separation-angle differences alone. These results show that lift generation arises from the coupled interaction of asymmetric transition, non-uniform separation, pressure-driven sidewash, and coherent wake reorganization.
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Optics
Quench, Glow, or Stay Silent: Distance-Controlled Up-Conversion Emission near Metallic Nanowires
Maciej Cwierzona, Michal Zebrowski, Pavel Dziarhai et al. (+5 more)
We demonstrate controlled transitions between competing radiative and nonradiative decay channels in the up-conversion luminescence of NaYF4:Er3+/Yb3+ nanocrystals placed in proximity to metallic nanowires. The nanocrystal-nanowire separation is used as a key control parameter governing the optical response. An essential aspect of our approach is the removal of inhomogeneous residual
polymer layers from the nanowires, eliminating any compromise on distance control and reproducibility in emitter-metal hybrid nanostructures. Replacing them with a well-defined
polymer spacer yields controlled access to three qualitatively distinct interaction regimes: luminescence quenching, plasmonic enhancement, and effective decoupling. Transitions between these regimes are shown to reflect changes in the dominant energy relaxation pathways: from nonradiative losses in direct contact with the metal, through modification of the local photonic density of states and coupling to plasmon-mediated modes, to behavior characteristic of quasi-isolated emitters. The plasmonic origin of the emission enhancement in the intermediate regime is evidenced by an increase in luminescence intensity accompanied by shortened decay times, as revealed by fluorescence lifetime imaging microscopy of up-conversion nanocrystals. All experiments were performed on single nanostructures, thereby excluding artefacts arising from aggregation effects and strengthening the interpretation of the observed phenomena. The presented approach provides controlled access to plasmon-modified decay channels and offers a basis for the rational design of functional nanophotonic and sensing structures with tailored optical properties.
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All authors Maciej Cwierzona, Michal Zebrowski, Pavel Dziarhai, Joanna Niedziolka-Jonsson, Martin Jonsson-Niedziolka, Marcin Nyk, Sebastian Mackowski, Dawid Piatkowski
Physics and Society
Tax Migration as Social Contagion: A Tipping-Point Model with Application to the Scandinavian Wealth Tax Debate
Anders G Frøseth
Blandhol (2025) estimates that wealth-tax-induced emigration from Norway reduces long-run GDP by 1.3%. Dansk Industri scaled this figure to argue that a Danish wealth tax would cost billions - a claim central to the 2026 Danish election campaign. We develop a social contagion model in which the emigration rate depends on a visibility-weighted fraction of prior emigrants, producing tipping-point dynamics.
Embedding the model in the Fokker-Planck framework of Froseth (2026, arXiv:2603.05283), we show that the micro-to-macro extrapolation underlying the 1.3% figure requires five identification conditions to hold simultaneously - each of which is violated. Using a panel of the 400 wealthiest Norwegians (2011-2025), we estimate the Pareto tail exponent (approximately 1.3, stable across years), identify the emigrants within Blandhol's 2016-2020 sample window, and document a hidden channel of heir-emigration - 36 recent cases carrying approximately 127 bn NOK - invisible in panel data because controlling owners retain their A-shares while heirs emigrate with economic exposure only. The event-study sample is dominated by passive wealth-holders with near-zero productivity haircuts, and the wealth-weighted integral that determines the GDP effect is controlled by individuals entirely absent from the sample. The Norwegian emigration wave is a non-scalable, path-dependent tipping event, not a smooth elasticity.
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Physics and Society · Cross-listed from q-fin.ST
A Spectral Generalisation of the Variance Ratio: Eigenstructure of Long-Horizon Portfolio Covariance and a Multi-Memory Factor Model of U.S. Equity Returns
Anders G Frøseth
We propose a multivariate generalisation of the Lo-MacKinlay (1988) variance ratio that decomposes long-horizon equity-return dynamics into separate return-channel and
volatility-channel
memory components across the cross-section of asset returns. The framework identifies a parsimonious five-factor model - capturing persistent, antipersistent, and multi-scale
memory in returns and
volatility - that fits four U.S. portfolio panels (the Fama-French 49-industry universe, its pre/post-1998 halves, and the Fama-French 100 size x book-to-
market sort) and a European replication (Fama-French Europe 25), recovering seven stylised facts of long-horizon equity dynamics simultaneously across all five panels. Three findings carry economic content. (i) The same five-factor decomposition fits all five panels, indicating a cross-sectional structure robust to industry vs. size-and-value sorts, to sub-periods, and to U.S. vs. developed-European
markets. (ii) U.S. equity
volatility memory underwent a regime transition in the late 1980s - not at the static 1998 split-half boundary - with the slowest component of the
volatility cascade lengthening from approximately two to four years; a 1000-replicate rolling-window bootstrap localises the transition with strictly non-overlapping 90% confidence bands separating pre- and post-transition windows. (iii) The cross-sectional loadings driving return-channel long
memory are economically distinct from those driving
volatility-channel cascade
memory: a cross-channel beta-inversion test finds no panel with the positive
alignment a single shared loading predicts, rejecting the shared-loading hypothesis toward anti-
alignment on the two largest panels at Bonferroni p = 0.0004. Characteristics that predict return-momentum patterns therefore need not predict
volatility-persistence patterns.
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Atomic and Molecular Clusters · Cross-listed from quant-ph
Matter-wave Induced Transparency
Tongkang wang, Yuqi Liu, Wenlan Chen et al. (+2 more)
Electromagnetically induced transparency suppresses optical absorption through destructive interference, playing a central role in light-matter interaction and
quantum information science. We report matter-wave induced transparency, where atomic collisional interactions induce transmission through a lossy molecular potential for the incident atomic scattering waves. Using cesium Bose-Einstein condensates and modulation-induced Feshbach resonances, we realize a three-level atom-molecule coupled system with unprecedented flexibility. Under the dark state condition, a narrow and tunable transparency window appears within a broad dissipative collisional resonance. The transparency window linewidth is controlled by modulation-induced coupling. And scattering pathways are selectable via multifrequency Floquet modulation. These results establish an interference-based route for exploring programmable nonequilibrium and non-Hermitian physics, steering
quantum chemistry and precision measurements.
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All authors Tongkang wang, Yuqi Liu, Wenlan Chen, Zhendong Zhang, Jiazhong Hu
Chemical Physics
Application of SAP-X2C to Spectroscopy and Comparison to Screened Nuclear Spin-Orbit Approximations
Yannick J. Franzke and Christof Holzer
Recently, Surjuse and Valeev [J. Chem. Theory Comput. 22, 3443-3452 (2026).] suggested to use a simple superposition of atomic potentials to account for the two-electron picture-change error in one-electron exact two-component (SAP-X2C) theory. Herein, we generalize this ansatz to analytical derivative theory and apply SAP-X2C to molecular spectroscopy. The accuracy is assessed for NMR, EPR, Mössbauer, UV/vis, as well as X-ray absorption spectroscopy. A thorough comparison with four-component results and the even simpler screened
nuclear spin-orbit (SNSO) approximation reveals that both SNSO-X2C and SAP-X2C perform excellently for spectroscopic properties, with SAP-X2C yielding slightly lower errors. Another major advantage is its well defined thermodynamic limit and less empirical nature. Therefore, SAP-X2C may be expected to become the default choice to mitigate the two-electron picture-change error in density functional theory approaches for spectroscopy thanks to its accuracy, simplicity, and efficiency. More complicated approaches to account for this error based on atomic mean-field ansätze may still be relevant for high-level correlated methods and highly accurate thermochemistry.
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Fluid Dynamics
A comprehensive Darcy-type law for viscoplastic fluids: II. Rheology & topology
Emad Chaparian
We extend our recently proposed framework (Chaparian, Phys. Rev. Fluids 10(9) 093301, 2025) for deriving a Darcy-type law governing viscoplastic flows through porous media to incorporate more applied aspects. In particular, the present work considers a more realistic rheological model (i.e. Herschel-Bulkley, describing the shear-thinning nature of practical yield-stress fluids) along with a wider range of porous media
topologies. In our earlier work, the problem was addressed by decomposing the full Bingham number spectrum (representing the ratio of the yield stress of the fluid to the characteristic viscous stress) into three main regions: (i) low Bingham numbers (weak yield stress limit) corresponding to Newtonian flow, (ii) high Bingham numbers (strong yield stress limit) representing yield limit/plastic flow, and (iii) intermediate Bingham numbers (transition regime). By deriving theoretical models for the two asymptotic limits of the spectrum and combining them, we obtained a Darcy-type law applicable across the entire range of Bingham numbers. In contrast to our original work, where the weak yield stress limit reduces to a Newtonian flow, here, this limit instead follows a power-law asymptote that captures the shear-thinning dominated behaviour of Herschel-Bulkley fluids. In the present study, we derive a scaling to address this limit. The framework is further generalised to incorporate a broader spectrum of porous media
topologies, enabling a systematic assessment of how pore geometry influences the resulting macroscopic flow law. The proposed framework provides a unified theoretical basis for predicting yield-stress fluid transport through complex porous media and establishes a pathway towards finding macroscopic models applicable to a wide range of natural systems and industrial processes.
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Chemical Physics
Single-Scan Characterization of $^{14}$N Nuclei via $^1$H-Detected Rotating-Frame Relaxometry
Florin Teleanu, Huijing Zou, David E. Korenchan et al. (+1 more)
$^{14}$N NMR is notoriously difficult to perform in
liquids due to the very fast
spin relaxation and the large quadrupolar couplings, which render many signals invisible. We show here how $^{14}$N
nuclei of biomolecular constituents can be probed indirectly by reintroducing the scalar relaxation of the second kind contribution to the polarization lifetimes of J-coupled
protons in double resonance
spin-locking experiments. The enhanced $^1$H relaxation rates in the rotating-frame allow for direct evaluation of nitrogen chemical shift and polarization lifetimes, from which one- and even two-bond $^1$H-$^{14}$N scalar couplings as well as $^{14}$N quadrupolar interactions can be determined. We demonstrate the versatility of this method by characterizing $^1$H-$^{14}$N
spin pairs in several molecules of biological importance, showing
proton relaxation enhancements beyond one order of magnitude. We further observe a pronounced effect from intermolecular hydrogen bonding. Our approach can be readily integrated into existing biomolecular NMR methodologies, as demonstrated here for $^1$H-detected relaxation-editing experiments with water suppression. This method provides access to nitrogen's picosecond-modulated quadrupolar interaction via single-scan
proton detection in systems that would otherwise yield almost no detectable direct $^{14}$N signal even after averaging over thousands of transients.
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All authors Florin Teleanu, Huijing Zou, David E. Korenchan, Alexej Jerschow
General Physics
On the Geometric Interpretation of Non-Singular Black Hole Interiors
Melih Gumus and Bilgehan Baris Oner
Black hole singularities still remain a central challenge in gravitational physics. In this work, we present a
geometric interpretation of non singular black hole cores within teleparallel
gravity based on
geometric drift vectors. Gravitational effects are encoded in a comoving tetrad framework through a dynamical drift field whose gradients generate torsion rather than spacetime
curvature. While the teleparallel equivalent of general relativity reproduces the Schwarzschild behavior in the weak field regime, nonlinear invariant contributions dominate in the strong field region, replacing the central singular behavior with a smooth de Sitter like core. Event horizons emerge as drift horizons associated with the limiting behavior of the
geometric flow, and null and timelike trajectories admit analytic extensions across the horizon and central region.
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Fluid Dynamics
A dual–continuum phase-field model for hydraulic fracturing: Viscosity-dominated regime and fluid lag
Tao You and Keita Yoshioka
The phase-field model regularizes sharp fractures into a diffuse representation, blurring the boundary between the fracture and the intact material. This blurring makes it difficult to capture distinct domain processes in hydraulic fracturing, where Reynolds flow governs the fracture and Darcy flow describes the surrounding porous
matrix. Consequently, the blurred delineation artificially smears the pressure field across the fracture–
matrix interface, which is acceptable in toughness-dominated hydraulic fracturing regimes where pressure drops within the fracture are negligible. However, in viscosity-dominated regimes, typically for actual subsurface injections due to high injection rates, the fluid pressure drops more drastically, and the fluid front may even lag behind the propagating fracture tip, a phenomenon that a smeared pressure field cannot capture. Despite its relevance, the viscosity-dominated regime has not been addressed by any existing phase-field models to date, likely due to its numerical instability. In this study, we propose a dual–continuum phase-field model based on double-porosity microporomechanics that explicitly separates mesoscale crack pressure from micropore pressure. The framework provides a variationally consistent formulation alongside phase-field–dependent poroelasticity. To ensure the numerical stability of the hydromechanical coupling, a fixed-stress split scheme is modified for two independent fluid pressures, while a variational inequality constraint is applied to reproduce fluid lag. Verified against the closed-form solutions in toughness-dominated, viscosity-dominated, and early-time transitional regimes, the model accurately captures complex fluid flow behavior and transient fluid lag within the fracture, and opens a new frontier for applying phase-field models to realistic viscosity-dominated hydraulic fracturing.
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Optics
Spatially variant arbitrary polarization shaping for optical skyrmions generation
Yu-Hao Lei, Zi-Ting Liu, Jun-Quan Guo et al. (+6 more)
Polarization is fundamental degree of freedom of light, crucial for applications from imaging to
quantum optics. Although numerous methods can spatially manipulate the polarization orientation, e.g., for generating vector beam, achieving simultaneous, spatially resolved control of both the orientation ({\psi}) and ellipticity (ḩi}) remains challenging. Here, we present an efficient and compact platform to generate spatially variant arbitrary polarization states, e.g., optical skyrmions, in free space, using cascaded spatially variant waveplates in a single silica glass plate via ultrafast
laser direct writing. We propose two configurations: (1) a spatially variant half-waveplate (S-HWP) and followed by a quarter-waveplate (S-HWP); and (2) two cascaded spatially variant quarter-waveplates (S-QWPs). Design rules linking the target polarization parameters (orientation {\psi} and ellipticity ḩi}) to the fast-axis distributions enable spatially resolved arbitrary polarization control. Using these devices, we realize Néel-, Bloch-, and anti-skyrmions of different orders (e.g., second and fourth) and n-{\pi} textures (2{\pi} and 3{\pi}), with polarization-resolved measurements in excellent agreement with simulations. We further demonstrate 3 by 3 arrays comprising either identical or hybrid skyrmions. This approach enables the realization of spatially variant arbitrary polarization state and scalable skyrmion
lattices.
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All authors Yu-Hao Lei, Zi-Ting Liu, Jun-Quan Guo, Xin Zhang, Minxin Ye, Qi-Dai Chen, Ke-Mi Xu, Shih-Chi Chen, Lei Wang
Applied Physics
Efficient Analysis of Carrier Transport and TM-TE Emission in AlGaN UVC LEDs via Multi-band Localization Landscape Theory
Yu-Ming Chang, Ping-Jie Zhuang, Marcel Filoche et al. (+3 more)
AlGaN-based UVC LEDs (220-250 nm) suffer from poor hole confinement and strain-induced |Z>-band dominance at high Al content (>60%), leading to increased TM emission and reduced external
quantum efficiency (EQE). While conventional k.p models combined with Schrodinger, Poisson, and drift-
diffusion solvers are widely used to study optical transitions, they are computationally expensive. In this work, we apply the multiband Localization Landscape (LL) model, including the effect of strain, as an alternative that replaces the
eigenvalue problem to efficiently capture
quantum effects and carrier localization. Using the 3D multi-band LL model with the Wigner-Weyl formalism, we reproduce emission and absorption spectra trends similar to the results in 3D k.p calculations, but with significantly reduced simulation time. The polarization ratio also agrees well with published experimental results across a wide spectral range. Furthermore, we analyze electrical characteristics such as band structure, polarization switching, and carrier confinement under
alloy fluctuations and strain. This multi-band LL-based approach provides a fast and reliable solution for understanding and optimizing UVC LED performance.
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All authors Yu-Ming Chang, Ping-Jie Zhuang, Marcel Filoche, Claude Weisbuch, James S. Speck, Yuh-Renn Wu
Computational Physics · Cross-listed from cond-mat.stat-mech
Free energies and optimal reaction coordinates via entropy production
Jérémy Diharce, Line Mouaffac, Axel Dian et al. (+1 more)
We show through theory and numerical experiments that a straightforward calculation of
entropy production on short molecular dynamics trajectories allows estimating free-energy barriers and identifying optimal reaction coordinates of activated processes. To this aim, we perform an analysis based on
stochastic energetics on a set of trajectories relaxing towards
equilibrium from a same initial configuration, projected on different putative coordinates. After demonstrating the approach on simple
benchmarks, we show that it is possible to estimate the free-energy barrier of a complex high-dimensional system (carbon nanoparticles in water) and to rank the quality of order parameters, in agreement with the committor probability. The results shed light on the
entanglement between the second law, free-energy landscapes, reaction coordinates and kinetic rates.
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All authors Jérémy Diharce, Line Mouaffac, Axel Dian, Fabio Pietrucci
Applied Physics · Cross-listed from cond-mat.supr-con
Tuning Superconductivity by Isovalent Antimony Substitution in PrFeAs(O,F)
Priya Singh, Konrad Kwatek, Tatiana Zajarniuk et al. (+6 more)
We investigate the effects of isovalent Sb substitution at the As site in fluorine-doped PrFeAs1-xSbxO0.7F0.3 (x = 0 to 1.0) through structural, Raman spectroscopy, density functional theory (DFT), transport, magnetotransport, and
magnetic measurements. The superconducting transition temperature decreases gradually from ~48 K for the parent compound to ~44 K up to x = 0.3, followed by a rapid suppression at higher Sb concentrations due to increasing disorder and secondary phase formation. Raman spectroscopy and DFT reveal
lattice expansion and pronounced softening of pnictogen related vibrational modes upon Sb substitution. Magnetotransport measurements up to 9 T show enhanced upper critical fields and increased
vortex activation energy for moderate Sb doping, indicating stronger
vortex pinning. However, the critical current density remains low because of poor intergranular connectivity. The results demonstrate a crossover from an electronically tuned superconducting state to a disorder-dominated regime in isovalently substituted iron pnictides.
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All authors Priya Singh, Konrad Kwatek, Tatiana Zajarniuk, Taras Palasyuk, Cezariusz Jastrzębski, Michał Wierzbicki, Tomasz Cetner, Andrzej Szewczyk, Shiv J. Singh
Applied Physics · Cross-listed from cond-mat.mes-hall
P. K. Rout, J. Godinho, F. Vilsmeier et al. (+9 more)
Antiferromagnets offer a promising route toward robust spintronic devices because of their compensated
magnetic order and exchange-enhanced
spin dynamics. Here, we demonstrate a
spin-orbit torque (SOT)-driven
antiferromagnetic oscillator based on a nanoconstriction patterned from a synthetic antiferromagnet (SAF).
Spin-rectification spectroscopy reveals electrical excitation of both acoustic and optical SAF eigenmodes, whose field and frequency dependences are quantitatively described by an
antiferromagnetic resonance model. In addition to these linear eigenmodes, we observe low-field
spin-rectification peaks that emerge only above a threshold DC current near the
spin-flop transition. Their current-polarity-dependent sign and locking to an injected RF frequency provide electrical
spin-rectification signatures consistent with current-selected
chiral self-oscillatory dynamics. Micromagnetic simulations reproduce the threshold excitation of SOT-driven self-oscillations and injection locking, while macrospin simulations predict stable and chaotic nonlinear dynamics within the same
spin-flop region. We interpret the multi-peak, weakly RF-frequency-dependent responses as a qualitative signature of complex nonlinear dynamics. These results establish SAF nanoconstrictions as an experimentally accessible platform for studying current-driven
antiferromagnetic-like oscillator dynamics and motivate future work on nonlinear spintronic devices for signal processing and reservoir-computing concepts.
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All authors P. K. Rout, J. Godinho, F. Vilsmeier, R. Salikhov, J. A. Vélez, Z. Šobáň, D. Laroze, O. Gomonay, R. M. Otxoa, C. H. Back, O. Hellwig, J. Wunderlich
Computational Physics · Cross-listed from cond-mat.mes-hall
Graph-Based Kirchhoff Modeling of Non-Ohmic Electron Transport in Self-Assembled Nanonecklace Networks
Obed Issakah, Srivathsan Badrinarayanan, Ravi F. Saraf et al. (+1 more)
Gold nanonecklace networks exhibit non-Ohmic current–voltage I-V characteristics with a sharp conduction threshold, making them promising for sensing and transistor-like devices. However, their conduction has been understood largely empirically, because experiments cannot see how conduction evolves inside the network. To address this, we develop a graph-based Kirchhoff modeling framework that resolves these internal processes, tracking the potential and current of every junction. Although every active element conducts linearly, the model reproduces the non-Ohmic response $I \propto (V-V_T)^\zeta$. It also captures the experimentally observed effects of junction properties, network density, and voids, which lends confidence to its predicted internal states. These states show that the non-Ohmic response emerges from voltage-driven percolation. Conduction is governed by how junctions are connected rather than by how many are active, with the current scaling approximately as \(N^{2.3}\) while the number of active junctions grows only linearly. Contrary to the expectation that junction heterogeneity strengthens the nonlinear response, homogeneous junctions in a well-connected network produce the most abrupt and reproducible turn-on. Thus, each structural parameter acts as a distinct control knob. The mean junction characteristics set the threshold, junction uniformity sets the switching sharpness, and network density and voids set the connectivity and current. These relationships provide design rules for tailoring nanonecklace networks to a desired conduction behavior through synthesis and fabrication.
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All authors Obed Issakah, Srivathsan Badrinarayanan, Ravi F. Saraf, Janghoon Ock
Optics
Monolithic Barium Titanate Nanophotonics and Electro-optics
Sarah Berman, Sina Dereshgi and David Barton
Barium titanate-on-
insulator (BTOI) is a compelling material for high-speed integrated photonic modulators due to its large Pockels coefficient (r42 > 1200 pm/V in bulk), which allows for the miniaturization of modulators while maintaining strong electro-optic performance. Sub-wavelength nanostructures monolithically etched into BTOI are particularly exciting, as they offer a path toward subwavelength light-matter interaction and reduced modulator energy consumption. Here, we design, fabricate, and characterize monolithic one-dimensional nanophotonic
crystals (PhCs) and high-Q (230k) photonic-
crystal Fabry-Perot (FP) cavities in BTOI. We develop and optimize a nanofabrication process that yields anisotropic (75-degree sidewalls) and deep etching that features low optical loss, with racetrack resonators achieving intrinsic quality factors near 1 million and propagation losses of about 0.5 dB/cm. Our photonic
crystals exhibit bandgap contrasts greater than 40 dB, and FP cavities reach loaded quality factors up to 230k. We verify ferroelectric domain
alignment via second-harmonic generation microscopy and extract an effective Pockels coefficient of 154 pm/V. By probing the microwave response at the PhC band edge, where modulation bandwidth is set by the material's electro-optic response rather than cavity
photon lifetime, we measure a 3-dB electro-optic bandwidth of 11 GHz and a 6-dB bandwidth of 21 GHz, consistent with the frequency-dependent roll-off of BTO's r42 coefficient near 10 GHz. Finally, we show a variety of modulation effects in resonators and at photonic
crystal band edges, including sideband-resolved modulation, resonant bandwidth-limited modulation, and photonic-
crystal based single sideband modulation and frequency comb generation.
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Optics
Research and Development of High-Efficiency Compressed Transmission Technologies for Holographic Communication in Beyond 5G Networks
Yuji Sakamoto, Takahiro Yamanoi and Seok Kang
This report summarizes the research outcomes achieved by the research group at Hokkaido University under the funding program "Innovative Information and Communications Technology Research and Development (Commissioned Research)" of the National Institute of Information and Communications Technology (NICT). Although this report is primarily written for specialists in the fields of optics and computational science, the content has been concisely organized to ensure accessibility and interest for a broader readership.
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Fluid Dynamics
SCoReT: Super-Resolution Compression and Reconstruction of Turbulent Flows
Royyuru Sai Prasanna Gangadhar, Shishir Srivastava, Nagabhushana Rao Vadlamani et al. (+1 more)
High-fidelity simulations of the Navier–Stokes equations (NSE) generate massive amounts of data, motivating the need for efficient compression and reconstruction strategies for turbulent flows. At the same time, reconstructing flow fields from sparse measurements while retaining spectral content,
turbulence statistics, and coherent structures remains a major challenge. This work investigates two complementary paradigms for turbulent flow reconstruction: supervised reconstruction and physics-informed reconstruction, in the context of transition to
turbulence induced by three-dimensional distributed roughness elements. We introduce a vorticity-augmented supervised approach and a physics-informed approach, implemented through a partially assisted compressible PINN formulation based on the three-dimensional unsteady compressible Navier–Stokes equations. Reconstruction performance is evaluated at different sparsity levels using instantaneous velocity fields, mean-squared error, energy spectra, Reynolds stresses, turbulent kinetic energy, and Q-criterion isosurfaces. Rather than establishing a universal winner, the present study characterises the respective strengths, limitations, and operating regimes of these two approaches. The results indicate that at lower sparsity levels, the vorticity-augmented supervised model yields the lowest reconstruction error, recovers key statistical and spectral features, and enables substantial data compression. The PINN shows potential to reconstruct turbulent flows from sparse measurements without high-resolution labels and exhibits comparatively stable held-out extrapolation behaviour at higher sparsity. These results suggest the potential of combining data-driven and physics-informed learning for flow data compression and physics-informed reconstruction of turbulent flows from sparse data.
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All authors Royyuru Sai Prasanna Gangadhar, Shishir Srivastava, Nagabhushana Rao Vadlamani, Arvind Easwaran
Data Analysis and Statistics · Cross-listed from astro-ph.EP
Spectral Mixture Modeling with Laboratory Near-Infrared Data II: Effects of Grain Size and Implications for Europa
A. Emran
Spectral analysis using linear mixture (LM) and radiative transfer-based (RT) intimate mixture modeling based on Hapke theory at near-infrared wavelengths are applied to estimate the abundance of surface materials on Europa. Previously, Emran (2026) compared these approaches against the laboratory spectra of H$_2$O ice and H$_2$SO$_4$$\cdot$8H$_2$O mixtures with $\sim$100 $\mu$m grains. Here, the effect of particle size on spectral modeling accuracy was assessed using laboratory spectra of H$_2$O ice mixtures with small ($\sim$70 $\mu$m spherical) and coarse ($\sim$1 mm irregular) grains, measured over the $\sim$1.2-2.5 $\mu$m wavelength range at 100 K and 120 K (Stephan et al., 2021). Modeled abundance estimates at both temperatures show consistent trends across all mixing ratios, with only minor temperature-dependent variations. The discrepancy in abundance estimates from both LM and RT models remains within $\pm$10% across all mixtures, with the error reduced to $\pm$5% when fine grains dominate. Across all mixtures, the average difference between RT- and LM-derived abundance estimates remains within $\pm$2% for mixtures containing both small and large grains. In contrast, mixtures composed solely of smaller grains render larger deviations between the models, with RT producing more accurate estimates (Emran, 2026) – indicating that the presence of coarse H$_2$O ice grains minimizes abundance differences between LM and RT modeling. Thus, I posit that Hapke-based RT modeling is the preferred spectral modeling approach – regardless of grain size or compositional mixture – for constraining Europa's surface composition. Nonetheless, LM modeling remains a reliable approach for compositional analysis of terrains containing H$_2$O ice with $\sim$mm-sized grains.
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