Atomic Physics · Cross-listed from cond-mat.mtrl-sci
Mechanisms of Nanoscroll Formation and Particle Encapsulation in Janus MXenes
Sasan Rezaee, Fatemeh Mohammad Dezashibi, Ould el Moctar et al. (+1 more)
Morphology transfer of 2D Janus MXenes into nanoscrolls unlocks unusual properties. Although a scalable synthesis route has been experimentally verified, the atomistic mechanism underlying nanoscroll formation remains poorly understood. We use large-scale reactive molecular dynamics simulations, validated against density functional theory (DFT) and experimental structural and elastic properties, to investigate stability and quantify the driving forces and geometry governing nanoscroll formation in three Janus MXenes, (Tx)Ti2C(Ty), where (Tx) and (Ty) denote the bottom and top surface terminations among bare (-b), -O, and -OH. Both square and infinitely wide flakes with lengths ranging from 10 to over 120 nm are simulated. We find that 1-7%
lattice-induced strain generates a bending moment in these structures. The sheet scrolls, curves, or forms a nanotube depending on the resulting
curvature and initial sheet size. For MXenes with an initial length of 120 nm, multiwalled nanoscrolls form with interlayer distances of around 0.7 nm and inner diameters of about 7 nm for (O)Ti2C(OH) and (b)Ti2C(OH), whereas (b)Ti2C(O) instead produces a much larger interlayer distance of around 1.7 nm and an inner diameter exceeding 20 nm. We show that spontaneous scrolling of a Janus MXene in the presence of an anchored nanoparticle produces a core@shell composite, in which the particle locally deforms the nanoscroll and widens the interlayer channels. This locally tunable, enlarged interlayer spacing offers a promising design route for MXene-based energy-storage electrodes. However, our simulations reveal H2 gas release during encapsulation, which promotes nanobubble formation that can reduce battery life.
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All authors Sasan Rezaee, Fatemeh Mohammad Dezashibi, Ould el Moctar, Hossein Darban
Physics Education
Pathways to Quantum Science for High-School and Incoming College Students
Dan-Adrian German, Rebekah Randall, Charles Pope et al. (+2 more)
The convergence of AI and
quantum computing requires a new approach to cybersecurity. Credible experts estimate that by 2030 a cryptographically relevant
quantum computer will be capable of breaking the encryption that underpins all of our digital communication. One of the most disruptive technology in history is coming and it's expected to change everything. In this context academic institutions will contribute to their states' future economic prosperity by leveraging their strengths and resources, particularly talent development, in key and emerging areas prioritized across the state. We report on current efforts to develop a Pathways Plus to
Quantum Information Science (QIS) degree, a set of dual credit courses for high-school (HS) students and incoming college students pursuing a minor or specialization in
Quantum Computing (QC). As of today, in the US,
quantum topics appear on the HS curriculum standards in just two states: OH (Computing) and TX (Physics). Reaching out to HS and even middle school students (and their teachers) presents obvious long-term benefits in terms of workforce development for the
quantum industrial ecosystem. Standing in the way of successful, widespread introduction of QC and QIS topics in HS and middle school are three distinct obstacles: (a) lack of materials at the right level for students and instructors, (b) funding and support for professional development for teachers, and (c) lack of state standards. In this paper we address all three aspects with a special focus on the benefits of
quantum virtual labs and ZX calculus in the classroom.
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All authors Dan-Adrian German, Rebekah Randall, Charles Pope, Michele Roberts, John Phillips
Fluid Dynamics · Cross-listed from gr-qc
On the Stability of the Euler-Poisson Dark-Fluid Model
Balázs Endre Szigeti, Imre Ferenc Barna and Gergely Gábor Barnaföldi
We present a stability analysis of a dark-fluid model described as a non-relativistic, rotating, non-viscous, self-gravitating fluid. We assume spherical
symmetry and model the matter by a polytropic equation of state. The resulting coupled nonlinear partial differential equation system is solved using a self-similar ansatz known from the Guderley-Landau-Stanyukovich problem. We find that three of the four Lyapunov exponents are negative, while only one is positive. This indicates one unstable direction and three contracting directions in phase space. The single positive exponent is relatively small, suggesting that the self-similar solution is only weakly unstable and remains dynamically robust over the investigated interval.
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Atmospheric and Oceanic Physics · Cross-listed from cs.LG
Earth observation embeddings are effective sub-grid descriptors for probabilistic weather downscaling
Pedro Sousa, Will Tebbutt, Sadiq Jaffer et al. (+3 more)
Global weather reanalyses and forecasts resolve the evolving atmospheric state on coarse grids, but site-specific applications require predictions at arbitrary locations where near-surface conditions also depend on unresolved terrain and land-surface properties. Existing probabilistic downscalers address this gap using hand-crafted topographic and surface descriptors. We ask instead whether Earth observation foundation models can provide transferable subgrid surface representations for probabilistic weather downscaling. We augment a convolutional conditional neural process (ConvCNP) that downscales coarse ERA5 reanalysis fields at ~25 km resolution with a learned local surface descriptor, obtained by compressing a patch of TESSERA
embeddings at 10 m resolution. Although these
embeddings summarize annual surface conditions, they improve downscaling by encoding persistent surface properties that capture a location's departure from the coarse-grid atmospheric state. Across five climatically diverse regions, the
embedding improves point and probabilistic skill at stations held out in both space and time, overall improving CRPS skill by 11.5% for 2 m temperature and 6.2% for 10 m wind speed relative to a topography-only ConvCNP baseline. A hand-crafted descriptor incorporating richer surface information than topography alone captures comparable persistent subgrid signal but yields far smaller predictive gains than the learned
embedding representation. These improvements persist when forecasts from the Aurora AI model replace ERA5 reanalysis fields and when predicting at newly deployed weather station networks. To our knowledge, this is the first evidence that long-timescale Earth observation
embeddings can support short-timescale weather downscaling where subgrid departures are systematically structured by persistent surface properties.
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All authors Pedro Sousa, Will Tebbutt, Sadiq Jaffer, Robin Young, Anil Madhavapeddy, Richard E. Turner
Applied Physics
Measurement of third-order elastic constants using thermal modulation of ultrasonic waves
Bibo Zhong and Jinying Zhu
Third-order elastic constants (TOEC) play an important role in nonlinear material characterization, but measurements of TOEC are laborious with large error margins. This Letter presents the equations of wave velocity changes caused by homogeneous temperature variation and uniaxial stress in isotropic media and the expression of TOEC in terms of thermally induced velocity change and thermal strain. TOEC of an aluminum sample were experimentally determined by measuring ultrasonic wave velocity changes in the uniaxial loading test and the thermal modulation test. Experimental results showed good agreement between the two test methods. Owing to the simple test setup and high measurement sensitivity, the thermal modulation test is a potential experimental method to determine TOEC and absolute acoustic nonlinearity parameters.
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Optics
Goos-Hanchen-Shift Photonic Sensor for Nanometer-Scale Delayering and Tamper Detection in Semiconductor Packages
Mia Mohammad Shoaib Hasan and Mohamed Elkabbash
We propose a co-packaged photonic tamper sensor that detects progressive delayering and localized drilling through changes in the Goos-Hanchen (GH) shift of a reflected optical beam. Frustrated total internal reflection (FTIR) couples the beam into a high-index sensing layer, where its transverse-wavevector components acquire a thickness-dependent propagation phase. Numerical simulations show an approximately linear response for sensing-layer thicknesses below 250 nm and a delayering sensitivity of 5.3 nm of beam displacement per nanometer of material removed, nearly three times that of a conventional total internal reflection (TIR) structure. The off-resonant response remains stable under representative refractive-index, wavelength, and incidence-angle variations. Localized drilling also produces a monotonic GH-shift change that increases with drill depth and width. These results establish GH-shift readout as a rapid, spatially encoded, and difficult-to-emulate approach for
semiconductor-package tamper detection.
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Fluid Dynamics
Effects of Soret Diffusion and Radiative Heat Loss on the Evolution of Buoyant Flame Kernels in Ultra-Lean Hydrogen-Air Mixture
Ivan S. Yakovenko and Alexey D. Kiverin
Ultra-lean hydrogen flames under terrestrial
gravity are governed by a coupled interaction among preferential
diffusion, thermal
diffusion, heat loss, and self-induced convection. This study numerically examines combustion in a quiescent 6~vol.% H$_2$–air mixture using detailed chemistry and a low-Mach-number formulation. A complete calculations set was considered, with Soret
diffusion and optically thin radiative heat loss independently enabled and disabled. One-dimensional spherical calculations were used to isolate the initial post-ignition flame kernel growth, while two-dimensional planar and axisymmetric simulations described its subsequent buoyant rise, deformation, and breakup. Over the analyzed interval, the spherical flame-front radius followed $R_f^2\approx Kt$ rather than constant-speed expansion. Soret
diffusion increased the effective growth coefficient $K$, whereas radiation reduced it. The axisymmetric calculations reproduced the experimentally measured leading-point trajectory substantially better than the planar formulation. Soret
diffusion produced larger, faster-rising kernels and maintained a more nearly circular upper cap, whereas radiation had a weaker effect on trajectory but increased relative lateral flattening. In all cases, a toroidal
vortex stretched the flame segment and caused local extinction and fragmentation. Soret
diffusion delayed breakup, while radiation advanced it; their combined effect on breakup time was nearly compensating. The results show that Soret transport and radiation primarily alter kernel growth and resistance to
vortex-induced extinction, while the qualitative breakup pathway remains hydrodynamically controlled.
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Biological Physics · Cross-listed from q-bio.PE
Dynamics of fluctuating populations in multi-state switching environments
Mauro Mobilia
Microbial populations generally evolve in fluctuating environments under time-varying conditions. These are often described by binary switching models, sometimes seen as coarse-grained feast-famine cycles, in which resource availability switches abruptly between abundant and scarce conditions. However, experimental studies suggest that feast-famine environments actually exhibit more complex temporal dynamics. Here, we study how two strains, one growing slightly slower than the other, compete for the same resources in fluctuating environments comprising a finite number of intermediate states, each having its own carrying capacity. Environmental switching between these states and their carrying capacities represents gradual changes in nutrient availability. This class of multi-state
stochastic switching models can be interpreted as a coarse-grained description of feast–famine cycles and allows us to investigate strain competition under the gradual recovery and depletion of resources. By computational and analytical means, we characterise the population dynamics in these multi-state fluctuating environments. In particular, we study how the switching rates and distribution of carrying capacities affect the population-size statistics, fixation probability, and mean fixation time. By comparing these results with their counterparts in binary environments, we clarify how the frequency and amplitude of environmental fluctuations influence population dynamics in coarse-grained feast-famine cycles.
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Plasma Physics
Derivation and application of sheath boundary conditions for drift-kinetic simulations in a linear plasma device based on a gyromoment approach
Jacob Emil Mencke, Thomas Stucker and Paolo Ricci
Boundary conditions for a drift-kinetic model at the collisional presheath entrance with perpendicular incidence of the
magnetic field to the wall are derived and numerically implemented. The drift-kinetic model for the
plasma is based on the expansion of the ion distribution function on a Hermite-Laguerre basis, and the
evolution of the resulting gyromoments. A linear-
plasma-device geometry is considered. Comparison with simpler simulations with previously used ad hoc boundary conditions is presented. For the new set of boundary conditions, a significant increase of the
plasma outflow to the wall is observed, leading to a significantly smaller
plasma density in the whole volume of the device.
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Medical Physics
A 2D Hydrothermodynamic Analytical Model for Rapid Tumor Ablation using High-Intensity Focused Ultrasound
D. Tsiklauri
We establish a self-consistent 2D hydrothermodynamic analytical model for high-intensity focused ultrasound tumor ablation. Expanding compressible Navier-Stokes equations to second order demonstrates that a stationary cellular
matrix suppresses acoustic streaming ($\mathbf{v}_2 = 0$). This constraint forces the absorbed wave momentum flux to convert entirely into localized, time-averaged static pressure gradients ($\nabla \langle p_2 \rangle = \mathbf{F}_2$), bridging non-linear hydrodynamics with thermodynamic dissipation. Solving the non-diffusive Pennes bioheat equation under a $1.0\,\text{s}$ top-hat pulse reveals that a spherically focusing geometry ($\propto 1/r^2$) overrides exponential damping past a critical
geometric threshold ($r_{\text{crit}} = 2x_0$), preventing upstream skin overheating. We derive an optimization criterion where the absorption coefficient matches half the inverse target depth ($\alpha = 1/2x_0$). Solving the non-isothermal Arrhenius integral yields a sharp lesion boundary radius at $r_b = 0.75\,w_0$, where the volume average reaches $72.1^\circ\text{C}$ while the core peaks at $90.0^\circ\text{C}$. Post-pulse 2D free-space Green's function convolution confirms immediate monotonic thermal decay ($\partial \theta/\partial t' < 0$) outside this boundary. This closed-form framework provides explicit scaling laws for non-invasive wave-matter thermal confinement, bypassing computationally heavy numerical simulations.
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Physics and Society
Economic Distance Structures Urban Mobility in 109 U.S. Cities
Wei-Peng Nie, Xiao-Yong Yan, Bin Jia et al. (+4 more)
Urban mobility promises social integration, yet daily movement is systematically constrained by socioeconomic hierarchies. Introducing "economic distance"–the continuous income gap between origin and destination–as a unified lens, we analyze large-scale mobility records across 109 U.S. cities to reveal how urban flows are structured. We identify a universal structural boundary: flows concentrate intensely within a narrow economic distance of 0.25
quantiles, defining the effective "economic radius" of routine mobility. This boundary exhibits profound asymmetry; upward mobility faces a uniform structural ceiling across cities, whereas downward mobility drives cross-city heterogeneity. Mechanistically, the boundary is physically anchored by meso-scale residential clustering but is further tightened by an independent economic-distance friction, validated via
gravity modeling. These interactions yield four distinct mobility regimes, with "affluent-confined" systems exhibiting the strongest stratification. These findings establish economic distance as a fundamental, asymmetric, and multi-scale filter shaping urban inequality, offering new theoretical grounds for interventions targeting structural barriers to cross-class interaction.
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All authors Wei-Peng Nie, Xiao-Yong Yan, Bin Jia, Fang Zhou, Er-Jian Liu, Tao Zhou, Zi-You Gao
Medical Physics
Reducing Spectral Oscillations for Robust Reference Frequency-Based Ultrasound Attenuation Estimation in Harmonic Imaging
U-Wai Lok, Jingke Zhang, Chengwu Huang et al. (+14 more)
Ultrasound attenuation coefficient estimation (ACE) has emerged as a quantitative imaging biomarker for noninvasive assessment of hepatic steatosis. A system-independent technique based on spectral normalization, known as the reference frequency method (RFM), was previously proposed to estimate ACE without requiring a well-calibrated reference phantom. Furthermore, incorporating harmonic imaging can significantly suppress reverberation signals. In previous clinical study, RFM has achieved high correlation with MRI-PDFF, demonstrating its potential for clinical application. However, a major challenge of RFM is the presence of oscillations in the frequency power-ratio decay curves (FPDCs), which can distort the linear fitting used to estimate the attenuation coefficient and consequently degrade ACE accuracy. These oscillations arise from constructive and destructive interference among backscattered echoes, resulting in oscillatory fluctuations in the measured power spectrum that propagate into the FPDCs. We propose a transmission scheme combining multiple frequencies and steering angles to mitigate oscillations in the FPDCs. Averaging these FPDCs suppresses the interference-induced oscillations while preserving the attenuation-dependent decay trend, thereby improving linearity and the accuracy of ACE results. In in-vitro experiments using calibrated phantoms (0.5 and 0.76 dB/cm/MHz) demonstrated that the proposed method improved FPDC linearity and ACE accuracy, achieving an R2 of 0.99 and attenuation coefficient estimates of 0.51 and 0.77 dB/cm/MHz, versus an R2 of 0.89 and estimates of 0.56 and 0.70 dB/cm/MHz for conventional RFM. The proposed method also demonstrated superior performance in a pilot patient study (n=15), achieving a stronger correlation with MRI-PDFF (R = 0.89 vs. 0.83) while reducing inter-measurement variability, indicating improved robustness and clinical potential.
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All authors U-Wai Lok, Jingke Zhang, Chengwu Huang, Tao Wu, Jieyang Jin, Ryan M. DeRuiter, Jingyi Yin, Lijie Huang, Yanzhe Zhao, Kaipeng Ji, Kate M. Knoll, Dawn Boynton, Kymberly D. Watt, Kathryn A. Robinson, Joshua D. Trzasko, Matthew Callstrom, Shigao Chen
Applied Physics · Cross-listed from eess.SP
Effects of Tool Wear on the Surface Texture in Turning: A Feature Characterization Approach Based on ISO 21920-2
Alexander Müller, Maximilian Berndt, Hagen Schmidt et al. (+5 more)
The surface texture of a turned component acts as a fingerprint of both the process parameters and the tool wear condition, imaging the cutting edge. Classical surface parameters such as $R_\mathrm{a}$ or $R_\mathrm{q}$ describe the topography only globally and allow no spatially resolved evaluation of the process-induced deterministic structures. This work investigates how far the feature characterization standardized in ISO 21920-2 makes this wear information accessible and physically interpretable. The database comprises roughness profiles of twelve AlTiN-coated carbide inserts (CNMG120408) machining normalized AISI 1045 steel, measured at nine wear states over the entire tool life, with three replicate profiles per state. The correlation of standardized field and feature parameters with crater wear, flank wear, and cutting time is first examined. Watershed
segmentation is then adapted to extract the rotational tool grooves and evaluate their geometry statistically. A newly developed mean-feature approach decomposes the profile into a deterministic and a
stochastic component. Wear-induced changes are almost entirely carried by the deterministic component, and within it by the trailing flank of the cutting groove. A comparison with confocal measurements confirms that the mean feature reconstructs the engaged cutting edge geometry, with the trailing-flank steepening attributable to notch wear on the secondary cutting edge. An exhaustive evaluation of more than 920,000 feature characterization combinations and multivariate models reveals that the groove-level mean maximum absolute gradient $\overline{R_\mathrm{dt}}_\mathrm{groove}$ alone explains 83-90% of the variance of the wear indicators, so that a single, physically motivated parameter suffices for robust wear estimation. A follow-up study will investigate inline monitoring using scattered light sensors.
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All authors Alexander Müller, Maximilian Berndt, Hagen Schmidt, Lars Müller, Matthias Eifler, Eberhard Kerscher, Benjamin Kirsch, Jörg Seewig
Physics and Society
Robustness over efficiency in climate coalitions: a bistable model and a map of architectures
Juergen Renn
Designs for international
climate cooperation face a trade-off between efficiency and robustness to institutional erosion. We formalize it in a stylized coalition-formation game with two enrolment channels, a membership premium read as the value of club goods and an outsider drain, stabilized with robust control. The free-rider gap is exact within the game, measurable, and separated from the architecture-specific channels. The drain decomposes into a border channel, capped by trade law at the rent it mirrors, and a compensated world-
market channel. With sufficiently strong channels the model is bistable, a remnant club and a near-universal coalition separated by a critical mass. For a proposed carbon currency, whose units are reissued each period, extinguished upon use, and enforced at the border, the minimal
nucleus is thirty per cent of global emissions, ignition from an EU-China
nucleus requires compensating one fifth to three fifths of the outsiders' world-
market loss, the established coalition withstands two to four times the erosion admissible at ignition, and the tipping survives heterogeneity to three times the premium. Two robustness coordinates place each architecture on a map with three regimes: the carbon currency is self-igniting, the border adjustment founding-dependent, the export rebate permanent-support-dependent. A third coordinate, the coalition size up to which outsiders' border payments cover joiners' compensation, marks where the full coalition comes to rest on an internal transfer. Architectures without a drain improve efficiency within a coalition but cannot form one. Robustness governs whether cooperation forms and endures; efficiency decides how much an established coalition delivers.
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Optics
Twist-Reconfigurable van der Waals Moiré Photonic Crystals
Hugo Quard, Jiyun Kim, Anastasiia Zalogina et al. (+7 more)
Moiré photonics has emerged as a fascinating concept to design and in situ control of the optical bands. Moiré enabled light localisation arises from the relative twist between periodic layers, rather than from fixed, pre-fabricated cavity features. So far, however, the realisation of practical moiré photonic
crystals in the visible range has been elusive, due to challenges in engineering nanoscale structures and twisting them dynamically post fabrication. Here, we realise a mechanically reconfigurable moiré photonic
crystal, comprising from two patterned van der Waals
crystals (tungsten di sulphide, WS$_2$) slabs separated by an optically active hexagonal boron nitride (hBN) spacer. We reconfigured the same pair of WS$_2$ slabs from a twist angle of 3.8{\deg} to 8.4{\deg} and reconstructed their three-dimensional dispersion using momentum-resolved reflectivity spectroscopy. Further, by reducing the twist angle between the slabs, we observe a denser
manifold of folded and hybridised resonances that coincides with a 30-fold enhancement of emission from embedded colour centres. Our results open exciting opportunities for in-situ dispersion engineering and programmable light matter interactions employing van der Waals nanostructures.
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All authors Hugo Quard, Jiyun Kim, Anastasiia Zalogina, Xuerong Hu, Evan Williams, Oscar J. Palma Chaundler, Owen R. Wolley, Alexander Tartakovskii, Haoning Tang, Igor Aharonovich
Optics · Cross-listed from cond-mat.mtrl-sci
Beam Routing through Excitons in Transition Metal Dichalcogenide Monolayers
Yonas Lebsir, Jacob Terndrup Heiden, Jorge Barcia Rodríguez et al. (+6 more)
Routing light at the nanoscale typically relies on nanostructured surfaces to imprint directionality on the emission. Using low-temperature, angle-resolved cathodoluminescence spectroscopy, we show that the intrinsic excitonic transitions of a
semiconductor can themselves produce routed emission. We probe monolayers of WSe$_2$, MoSe$_2$, and MoTe$_2$ and resolve the excitonic species of monolayer WSe$_2$ – the bright
exciton, the trion, and the
spin-forbidden dark
exciton – through their distinct angular emission profiles. While the in-plane transition dipoles of the bright
exciton and trion radiate predominantly toward the surface normal, the out-of-plane dipole of the dark
exciton, inaccessible under normal-incidence optical excitation, produces a directional emission channel at large angles. We further tune the balance between neutral and charged
exciton emission through the local dielectric environment. Our results establish dark
excitons in TMD monolayers as a platform for directional light emission in compact photonic architectures without additional nanostructuring.
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All authors Yonas Lebsir, Jacob Terndrup Heiden, Jorge Barcia Rodríguez, Maria Papadopoulou, Kenji Watanabe, Takashi Taniguchi, N. Asger Mortensen, Sergii Morozov, Nicolas Ubrig
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Thermoelastic Harvesting Outperforming Thermoelectric Generators Below 100 {\deg}C
Bruno Neumann, Andreas Henschke, Morik Nikolic et al. (+1 more)
Low-grade waste heat below 100 degC is one of the largest untapped opportunities in solid-state energy conversion. Three ferroic routes are candidates for recovering this resource: thermomagnetic, pyroelectric, and thermoelastic harvesters. The last has remained the most unexplored, despite decades of progress on the underlying NiTi shape-
memory alloy wires. Three system-design changes close this gap: a protagonist-antagonist architecture that recovers the energy for prestraining, a continuously tunable prestrain mechanism that sets the force-strain balance, and transversal water flow that decouples cycle frequency from wire length. The resulting harvester delivers a directly measured power density of 366 mW/cm^3 with respect to the active material, about 1.7 times the next-best thermoelastic device, ahead of every reported thermomagnetic and pyroelectric generator, and outperforming the best thermoelectric generators in this temperature range also with respect to power per material cost. The system maps the parameter space directly through force and displacement measurements, without using material-property estimates, giving a quantitative picture of how the
alloy responds while the device is doing work.
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All authors Bruno Neumann, Andreas Henschke, Morik Nikolic, Sebastian Fähler
Instrumentation and Detectors
From Simulation to Real Scans: Anomaly Detection in Maritime Cargo with Muon Scattering Tomography
Angel Bueno Rodriguez, Christina Hrytsiuk, Maximilian Perez Prada et al. (+6 more)
Maritime cargo inspection requires imaging technologies capable of detecting concealed threats within dense, sealed containers, a role for which
Muon Scattering
Tomography (MST) is well suited: it images their interior through the density-dependent deflection of naturally occurring
cosmic muons. However, MST remains constrained by the scarcity of labeled scans and by a
cosmic muon flux that is both low and
stochastic. Anomaly detection
algorithms must therefore be trained on simulations, yet operate on measured scans acquired under different conditions, a sim-to-real gap that remains a central obstacle to operational deployment. We present the first end-to-end anomaly detection framework for maritime MST, from physically consistent simulations to validation on real container scans from the SilentBorder demonstration campaign. The task is cast as an out-of-distribution problem: the framework learns the spatial configurations of benign cargo and flags threats as deviations in the reconstruction error space, remaining agnostic to threat type and geometry. An
attention U-Net, trained exclusively on benign synthetic scenes, preserves small-scale scattering signatures through its skip connections, and contraband consequently persists in the pixel-wise reconstruction error instead of being absorbed into the reconstructed background. A scoring function, the Homogeneity Index (HI), suppresses spatially uniform
cosmic-ray statistical noise while amplifying coherent anomaly signatures: where pixel-level metrics collapse under a change of cargo configuration, HI retains its discriminative power. We evaluate three training strategies across two distinct cargo configurations under operational one-hour scan times, and test the best model on real
muon cargo scans. The results for the studied scenarios indicate that the sim-to-real gap can be bridged.
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All authors Angel Bueno Rodriguez, Christina Hrytsiuk, Maximilian Perez Prada, Kaarel Tark, Felix Sattler, Jean Marco Alameddine, Madis Kiisk, Maurice Stephan, Sarah Barnes
Instrumentation and Detectors
Background decomposition of the CONUS+ run 1 data
N. Ackermann, H. Bonet, C. Buck et al. (+13 more)
The CONUS+ experiment is measuring the coherent elastic
neutrino nucleus scattering (CE$\nu$NS) process using reactor anti-
neutrinos as a source and four low energy threshold point-contact high-purity germanium spectrometers for their detection. It achieved the first measurement of coherent
neutrino scattering at a
nuclear reactor in run 1 of the experiment with a detection energy threshold of 160 eV$_{ee}$. This work presents the decomposition of the background spectra of the three detectors used in the run 1 analysis and the development of the corresponding background model with Geant4-based Monte Carlo simulations. The background model is used as the underlying input for the likelihood fit of the analysis. It is shown that reactor-correlated backgrounds are subdominant in all energy regions, specifically in the region of interest for CE$\nu$NS searches below 350 eV$_{ee}$ where their contribution is one order of magnitude below the expected CE$\nu$NS signal. Furthermore,
cosmic ray
muons and
neutrons are identified as the dominant background source below 1 keV$_{ee}$ contributing approximately 75 - 90 % of the recorded background rate. The final background model predicts an average rate of (47.5 $\pm$ 3.2) d$^{-1}$ kg$^{-1}$ in reactor on measurement in the energy region between [0.4, 1.0] keV$_{ee}$, which is in excellent agreement with the average measured value of (48.0 $\pm$ 0.6) d$^{-1}$ kg$^{-1}$. Similar agreement is found in all energy regions of both reactor on and off measurements.
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All authors N. Ackermann, H. Bonet, C. Buck, J. Hakenmüller, G. Heusser, M. Lindner, W. Maneschg, S. Mertens, K. Ni, D. Piani, M. Rank, T. Rink, E. Sánchez García, I. Stalder, H. Strecker, J. Woenckhaus
Fluid Dynamics
Strain-coupled one-dimensional turbulence: a single-line closure, its limits, and the consequence for leading-edge noise
Sparsh Sharma and Alan R. Kerstein
Turbulence approaching a solid surface is strained before it arrives, and the distortion of its spectrum is often what governs the downstream response; yet reduced-order predictions, leading-edge-noise theory among them, still take the incoming spectrum as frozen. We develop a strain-coupled formulation of one-dimensional
turbulence (ODT) that evolves strained
turbulence with full spatial resolution at a cost compatible with parametric study, carrying the rapid distortion and the nonlinear relaxation together. The obstacle is that the rapid pressure-strain is non-local and three-dimensional while an ODT line resolves only the flow state along its own coordinate. Splitting the distortion physics by structure captures the phenomenology: the off-axis production and a spectrally closed rapid operator enter as continuous-in-time forcing along the model coordinate, while `eddy events' capture the on-line production and the
turbulence-driven relaxation. Carried through to leading-edge noise, the evolved inflow shifts the predicted level by 5-20 dB at the energy-containing scales relative to the conventional frozen-spectrum assumption.
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Optics
Spatial and energetic correlations of ultrashort two electron pulses
Stefan Meier, Jonas Heimerl, Felix López Hoffmann et al. (+3 more)
When two electrons are emitted from a metallic needle tip into a nanometric volume on femtosecond timescales, strong Coulomb correlations arise. While longitudinal correlations, manifested as energy shifts, have been observed both from bare tips and in electron microscopes, transverse correlations remain hardly explored. Here, we present the first complete experimental characterization of such 3D correlations from needle tips. We find that electron pairs of small transversal spatial separation exhibit a pronounced energy gap of 3.3 eV width, while electrons of small longitudinal energy separation show strong transverse repulsion, increasing their average mutual divergence angle by a substantial 34.5%. The measurements are in excellent agreement with semiclassical point-particle simulations. These reveal that the maximal energy-gap magnitude is primarily determined by the
laser pulse duration, whereas the maximal spatial separation is governed by the tip radius. The latter can be exploited in a remarkably simple method to generate strongly sub-Poissonian electron beams: A mere aperture, notably present in most electron-optical setups anyway, can act as an electron number sensitive filter. In combination with energy filtering we find an unprecedented suppression of multi-electron pulses reaching g(2) = 0.02 when keeping 3% of the electron beam. These results provide a foundation for future studies of electron
entanglement, correlated electron microscopy, and the design of ultrafast electron-optical instruments.
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All authors Stefan Meier, Jonas Heimerl, Felix López Hoffmann, Tobias Volk, Marco Knipfer, Peter Hommelhoff
Fluid Dynamics
A transport geometry of acoustic analogies:exact holonomy of source re-attribution and its observable consequences
Sparsh Sharma
The source term of an acoustic analogy is not unique: different rearrangements of the Navier-Stokes equations attribute the same radiated sound to different apparent sources. Although this non-uniqueness has long been recognised, it has never been given a quantitative structure. We provide one by organising acoustic analogies into a fibre-like family over the space of effective media and defining transport between analogies through unique frequency-preserving, rotation-free linear space-time maps. Three exact results follow. First, the classical family of convected analogies is not closed under transport: successive uniform-flow regaugings generate effective media with anisotropic sound-speed tensors, recovering the generalised media introduced by Goldstein. Second, the discrete holonomy of analogy transport is obtained in closed form. It consists of an exact spectral dilation and a rotation that vanishes to fourth order in Mach number; transport becomes singular on a sonic horizon in analogy space. Third, in the continuum limit the boost sector is flat, while
curvature is confined to anisotropy directions and is given by the commutator of sound-speed-tensor increments. The geometry does not imply any change in the physical sound field: all exact analogies yield the same far field. Its significance is operational. When an approximate source model is transported between analogies, as commonly occurs in hybrid prediction methods, the resulting far-field predictions acquire an exact, parameter-free bias consisting of a rigid spectral dilation and directivity rotation. An exact far-field law for anisotropic media extends these results to open transport paths. All identities are verified symbolically and numerically.
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Instrumentation and Detectors · Cross-listed from cond-mat.other
Formally Verified Lock-Free Software Transactional Memory for Scientific Measurement
Kentaro Kitagawa
Automated measurement of condensed-matter experiments requires instrument-control, data-acquisition, and user-interface threads to access shared, naturally hierarchical state concurrently. Coarse-grained locking can delay acquisition and cause sample loss, whereas fine-grained locking requires deadlock-prone lock ordering across instruments. Instead, we describe the lock-free software transactional
memory (STM) that has been at the core of an open-source measurement platform for 16 years, in
nuclear magnetic resonance experiments and, more recently, in optically detected
magnetic resonance experiments. The STM organizes this state as a tree and provides atomic subtree updates and consistent subtree snapshots. After initial bundling, an unchanged subtree snapshot is acquired in $O(1)$ time through a custom lock-free atomic shared pointer. Within each bounded TLA+ configuration, TLC exhaustively checks the state space, establishing the safety and livelock-freedom properties specified for that configuration. Bounded executions of the atomic shared-pointer implementation are separately checked under the C11 weak-
memory model. The same Snapshot and Transaction interfaces are exposed to Python scripting and AI-assisted automation.
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Physics and Society
Sectoral inter-dependencies drive the loss of structural balance in signed financial networks
Kartik Dahake and Abhijit Chakraborty
Signed graphs provide an effective architecture for portraying a system in which cooperation and conflict coexist. Emerging from the concept of balance in psychological sciences, they have found applications across several domains. Financial
markets are one such example that can be modeled using signed networks, where assets exhibit correlations in price movements. During periods of systemic risk, such a signed financial network shows a loss of balance, which has been consistently demonstrated. Here, we explore how this structural imbalance is distributed across scales within the financial network, revealing its mesoscopic origin. Adopting the framework of structural balance theory, we use a measure of polarization based on triadic motifs to investigate the distribution of structural imbalance across varying sectoral scales. We analyze the temporal
evolution of global polarization and its sectoral constituents using longitudinal data derived from the S&P 500 index. By decomposing global polarization into intra-sectoral and inter-sectoral constituents, we show that structural imbalance arises predominantly from interactions between sectors rather than within them during periods marked by systemic risk. We employ randomization protocols to confirm that observed imbalance configurations are statistically significant and not artifacts of lower-order interactions. We derive a regression equation demonstrating that the variance in global polarization is well explained by macroeconomic variables, indicating that low levels of global polarization during economic crises are driven by compounding pressures from supply chain disruptions and inflation uncertainty. Collectively, these findings provide a quantitative framework for understanding how localized sectoral conflicts propagate across the financial network and contribute to large-scale structural instability during periods of economic crisis.
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Atomic Physics · Cross-listed from cond-mat.mtrl-sci
Energy-Dependent Dechanneling in Cu: Insights from Monte Carlo Channeling Simulations
Przemyslaw Jozwik, Cyprian Mieszczynski, Renata Ratajczak et al. (+1 more)
Ion channeling and backscattering techniques are powerful tools for studying
crystal lattice disorders and defect structures in crystalline materials. However, the accurate interpretation of channeling phenomena necessitates the utilization of simulation models that account for the intricate interactions between point defects, dislocations, and extended defect clusters. The present paper introduces a Monte Carlo method that reproduces experimental spectra over a wide range of analyzing beam energies and enables quantitative identification of defect types and distributions. The simulations reveal characteristic energy dependencies that distinguish point defects from extended defects, offering a novel perspective on disturbances caused, for example, by ion implantation in metals and
semiconductors. To this end, the McChasy code has been developed as a flexible and accessible tool for scientists, enabling the modeling of various
crystal systems, including complex
semiconductors, multilayer epitaxial films, and
oxide crystals. The program's integration of experimental data on ion channeling with defect modeling establishes a robust framework for defect analysis in materials science. The present article expounds upon the simulation capabilities of the program by reproducing the characteristic "elbows" in channeling spectra that were previously observed in experiments conducted on Cu
crystals.
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All authors Przemyslaw Jozwik, Cyprian Mieszczynski, Renata Ratajczak, Andrzej Turos
Plasma Physics
The Ambipolar electric field in multispecies plasma atmospheres: effects of alpha particles and stochastic heating
Luca Barbieri, Pascal Démoulin and Daniel Verscharen
We investigate stationary states of a collisionless, gravitationally stratified
plasma atmosphere composed of electrons,
protons, and alpha particles by extending Pannekoek–Rosseland theory to multispecies and multi-temperature
plasmas. Starting from Liouville's
theorem, we derive the self-consistent ambipolar electric field from kinetic
equilibrium and charge neutrality. For a single-temperature atmosphere, we obtain analytical expressions for the ambipolar field, show its dependence on alpha-particle abundance, and determine the relative stratification of the three species. A first-order analytical approximation to the electrostatic potential accurately reproduces the numerical solution. We then generalize the formalism to multi-temperature
plasmas generated by
stochastic boundary heating, representing the stationary distribution as a superposition of Maxwellian populations. Gravitational filtering produces non-exponential density profiles and increasing temperatures with altitude, while preserving the relative species stratification, with alpha particles most strongly stratified and
protons least. The ambipolar electric field contains a dominant gravitational contribution, corresponding to the generalized Pannekoek–Rosseland field, and a thermoelectric contribution arising from species-dependent temperature gradients, which accounts for its non-monotonic structure. These results provide a framework for studying the combined effects of
plasma composition and
stochastic heating in gravitationally stratified astrophysical
plasmas.
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Optics
Bridging the gap: Using deep learning to reconstruct noise-reduced super-resolved OCT images from gapped spectra
Jonas Nienhaus, Thomas Schlegl, Wolfgang Drexler et al. (+2 more)
Fourier-domain (FD) optical coherence
tomography (OCT) depends on broadband sources to maximize axial resolution and image quality. However, these
lasers significantly drive device cost or may be unavailable at desired wavelength and bandwidth ranges. A potential solution lies in integrating multiple, more affordable sources with lower individual bandwidth into a single system. However, difficulties arise if the resulting spectrum exhibits discontinuities. In this letter, we present a method that can combine OCT images from a flexible number of spectra with arbitrary, possibly non-overlapping gaps using a neural network. Compared to low-resolution input images, reconstructed B-scans are super-resolved, preserve even fine and low-contrast details and edges, and exhibit strong noise reduction that increases with the band gap. The proposed method could thereby provide a major step towards high-quality OCT imaging using spectrally disjoint, low-bandwidth sources. In broadband settings, it can be directly applied as a
Fourier-domain masked autoencoder for self-supervised image quality enhancement.
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All authors Jonas Nienhaus, Thomas Schlegl, Wolfgang Drexler, Tilman Schmoll, Rainer A. Leitgeb
Computational Physics · Cross-listed from astro-ph.HE
Spiral structure from the interference of gravitational eigenmodes in ultralight dark matter halos
Jacob Reinach and Hubert Bray
We use a variety of analytic and numerical techniques to approximate the geometry of individual dark matter
halos when modeled as collections of ultralight scalar
bosons (ULDM), followed by an analysis on the future directions and implications of this work. Ultimately, we aim to understand the morphology and creation of complex structures (like spirals) in
galaxies from a
geometric standpoint and to investigate the connection between dark matter and baryonic matter in
galaxies. We find that superpositions of gravitational eigenmodes for ULDM in a fixed background potential can yield spiral density perturbations which rotate on the order of one hundred million years and appear within ten to twenty kpc of the
halo center, both features comparable to realistic
galaxies, and that this model provides a natural explanation for the density waves necessary to seed baryonic spirals.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Electronic structure, band offset, and interface electron population of the LaInO$_3$/BaSnO$_3$ system
G. Hoffmann, A. A. Riaz, C. Kalha et al. (+7 more)
Perovskite
oxides and their
heterostructures exhibit a wide range of functional properties. Among these materials, BaSnO$_3$/LaInO$_3$
heterostructures form high-mobility two-dimensional electron gases (2DEGs) at their interfaces. In particular, room-temperature electron mobilities exceeding 100~cm$^2$/Vs were enabled by recent advances in thin-film growth. This work presents a combined experimental and theoretical study of the electronic structure of BaSnO$_3$, LaInO$_3$, and BaSnO$_3$/LaInO$_3$
heterostructures with varying LaInO$_3$ overlayer thicknesses. Soft and hard X-ray photoelectron spectroscopy (SXPS and HAXPES) measurements are combined with densities of states (DOS) derived from hybrid density functional theory (DFT) calculations. The analysis of core, semi-core, and valence states allows to arrive at a comprehensive understanding of the chemical bonding and electronic structure in the parent
oxides as well as the formed
heterostructures. For the BaSnO$_3$/LaInO$_3$
heterostructure, the band offset and population of 2DEG states at the interface is directly probed using HAXPES.
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All authors G. Hoffmann, A. A. Riaz, C. Kalha, A. Gloskovskii, C. Schlueter, O. Brandt, W. Aggoune, C. Draxl, O. Bierwagen, A. Regoutz
Accelerator Physics
State-resolved quantum transport of vortex electrons in accelerators
S.S.Baturin
Vortex electrons carry a quantized orbital angular momentum (OAM) degree of freedom, but whether this internal structure can survive repeated transport through an accelerator
lattice remains unclear. Here we formulate a density-
matrix theory for periodic round
lattices and show that the
symmetry-protected quantity is a Lewis-Floquet OAM invariant, rather than the instantaneous kinetic OAM. The classical transfer map lifts to
unitary state
evolution, while
stochastic field errors generate a Lindblad channel. This framework exposes a sharp separation between visibility and state survival. Dipole jitter displaces the wavepacket, rapidly smearing a
vortex signature measured about a fixed origin without altering its recentered internal OAM distribution. Quadrupole fluctuations instead drive genuine $\Delta\ell=\pm2$ leakage. For a matched $n=0$, $|\ell|=1$ mode, white-noise estimates based on representative IOTA and PETRA III parameters give fixed-frame smearing scales of $4.9\times10^2$ and $3.3$ turns, but intrinsic-leakage scales of $2.1\times10^5$ and $2.2\times10^6$ turns, respectively. Thus loss of an unrecentered
vortex image need not signal destruction of the
vortex state: its internal OAM structure can persist hundreds to hundreds of thousands of times longer. Centroid tracking and quadrupole stability are therefore distinct experimental requirements for observability and state survival, respectively.
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