Computational Physics · Cross-listed from astro-ph.SR
Two-Dimensional Kelvin-Helmholtz Instability with Anisotropic Pressure
Shishir Biswas, Masaru Nakanotani, Dinshaw S. Balsara et al. (+2 more)
The Kelvin-Helmholtz (KH) instability occurs in multiple heliospheric (
solar-wind stream interfaces, planetary magnetospheres, cometary tails, heliopause flanks) and interstellar (protoplanetary disks, relativistic jets,
neutron star accretion disks) environments. While the KH instability has been well-studied in the magnetohydrodynamic (MHD) limit, only limited studies were performed in the collisionless regime, which is conducive to development of anisotropic pressures. Collisionless
plasmas are often described using the Chew Goldberger and Low (CGL) equations which feature an anisotropic pressure tensor. This paper presents a comprehensive analysis of the CGL version of the KH instability using linearised and numerical techniques. We find that the largest growth rates and the greatest incidence of
magnetic effects occur in the MHD limit. In the large relaxation time CGL limit, part of the energy goes into the formation of pressure anisotropies, resulting in smaller amounts of energy being available for bending the field lines. Consequently, when we cross-compare CGL and MHD simulations that are otherwise identical, the current densities are largest in the MHD limit, and the largest
magnetic islands also form in that limit. Early and late time formation of pressure anisotropies have also been studied. We also find that the strongest trend for forming intermittencies in the flow also occurs in the MHD limit. The paper also discusses possible consequences of our results for
turbulence and reconnection in the heliosheath (the layer between the
solar wind termination shock and the heliopause).
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All authors Shishir Biswas, Masaru Nakanotani, Dinshaw S. Balsara, Vladimir Florinski, Merav Opher
Fluid Dynamics
A melting mode of frozen sessile droplets with unmelted ice layer deposited at the bottom
Jiawang Cui, Yugang Zhao, Tianyou Wang et al. (+1 more)
Water-repellent properties of superhydrophobic surfaces make them promising for anti-icing and deicing applications. Through experimental visualization of frozen sessile droplets undergoing melting on superhydrophobic surfaces, we identify a melting mode with the unmelted ice layer deposited at the bottom of the melting droplet, even though the density of ice is lower than that of water. In the deposited mode of the melting process, the time required for the frozen droplet to melt completely is much shorter than that in the floating mode. Force analysis shows that the melted fluid flows along the gas-
liquid interface toward the top of the melting droplet, thereby exerting force and then suppressing the upward movement of the unmelted ice layer. Moreover, the flow within the
liquid film formed between the unmelted ice layer and the heating wall is dominated by the viscous force, which has a lubrication effect and maintains the deposition of the unmelted ice layer. High heating temperature, large contact angle, and low particle concentration are helpful for the occurrence of the deposited mode.
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All authors Jiawang Cui, Yugang Zhao, Tianyou Wang, Zhizhao Che
Applied Physics · Cross-listed from quant-ph
Heterogeneous Optically-Detected Spin-Acoustic Resonance in Solid-State Molecular Thin-film
Kuan-Cheng Chen, Yongqiang Wen, Xiaotian Xu et al. (+7 more)
We report an implementation of
spin-acoustic resonance in pentacene thin films integrated on a high-quality-factor (high-Q) surface acoustic wave (SAW) resonator on a lithium niobate substrate. Heterogeneous optically detected
spin-acoustic resonance (HODSAR) is an optically detected
spin-resonance measurement in which the resonant drive is delivered mechanically by a surface acoustic wave (SAW). By leveraging the photo-excited triplet state of pentacene at room temperature, we demonstrate coherent
spin manipulation via acoustic driving under zero externally applied
magnetic field. The heterogeneously integrated device, referred to as HODSAR, utilizes
spin-
phonon coupling to achieve mechanically driven, zero-field
spin resonance, opening avenues for room-temperature mechanically addressable
spin control and device integration. We show that the high-Q multimode response of the SAW resonator enables spectrally selective acoustic addressing of triplet transitions near 105 MHz. Coherent control is evidenced by Rabi oscillations, with a Rabi frequency that increases linearly with the square root of the applied RF input power over the measured drive range, consistent with driven two-level dynamics under acoustic excitation. These results establish
spin-acoustic resonance in a heterogeneously integrated molecular thin-film platform and provide a quantitative basis for benchmarking mechanically mediated
spin control.
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All authors Kuan-Cheng Chen, Yongqiang Wen, Xiaotian Xu, Max Attwood, Jingdong Xu, Chen Fu, Sami Ramadan, Shang Yu, Sandrine Heutz, Mark Oxborrow
Fluid Dynamics
Small Rarefaction, Large Consequences: Limits of Navier Stokes Turbulence Simulations
Songyan Tian and Lei Wu
We conduct numerical simulations of rocket plume impingement on a lunar landing surface using two complementary frameworks: the Boltzmann equation, which naturally captures rarefied gas dynamics, and the Navier Stokes (NS) equations, the conventional workhorse for turbulent flow simulations. We show that subtle rarefaction effects, long considered negligible in turbulent regimes, can become locally dominant within shear layers where viscous stresses predicted by the NS constitutive relation undergo sign reversals. This phenomenon, which we term constitutive degeneracy, produces order-one relative errors in predicted surface shear stress and heat flux. Our results demonstrate that
turbulence can expose hidden limits of NS equations with broad implications for high-speed aerodynamics and planetary exploration.
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Applied Physics
Germanium Thermophotovoltaic Devices Achieving 7.3% Efficiency Under High-Temperature Emission by Empirical Calorimetry
A. M. Medrano, E. Lopez, Pablo Garcia-Linares et al. (+6 more)
We report the first empirical efficiency measurement of germanium-based thermophotovoltaic devices under high-temperature, high-irradiance conditions using a high view-factor calorimetric setup. Two TPV
cell architectures were fabricated on p-type, highly doped (10^17 cm-3) Ge substrates, differing only in rear contact configuration. A standard device with a gold rear contact achieves a peak efficiency of 7.3 % and a power density of 1.77 W/cm2 at an emitter temperature of 1480 C, while a PERC-type device reaches 6.3 % efficiency and 1.22 W/cm2 at 1426 C. The superior performance of the standard device is attributed to lower series resistance, whereas the PERC design exhibits slightly higher efficiency at lower emitter temperatures (4.0 % vs. 3.8 % at 1150 C) due to enhanced rear-surface reflectivity. A detailed TPV model has been developed and validated across both device architectures. The model identifies out-of-band optical losses as the dominant efficiency-limiting mechanism, primarily caused by strong free-carrier absorption in the highly doped Ge substrate. Using this model, we predict device performance under idealized spectral conditions commonly assumed in prior literature. For a simulated AlN/W spectrally selective emitter, efficiencies as high as 22.3 % at 1800 C are obtained, consistent with previous semi-empirical predictions. In contrast, when previously reported Ge devices are modeled under the realistic graphite emitter spectrum used here, projected efficiencies decrease to as low as 8.1 % at 1480 C. These results show that earlier projections remain valid but idealized and underscore the importance of emitter spectral engineering and substrate optimization. Finally, we present the first direct comparison of Ge and InGaAs TPV devices under identical conditions, demonstrating the superior performance of InGaAs while confirming the cost-driven competitiveness of Ge.
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All authors A. M. Medrano, E. Lopez, Pablo Garcia-Linares, J. Villa, M. Gamel, M. Garin, I. Martin, C. Canizo, A. Datas
Plasma Physics
Preprint: Sheath thickness measurements with the biased plasma impedance probe, Agreement with Child Langmuir scaling
John Whitlock Brooks and Richeek Dutta
Plasma sheaths play a central role in
plasma-surface interactions, yet their thickness remains challenging to measure experimentally. Although classical analytical models such as the Child-Langmuir (CL) sheath model provide clear predictions for sheath thickness, experimental validation has been limited because most diagnostics either rely on indirect, multi-step inference (e.g., Langmuir probes) or require invasive and technically demanding techniques. In this work, we demonstrate that the
plasma impedance probe (PIP), when operated with a controlled DC bias, enables relatively direct, model-informed measurements of sheath thickness that are reasonably straightforward to implement experimentally. Across a range of discharge conditions, biased-PIP sheath thickness measurements are found to follow CL scaling closely, requiring a single, consistent empirical correction factor of $\alpha \approx 0.74$ to reconcile the measured thickness with CL predictions. Concurrent measurements of
plasma density and electron damping show that probe biasing does not significantly perturb the bulk
plasma density, supporting the validity of the biased-PIP approach. Building on this validation, we leverage the empirically determined $\alpha$ factor to extend the floating (unbiased) PIP analysis to obtain model-dependent estimates of electron temperature and
plasma potential without electrical biasing. A side-by-side comparison demonstrates close agreement between floating-PIP results and those obtained from a biased Langmuir probe. Taken together, these results establish the PIP as a complementary diagnostic to the Langmuir probe, expanding the range of accessible
plasma measurements while providing experimental support for classical sheath models.
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Biological Physics
Cell strain-stiffening drives cell breakout from embedded spheroids
Shabeeb Ameen, Kyungeun Kim, Ligesh Theeyancheri et al. (+5 more)
Understanding how
cells escape from embedded spheroids requires a mechanical framework linking stress generation within
cells, across
cells, and between
cells and the surrounding extracellular
matrix (ECM). We develop such a framework by coupling a 3D vertex model of a spheroid to a fibrous ECM network and deriving a 3D Cauchy stress tensor for deformable polyhedral
cells, enabling direct
cell-level stress quantification in three dimensions. We analyze maximum shear stress in solid-like and fluid-like spheroids: solid-like spheroids exhibit broader stress distributions and radial stress gradients, while fluid-like spheroids show lower stresses with weak spatial organization.
Cell shape anisotropy is not generically aligned with principal stress directions, indicating that morphology alone is an unreliable proxy for mechanical state. We further demonstrate strain stiffening at the single-
cell level, where elongation produces nonlinear increases in maximum shear stress, allowing boundary
cells in otherwise low-stress, fluid-like spheroids to transiently generate forces sufficient to remodel the
matrix. To connect strain-induced stress amplification to invasion modes, we introduce an extended 3D vertex model with explicit, tunable
cell-
cell adhesion springs. In this minimal mechanical framework, single-
cell breakout results from strain stiffening combined with reduced adhesion, whereas multi-
cell streaming additionally requires anisotropic adhesion strengthened along the elongation axis and weakened orthogonally. Together, these results identify distinct mechanical pathways coupling
cell strain, stress amplification, and adhesion organization to spheroid invasion.
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All authors Shabeeb Ameen, Kyungeun Kim, Ligesh Theeyancheri, Minh Thanh, Mingming Wu, Alison E. Patteson, J. M. Schwarz, Tao Zhang
Chemical Physics
Influence of octupole field on quadrupole mass filter performance in the second stability zone
Anushree Dutta, Pintu Mandal and Nabanita Deb
Radial asymmetry in a quadrupole mass filter (QMF), introduced by symmetric displacement of a diagonally opposite rod pair, modifies the confinement potential and alters the ion stability characteristics. In this work, the influence of such radial asymmetry on QMF operation in the second stability zone is investigated through simulations. Using an existing potential formulation for a radially asymmetric QMF, the stability diagram in the second stability zone is extracted for the first time, revealing a systematic shift of the stability apex with the asymmetry parameter. Radial asymmetry introduces additional multipole components, notably an octupole term whose magnitude scales with the asymmetry parameter and whose sign depends on the DC polarity applied to the displaced rods. Transmission simulations show that the transmission peak shifts in accordance with the displaced stability apex, while the resolution exhibits a strong dependence on both the asymmetry parameter and the DC polarity. Comparable maximum resolution is obtained for inward and outward displacements under suitable polarity configurations, with outward displacement providing higher transmission efficiency due to an increased effective aperture. These results demonstrate that controlled radial asymmetry provides an effective means to tailor the resolution and transmission characteristics of QMFs operating in the second stability zone.
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Fluid Dynamics
On the vortex transport and blade interactions in a reversible pump-turbine
Chirag Trivedi
Pumped storage type hydropower plants play an important role in mitigating real-time energy flexibility. Reversible pump-turbines undergo extreme operating conditions such as runaway and speed-no-load. Very limited studies are undertaken to understand the
stochastic flow under these conditions in the reversible pump-turbine. The present study investigates the unsteady vortical flow, its transportation, and interaction with the blades at speed-no-load. Large eddy simulations are conducted in both turbine and pump modes. The computational domain contains 120 million nodes. Numerical results provided evidence of a large longitudinal
vortex that develops on the high-pressure side of the blade, and transports into the blade passage and develops the unsteady "string of swirls". The results also showed another "string of swirls" in the draft tube, where flow in the center is reversible (pumping). The resulting flow instability is very high, and it has the potential to induce fatigue damage to the blades.
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Optics
Chiral phase memory of twisted light through multiple scattering
Igor Meglinski, Anton Sdobnov and Alexander Bykov
Chiroptical signals, optical responses sensitive to molecular handedness, are rapidly suppressed by multiple scattering, fundamentally limiting their use in turbid media. Here we show that coupling molecular chirality to the topological structure of twisted light generates a protected phase observable that survives strong scattering. When Laguerre-Gaussian beams carrying orbital angular momentum propagate through
chiral media,
spin-orbit interaction converts circular birefringence into an azimuthal rotation of the helical wavefront. Remarkably, this
chiral phase
memory persists at scattering strengths that fully depolarize conventional beams, with the rotation magnitude preserved quantitatively between transparent solutions and strongly scattering tissue. The sign of the azimuthal rotation encodes molecular handedness: opposite enantiomers produce mirror-symmetric phase maps even after multiple scattering. Differential measurements between conjugate topological charges isolate the
chiral contribution while cancelling achiral background, enabling the resolution of refractive-index changes of order 10-6. These results establish topological phase observables as robust carriers of weak
chiral light-matter interactions in complex media, opening new routes for chiroptical spectroscopy and sensing beyond the ballistic-
photon regime.
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Computational Physics · Cross-listed from cs.CV
A Machine Learning accelerated geophysical fluid solver
Yang Bai
Machine learning methods have been successful in many areas, like image classification and natural
language processing. However, it still needs to be determined how to apply ML to areas with mathematical constraints, like solving PDEs. Among various approaches to applying ML techniques to solving PDEs, the data-driven discretization method presents a promising way of accelerating and improving existing PDE solver on structured grids where it predicts the coefficients of quasi-linear stencils for computing values or derivatives of a function at given positions. It can improve the accuracy and stability of low-resolution simulation compared with using traditional finite difference or finite volume schemes. Meanwhile, it can also benefit from traditional numerical schemes like achieving conservation law by adapting finite volume type formulations. In this thesis, we have implemented the shallow water equation and Euler equation classic solver under a different framework. Experiments show that our classic solver performs much better than the Pyclaw solver. Then we propose four different deep neural networks for the ML-based solver. The results indicate that two of these approaches could output satisfactory solutions.
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Optics
Enhanced third harmonic response of the PtTe$_2$ transition metal dichalcogenide
Leone Di Mauro Villari, Simone Grillo, Olivia Pulci et al. (+3 more)
We investigate the third harmonic response of platinum ditelluride (PtTe$_2$), a Dirac semimetal belonging to the transition metal dichalcogenides class. Due to its topological properties, this material has drawn a lot of
attention, particularly because it hosts type-II (super-critically tilted) Dirac
fermions in the $\rm A-\Gamma-\rm A$ high
symmetry direction. Adopting a low-energy model fitted directly from density functional theory band structure simulations, we calculate analytically the nonlinear conductivity. We observe that third-order optical nonlinearities are efficiently modulated by the cones tilting, which produces a significant enhancement of the nonlinear susceptibility. Our results, besides shedding light on topological transitions of platinum ditelluride, are relevant for future nanophotonic devices exploiting the tunable nonlinear properties of type-II Dirac
fermions.
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All authors Leone Di Mauro Villari, Simone Grillo, Olivia Pulci, Salvatore Macis, Stefano Lupi, Andrea Marini
Optics
Compact linearly uncoupled resonators for efficient spontaneous parametric downconversion via angular phase matching
Alessia Stefano, Matteo Piccolini and Marco Liscidini
We report an integrated platform for efficient second-order nonlinear interactions based on linearly uncoupled resonators and angular phase matching. The proposed architecture confines phase control to a limited section of the device, maximizing field enhancement and effective nonlinear interaction length while simultaneously reducing the overall footprint. As an example we show the results for an AlGaAs-on-
insulator structure demonstrating a
photon-pair generation rate of 3.16 GHz/mW in the continuous-wave regime and 5.89 MHz under pulsed pumping. The generated biphoton state exhibits a Schmidt number K=1.02, indicating nearly uncorrelated
photon pairs. The compact and reconfigurable nature of this approach, together with its independence from material-specific poling techniques, makes it applicable to a broad class of integrated $\chi_2$ nonlinear platforms.
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Accelerator Physics
Modelling Conduction Cooling of Superconducting Accelerator Magnets using a Thermal Thin Shell Approximation
Emma Vancayseele, Erik Schnaubelt, Louis Denis et al. (+3 more)
Understanding the thermal behaviour of superconducting accelerator magnets is essential to ensure their stable and reliable operation. This work presents an extension of the Finite Element Quench Simulator (FiQuS) Multipole module to include collar and pole regions of accelerator magnets, which influences the overall thermal response. A thermal thin shell approximation (TSA), which is shown to be effective from previous works, is employed to model thermal insulation layers efficiently, replacing an insulation surface mesh. The main novelty of this work lies in the development of a method to model the thermal connection between the magnet winding and the collar and pole regions via the TSA. To assess the accuracy and computational efficiency of this method, temperature and field variations are computed for a current ramp-up scenario. The thermal solution is coupled to a fully resolved magnetodynamic solution to capture the interaction between thermal and electromagnetic behaviour. The results obtained with the TSA are then compared to classical finite element (FE) solutions with explicitly meshed insulation domains. The TSA predicts the maximum temperature within 2-4 % of the reference solution while substantially reducing mesh complexity and achieving up to a 5 times speed-up in computation time. While the TSA has traditionally been employed for short-duration quench simulations with high heat fluxes between magnet turns, these results demonstrate its reliability and efficiency for current ramp scenarios with low heat fluxes, significantly expanding its application range beyond what has been previously reported in the literature. To illustrate potential applications of this new functionality, conduction cooling through the collar region is studied, comparing different cooling configurations and collar materials.
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All authors Emma Vancayseele, Erik Schnaubelt, Louis Denis, Christophe Geuzaine, Arjan Verweij, Mariusz Wozniak
Fluid Dynamics
Fully coupled implicit finite-volume algorithm for viscoelastic interfacial flows
Ayman Mazloum, Gabriele Gennari, Fabian Denner et al. (+1 more)
A fully coupled implicit finite-volume
algorithm for incompressible viscoelastic interfacial flows is proposed, whereby the viscoelasticity of the flow is described by an upper-convected Maxwell constitutive model, including limited extensibility and shear-thinning behaviour. The governing equations describing the conservation of continuity and momentum, as well as the constitutive model are discretized using standard finite-volume methods and are solved for pressure, velocity and the
polymer stress tensor in a single linear system of equations. Treating all terms of the linearized and discretized governing equations implicit in velocity, pressure and/or the components of the
polymer stress tensor, a tightly coupled system of equations is obtained. The interface separating the interacting bulk phases and the surface tension acting at the fluid interface are modelled using a state-of-the-art front-tracking method. We demonstrate the capabilities of the proposed numerical framework with four representative test cases, including the deformation of a viscoelastic droplet in shear flow at large Weissenberg numbers of up to Wi=10^4, and the jump discontinuity of the rise velocity of a bubble rising in a viscoelastic
liquid as a result of a "negative wake". Contrary to previous studies using segregated
algorithms, the proposed fully coupled implicit
algorithm does not apply or require a log-conformation approach to predict these flows. Overall, the fully implicit coupled front-tracking formulation provides a robust framework to reliable numerical predictions of strongly elastic interfacial flows at large Weissenberg numbers.
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All authors Ayman Mazloum, Gabriele Gennari, Fabian Denner, Berend van Wachem
Optics
Topological beam stirring in a multicore fiber
Alena Kolesnikova, Mikhail Gervaziev, Nikita Bochkarev et al. (+3 more)
Multicore fibers (MCF) are perspective media for telecommunications, sensing, imaging and
laser technologies. Here, the effect of beam stirring between weakly coupled cores is observed for sub-nanosecond transform-limited pulses of several kW peak power propagating in ~10 m long 7-core fiber, for the first time to our knowledge. In contrast to low-power domain where the output power distribution in the cores is random with large fluctuations sensitive to fiber disturbances, at high power of the input pulse injected in the central core the output power becomes equalized between the cores with fluctuations reduced to <5% being insensitive to disturbances. Similar behavior is observed in cut-back experiments showing that equi-partition is approached at a distance of ~5 m. The performed modeling describes well the experimental results and clarifies mechanisms of the new effect reasoned by a large nonlinear phase shift changing along the pulse and thereby resulting in statistical averaging over the pulse length of multidirectional power transfer processes between cores, thus leading to the robust
equilibrium (equi-partitition for hexagonal MCF
topology). At the same time, the combined output beam measured in a far field takes a stable bell-shaped profile instead of speckled beam at low powers, similar to the beam self-cleaning effect in multimode fibers.
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All authors Alena Kolesnikova, Mikhail Gervaziev, Nikita Bochkarev, Denis Kharenko, Evgeny Podivilov, Sergey Babin
Plasma Physics
JOREK simulations of the X-point radiator formation and its movement in ASDEX Upgrade
Y. C. Liang, A. Cathey, M. Hoelzl et al. (+7 more)
Future large-scale
magnetic confinement fusion reactors require operational regimes that can avoid extreme heat fluxes onto the
plasma-facing components. One promising regime is the X-point radiator (XPR), which relies on a highly radiative, cold and dense
plasma volume forming above the X-point, and which can be accessed via
impurity seeding. Experimentally, the height of the XPR can be controlled by adjusting the seeding rate and heating power. This contribution presents axisymmetric (2D) simulations of the XPR regime in ASDEX Upgrade using the nonlinear MHD code JOREK extended with a kinetic particle framework for the main species neutrals and nitrogen
impurities. With the time-dependent simulations, the progression from attached divertors to a complete detachment with the XPR formation is shown, highlighting the effects of the neutrals and
impurities separately. Amidst this progression, the formation and the loss of the high-field-side high-density are observed. After the XPR is well-formed at the height of 6.8 cm, the fuelling and seeding rates are adjusted so that the XPR remains stationary. From the stationary case, the seeding rate is then changed to see how the XPR location reacts. By increasing and decreasing the seeding rate, the XPR responds by moving upwards and downwards, respectively. These simulations show JOREK's capability of simulating time-varying XPR, which will provide a baseline for the transition to 3D simulations, so the MHD activities and their interaction with the XPR can be studied.
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All authors Y. C. Liang, A. Cathey, M. Hoelzl, S. Q. Korving, M. Szucs, O. Pan, D. Maris, F. Antlitz, the JOREK Team, the ASDEX Upgrade Team
Computational Physics
Tikhonov regularization-based reconstruction of partial scattering functions obtained from contrast variation small-angle neutron scattering
Manabu Machida and Koichi Mayumi
Contrast variation small-angle
neutron scattering (CV-SANS) has been widely employed for nano structural analysis of multicomponent systems. In CV-SANS experiments, scattering intensities of samples with different scattering co\ ntrasts are decomposed into partial scattering functions, corresponding to structure of each component and cross-correlation between different components, by singular value decomposition (SVD). However, the estimation of partial scattering functions with small absolute values often suffers from instability due to the significant differences in the singular values. In this paper, we propose a remedy for this instability by introducing the Tikhonov regularization, which ensures more stable reconstruction of the partial scattering functions.
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Fluid Dynamics
The Impact of Turbulence on Hydroacoustic Waves
Kai-Xin Hu and Yue-Jin Hu
Traditional research suggests that when sound waves pass through a turbulent region, scattering occurs, causing the incident wave to attenuate and wave parameters to fluctuate. In contrast, our previous paper reported a new phenomenon in which
turbulence causes changes in the amplitude of sound waves, a change that cannot be explained by scattering or resonance (HU, K.X, & HU, Y. J. 2025. Hydroacoustic Absorption and Amplification by
Turbulence. arXiv:2512.07920). This work presents a more in-depth investigation into the impact of
turbulence on hydroacoustic waves, including phase changes, amplification factors and the temporal
evolution of the acoustic wave. Experiments indicate that
turbulence simultaneously changes both the amplitude and phase of acoustic waves. The total phase shift along the entire pipe equals the sum of the phase shifts of the segments. Both the amplification factor and the phase shift due to
turbulence vary periodically with frequency. In pipe flow, after the valve is closed, the temporal
evolution of the acoustic waves during the subsequent
turbulence decay process can be classified into six types. Acoustic waves with frequencies below and above specific thresholds are essentially unaffected by
turbulence. In addition,
vortices and unsteady flow in the laminar state do not cause changes in the amplitude and phase of sound waves, showing the essential difference between turbulent fluctuations and the two.
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Applied Physics
Estimation of Fish Catch Using Sentinel-2, 3 and XGBoost-Kernel-Based Kernel Ridge Regression
Kanu Mohammed, Vaishnavi Joshi, Pranjali Diliprao Patil et al. (+3 more)
Oceanographic factors, such as sea surface temperature and upper-ocean dynamics, have a significant impact on fish distribution. Maintaining fisheries that contribute to global food security requires quantifying these connections. This study uses multispectral images from Sentinel-2 MSI and Sentinel-3 OLCI to estimate fish catch using an Extreme Gradient Boosting (XGBoost)-kernelized Kernel Ridge Regression (KRR) technique. According to model evaluation, the XGBoost-KRR framework achieves the strongest correlation and the lowest prediction error across both sensors, suggesting improved capacity to capture nonlinear ocean-fish connections. While Sentinel-2 MSI resolves finer-scale spatial variability, emphasizing localized ecological interactions, Sentinel-3 OLCI displays smoother spectral responses associated with poorer spatial resolution. By supporting sustainable ecosystem management and strengthening satellite-based fisheries assessment, the proposed approach advances SDGs 2 (Zero Hunger) and 14 (Life Below Water).
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All authors Kanu Mohammed, Vaishnavi Joshi, Pranjali Diliprao Patil, Sandipan Mondal, Ming-An Lee, Subhadip Dey
Computational Physics
An intramembranous ossification model for the in-silico analysis of bone tissue formation in tooth extraction sites
Jennifer Paola Corredor-Gómez, Andrés Mauricio Rueda-Ramírez, Miguel Alejandro Gamboa-Márquez et al. (+2 more)
The accurate modeling of biological processes allows to predict the spatio-temporal behavior of living tissues by computer-aided (in-silico) testing, a useful tool for the development of medical strategies, avoiding the expenses and potential ethical implications of in-vivo experimentation. A model for bone healing in mouth would be useful for selecting proper
surgical techniques in dental procedures. In this paper, the formulation and implementation of a model for Intramembranous Ossification is presented aiming to describe the complex process of bone tissue formation in tooth extraction sites. The model consists in a mathematical description of the mechanisms in which different types of
cells interact, synthesize and degrade extra-cellular
matrices under the influence of biochemical factors. Special
attention is given to angiogenesis, oxygen-dependent effects and growth factor-induced apoptosis of fibroblasts. Furthermore, considering the depth-dependent vascularization of mandibular bone and its influence on bone healing, a functional description of the
cell distribution on the severed periodontal ligament (PDL) is proposed. The developed model was implemented using the finite element method (FEM) and successfully validated by simulating an animal in-vivo experiment on dogs reported in the literature. A good fit between model outcome and experimental data was obtained with a mean absolute error of 3.04%. The mathematical framework presented here may represent an important tool for the design of future in-vitro and in-vivo tests, as well as a precedent for future in-silico studies on osseointegration and mechanobiology.
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All authors Jennifer Paola Corredor-Gómez, Andrés Mauricio Rueda-Ramírez, Miguel Alejandro Gamboa-Márquez, Carolina Torres-Rodríguez, Carlos Julio Cortés-Rodríguez
Instrumentation and Detectors
A Comparative Analysis of the CERN ATLAS ITk MOPS Readout: A Feasibility Study on Production and Development Setups
Lukas Flad, Felix Sebastian Nitz and Tobias Krawutschke
The upcoming High-Luminosity upgrade of the Large
Hadron Collider (LHC) necessitates a complete replacement of the ATLAS Inner Detector with the new Inner Tracker (ITk). This upgrade imposes stringent requirements on the associated Detector Control System (DCS), which is responsible for the monitoring, control, and safety of the detector. A critical component of the ITk DCS is the Monitoring of Pixel System (MOPS), which supervises the local voltages and temperatures of the new pixel detector modules. This paper introduces a dedicated testbed and verification methodology for the MOPS readout, defining a structured set of test cases for two DCS-readout architectures: a preliminary Raspberry Pi-based controller, the "MOPS-Hub Mock-up"(MH Mock-up), and the final production FPGA-based "MOPS-Hub" (MH). The methodology specifies the measurement chain for end-to-end latency, jitter, and data integrity across CAN and UART interfaces, including a unified time-stamping scheme, non-intrusive signal taps, and a consistent data-logging and analysis pipeline. This work details the load profiles and scalability scenarios (baseline operation, full-crate stress, and CAN Interface Card channel isolation), together with acceptance criteria and considerations for measurement uncertainty to ensure reproducibility. The objective is to provide a clear, repeatable procedure to qualify the MH architecture for production and deployment in the ATLAS ITk DCS. A companion paper will present the experimental results and the comparative analysis obtained using this testbed.
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Biological Physics
Emergence of Superintelligence from Collective Near-Critical Dynamics in Reentrant Neural Fields
Byung Gyu Chae
Superintelligence is commonly envisioned as a quantitative extrapolation of human cognitive abilities driven by scale and computational power. Here we show that qualitative transitions in intelligence instead arise as dynamical phase transitions governed by collective critical dynamics. Building on a unified dynamical field-theoretic framework for cognition, we demonstrate that progressive collective coupling generated by reentrant mixing drives the system toward an infrared critical regime in which an extensive band of slow collective modes emerges. This spectral condensation reorganizes cognitive dynamics from localized relaxation to coherent motion along emergent low-dimensional
manifolds. Through numerical analysis of the time-scale density of states, we identify robust power-law scaling of collective relaxation rates with well-defined critical exponents, placing the system within the universality class of self-organized critical many-body dynamics. Criticality alone would generically lead to instability. We further show that homeostatic regulation introduces a gapped stabilizing direction that protects the collective critical sector, yielding a dynamically maintained meta-stable infrared phase in which long-lived inference trajectories persist without collapse. The coexistence of scale-free collective dynamics and global stabilization defines a protected sector-critical regime in which coherence and internal flexibility coexist. Superintelligence therefore corresponds to a distinct dynamical stability class–a self-organized critical phase embedded within a stabilized cognitive
manifold–rather than a smooth quantitative continuation of existing cognitive systems.
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Atomic Physics · Cross-listed from quant-ph
A building block of quantum repeaters for scalable quantum networks
Wen-Zhao Liu, Ya-Bin Zhou, Jiu-Peng Chen et al. (+26 more)
Quantum networks, integrating
quantum communication,
quantum metrology, and distributed
quantum computing, could provide secure and efficient information transfer, high-resolution sensing, and an exponential speed-up in information processing. Deterministic
entanglement distribution over long distances is a prerequisite for scalable
quantum networks, enabling the utilization of device-independent
quantum key distribution (DI-QKD) and
quantum teleportation to achieve secure and efficient information transfer. However, the exponential
photon loss in optical fibres prohibits efficient and deterministic
entanglement distribution.
Quantum repeaters, incorporating
entanglement swapping and
entanglement purification with
quantum memories, offer the most promising means to overcome this limitation in fibre-based
quantum networks. Despite numerous pioneering efforts toward realizing
quantum repeaters, a critical bottleneck remains, as remote
memory-
memory entanglement suffers from decoherence more rapidly than it can be established and purified over long distances. We overcome this by developing long-lived trapped-ion
memories, an efficient telecom interface, and a high-visibility single-
photon entanglement protocol. This allows us to establish and maintain
memory-
memory entanglement over a 10 km fibre within the average
entanglement establishment time for the same distance. As a direct application, we demonstrate metropolitan-scale DI-QKD, distilling 1,917 secret keys out of 4.05*10^5 Bell pairs over 10 km. We further report a positive key rate over 101 km in the asymptotic limit, extending the achievable distance by more than two orders of magnitude. Our work provides a critical building block for
quantum repeaters and marks an important step toward scalable
quantum networks.
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All authors Wen-Zhao Liu, Ya-Bin Zhou, Jiu-Peng Chen, Bin Wang, Ao Teng, Xiao-Wen Han, Guang-Cheng Liu, Zhi-Jiong Zhang, Yi Yang, Feng-Guang Liu, ChaoHui Xue, Bo-Wen Yang, Jin Yang, Chao Zeng, Du-Ruo Pan, Ming-Yang Zheng, Xing-Jian Zhang, Cao Shen, Yi-Zheng Zhen, You Xiao, Hao Li, Li-Xing You, XiongFeng Ma, Qi Zhao, Feihu Xu, Ye Wang, Yong Wan, Qiang Zhang, Jian-Wei Pan
Plasma Physics
Azimuthally polarized terahertz radiation generation using radially polarized laser pulse in magnetized plasma
Shivani Aggarwal, Dinkar Mishra, Saumya Singh et al. (+2 more)
An analytical formulation of a radially polarized
laser pulse propagating in a homogeneous, magnetized
plasma is presented using Lorentz force, continuity and Maxwells equations. Perturbation technique and quasi-static approximation (QSA) have been used to study the generated fields in nonlinear regime. The generated slow, oscillating, transverse electric and
magnetic fields having equal amplitude, constitute a radiation field having frequency in the terahertz (THz) range. Particle-in-
cell (PIC) simulation code FBPIC is used to validate analytical findings. Simulation studies also show that the generated THz radiation field propagates beyond the
plasma boundary, indicating coherent electromagnetic radiation emission. Furthermore, the field amplitude scales nonlinearly with
plasma density and increases linearly with external
magnetic field strength, highlighting the role of these parameters in controlling radiation amplitude.
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All authors Shivani Aggarwal, Dinkar Mishra, Saumya Singh, Bhupesh Kumar, Pallavi Jha
Optics
CSPR-Net: Self-supervised Curved Surface Projection Rectification Network for Geometric Distortion Correction in Non-planar Projections
Kejin Peng, Jia Wei and Xiang Hao
Projecting images onto non-planar surfaces inevitably introduces
geometric distortions that degrade visual quality. Traditional correction methods often require tedious manual calibration or structured light sequences to establish pixel-wise correspondences. In this paper, we develop the Curved Surface Projection Rectification Network (CSPR-Net), a self-supervised deep learning framework for automated distortion correction. Our approach employs dual coordinate-based neural networks to learn the bi-directional mapping between the projector and camera spaces. By enforcing a robust cycle-consistency constraint, CSPR-Net autonomously resolves complex
geometric transformations without requiring ground-truth deformation fields. Furthermore, a gradient-based loss function is introduced to mitigate the impact of complex ambient light interference and accurately capture high-frequency
geometric variations. Quantitative evaluations in physical experimental scenarios demonstrate that CSPR-Net achieves a 20.7% improvement in end-to-end fidelity (SSIM) and outperforms the
polynomial baseline by 3.8% and 5.4% in forward and inverse mapping in terms of SSIM respectively, effectively generating high-precision pre-warped images for seamless projection.
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Optics
Optimizing Spectral Prediction in MXene-Based Metasurfaces Through Multi-Channel Spectral Refinement and Savitzky-Golay Smoothing
Shujaat Khan, Waleed Iqbal Waseer and Muhammad Shahid Jabbar
The prediction of electromagnetic spectra for MXene-based
solar absorbers, where MXenes are a family of two-dimensional transition metal carbides and nitrides, is a computationally intensive task traditionally addressed using full-wave solvers. This study introduces an efficient deep learning framework incorporating transfer learning, multi-channel spectral refinement, and Savitzky-Golay smoothing to accelerate and enhance spectral prediction accuracy. The proposed architecture leverages a pretrained MobileNet version 2 model, fine-tuned to predict 102-point absorption spectra from ($64\times64$) metasurface designs. Additionally, the multi-channel spectral refinement module processes the feature map through multiple convolutional channels, enhancing feature extraction, while Savitzky-Golay smoothing mitigates high-frequency noise. Experimental evaluations demonstrate that the proposed model significantly outperforms baseline convolutional neural network and deformable convolutional neural network models, achieving an average root mean squared error of 0.0227, coefficient of determination ($R^2$) of 0.9563, and peak signal-to-noise ratio of 33.10 decibels. The proposed framework presents a scalable and computationally efficient alternative to conventional solvers, positioning it as a viable candidate for rapid spectral prediction in nanophotonic design workflows.
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Instrumentation and Detectors
Geometry-driven impact of photosensor placement on S2-based XY reconstruction in a dual-phase argon TPC
Jilong Yin and Yi Wang
Accurate reconstruction of the horizontal vertex $(x,y)$ from the S2 electroluminescence pattern is essential for fiducialization and background rejection in dual-phase argon time projection chambers. In this work, we perform a Geant4-based simulation study using the G4DS framework to investigate how detector geometry, in particular the distance between the top photodetector plane and the gas pocket, impacts S2-based XY reconstruction. A compact dual-phase argon TPC instrumented with seven Hamamatsu R8520-506 PMTs is simulated with electron
recoils at 41.5 keV (corresponding to the ${}^{83m}\mathrm{Kr}$ calibration energy), as well as 1.0 keV to probe the low-S2 regime. The PMT array height is scanned from 0 mm to 50 mm, and XY positions are reconstructed using a geometrical solid-angle (GSA) method with the S2 emission modeled by 1 mm-thick slices across the 7 mm gas pocket. The results show a clear non-monotonic dependence of reconstruction bias and resolution on PMT height, driven by the trade-off between S2 light sharing and
photon statistics. These findings provide guidance for geometry optimization in future low-threshold dual-phase argon detectors and will be validated with upcoming prototype measurements.
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Fluid Dynamics
High-resolution numerical simulations of turbulent non-catalytic reverse water gas shift
Nils Erland L. Haugen, Axel Brandenburg, Ewa Karchniwy et al. (+5 more)
A green transition in aviation requires a drastic upscaling of Sustainable Aviation Fuel (SAF). The power-to-
liquid process for the production of CO2-neutral jet fuel via electricity, called e-SAF, directly replaces fossil jet fuel without having to change infrastructure, aeroplanes, or jet-engines. The process combines green hydrogen with industrial exhaust gas, or captured carbon dioxide, in a circular economy concept. A key element of the e-SAF production plant is the reactor where syngas is produced. Traditional reactors use catalytic technology, which faces severe challenges due to the reduced performance over time because of catalyst degradation, clogging, and breakup due to embrittlement. A high-potential alternative is the catalyst-free reverse water-gas-shift (RWGS) reactor concept. The primary aim of this paper is to investigate the fundamental aspects of the catalyst-free RWGS process, such as reaction kinetics and the interactions between
turbulence and chemistry. The secondary aim is to identify how a typical combustion subgrid scale models for Large Eddy Simulations (LES) perform when the chemical reactions are endothermic, in contrast to the strong endothermicity associated with classical combustion. It is found that even small traces of O2 in the CO2 stream can significantly increase the production rate of CO. This is attributed to the increased pool of OH. The effect is strongest at atmospheric pressure and less pronounced at higher pressure. By using the temporal jet framework to study
turbulence-chemistry interactions, an algebraic equation for the prediction of the CO conversion time in a turbulent flow as a function of Damkohler number and chemical timescale is employed. Finally, it is concluded that the PaSR LES subgrid model designed for combustion reactions perform well also for the endothermic reverse water-gas-shift reaction.
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All authors Nils Erland L. Haugen, Axel Brandenburg, Ewa Karchniwy, Ole Hauke Heinz Meyer, Åsmund Ervik, Hursanay Fyhn, Ladan Samaei, Bjørn Bringedal
Optics
Wide-angle emission in cylindrical moiré lattices enabled by rolling origami
Min Tang, Fanzhou Lv, Haiyun Dong et al. (+8 more)
Twisted photonic
lattices that form moiré superlattices have attracted significant
attention owing to their unique properties, such as strong field confinement and high-quality factors, in which the localized optical modes can serve as efficient light sources. However, in conventional moiré
lattices, the emission direction of confined modes is typically fixed, and achieving a broad range of emission angles through simple modulation remains a significant challenge. Here, we design and fabricate single-layer moiré photonic
lattices into cylindrical geometries using a nanomembrane origami technique. This approach enables wide-angle localized-mode emission while maintaining stable single-mode operation and excellent spectral uniformity. The moiré supercells support localized flat-band modes under various effective twist angles, resulting in the observation of periodic localized-mode emission over a wide range of azimuthal angles. Our research provides an approach for developing moiré light sources on curved surfaces, offering significant potential in applications that demand spatial light control, including three dimensional imaging, light detection and ranging, and topological states manipulation.
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All authors Min Tang, Fanzhou Lv, Haiyun Dong, Jiawei Wang, Chaoyuan Jin, Tun Cao, Ching Hua Lee, Ronny Thomale, Sebastian Klembt, Yana Vaynzof, Libo Ma