Instrumentation and Detectors
Terrestrial Test of Shapiro Time Delay: Forth test of Einstein General Theory of Relativity
Farhad Hakimi and Hosain Hakimi
The Shapiro time delay is one of the four classical tests of Einstein general theory of relativity and is commonly interpreted as a constrain on the parametrized post Newtonian (PPN) parameter gamma, which is exactly unity in general relativity. To date all measurement of the Shapiro time delay have been confined to astrophysical and
solar system observations, yielding constrains on the PPN parameter gamma at the 10-5 level. In this work, we propose a fiber based Sagnac interferometer for precision terrestrial measurements of the Shapiro time delay, enabling a laboratory scale determination of gamma with an intrinsic sensitivity approaching 10-9. This approach provides an independent test of general relativity in a previously unexplored regime.
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Physics and Society
Coupling with opinion dynamics promotes prosocial behavior in multilayer networks
Jnanajyoti Bhaumik and Naoki Masuda
Various theoretical and empirical studies have accounted for why humans cooperate in competitive environments. Although prior work has revealed that network structure and multiplex interactions can promote cooperation, most theory assumes that individuals play dilemma games in all social contexts. However, real-world
agents may participate in a diversity of interactions, not all of which present dilemmas. We develop an evolutionary game model on multilayer networks in which one layer supports the prisoner's dilemma game, while the other follows constant-selection dynamics, representing biased but non-dilemmatic competition, akin to opinion or fad spreading. Our theoretical analysis reveals that coupling a social dilemma layer to a non-dilemmatic constant-selection layer robustly enhances cooperation in many cases, across different multilayer networks, updating rules, and payoff schemes. These findings suggest that
embedding individuals within diverse networked settings—even those unrelated to direct social dilemmas—can be a principled approach to engineering cooperation in socio-ecological and organizational systems.
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Computational Physics · Cross-listed from cond-mat.stat-mech
Combining multiple interface set path ensembles with MBAR reweighting
Rik S. Breebaart and Peter G. Bolhuis
We introduce a method to compute the reweighted path ensemble by combining transition interface sampling simulations conditioned on different collective variables. The approach is based on the Multistate Bennett Acceptance Ratio (MBAR) methodology applied to entire trajectories. Illustrating the technique with simple 2D potential models and a more complex host-guest system, we show that the statistics can significantly improve compared to a straightforward combination.
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Plasma Physics · Cross-listed from astro-ph.HE
Magnetic plasmoid explosions in the context of magnetar giant flares and fast radio bursts
Konstantinos N. Gourgouliatos
Magnetar
flares are highly energetic and rare events in which intense X and {\gamma}-ray emission is released from strongly magnetised
neutron stars. The events are also accompanied by mass ejection from the
neutron star. Fast
radio bursts are short and intense pulses of coherent
radio emission. Their large dispersion measures support an extragalactic origin. While their exact origin still remains elusive, a substantial number of models associates them with strong
magnetic field and high-energy relativistic
plasma found in the vicinity of magnetars. There is growing evidence that some fast
radio bursts are associated with
flare-type events from magnetars. We provide a set of configurations describing a relativistic, spherical,
magnetic plasmoid explosion. We proceed by solving the equations of relativistic magnetohydrodynamics for a system that expands while maintaining its internal
equilibrium. We find the interdependent relation between pressure, mass density, Lorentz factor, and
magnetic field that determines the detailed properties of the solutions. A dichotomy of solutions exists that correspond to higher and lower density and thermal pressure compared to the external one. For stronger toroidal
magnetic fields, the maximum permitted expansion velocity becomes lower than the weaker toroidal fields. These solution classes can be applied to magnetar
giant flares and fast
radio bursts. Those that corresponding to over densities and higher pressure can be associated with magnetar
flares, and those corresponding to underdensities can be relevant to fast
radio bursts that correspond to magnetically dominated events with low mass loading. [Abridged]
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Physics and Society
The dynamics of cultural systems
Fredrik Jansson
Culture is not just traits but a dynamic system of interdependent beliefs, practices and artefacts embedded in cognitive, social and material structures. Culture evolves as these entities interact, generating path dependence, attractor states and tension, with long-term stability punctuated by rapid systemic transformations. Cultural learning and creativity is modelled as coherence-seeking information processing: individuals filter, transform and recombine input in light of prior acquisitions and dissonance reduction, thereby creating increasingly structured worldviews. Higher-order traits such as goals, skills, norms and cognitive gadgets act as emergent metafilters that regulate subsequent selection by defining what counts as coherent. Together, these filtering processes self-organise into epistemic niches, echo chambers, polarised groups and institutions that channel information flows and constrain future
evolution. In this view, LLMs and recommender
algorithms are products of cultural
embeddings that now act back on cultural systems by automated filtering and recombination of information, reshaping future dynamics of cultural systems.
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Physics and Society
Modelling cultural evolution
Fredrik Jansson
Formal modelling provides a toolkit for understanding cultural dynamics, from individual decisions to recurring patterns of change. This chapter explains what models are and why they matter. Using a precise, shared
language, they aid thinking and communication by turning fuzzy assumptions into clear, comparable, testable claims. The chapter describes the modelling process, trading explanatory clarity against predictive specificity. Four families of models are surveyed, from the micro-level with optimising
agents to macro-level dynamics with heuristic or even implicit
agents, covering
reasoning (
Bayesian inference, game theory), adaptive updating (reinforcement learning, evolutionary games), mean-field approaches (compartmental models, population dynamics), and complex systems (
agent-based models, social networks). Building on these, a general template for modelling cultural
evolution is outlined that connects system states, cognitive processes, behaviour, and macro-level outcomes in dynamic loops, linking individuals, groups, institutions, and their environments. Taken together, these tools support a pluralist but coherent understanding of cultural change.
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Chemical Physics · Cross-listed from quant-ph
Multistep quantum master equation theory for response functions in four wave mixing electronic spectroscopy of multichromophoric macromolecules
Seogjoo J. Jang
This work provides an alternative derivation of third order response functions in four wave mixing spectroscopy of multichromophoric macromolecular systems considering only single
exciton states. For the case of harmonic oscillator bath linearly and diagonally coupled to
exciton states, closed form expressions showing all the explicit time dependences are derived. These expressions can provide more solid physical basis for understanding 2-dimensional electronic spectroscopy signals. For more general cases of system-bath coupling, the
quantum master equation (QME) approach is employed for the derivation of multistep time
evolution equations for Green function-like operators. Solution of these equations is feasible at the level of 2nd order non-Markovian QME, and the new approach can account for inter-
exciton coupling, dephasing, relaxation, and non-Markovian effects in a consistent manner.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Effect of electron-hole asymmetry on $\Delta_T$ noise in metal/quantum point contact/metal and metal/quantum point contact/superconductor junctions
Sachiraj Mishra and Colin Benjamin
This work examines charge $\Delta_T$ noise in two-terminal hybrid nanostructures featuring a
quantum point contact (QPC), realized either between two normal metallic leads (NQN) or between a normal metal and a superconducting lead (NQS). The energy-dependent transmission of a QPC breaks electron-hole (e-h)
symmetry, leading to a finite thermovoltage under an applied temperature and voltage bias. In contrast, in earlier studies on hybrid junctions incorporating insulating barriers, as electron-hole
symmetry is preserved, have vanishing thermovoltage, and consequently, charge $\Delta_T$ noise is calculated at zero thermovoltage. In our setup, the broken e-h
symmetry allows for a finite thermovoltage, at which we compute the corresponding charge $\Delta_T$ noise. Unlike earlier studies restricted by electron-hole
symmetry and vanishing thermovoltage, our work establishes a self-consistent thermoelectric noise framework in mesoscopic hybrid junctions, revealing how Andreev reflection fundamentally reshapes charge $\Delta_T$ noise once electron-hole
symmetry is broken. This broad access to charge fluctuation signatures provides a more comprehensive understanding of non-
equilibrium transport in linear response. To the best of our knowledge, this is the first work that systematically explores the interplay between Andreev reflection and electron-hole
symmetry breaking in the context of
quantum noise and $\Delta_T$ noise in mesoscopic hybrid structures.
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Plasma Physics
Influence of Cathode Boundary and Initial Electron Swarm Width on Electron Swarm Parameter Determination with the Pulsed Townsend Experiment
Mücahid Akbas
The Pulsed Townsend experiment enables the extraction of relevant electron transport properties in different gases such as the electron drift velocity $W$ (or equivalently the mobility $\mu$), the longitudinal
diffusion coefficient $D_{\mathrm{L}}$, and the effective ionization rate $R_{\mathrm{net}}$ (or equivalently the effective ionization coefficient $\alpha_{\mathrm{eff}}$). Existing analysis techniques lack an accurate representation of the experimental initial and boundary conditions. This work provides an improved evaluation approach by appropriately considering both initial and boundary conditions in order to extract more accurate swarm parameters from measurement data. Simulative and experimental measurement results verify an increased evaluation accuracy. Furthermore, the longitudinal
diffusion coefficient $D_{\mathrm{L}}$ can now be accurately extracted from Pulsed Townsend measurements, which was previously not possible with existing evaluation approaches. The developed curve fitting code is made publicly available.
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Fluid Dynamics · Cross-listed from astro-ph.SR
On the Theory of Absorption of Sound Waves via the Bulk Viscosity in the Partially Ionized Solar Chromosphere
Albert M. Varonov and Todor M. Mishonov
Bulk viscosity and thermodynamic variables of a hydrogen-helium cocktail: internal energy, enthalpy, pressure, their derivatives, heat capacities per constant density and pressure are obtained using temperature and density height profiles of the
solar atmosphere [Avrett & Loeser, ApJS Vol. 175, 229 (2008)]. The qualitative evaluation for the necessary sound wave energy flux to heat the
solar chromosphere is determined to be 320 kW/m$^2$. It is concluded that the bulk viscosity creates the dominating mechanism of acoustic waves damping and it is not necessary to introduce artificial viscosity or to conclude that shear viscosity is not sufficient for chromosphere heating; the volume viscosity induced wave absorption is sufficient.
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Atmospheric and Oceanic Physics · Cross-listed from nlin.CD
A Topological Framework for Atmospheric River Interaction Using Framed Braids
Ioannis Diamantis
Atmospheric Rivers (ARs) are filamentary moisture pathways responsible for a large fraction of extreme precipitation and often occur as interacting filament bundles within the same synoptic regime. Existing diagnostics typically analyze ARs in isolation, despite the frequent coexistence and interaction of multiple filaments. We introduce a topological framework for AR analysis based on framed braids and framed braidoids, which encodes both the
geometric interaction of AR centroids and the internal
evolution of moisture transport. In this approach, AR filaments are represented as strands whose time-ordered crossings form braid words, while moisture-based framing captures internal intensification or weakening along each filament. Applying this framework to reanalysis-derived Atmospheric River track data, we construct braid and framed braid representations over sliding time windows and analyze a strongly interacting multi-filament AR episode in the North Pacific. The results show that braid-based indicators capture structural reorganizations and moisture intensification episodes that are not apparent from centroid geometry or IVT magnitude alone, offering a complementary structural perspective on atmospheric moisture transport.
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Fluid Dynamics
Solving nonlinear subsonic compressible flow in infinite domain via multi-stage neural networks
Xuehui Qian, Hongkai Tao and Yongji Wang
In aerodynamics, accurately modeling subsonic compressible flow over airfoils is critical for aircraft design. However, solving the governing nonlinear perturbation velocity potential equation presents computational challenges. Traditional approaches often rely on linearized equations or finite, truncated domains, which introduce non-negligible errors and limit applicability in real-world scenarios. In this study, we propose a novel framework utilizing Physics-Informed Neural Networks (PINNs) to solve the full nonlinear compressible potential equation in an unbounded (infinite) domain. We address the unbounded-domain and convergence challenges inherent in standard PINNs by incorporating a coordinate transformation and
embedding physical asymptotic constraints directly into the network architecture. Furthermore, we employ a Multi-Stage PINN (MS-PINN) approach to iteratively minimize residuals, achieving solution accuracy approaching machine precision. We validate this framework by simulating flow over circular and elliptical geometries, comparing our results against traditional finite-domain and linearized solutions. Our findings quantify the noticeable discrepancies introduced by domain truncation and linearization, particularly at higher Mach numbers, and demonstrate that this new framework is a robust, high-fidelity tool for computational fluid dynamics.
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Physics and Society
Effective Graph Resistance as Cumulative Heat Dissipation
Xiangrong Wang, Xin Yu, Zongze Wu et al. (+1 more)
Effective graph resistance is a fundamental structural metric in network science, widely used to quantify global connectivity, compare network architectures, and assess robustness in flow-based systems. Despite its importance, current formulations rely mainly on spectral or pseudo-inverse
Laplacian representations, offering limited physical insight into how structural features shape this quantity or how it can be efficiently optimized. Here, we establish an exact and physically transparent relationship between effective graph resistance and the cumulative heat dissipation generated by
Laplacian diffusion dynamics. We show that the total heat dissipated during relaxation to
equilibrium precisely equals the effective graph resistance. This dynamical viewpoint uncovers a natural multi-scale decomposition of the
Laplacian spectrum: early-time dissipation is governed by degree-based local structure, intermediate times isolate
eigenvalues below the spectral mean, and long times are dominated by the algebraic connectivity. These multi-scale properties yield continuous and interpretable strategies for modifying network structure and constructing optimized ensembles, enabling improvements that are otherwise NP-hard to achieve via combinatorial methods. Our results unify structural and dynamical perspectives on network connectivity and provide new tools for analyzing, comparing, and optimizing complex networks across domains.
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All authors Xiangrong Wang, Xin Yu, Zongze Wu, Yamir Moreno
Geophysics · Cross-listed from nlin.PS
Self-assembled versus biological pattern formation in geology
Julyan H. E. Cartwright, Charles S. Cockell, Julie G. Cosmidis et al. (+11 more)
Both abiotic self-organization and biological mechanisms have been put forward as the origin of a number of geological patterns. It is important to comprehend the formation mechanisms of such structures both to understand geological self-organization and in order to differentiate them from biological patterns – fossils and bio-influenced structures – seen in geological systems. Being able to distinguish the traces of biological activity from geological self-organization is fundamental both for understanding the origin of life on Earth and for the search for life beyond Earth.
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All authors Julyan H. E. Cartwright, Charles S. Cockell, Julie G. Cosmidis, Silvia Holler, F. Javier Huertas, Sean F. Jordan, Pamela Knoll, Electra Kotopoulou, Corentin C. Loron, Sean McMahon, Anna Neubeck, Carlos Pimentel, C. Ignacio Sainz-Díaz, Piotr Szymczak
Instrumentation and Detectors
Multispectral UV Imaging on Capacitive CMOS Arrays Enabled by Solution-Processed Metal-Oxide Nanoparticles
Suman Kundu, Tao Shen, Kai Betlem et al. (+3 more)
Ultraviolet (UV) imagers are important for a variety of applications, such as quality inspection in the
semiconductor industry, forensics and food quality inspection, but are often costly because they require dedicated
semiconductor process flows. Here, an imaging chip is introduced that has been fabricated using standard 40 nm complementary metal-oxidesemiconductor (CMOS) technology. Instead of using a conventional charge-based photodetection principle, the imager uses a capacitive operation principle where UV-light causes capacitance changes via the photodielectric effect in a functionalization layer, which are measured by the underlying CMOS circuitry. This
spin-coated or inkjet-printed functionalization layer consists of solution-processed, wide-bandgap, semiconducting metaloxide nanoparticles, and facilitates multispectral imaging. The sensors exhibit low noiseequivalent powers (17-138 fW Hz^-1/2) across the UV bands. Unlike conventional silicon CMOS imagers, the present capacitive-CMOS platform is inherently visible-blind, providing selective UV detection. This work positions late-functionalized capacitive-CMOS arrays as a route toward reducing the cost of UV imagers, which can lead to their more widespread implementation in consumer and low-volume application-specific products.
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All authors Suman Kundu, Tao Shen, Kai Betlem, Murali K Ghatkesar, Peter G Steeneken, Frans P Widdershoven
Chemical Physics
Reassessing carotenoid photophysics: shedding light on dark states
Roxanne Bercy, Viola Dmello, Andrew Gall et al. (+5 more)
Carotenoid molecules are critical in photosynthesis, performing functions at the heart of both light-harvesting and photoprotection. As both these processes involve excitation energy transfer, fully understanding them requires a precise description of the electronic states involved. The excited state
manifold of carotenoids is not yet fully characterized, and includes several dark electronic states that remain elusive. Using femtosecond stimulated resonance Raman spectroscopy, where the vibrational contributions of each excited state can be observed selectively as a function of the Raman excitation, we resolve vibrational signatures consistent with three additional dark-state contributions and propose assignments for them. These results address long-standing controversies in carotenoid research and provide a spectroscopic framework relevant to the multiple roles of these molecules.
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All authors Roxanne Bercy, Viola Dmello, Andrew Gall, Cristian Ilioaia, Andrew A. Pascal, Juan Jose Romero, Bruno Robert, Manuel J. Llansola-Portoles
Plasma Physics
Enhanced wakefield generation in homogeneous plasma via two co-propagating laser pulses
Abhishek Kumar Maurya, Dinkar Mishra, Bhupesh Kumar et al. (+5 more)
This investigation deals with enhanced
plasma wakefield amplitude generated using two co-propagating
laser pulses in homogeneous
plasma. The configuration consists of a seed pulse followed by a trailing pulse, both linearly polarized and sharing identical
laser parameters. The enhancement in wakefield amplitude corresponding to fixed spatial separation is optimized for various pulse widths and intensities of the seed and trailing
lasers. Analytical modelling and particle-in-
cell simulations reveal that the maximum amplification in wakefield amplitude is obtained when spatial separation equals the
plasma wavelength (\lambda_p). The spatial intervals between
laser pulses critically influence the wakefield amplification. These findings confirm that the two co-propagating
lasers scheme provides a promising route toward stronger
plasma wakefield excitation, potentially important for various applications.
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All authors Abhishek Kumar Maurya, Dinkar Mishra, Bhupesh Kumar, Ramesh C Sharma, Lal C Mangal, Binoy K Das, Vijay K Saraswat, Brijesh Kumar
Fluid Dynamics
Coupled Modal-Nonmodal Interactions Due to Periodic, Infinite Train of Convecting Vortices (TCV)
Jyothi Kumar Puttam, Prasannabalaji Sundaram, Vajjala K. Suman et al. (+4 more)
Events during transition to
turbulence either follow modal or non-modal routes, or combinations of the two. Here, we report a computational investigation of strong freestream excitation caused by a train of convecting
vortices. For this TCV excitation, we show a strong interaction of modal and non-modal components causing a spectacular growth of disturbances. We propose this as the mechanism for the severe encounters due to convective vortical disturbances on the underlying shear layer.
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All authors Jyothi Kumar Puttam, Prasannabalaji Sundaram, Vajjala K. Suman, Ankan Sarkar, Tapan K. Sengupta, Tirupathur N. Venkatesh, Rakesh K. Mathpal
Fluid Dynamics · Cross-listed from cond-mat.soft
Self-diffusiophoretic propulsion in wedge confinement: The role of phoretic interactions
Abdallah Daddi-Moussa-Ider and Ramin Golestanian
We investigate the self-diffusiophoretic motion of a catalytically active spherical particle confined within a wedge-shaped domain. Using the
Fourier-Kontorovich-Lebedev transform, we solve the Laplace equation for the concentration field in the
diffusion-dominated regime. The method of images is employed to obtain the first and second reflections of the concentration field, accounting for both monopole and dipole contributions of the particle's surface activity. Based on these results, we derive leading-order expressions for the self-induced phoretic velocity in the far-field limit and examine how it varies with the wedge opening angle and the particle's position within the domain. We focus on the contributions to the phoretic velocities arising from phoretic interactions, without accounting for hydrodynamic effects. Our findings reveal that the wedge geometry significantly affects both the magnitude and direction of particle motion. Our study provides a systematic framework for calculating the contributions to the phoretic velocity arising from concentration disturbances near corners, with implications for microfluidic design and control of autophoretic particles in confined geometries.
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Fluid Dynamics
Hydrodynamic flows induced by localized torques (rotlets) in wedge-shaped geometries
Abdallah Daddi-Moussa-Ider, Jakob Mihatsch, Michael J. Mitchell et al. (+2 more)
Wedge-shaped geometries in low-Reynolds-number flows are of increasing importance, for instance, in the design of microfluidic devices. The corresponding Green's functions describing the induced flow in response to a locally applied force were derived some time ago. To achieve a complete characterization of particle motion at low Reynolds numbers, we derive the flow response to locally applied torques. This is accomplished through a direct calculation based on the
Fourier-Kontorovich-Lebedev transform using the Papkovich-Neuber representation of the hydrodynamic fields. We then illustrate the resulting flow fields, highlighting their structure, key features, and dependence on the geometry and orientation of the applied torque. Based on these solutions, we compute the corresponding hydrodynamic mobility tensor that couples torque and motion. Owing to the broken spatial
symmetry imposed by the wedge-shaped confinement, a particle subjected to a torque will experience not only rotational motion but also translational motion. These results provide analytical tools relevant for predicting and controlling particle behavior in confined microfluidic environments.
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All authors Abdallah Daddi-Moussa-Ider, Jakob Mihatsch, Michael J. Mitchell, Elsen Tjhung, Andreas M. Menzel
Fluid Dynamics
Data-driven reduced order model for residence time distribution analysis of an industrial-scale continuous casting tundish
Harshith Gowrachari, Mattia Giuseppe Barra, Giovanni Stabile et al. (+2 more)
The continuous casting tundish plays a critical role as a metallurgical reactor in the continuous casting process, with its flow characteristics serving as a key parameter in the production of high-quality steel. These characteristics are typically assessed through residence time distribution (RTD) curves. This study examines the flow behaviour in a single-strand continuous casting tundish through a combination of numerical simulations and experimental validation. Steady-state full order model (FOM) simulations are performed under both isothermal and non-isothermal conditions to evaluate the influence of thermal buoyancy on the velocity field, which is found to be negligible. The resulting flow fields are used to initialize transient tracer transport simulations for determining the RTD and flow volume partitioning. Subsequently, a data-driven reduced order model (ROM) is developed to predict the RTD response. Comparison of RTD curves obtained from experiments, FOM, and ROM shows excellent agreement, with the ROM accurately capturing the key flow characteristics at a fraction of the computational cost. These results highlight the potential of ROM techniques for efficient real-time analysis, design, and optimization of tundish operations in metallurgical processes.
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All authors Harshith Gowrachari, Mattia Giuseppe Barra, Giovanni Stabile, Gianluca Bazzaro, Gianluigi Rozza
Plasma Physics · Cross-listed from nucl-th
Revisiting p-$^{11}$B Fusion: Updated Cross-sections, Reactivity, and Energy Balance
Hong-Yi Wang, Yu-Qi Li, Qian Wu et al. (+1 more)
Recent experimental progress has substantially improved the available cross-section data for the p-$^{11}$B fusion reaction, particularly in energy regions that previously lacked direct measurements. In this study, we develop a high-precision analytical parameterization of the p-$^{11}$B reaction cross-section over the 0–10 MeV energy range, incorporating the new experimental data into a continuous and numerically efficient representation. Using this parameterization, we evaluate the thermonuclear reactivity of the p-$^{11}$B reaction and examine the effects of the dominant resonance at 0.6 MeV and a newly observed resonance around 4.7 MeV. Furthermore, we assess the energy balance by analyzing the fusion power density and the electron bremsstrahlung power density. Our results indicate that p-$^{11}$B fusion is not precluded by bremsstrahlung constraints when contemporary cross-section data and self-consistent thermal modeling are employed.
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All authors Hong-Yi Wang, Yu-Qi Li, Qian Wu, Zhu-Fang Cui
Plasma Physics
Transient spark dielectric barrier post-discharge plasma reactor with a liquid electrode for dye degradation: A primary study
Mangilal Choudhary, Vanshika and Surya
The potential application of non-thermal
plasma in treating textile industrial wastewater motivates researchers to develop innovative techniques at a laboratory scale to achieve the goal of wastewater mineralization. In line with this objective, a dielectric barrier post-discharge
plasma reactor with a
liquid electrode has been built for the study of synthetic dye degradation. The
plasma reactor was optimized by altering various operating conditions to achieve a higher degradation efficiency at given discharge conditions. The reaction kinetics of
crystal violet degradation were studied, and the same
plasma reactor was tested for other synthetic dyes (wastewater model samples). The results suggest that the proposed dielectric barrier post-discharge
plasma reactor may offer a promising solution for treating dye effluents from the textile industry.
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Medical Physics · Cross-listed from eess.IV
Let Distortion Guide Restoration (DGR): A physics-informed learning framework for Prostate Diffusion MRI
Ziyang Long, Binesh Nader, Lixia Wang et al. (+9 more)
We present Distortion-Guided Restoration (DGR), a physics-informed hybrid CNN-
diffusion framework for acquisition-free correction of severe susceptibility-induced distortions in prostate single-shot EPI
diffusion-weighted imaging (DWI). DGR is trained to invert a realistic forward distortion model using large-scale paired distorted and undistorted data synthesized from distortion-free prostate DWI and co-registered T2-weighted images from 410 multi-institutional studies, together with 11 measured B0 field maps from metal-implant cases incorporated into a forward simulator to generate low-b DWI (b = 50 s per mm squared), high-b DWI (b = 1400 s per mm squared), and ADC distortions. The network couples a CNN-based
geometric correction module with conditional
diffusion refinement under T2-weighted anatomical guidance. On a held-out synthetic validation set (n = 34) using ground-truth simulated distortion fields, DGR achieved higher PSNR and lower NMSE than FSL TOPUP and FUGUE. In 34 real clinical studies with severe distortion, including hip prostheses and marked rectal distension, DGR improved
geometric fidelity and increased radiologist-rated image quality and diagnostic confidence. Overall, learning the inverse of a physically simulated forward process provides a practical alternative to acquisition-dependent distortion-correction pipelines for prostate DWI.
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All authors Ziyang Long, Binesh Nader, Lixia Wang, Archana Vadiraj Malaji, Chia-Chi Yang, Haoran Sun, Rola Saouaf, Timothy Daskivich, Hyung Kim, Yibin Xie, Debiao Li, Hsin-Jung Yang
Atmospheric and Oceanic Physics
Stratosphere Model Verification with Manufactured Geometry
Johannes Lawen, George Salman and Akshita Bhardwaj
We propose an exact solution for a stratosphere dynamical core formulated in geopotential/pressure coordinates with a time-evolving lower boundary supplied by the troposphere. Rather than constraining the stratospheric circulation via specified dynamics (“nudging”) to a reanalysis, we treat the tropopause as a moving
geometric boundary. The stratospheric domain thus expands, contracts, and undulates in response to tropospheric variability while preserving familiar hybrid $\sigma$–$p$ structure and pressure-gradient calculations. The approach integrates naturally with arbitrary Lagrangian–Eulerian (ALE) updates and conservative remap to maintain positive layer thickness and tracer monotonicity. We outline the formulation, highlight analytical properties (well-posedness, energetics, wave propagation), and sketch a verification/validation path based on modified standard test cases and reanalysis-driven experiments.
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Optics
A POD-DeepONet Framework for Forward and Inverse Design of 2D Photonic Crystals
Yueqi Wang, Guanglian Li and Guang Lin
We develop a reduced-order operator-learning framework for forward and inverse band-structure design of two-dimensional photonic
crystals with binary, pixel-based $p4m$-symmetric unit
cells. We construct a POD–DeepONet surrogate for the discrete band map along the standard high-
symmetry path by coupling a POD trunk extracted from high-fidelity finite-element band snapshots with a neural branch network that predicts reduced coefficients. This architecture yields a compact and differentiable forward model that is tailored to the underlying Bloch
eigenvalue discretization. We establish continuity of the discrete band map on the relaxed design space and prove a uniform approximation property of the POD–DeepONet surrogate, leading to a natural decomposition of the total surrogate error into POD truncation and network approximation contributions. Building on this forward surrogate, we formulate two end-to-end neural inverse design procedures, namely dispersion-to-structure and band-gap inverse design, with training objectives that combine data misfit, binarity promotion, and supervised regularization to address the intrinsic non-uniqueness of the inverse mapping and to enable stable gradient-based optimization in the relaxed space. Our numerical results show that the proposed framework achieves accurate forward predictions and produces effective inverse designs on practical high-contrast, pixel-based photonic layouts.
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Optics
Polar enhancement of optical nonlinearities and domain-driven second harmonic contrast in bismuth telluro-halide van der Waals crystals
Kevin W. C. Kwock, Tenzin Norden, Thomas P. Darlington et al. (+11 more)
The BiTeX family of polar van der Waals (vdW)
semiconductors offers a unique platform for exploring the interplay between polar crystalline structure and nonlinear optical phenomena. Here, we utilize second harmonic generation (SHG) polarimetry to demonstrate
giant anisotropic optical nonlinearities in BiTeBr and BiTeI driven by contributions to the
crystals' nonlinear polarizability originating from their permanent dipole moment. In addition, using SHG microscopy, we show that BiTeI displays a distinctive SHG spatial texture consisting of thread-like regions of reduced harmonic intensity. These features demark the boundaries between phase and anti-phase polar domains, confirmed via piezoresponse force microscopy and are attributable to disorder-driven restoration of inversion
symmetry and concomitant optical interference effects. Our results unveil the power of polarization-resolved SHG microscopy in elucidating the intricate relationship between structure,
symmetry, and nonlinear optical responses in polar vdW materials and highlight the promise of BiTeX as a material platform for domain-engineered nanoscale nonlinear photonics.
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All authors Kevin W. C. Kwock, Tenzin Norden, Thomas P. Darlington, Kaiyuan Yao, Kai Du, Ana-Marija Nedić, Thaís V. Trevisan, Ekaterina Dolgopolova, Peter P. Orth, Rohit P. Prasankumar, P. James Schuck, Sang-Wook Cheong, Wilton J. M. Kort-Kamp, Prashant Padmanabhan
Optics · Cross-listed from nlin.PS
Collisions and fusion of one- and two-dimensional solitons driven by potential troughs in the cubic-quintic nonlinear Schrödinger equations
Liangwei Zeng, Boris A. Malomed, Dumitru Mihalache et al. (+2 more)
We study the formation and collision of one- and two-dimensional (1D and 2D) Gaussian-shaped and flat-top (FT)
solitons in the framework of the nonlinear Schrödinger equation with the cubic-quintic nonlinearity and two intersecting potential troughs. We find that Gaussian-Gaussian and Gaussian-FT collisions between the
solitons, steered by the troughs, are quasi-elastic, while the collisions between FT
solitons may be either quasi-elastic or inelastic, in the form of merger into a single FT
soliton, thus spontaneously breaking the
symmetry between the steering troughs. The Gaussian-FT collisions, being overall quasi-elastic, generate weak radiation fields.
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All authors Liangwei Zeng, Boris A. Malomed, Dumitru Mihalache, Jingzhen Li, Xing Zhu
Applied Physics
Experimental study on an S-band near-field microwave magnetron power transmission system on hundred-watt level
Biao Zhang, Wan Jiang, Yang Yang et al. (+3 more)
A multi-magnetron microwave source, a metamaterial transmitting
antenna, and a large power rectenna array are presented to build a near-field 2.45 GHz microwave power transmission system. The square 1 m2 rectenna array consists of sixteen rectennas with 2048 Schottky diodes for large power microwave rectifying. It receives microwave power and converts them into DC power. The design, structure, and measured performance of a unit rectenna as well as the entail rectenna array are presented in detail. The multi-magnetron microwave power source switches between half and full output power levels, i.e. the half-wave and full-wave modes. The transmission
antenna is formed by a double-layer metallic hole array, which is applied to combine the output power of each magnetron. The rectenna array DC output power reaches 67.3 W on a 1.2 ohm DC load at a distance of 5.5 m from the transmission
antenna. DC output power is affected by the distance, DC load, and the mode of microwave power source. It shows that conventional low power Schottky diodes can be applied to a microwave power transmission system with simple magnetrons to realise large power microwave rectifying.
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All authors Biao Zhang, Wan Jiang, Yang Yang, Chengyang Yu, Kama Huang, Changjun Liu
Optics
Generalized model of anisotropic thermo-optic response on thin-film lithium niobate platform
Joonsup Shim, Seonghun Kim, Shengyuan Lu et al. (+5 more)
Thermo-optic (TO) control is crucial for thin-film lithium niobate (TFLN) photonic integrated
circuits (PICs), offering a simple and practical method for low-frequency and DC tuning while remaining compatible with high-frequency electro-optic (EO) modulation. In x-cut TFLN, the TO response is inherently anisotropic, depending on both waveguide propagation angle and polarization due to the mode-specific overlap of the electric field with the ordinary and extraordinary refractive index axes of the
crystal. Despite its significance, a systematic and quantitative analysis of this anisotropy has remained elusive. Here, we present the first generalized analytical model that describes the anisotropic TO response as a function of polarization and arbitrary waveguide orientation, and rigorously validate it through numerical simulations and experiments. This study provides foundational insight into anisotropic thermal tuning and enables new opportunities for engineering energy-efficient and scalable photonic design in next-generation TFLN PICs.
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All authors Joonsup Shim, Seonghun Kim, Shengyuan Lu, Jiayu Yang, Seongjin Jeon, Sanghyeon Kim, Marko Lončar, Young-Ik Sohn