Plasma Physics
GPU Acceleration and Portability of the TRIMEG Code for Gyrokinetic Plasma Simulations using OpenMP
Giorgio Daneri
The field of
plasma physics heavily relies on simulations to model various phenomena, such as instabilities,
turbulence, and nonlinear behaviors that would otherwise be difficult to study from a purely theoretical approach. Simulations are fundamental in accurately setting up experiments, which can be extremely costly and complex. As high-fidelity tools, gyrokinetic simulations play a crucial role in discovering new physics, interpreting experimental results, and improving the design of next-generation devices. However, their high computational costs necessitate the use of acceleration platforms to reduce execution time. This work revolves around the TRIangular MEsh based Gyrokinetic (TRIMEG) code, which performs high-accuracy particle-in-
cell plasma simulations in tokamak geometries, leveraging a novel finite element approach. The rise of graphical processing units (GPUs) constitutes an occasion to satisfy such computational needs, by offloading the most expensive portion of the code to the accelerators. The chosen approach features GPU offloading with the OpenMP API, which grants portability of the code to different architectures, namely AMD and NVIDIA. The particle pushing as well as the grid-to-particle operations have been ported to GPU platforms. Compiler limitations had to be overcome, and portions of the code were restructured to be suitable for GPU acceleration. Kernel performance was evaluated by carrying out GPU grid size exploration, as well as scalability studies. In addition, the efficiency of hybrid MPI-OpenMP offloading parallelization was assessed. The speedup of the GPU implementation was calculated by comparing it with the pure CPU version using different rationales. The Ion Temperature Gradient (ITG) mode was simulated using the GPU-accelerated version, and its correctness was verified in terms of the energy growth rate and the two-dimensional mode structures.
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Computational Physics
Best practices for second-generation Car-Parrinello ab initio molecular dynamics with CP2K/Quickstep
Thomas D. Kühne
Second-generation Car–Parrinello ab initio molecular dynamics (CP2G AIMD) combines a Born–Oppenheimer-like
nuclear equation of motion with a predictor-corrector propagation of the one-particle density
matrix and a modified Langevin equation to ensure an accurate sampling of the Boltzmann distribution. In the CP2K implementation, this approach can substantially reduce the number of self-consistent-field iterations required per molecular-dynamics step, but only if the density-
matrix propagation, the orbital-transformation corrector, and the modified Langevin friction parameters are tuned consistently. This tutorial gives a practical workflow for setting up CP2G AIMD calculations in CP2K, starting from Born–Oppenheimer pre-equilibration and proceeding through corrector-step-size selection, always-stable predictor-corrector order optimization, final relaxation, and the calibration of the dissipative and
stochastic terms used for canonical sampling. The protocol is demonstrated for a 32-molecule
liquid-water
benchmark and is written for users who already know the basics of CP2K input files but want a reliable route from a conventional AIMD setup to a production-ready CP2G simulation.
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Chemical Physics
Accurate starting points for one-shot $G_0W_0$ and Bethe-Salpeter Equation calculations via effective tuning of range-separated hybrid functionals
Aditi Singh, Subrata Jana and Szymon Śmiga
The accuracy of one-shot $G_0W_0$ and Bethe-Salpeter equation (BSE) calculations depends strongly on the underlying starting-point eigensystem, which is commonly obtained from a mean-field density-functional approximation. Range-separated hybrid (RSH) functionals provide a particularly effective starting point, however, conventional optimally tuned RSH procedures often require costly, system-specific, multi-step optimizations of the range-separation parameter $\omega$. In this work, we show that a recently proposed effective tuning protocol [Singh et. al., Journal of Physical Chemistry Letters, 16, 32, 8198-8208, (2025)] for RSH functionals can serve as an efficient alternative for determining $\omega$ used in $G_0W_0$ and BSE calculations. This simplified tuning scheme yields range-separation parameters that are effectively equivalent to those obtained from more elaborate tuning strategies, while avoiding their substantial computational overhead. The resulting tuned RSH eigensystems provide reliable starting points for many-body perturbation theory. In particular, one-shot $G_0W_0$ calculations based on effectively tuned RSH orbitals reproduce reference ionization potentials with high accuracy, while subsequent BSE calculations yield quantitatively reliable neutral excitation energies, optical absorption spectra, and excitonic properties for a diverse set of molecular systems and clusters. These results demonstrate that effective RSH tuning offers a practical and broadly applicable route to accurate quasiparticle and excited-state calculations, combining the accuracy of optimally tuned starting points with the low computational cost required for routine applications of $G_0W_0$ and BSE.
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Fluid Dynamics
Wave Phenomena and Wave Equations
Gerd Leuchs and Mojdeh S. Najafabadi
For any kind of wave phenomenon one can find ways to derive the respective dispersion relation from experimental observations and measurements. This dispersion relation determines the structure of the wave equation and thus characterizes the dynamics of the respective wave. Different wave phenomena are thus governed by different differential equations. Here we want to emphasize the experimental approach to matter waves, but before doing so we will discuss and test the procedure for other types of waves, in particular water waves.
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Optics · Cross-listed from quant-ph
State Engineering via Nonlinear Interferometry with Linear Spectral Phases
Cody Charles Payne, Elaganuru Bashaiah and Markus Allgaier
Many protocols within
quantum cryptography, communications, and computing require the ability to generate entangled states as well as spectral qudits. Nonlinear interferometry is a viable way to engineer these complex
quantum states of light. However, it is difficult to achieve a high level of control over spectral correlations. Here, we present a protocol utilizing a nonlinear interferometer with linear spectral phases that can generate both high-dimensional spectral qudits and high-dimensional entangled states. We model the effect of loss and loss of overlap on interference visibility and thereby on the states generated.
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Optics
Four-dimensional video imaging via generative deep learning and a diffuser-encoded image sensor
Max T. Kauss, William Walker, Alexander Ingold et al. (+3 more)
Light carries rich information across space, spectrum, polarization, and time, yet conventional cameras capture only a narrow projection of this multidimensional structure. A thin diffuser encodes wavelength-dependent information into single-shot scatterograms, captured by a polarization-resolving CMOS sensor that simultaneously measures four linear polarization states. We use 4DCam to image a live Betta splendens fish, uncovering polarization-dependent color modulations that remain invisible to conventional cameras. We experimentally show that the 4D information encoded in the scatterograms markedly improves material discrimination, achieving 96% accuracy for textile classification and 90% for camouflage detection, compared with 70% and 80%, respectively, using 3D hyperspectral imaging alone. Built entirely from passive optics, 4DCam seamlessly integrates physical encoding, generative decoding, and direct inference, enabling real-time, information-complete optical sensing.
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All authors Max T. Kauss, William Walker, Alexander Ingold, Jakob Dammann, Apratim Majumder, Rajesh Menon
Computational Physics · Cross-listed from math.NA
Streaming Operator Inference for Model Reduction of Large-Scale Dynamical Systems
Tomoki Koike, Prakash Mohan, Marc T. Henry de Frahan et al. (+2 more)
Projection-based model reduction enables efficient simulation of complex dynamical systems by constructing low-dimensional surrogate models from high-dimensional data. The Operator Inference (OpInf) approach learns such reduced surrogate models through a two-step process: constructing a low-dimensional basis via Singular Value Decomposition (SVD) to compress the data, then solving a linear least-squares (LS) problem to infer reduced operators that govern the dynamics in this compressed space, all without access to the underlying code or full model operators, i.e., non-intrusively. Traditional OpInf operates as a batch learning method, where both the SVD and LS steps process all data simultaneously. This poses a barrier to deployment of the approach on large-scale applications where
dataset sizes prevent the loading of all data into
memory at once. Additionally, the traditional batch approach does not naturally allow model updates using new data acquired during online computation. To address these limitations, we propose Streaming OpInf, which learns reduced models from sequentially arriving data streams. Our approach employs incremental SVD for adaptive basis construction and recursive LS for streaming operator updates, eliminating the need to store complete data sets while enabling online model adaptation. The approach can flexibly combine different choices of streaming
algorithms for numerical linear
algebra: we systematically explore the impact of these choices both analytically and numerically to identify effective combinations for accurate reduced model learning. Numerical experiments on
benchmark problems and a large-scale turbulent channel flow demonstrate that Streaming OpInf achieves accuracy comparable to batch OpInf while reducing
memory requirements by over 99% and enabling dimension reductions exceeding 31,000x, resulting in orders-of-magnitude faster predictions.
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All authors Tomoki Koike, Prakash Mohan, Marc T. Henry de Frahan, Julie Bessac, Elizabeth Qian
History and Philosophy of Physics · Cross-listed from quant-ph
Physical probability in the Everett interpretation and Bell inequalities
Simon Saunders
I define a notion of locality LOC, closely modelled on Bell's principle of local causality, construed as the condition that single-case probabilities cannot be modified by actions at spacelike separation. The new principle, like Bell's, forces Bell inequalities, but with two loopholes: one is violation of measurement independence, known to Bell, but the other is non-uniqueness of remote outcomes, a loophole only for LOC, not for Bell's principle. I also set out a theory of physical probability, applicable to the Everett interpretation, in which the Born rule is derived, and which therefore violates Bell inequalities. I show it is consistent with LOC. Surprisingly, both loopholes are exploited. I conclude not only that physical probability in the Everett interpretation involves no action at a distance, in the sense of LOC, but that the observed violation of Bell inequalities is powerful evidence for many worlds.
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Classical Physics · Cross-listed from cond-mat.stat-mech
Stochastic dynamics from maximum entropy in action space
Fabricio de Souza Luiz, José Carlos Bellizotti Souza, Luísa Toledo Tude et al. (+1 more)
We develop an information-theoretic formulation of
stochastic dynamics in which the fundamental
stochastic variable is the total action connecting spacetime points, rather than individual paths. By maximizing Shannon
entropy over a joint distribution of actions and endpoints, subject to normalization and a constraint on the mean action, we obtain a Boltzmann-like distribution in action space. This framework reproduces the standard Brownian propagator in the nonrelativistic limit and naturally extends to relativistic regimes, where the Wiener construction fails to preserve Lorentz covariance. The approach bypasses functional integration over paths, makes the role of entropic degeneracy explicit through an action-space density of states, and provides a transparent connection between the principle of least action and statistical inference. We derive the density of states explicitly using large deviation theory, showing that it takes a Gaussian form centered at the minimal action, and rigorously justify the saddle-point approximation in the diffusive regime. The Markovian property of the resulting propagator is verified to hold via the Chapman–Kolmogorov equation, following from the additivity of the minimal action for free-particle dynamics. In the diffusive regime, the resulting dynamics are governed by a competition between extremization of the action and entropic effects, which can be interpreted in terms of an effective action free energy. Our results establish an unified, covariant, and information-based foundation for classical and relativistic
stochastic processes.
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All authors Fabricio de Souza Luiz, José Carlos Bellizotti Souza, Luísa Toledo Tude, Marcos César de Oliveira
Physics and Society
Evolutionary vaccination dynamics under higher-order reinforcement pressure
Yikang Lu, Ying Wang, Alfonso de Miguel-Arribas et al. (+2 more)
Vaccination games in higher-order settings remain underexplored, despite their importance in shaping opinions and collective decisions. Here, we introduce a parsimonious behavioral-epidemiological model to evaluate how peer reinforcement pressure influences vaccination uptake. The framework consists of a two-layer multiplex: an epidemic layer governed by the SIR process on a square
lattice, and a behavioral layer represented by a hypergraph of triadic interactions. Individuals update their vaccination strategy via imitation, modulated by a reinforcement parameter $\alpha$ when peer support is present. We find that higher-order structure alone induces clusters of vaccinated individuals that act as protective barriers. Low but nonzero reinforcement ($\alpha \approx 0.5$) maximizes coverage and suppresses outbreaks, while both negligible ($\alpha \approx 0$) and moderate ($\alpha > 0.1$) reinforcement reduce uptake, as excessive confirmation lowers adaptability and enables non-vaccinators to re-emerge. Our work bridges complex contagion theory with evolutionary game dynamics, offering insights into how contact structure and peer reinforcement jointly shape vaccination behavior.
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All authors Yikang Lu, Ying Wang, Alfonso de Miguel-Arribas, Lei Shi, Yamir Moreno
Computational Physics
Real-Symmetric Hamiltonian Enables Near-Linear Scaling for Fast Million-Atom Electronic Structure Computations
Zichong Zhang and Shuze Zhu
The exploration of
quantum phenomena in mesoscale materials, such as moire superlattices, is limited by the cubic scaling cost of conventional electronic structure methods. Here, we introduce a scalable tight binding framework that achieves near linear scaling, enabling mesoscopic
quantum simulations. By transforming the complex Hermitian Bloch
Hamiltonian into an equivalent real symmetric form, the method avoids dense diagonalization by combining sparse LDL decomposition with Sylvester's law of inertia for spectral slicing and global rank calibration. This formulation enables efficient band structure calculations for large scale systems, solving magic angle twisted
bilayer graphene in minutes on a standard laptop and extending to 1.5 million atoms within days on a single workstation. Applying this framework to ultra low twist angle structures with atomistic strain relaxation, we find robust isolated low-energy band clusters over several finite ultra low angle windows down to 0.09 degree. Our framework provides an efficient computational platform for studying
quantum materials at experimentally relevant length scales and supports data driven discovery in large scale moire systems.
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Applied Physics
Second- and Third-Harmonic Backscatter Through a Bandstop Filter Using Defected Ground Structure
Dan Che, Changjun Liu, Haoming He et al. (+2 more)
In this brief, a novel harmonic-backscatter-rectifier (HBR) is introduced for simultaneous rectification and harmonic-based uplink. The proposed (HBR) employs a rectifier to generate both DC power and the harmonic carriers for backscattering communication, and a dual-band reconfigurable band-stop filter using defected ground structure(DGS) to modulate the second and third harmonics with low-power consumption and same input impedance at f0 all the time. As a proof of concept, an HBR prototype operating at 1.85 GHz was designed and experimented. An uplink data rate of 8Mbps (4Mbps x 2 ) was achieved when the HBR was fed with -10 dBm RF power, and the data modulation consumed less than 27.7pJ/bit. In addition, a passive harmonic tag was implemented with the proposed HBR and a low-power binary sequence generator, which demonstrated a continuous uplink of 12 kbps at -6 dBm RF power.
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All authors Dan Che, Changjun Liu, Haoming He, Zhi Hua Ren, Pengde Wu
Atmospheric and Oceanic Physics · Cross-listed from nlin.PS
An Open-Source Pseudo-Spectral Solver for Idealized Korteweg-de Vries Soliton Simulations
Dasapta E. Irawan, Sandy H. S. Herho, Faruq Khadami et al. (+5 more)
The Korteweg-de Vries (KdV) equation governs the propagation of nonlinear internal and surface
gravity waves in shallow ocean environments, where the balance between nonlinear steepening and frequency-dependent dispersion produces
solitons. This article presents sangkuriang, an open-source Python library that solves the KdV equation using
Fourier pseudo-spectral spatial discretization and adaptive eighth-order Runge-Kutta time integration, accelerated via just-in-time (JIT) compilation. Validation across four progressively complex scenarios-isolated
soliton propagation, symmetric interactions, overtaking collisions, and three-body interactions-demonstrates high-fidelity conservation of mass, momentum, and energy, with relative errors below $O(10^{-4})$. Measured
soliton velocities agree with theoretical predictions within $5\%$, and complementary diagnostics based on spectral
entropy and recurrence quantification analysis (RQA) confirm that computed solutions preserve the regular phase-space structure characteristic of integrable
Hamiltonian systems. Running on a standard laptop, sangkuriang provides a robust, lightweight platform for reproducible numerical investigation of idealized nonlinear dispersive wave dynamics relevant to coastal and ocean engineering applications.
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All authors Dasapta E. Irawan, Sandy H. S. Herho, Faruq Khadami, Iwan P. Anwar, Karina A. Sujatmiko, Alfita P. Handayani, Faiz R. Fajary, Rusmawan Suwarman
Space Physics · Cross-listed from astro-ph.EP
Stability of equilibrium points in modified elliptic restricted three-body problem with various perturbation sources
M. B. Saputra, H. S. Ramadhan, Ibnu N. Huda et al. (+1 more)
This study examines the dynamics of the third body in an
elliptic restricted three-body problem (ERTBP) framework, taking into account perturbations from radiation pressure, oblateness, and elongation of the primary bodies, as well as disk-like structures. The objectives are to determine the positions and stability of the
equilibrium points, asses how these points shift under the influence of perturbations, and evaluate the dependence of their stability on the orbital eccentricity and perturbation parameters. The ERTBP model is modified to include a radiating, oblate primary body and an elongated secondary body modeled as a finite straight segment, alongside perturbations from a surrounding disk. The system's equations of motion are numerically solved using parameters from perturbed and classical cases.
Equilibrium positions are computed over a range of eccentricities and perturbation values, and stability is analyzed using linearized equations and
eigenvalue methods. In all cases, we have found three collinear ($L_1$, $L_2$, $L_3$) and two non-collinear ($L_4$, $L_5$)
equilibrium points solutions. The inclusion of radiations, oblateness, elongation using a finite straight segment, and disk perturbation systematically displaces each
equilibrium point from its classical location, with the magnitude and direction of the displacement varying with the perturbation parameter. Stability analysis confirms that the collinear points remain linearly stable under all tested conditions. Meanwhile, non-collinear points are stable under a specific condition. We investigate the stability boundary of these points as a function of orbital eccentricity and we found there is a critical range of eccentricity values within which stability is preserved.
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All authors M. B. Saputra, H. S. Ramadhan, Ibnu N. Huda, Leonardus B. Putra
Optics
Temporal Beam Self-Cleaning in Second-Harmonic Generation
Siyu Chen, Jun Ye, Lei Du et al. (+5 more)
The spatial-temporal beam quality of
laser sources is crucial for applications such as nonlinear spectroscopy and master oscillator power amplification systems. However, the temporal stability remains challenged by issues like line-width broadening and high-power demand in efforts to improve it. In this work, we investigate the effect of the second-harmonic generation process on the
laser characteristics under three longitudinal mode regimes: single-longitudinal-mode, dual-longitudinal-mode, and multi-longitudinal-mode. The results demonstrate that the second-harmonic generation process effectively stabilizes the temporal characteristics of the
laser and enhances its correlation, leading to a temporally clean output beam. The physical mechanism of the observed temporal stabilization effect can be attributed to a high-peak-pulse attenuation effect, jointly induced by nonuniform longitudinal-mode depletion and phase preservation in the residual fundamental wave. Statistical analysis indicates that at the maximum fundamental-wave power in the multi-longitudinal-mode regime, the standard deviation and peak-to-valley values derived from the normalized temporal profile decrease from 0.6122 and 5.6846 for the fundamental wave to 0.189 and 0.8847 for the residual fundamental wave. Meanwhile, the background level of the intensity auto-correlation function rises from ~0.72 to ~0.96, revealing its
evolution toward a more coherent state. To the best of our knowledge, this research presents the first demonstration of
laser temporal stabilization and correlation enhancement via second-harmonic generation. It not only deepens the comprehension of second-harmonic generation mechanisms, but also opens up a new avenue for realizing temporal beam self-cleaning of light.
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All authors Siyu Chen, Jun Ye, Lei Du, Wenwen Cheng, Jiangming Xu, Rongtao Su, Pu Zhou, Zongfu Jiang
Computational Physics
Padé Approximation and Partition Function Zeros
R. G. M. Rodrigues
Fisher zeros play a central role in the theoretical understanding of phase transitions. However, their computation requires knowledge of the density of states, which limits their practical applicability. Alternative approaches based on the Energy Probability Distribution (EPD) and Moment Generating Function (MGF) alleviate the computational cost but suffer from convergence issues in the two-dimensional anisotropic Heisenberg model (XY model). In this work, we introduce a Padé approximation to systematically reduce the number of zeros required in the Fisher, EPD, and MGF formulations without loss of accuracy. Moreover, since the Fisher zeros formulation does not rely on a convergence
algorithm, combining this approach with a Padé approximation enables a reliable analysis of the XY model while significantly reducing computational cost. Applications to the two-dimensional Ising and XY models demonstrate substantial decreases in
polynomial degree and computation time while preserving accurate estimates of the critical temperature.
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Instrumentation and Detectors
A prototype gas cell for the stopping, extraction and neutralization of radioactive nuclei from the SPIRAL2 Super Separator Spectrometer (S$^3$)
W. Dong, V. Manea, R. Ferrer et al. (+9 more)
We present the design and simulation of a prototype gas
cell for in-gas-jet
laser-ionization and spectroscopy studies using the low energy branch of the SPIRAL2-S$^3$ radioactive-ion-beam facility. The prototype aims to demonstrate the possibility to reduce the extraction time of radioactive ions from the gas
cell, while implementing a controlled neutralization mechanism, necessary for
laser-spectroscopy studies. Different simulation methods of ion processes in gas are comparatively discussed. Design considerations and detailed simulations of the ion extraction time and efficiency are presented. A study of the dynamics of electrons obtained in the gas
cell by ionization is also performed to assess the achievable electron densities.
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All authors W. Dong, V. Manea, R. Ferrer, S. Franchoo, S. Geldhof, F. Ivandikov, N. Lecesne, D. Lunney, V. Marchand, E. Minaya Ramirez, E. Morin, S. Raeder
Physics and Society
Observing rurality of a geographical area from road graph geometry – a qualitative study
Rami Luisto
In this paper we analyze the Finnish road network as a graph in order to measure whether the "rurality" or "urbanity" of an area correlates with local geometrical properties of the graph. Our primary motivation is the observation that the road systems in rural areas look similar to
hyperbolic graphs, while in large cities they resemble more the Cayley graph of $\mathbb{Z}^2$. We do not aim for a comprehensive analysis, but rather wish to demonstrate that this observation can be measured and analyzed through looking at various "hyperbolicity measures" of randomly sampled geodesic triangles in the road graph.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
The CP-PAW code package for first-principles calculations from a user's perspective
Peter E. Blöchl, Robert Schade, Lukas Allen-Rump et al. (+5 more)
CP-PAW is a combined electronic structure and ab-initio molecular dynamics code to perform mixed
quantum and classical simulations of atomistic condensed phase systems, such as solids,
liquids, and molecular systems. As the name suggests, the CP-PAW code unifies the all-electron projector augmented-wave method with the Car-Parrinello approach to determine not only the electronic and
nuclear ground state of condensed matter, but also to study their properties and dynamics. In addition to briefly outlining the underlying theory, the focus will be on unique aspects of CP-PAW and how to correctly employ them as a user. How to install CP-PAW using the new build system will also be briefly mentioned.
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All authors Peter E. Blöchl, Robert Schade, Lukas Allen-Rump, Sangeeta Rajpurohit, Amrith Rathnakaran, Konstantin Tamoev, Mani Lokamani, Thomas D. Kühne
Accelerator Physics
Topological aspects of zero modes in cavity resonators
Osamu Kamigaito
We discuss the relationship between the zero modes of electromagnetic fields in a cavity resonator and the cavity's topological characteristics. We show that the dimension of the electromagnetic zero-mode space coincides with the dimension of the corresponding homology group of the cavity. Moreover, we prove that the alternating sum of the dimensions of the electromagnetic zero-mode spaces is closely related to the Euler characteristic of the cavity boundary, and hence to the integral of the
curvature.
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Instrumentation and Detectors
Comprehensive study of cosmogenic neutron production in large liquid scintillator detectors
Yijian Jiang, Jie Cheng, Haoqi Lu et al. (+1 more)
Neutrons produced by
cosmic ray
muons constitute a significant background for underground experiments investigating
neutron oscillations, neutrinoless double beta decay, dark matter, and other rare event signals. This work
benchmarks measured
neutron yields and
neutron multiplicities–with a focus on data from the Daya Bay Reactor
Neutrino Experiment–against comprehensive simulations using three GEANT4 hadronic physics lists. These simulations are further refined via a TALYS-based adjustment of hadronic cross sections. For the BERT-based models, the adjustment reduces the discrepancy in the total
neutron yield from about 20% to approximately 6%, while for the BIC-based models it improves the agreement from roughly 13% to the sub-percent level (~0.3%), indicating a markedly better consistency of the BIC-based models with the experimental data. Nevertheless, a clear tension persists: simulations systematically underproduce single-
neutron events while overproducing multi-
neutron events. The study establishes a reproducible
benchmark for cosmogenic
neutron modeling and proposes a targeted refinement strategy–including channel-specific reweighting and intranuclear cascade parameter tuning–to guide future model development.
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All authors Yijian Jiang, Jie Cheng, Haoqi Lu, Yaoguang Wang
Fluid Dynamics
Minimal seed in supersonic boundary layer at $M=3$
Nobutaka Taniguchi and Aiko Yakeno
This study investigates the minimal seed for laminar-to-turbulent transition in a supersonic boundary layer at $M=3.0$ and $Re=300$ using adjoint-based nonlinear non-modal analysis. While linear theory identifies oblique waves as the optimal disturbances for transient growth, we demonstrate that nonlinear effects fundamentally alter the optimal perturbation structure as the initial amplitude exceeds a critical threshold. Our analysis reveals that the nonlinear optimal perturbation exhibits a distinctive spatial distribution characterized by flattened structures in the outer layer and streamwise
vortices near the wall, leading to a more rapid transition compared to the linear counterpart. A key finding is that this nonlinear amplification mechanism remains robust even under wall-cooled conditions ($T_w = 0.6 T_{ad}$), where the disappearance of the generalized inflection point (GIP) suppresses linear instabilities of Mack's first mode. This rapid growth is driven by the nonlinear interaction between two-dimensional planar waves near the wall and staggered
vortex patterns in the outer layer, facilitating streak formation through
vortex self-induction. Although the late-stage
evolution eventually converges to the classical oblique breakdown scenario as characterized by the formation of $\Lambda$-
vortices, the identified nonlinear path significantly reduces the disturbance energy required for transition.
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Optics
Broadband silicon polarization beam splitter based on Floquet engineering
Ning Ma, Yu Chen, Yunjie Li et al. (+4 more)
A broadband silicon polarization beam splitter (PBS) is proposed and experimentally demonstrated based on Floquet-engineered directional couplers. The total length of the coupling structure is 20 um . By periodically modulating the waveguide width of the directional couplers, the power exchange between the two waveguides for the transverse-electric (TE) mode is suppressed, whereas the power coupling for the transverse-
magnetic (TM) mode is enhanced. The fabricated PBS exhibits polarization extinction ratios (PERs) > 20 dB for both polarizations over a broad wavelength range of 1483 nm-1620 nm. Additionally, the measured insertion losses (ILs) are 0.15 dB and 1.2 dB at 1550 nm for TE and TM polarizations, respectively.
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All authors Ning Ma, Yu Chen, Yunjie Li, Shubin Huang, Wen-di Li, Minghua Chen, Ciyuan Qiu
Biological Physics
Intelligent Nano-Fingerprinting: An Efficient and Precise Approach for Liquid Biopsy
Yuxin Yang, Hexiang Bai, Meihua Shangguan et al. (+11 more)
Biological
matrices are rich in information related to life processes, serving as invaluable media for assessing an individual's overall physiological status and its dynamic fluctuations, as well as crucial foundations for disease diagnosis. However, the inherent complexity of these
matrices, coupled with our incomplete understanding of their full composition, presents significant challenges for comprehensive analysis and accurate diagnostic interpretation. The advent of single-molecule technologies has revolutionized biomedical research, enabling the direct observation of life processes at the molecular scale. We have proposed an Intelligent Nano-Fingerprinting strategy based on single-molecule nanopore technology, designed to capture the global molecular fingerprints of complex
plasma matrices. Furthermore, we developed an intelligent algorithmic model capable of achieving precise classification of
plasma samples. This approach is characterized by its simplicity, efficiency, and considerable potential for large-scale adoption and transferable applications.
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All authors Yuxin Yang, Hexiang Bai, Meihua Shangguan, Siying Shao, Yizheng Fang, Long Yi, Haozhong Ma, Hongxia Xu, Xiawei Li, Yulian Wu, Zhenrong Zheng, Xu Liu, Jian Wu, Longhua Tang