Fluid Dynamics
A framework for diagnosing inertial lift generation in wall-bounded flows: application to eccentric rotating cylinders in Newtonian and shear-thinning fluids
Masafumi Hayashi and Kazuyasu Sugiyama
A body moving in a wall-bounded flow often experiences a hydrodynamic lift force normal to the wall, which plays an important role in many fluid systems. In this study, we develop a framework for diagnosing steady inertial lift from the internal structure of the flow field. Based on the generalised reciprocal
theorem for finite-Reynolds-number flows, the lift is expressed as a volume integral that identifies both the dominant contributions and the regions from which they arise. We apply this framework to numerically obtained steady flows of Newtonian and shear-thinning fluids between eccentric rotating cylinders, and analyse the lift acting on the inner cylinder undergoing rotation and orbital motion. In particular, we focus on lift reversal induced by increasing eccentricity in a Newtonian fluid and on lift reversal induced by stronger shear-thinning behaviour at high eccentricity. The volume-integral expression decomposes the lift into a
vortex-force contribution associated with inertia and a viscous stress contribution associated with the non-uniform viscosity field, and shows that the former dominates over the parameter range considered here. As the eccentricity increases, negative relative vorticity, and in some cases tangential velocity, become stronger in the narrow-gap region, thereby enhancing the negative local
vortex-force contribution and inducing lift reversal. Stronger shear-thinning behaviour, on the other hand, amplifies negative relative vorticity near the inner cylinder, thereby increasing the positive local
vortex-force contribution and inducing lift reversal. These results demonstrate that the proposed framework is useful for diagnosing and interpreting steady inertial lift in wall-bounded flows.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Superfluid response of bosonic fluids in composite optical potentials: angular dependence and Leggett's bounds
Daniel Pérez-Cruz, Grigori E. Astrakharchik and Pietro Massignan
We study the superfluid response of a dilute bosonic fluid in the presence of two-dimensional composite potentials (such as triangular, Kagomé and quasiperiodic potentials, or superlattices), which may be obtained for example by superposing multiple
laser beams. We first find a sufficient condition for the external potential to yield a fully isotropic superfluid response. Then, we derive analytical expressions for Leggett's upper and lower bounds to the superfluid fraction (valid in the perturbative regime) that allow us to find the optimal direction along which each bound should be measured. Finally, we solve the problem numerically, and we confirm our analytical findings.
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Physics and Society
Be Water: An Evolutionary Proof for Trend-Following
Yijia Chen
The proliferation of diverse, high-leverage trading instruments in modern financial
markets presents a complex, "noisy" environment, leading to a critical question: which trading strategies are evolutionarily viable? To investigate this, we construct a large-scale
agent-based model, "MAS-Utopia," comprising 10,000
agents with five distinct archetypes. This society is immersed in five years of high-frequency data under a counterfactual baseline: zero transaction friction and a robust Unconditional Basic Income (UBI) safety net. The simulation reveals a powerful evolutionary convergence. Strategies that attempt to fight the
market's current - namely Mean-Reversion ("buy-the-dip") - prove structurally fragile. In contrast, the Trend-Following archetype, which adapts to the
market's flow, emerges as the dominant phenotype. Translating this finding, we architect an LLM-driven system that emulates this successful logic. Our findings offer profound implications, echoing the ancient wisdom of "Be Water": for investors, it demonstrates that survival is achieved not by rigid opposition, but by disciplined
alignment with the prevailing current; for
markets, it critiques tools that encourage contrarian gambling; for society, it underscores the stabilizing power of economic safety nets.
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Atomic Physics
Rapid axial loading of a grating MOT with a cold-atom beam
Rachel Cannon, Aidan S. Arnold, Paul F. Griffin et al. (+2 more)
Laser-cooled atoms are increasingly being used to realise practical
quantum devices, motivating the development of compact and robust atom sources. Grating magneto-optical traps (gMOTs) simplify the cold-atom source architecture but are typically vapour-loaded and provide limited atomic flux. Here we explore the loading of gMOTs from cold-atom beams. We numerically simulate loading to show that unbalanced diffracted beams deflect incoming atoms away from the trap centre, thereby strongly constraining radial loading. In contrast, axial loading injects atoms directly into the trapping volume and largely avoids these effects. We experimentally demonstrate rapid axial loading of a gMOT, achieving loading rates of $2.1 \times 10^9$ atoms~s$^{-1}$ using a moving optical molasses to transfer atoms from a 2D MOT into the gMOT. These results establish axial loading as a robust route to high-flux gMOT operation for portable cold-atom systems.
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All authors Rachel Cannon, Aidan S. Arnold, Paul F. Griffin, Erling Riis, Oliver S. Burrow
Plasma Physics
FDTD Simulation of O-X Mode Conversion Process in Non-uniform Magnetized Plasma
Chenxu Wang, Ryota Usui, Hiroaki Nakamura et al. (+2 more)
Electron Bernstein Waves (EBWs) are electrostatic waves than can propagate in overdense
plasmas without density cutoff, making them suitable for high density
plasma heating. Since EBWs cannot be directly launched from
vacuum, mode conversion processes such as O-X-B conversion are required. In this study, the O-X mode conversion process is investigated using the finite difference time-domain (FDTD) method in a magnetized
plasma with non-uniform density. In particular, the dependence of mode conversion characteristics on the incident angle of the injected wave is studied. The results show that an optimal incident angle exists at which the wave propagates without significant attenuation and strong electric field enhancement is observed near the upper hybrid resonance (UHR) layer. When the incident angle deviates from this optimal angle, an evanescent region appears, resulting in attenuation of the wave. These results demonstrate that angular optimization is essential for efficient wave propagation toward the UHR region and EBW excitation.
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All authors Chenxu Wang, Ryota Usui, Hiroaki Nakamura, Hideki Kawaguchi, Kubo Shin
Chemical Physics
Quantum Sensing with Triplet Pair States: A Theoretical Study
Maria Grazia Concilio, Yiwen Wang, Siyuan Wang et al. (+1 more)
Molecular
quantum sensors represent a promising frontier for the detection of
nuclear magnetic resonance signals and alternating current
magnetic fields at the nanoscale, potentially reaching single-
proton sensitivity. Although the triplet states of molecular pentacene provide a viable sensing architecture, the triplet pair states produced by singlet fission of pentacene dimers could enable more flexible
quantum manipulations through
entanglement. In this work, we model the
quantum sensing efficacy of a
spin-polarized quintet
manifold in a photoexcited pentacene dimer generated via intramolecular singlet fission. Using a Lindblad master equation approach, we simulate the
evolution of the triplet pair state under standard dynamical decoupling sequences, including
spin echo, XY4, and XY8 and provide a direct performance comparison to the traditional pentacene monomer
benchmark. While both architectures exhibit comparable sensitivity for isolated single-
spin detection, our findings indicate that the dimer architecture provides a superior interaction cross-section for detecting small ensembles of
nuclear spins. Analytical expressions derived for fluorescence modulation demonstrate that sensitivity is optimized in the low-
magnetic field regime and scales with the number of pulses in the sensing protocol. This study establishes a theoretical baseline for utilizing high-
spin multi-excitonic states as chemically tunable, high-sensitivity
quantum probes.
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All authors Maria Grazia Concilio, Yiwen Wang, Siyuan Wang, Xueqian Kong
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Phase-Singularity Control of Topological Acoustic Spin Textures
Huaijin Ma, Te Liu, Jiachen Sheng et al. (+6 more)
Acoustic
spin textures provide a degree of freedom for programmable topological field states, yet a unified framework for constructing and classifying higher-order textures in open-air acoustics remains lacking. Here we introduce polygonal standing-wave interference as a framework connecting discrete
symmetry, angular phase encoding, phase singularities,
chiral time-averaged energy flux, and acoustic
spin. By controlling the number and relative phases of the standing-wave channels, we experimentally realize D4 meron/anti-meron
lattice, D6 double-skyrmion superlattice, and D8 acoustic-
spin quasicrystal composed of four meron/anti-meron sublattices. Finite polygonal fields are normalized angular discretizations of continuous standing-wave spectra. Under the m=2 phase encoding, the D6 and D8 fields reproduce the local q=+2 core of a second-order Bessel
vortex while retaining distinct long-range order through their discrete interference channels. At fixed m increasing N under normalized angular sampling yields the continuous Bessel limit. These results establish phase encoding, pairwise interference, reciprocal-space composition, and angular discretization as a unified design principle for programmable topological acoustic
spin textures.
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All authors Huaijin Ma, Te Liu, Jiachen Sheng, Xiaochang Pan, Wenwei Qian, Xiangyu Chen, Kaiyuan Cao, Jinpeng Yang, Jian Wang
Computational Physics · Cross-listed from quant-ph
Open Quantum Systems from Dynamical Constraints
Yu Su and Yao Wang
Open
quantum systems are traditionally described by decomposing the total
Hilbert space into a system and an external environment, linked by an explicit interaction
Hamiltonian. We propose an alternative framework in which the environment is not introduced as an independent sector a priori, but instead emerges from the dynamical activation of constraints in an initially constrained
quantum system. Within Dirac quantization, the physical degrees of freedom define the system, whereas the constraint sector, once promoted to carry its own dynamics, functions as an environment. In this picture, the system-environment coupling is not added through a separate interaction term, but is encoded directly in the constraint structure. As an example, we study a
quantum particle coupled to a Brownian-oscillator environment and show how the resulting environmental influence can be formulated in this constraint-based setting. Our results provide a new perspective on the origin of
quantum environments and point toward a general framework for open
quantum systems rooted in constrained quantization.
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Atomic Physics
Thomas-Fermi equation revisited: A variation on a theme by Majorana
Berthold-Georg Englert
Majorana found a way to exploit the scaling properties of the Thomas-
Fermi equation for converting this second-order differential equation into one of first order. We explore his method for the familiar neutral-atom solution and extend it to the solution that is relevant for weakly ionized atoms. Various integrals and other quantities with importance for atomic physics are recalculated and their values compared with the ones obtained in the 1980s by more tedious numerical procedures.
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Atmospheric and Oceanic Physics
30-meter Land Surface Temperature from Landsat via Progressive Self-Training Downscaling
Huanfeng Shen, Chan Li, Menghui Jiang et al. (+3 more)
Land surface temperature (LST) is a critical parameter for characterizing surface energy balance and hydrothermal processes. While Landsat provides invaluable LST observations at medium spatial resolution for over 40 years, its native spatial resolution of thermal bands (e.g., 100 m) remains insufficient compared to its 30 m optical bands, failing to meet the demands of fine-scale studies. To address this issues, this study proposes a progressive self-training framework for downscaling Landsat LST to 30 m without relying on fine-scale ground truth, while maintaining minimal data dependence. The framework progressively optimizes a cross-modal fusion network to refine thermal details in a coarse-to-fine manner, characterized by one pre-training and two fine-tuning stages. Spatial validation against SDGSAT-1 30 m LST and temporal validation using in situ measurements confirm its reliability and accuracy, with both station-averaged MAE and RMSE outperforming the official cubic product by approximately 0.4 K. Further performance comparison experiments demonstrate that the proposed framework consistently reconstructs coherent fine-scale thermal patterns while preserving spatial heterogeneity. Multi spatial resolution evaluations and ablation studies verify the effectiveness of the proposed strategy and network design. Overall, the framework provides a stable pathway for enhancing the spatial resolution of Landsat LST, providing fine-resolution data support for fine-scale surface process studies and localized environmental monitoring.
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All authors Huanfeng Shen, Chan Li, Menghui Jiang, Penghai Wu, Guanhao Zhang, Tian Xie
Accelerator Physics
Seeding of Self-Modulation using Truncated Seed Bunches as a Path to High Gradient Acceleration
N. Z. van Gils, E. Belli, M. Bergamaschi et al. (+11 more)
This manuscript proposes a method to enable controlled high-gradient particle acceleration when requiring self-modulation of the drive bunch. While electron bunch seeding of self-modulation (eSSM) has been realised at a
plasma electron density $n_\mathrm{pe}\cong10^{14}\mathrm{cm}^{-3}$, it has not been demonstrated at higher
plasma densities due to limitations of available seed bunch properties. As experimentally shown in this manuscript, truncating available seed bunches with a relativistic ionisation front allows these limitations to be overcome. This seeding method is called truncated electron bunch seeding of self-modulation (teSSM) and experiments confirm that – when using teSSM – self-modulation becomes reproducible at $n_\mathrm{pe}=7\times10^{14}\mathrm{cm}^{-3}$. Additionally, the seed wakefield amplitude is also increased, which is known to be advantageous because it shortens the length needed to reach self-modulation saturation. The presented results establish teSSM as a method for achieving controlled, high-gradient particle acceleration with long drivers and available seed bunches.
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All authors N. Z. van Gils, E. Belli, M. Bergamaschi, A. Clairembaud, A. Gerbershagen, E. Gschwendtner, H. Jaworska, J. Mezger, M. Moreira, P. Muggli, F. Pannell, L. Ranc, M. Turner, the AWAKE Collaboration
Classical Physics
Magnetic transport and chaotic orbits of charged particles
Dirk Dubbers
I study electron movement in electromagnetic fields beyond the adiabatic approximation, using so-called Stormer theory. Some of the electron orbits are regular or integrable, but their measure is zero. Other orbits, called quasiperiodic, are unstable, but only for infinite times. All other orbits are chaotic or hyperchaotic, or simple scattering states. Examples for typical electron orbits are given for all these cases. An open question still is whether the spectral changes due to Stormer will translate into changes in the limits on
neutrino masses and on errors in
neutrino-electron correlation experiments.
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Chemical Physics
Local thermal probe in a one-dimensional chain: An efficient dissipaton-based approach
Hao-Yang Qi, Zi-Fan Zhu, Yao Wang et al. (+2 more)
We study a system consisting of an infinite one-dimensional molecular chain and a locally coupled probe. Starting from the
Hamiltonian of the chain-probe composite and the corresponding spectral densities, we evaluate the heat current between the probe and the chain. For this purpose, we develop a dissipaton-based
quantum approach that is fully nonperturbative and non-Markovian. The dissipaton
algebra yields a set of hierarchically coupled equations of motion for the dissipaton moments, with cross-tier connections in an iterative manner if higher-order chain-probe interactions are included. Numerical results demonstrate the effects of temperature, frequency, onsite energy modification and higher-order couplings on heat transport. This work provides a general framework for thermal transport and other properties in locally probed systems and can be straightforwardly extended to higher-dimensional materials and electronic transport problems with strong many-body effects.
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All authors Hao-Yang Qi, Zi-Fan Zhu, Yao Wang, Rui-Xue Xu, YiJing Yan
Biological Physics · Cross-listed from cond-mat.stat-mech
Force Geometry and Irreversibility in Nonequilibrium Overdamped Dynamics
Erez Aghion and Swetamber Das
Recent experiments have revealed heterogeneous dissipation in optically trapped systems, often anticorrelated with local positional fluctuations, exposing a structural gap in the scalar
stochastic thermodynamic description. While the scalar framework successfully quantifies dissipation through currents and
entropy production rates, it does not reveal the underlying vectorial force geometry that shapes spatial dissipation patterns. Here, we bridge this gap by identifying force geometry as an organizing principle for nonequilibrium thermodynamics, introducing force
alignment as a
geometric determinant of irreversibility. We show that
entropy production depends not only on force magnitudes but also on the relative orientation between deterministic driving forces and entropic gradients, vanishing only under exact anti-
alignment with matched magnitudes. We formalize this
geometric alignment through a time-dependent force-correlation coefficient, quantifying the relative orientation between the forces. This yields an instantaneous
geometric lower bound on
entropy production that remains valid even when force magnitudes are matched. For overdamped dynamics, perfect anti-
alignment defines a thermodynamic stall where net transport vanishes and the lower bound on
entropy production is saturated. This force-level perspective provides a structural explanation for the experimentally observed fluctuation-dissipation anticorrelation and nonuniform dissipation. We construct
geometric control charts for both constant dragging and sinusoidal driving protocols, explicitly locating experimental operating points within this force-space representation. Together, these results position force geometry as a unifying structural perspective on irreversibility, spanning active biological systems, microrheology, and naturally extending to underdamped dynamics.
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Instrumentation and Detectors
Using Fast Reading Current Integrator for Advanced Ion Beam Diagnostics Across Continuous and Pulsed Modes
I-Chun Cho, Chien-Hsu Chen, Huan Niu et al. (+3 more)
A fast-reading current integrator is developed for high time-resolution and low-noise ion beam diagnostics under both continuous-wave and pulsed operating conditions. The system combines a low-leakage transimpedance front-end with a hybrid digitization architecture based on charge-balancing and voltage-to-frequency conversion. The input current is converted into a pulse stream corresponding to discrete charge quanta, enabling event-driven measurement with temporal resolution down to 0.5 ms while preserving a wide dynamic range and high linearity. The system further enables real-time pulse selection for instantaneous dose-rate estimation and reconstruction of time-dependent beam structures. A deterministic beam-interrupt signal is generated within <1 us upon reaching a predefined charge threshold, enabling fast feedback control. Additional functionalities, including threshold- and slope-based gating as well as phase-sensitive detection, enhance performance under noisy or modulated beam conditions. Calibration with precision current sources and beamline detectors demonstrates stable operation with excellent linearity and timing fidelity. The proposed system provides a compact and flexible platform for next-generation ion beam diagnostics requiring fast response, large dynamic range, and time-resolved measurement.
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All authors I-Chun Cho, Chien-Hsu Chen, Huan Niu, Cheng-Ya Pan, Chun-Hui Hsing, Tung-Yuan Hsiao
Optics
Model-Based Beam-Steered Optical Wireless Positioning with Single-LED Single-Photodiode for 3D Localization
Kevin Acuna-Condori, Bastien Béchadergue, Hongyu Guan et al. (+1 more)
State-of-the-art optical wireless positioning (OWP) commonly reaches centimeter-level accuracy by depending on dense multi-light-emitting diodes (LED) infrastructures, photodiode (PD) arrays, or image-sensor receivers, incurring hardware complexity and deployment cost. This paper introduces a single beam-steered LED, single-PD OWP architecture that achieves three-dimensional (3D) localization without receiver rotation, cameras, or PD arrays; the core idea is to steer the transmitter through K known orientations and exploit the resulting received-signal-strength variations at the PD to estimate LED-to-PD direction and distance. We derive a composite Cramer-Rao lower bound and position-error bound (PEB) for the joint observation model, and cast the steering-pattern design as a genetic
algorithm that minimizes the PEB over a 3D testbed. We develop both model-based a constrained nonlinear
estimator and closed-form direction
estimators: a statistically efficient generalized least squares solution, and a lightweight weighted least squares approximation. Simulations demonstrate centimeter-level accuracy for 3D OWP with a single beam-steered LED and a single PD.
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All authors Kevin Acuna-Condori, Bastien Béchadergue, Hongyu Guan, Luc Chassagne
Fluid Dynamics · Cross-listed from cond-mat.mes-hall
Nonlinear hydrodynamic response of a quantum Hall system
Hiroki Isobe
The
quantum Hall effect realizes a quantized
Hall resistance $R_{xy} = h/(\nu e^2)$ whereas the longitudinal resistance vanishes. The quantized value consists of the fundamental physical quantities, the elementary charge $e$ and the Planck constant $h$, along with an integer or fractional constant $\nu$. High precision measurements of $R_{xy}$ allude to a linear relation between the applied current $I$ and the
Hall voltage $V_\mathrm{H}$. Here, we argue that a nonlinear relation between $I$ and $V_\mathrm{H}$ could arise when the electric field is spatially inhomogeneous. We first discuss that the linear $I$-$V_\mathrm{H}$ relation holds with Galilean invariance. Then we consider a hydrodynamic description of a
quantum Hall liquid to deal with an axially symmetric electric field. It reveals a nonlinear electronic response arising from the centrifugal force exerted on a curved flow and the density gradient invoked by vorticity.
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Space Physics
Closed-Form Solutions to the Fokker-Planck Equation for Orbital Uncertainty Propagation
Jose Antonio Rebollo, Rafael Vazquez and Claudio Bombardelli
Non-Gaussian tails dominate collision probability estimates in conjunction assessment, yet capturing them without Monte Carlo sampling is challenging, especially when process noise is included. We present a closed-form, grid-free solution to the Fokker-Planck equation by proving that an exponential-of-quadratic-form ansatz is structurally preserved under advection and
diffusion. The probability density function propagates via a compact ODE system, significantly cheaper than Monte Carlo and without spatial discretization. As an application, the method performs orbit uncertainty propagation under
stochastic forcing representative of atmospheric drag. Results demonstrate the method faithfully captures non-Gaussian features, asymmetric tails, and
stochastic broadening, matching a Monte Carlo
benchmark.
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Optics
Recirculating frequency-shifting loop for flexible optical chirp generation and FMCW LiDAR
Alexander Mrokon, Sebastian Schöler, Leonard Vossgrag et al. (+2 more)
A recirculating frequency-shifting loop (FSL) provides a highly flexible platform for generating coherent optically chirped light with tunable bandwidth, duration, chirp rate and repetition rate. The properties of the chirped light are controlled using low-frequency sinusoidal electronic drive signals, enabling deterministic waveform synthesis without complex high-speed electronics. We achieve chirp bandwidths of 10 GHz with a duration in the nanosecond regime, representing one of the fastest tunable
laser sources to date. Using such chirped
laser pulses, we demonstrate coherent FMCW
LiDAR measurements over distances up to 3 m, highlighting the potential of FSL-based sources for compact, scalable and high-performance ranging systems.
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All authors Alexander Mrokon, Sebastian Schöler, Leonard Vossgrag, Karsten Buse, Ingo Breunig
Chemical Physics · Cross-listed from cond-mat.mes-hall
Layer-selective hydrogenation and proton transport in twisted bilayer graphene
J. Tong, G. Chen, H. Li et al. (+13 more)
Recent work investigated
graphene's hydrogenation with independent control of the electric field, E, and charge density, n, in the
crystal and showed that the process is controlled by n. Here, we demonstrate layer-selective conductor-
insulator transitions in twisted
bilayer graphene, driven by hydrogenation at fixed n under strong E. This process is accompanied by
proton transport through the
bilayer, enabling several parallel and configurable logic gates in the devices. Selectivity arises because the large twist angle decouples the two layers' electronic systems, enabling independent control of their charge densities. Polarisation by the field then induces a charge imbalance at fixed total n, triggering hydrogenation when one of the layers' charge densities reaches the threshold for monolayer hydrogenation. Our results introduce a new type of electrode-electrolyte interface in which electrochemical processes are controlled with two decoupled 2D electron gases, opening new design opportunities for energy and information processing devices.
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All authors J. Tong, G. Chen, H. Li, E. Hoenig, M. Alhashmi, X. Zhang, D. Bahamon, G. R. Tainton, S. Sullivan-Allsop, Y. Mayamei, D. R. da Costa, L. F. Vega, S. J. Haigh, D. Domaretskiy, F. M. Peeters, M. Lozada-Hidalgo
Popular Physics · Cross-listed from astro-ph.CO
The Universe Favors Primes: A Study in the Primality of Cosmic Structures
Nan Li and Shiyin Shen
The cosmological principle states that the universe is uniform and does not favor any specific position or direction. However, research conducted by \cite{Shen2025} has revealed that the universe demonstrates a notable inclination towards parity-odd states. Furthermore, it remains uncertain whether the universe also favors
prime numbers. In this study, we examine the largest available catalogs of
galaxy groups to investigate this hypothesis. Specifically, we assess whether the number of
galaxies within a
galaxy group or cluster is more likely to be a
prime number. Our results strongly suggest that the universe does indeed have a preference for
prime numbers, with findings exceeding the 4.1 sigma significance threshold. This insight explains why the
Primes consistently triumphs over Unicorn. Consequently, it may be necessary to consider revising the cosmological principle in the context of a higher-dimensional feature space. Moreover, our research establishes a connection between the Riemann
Zeta function and cosmology pioneeringly, paving the way for the development of Cosmozetaology.
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Physics and Society
A Preliminary Theory of Infantile Dynamics
Lei Ma
We present a concise dynamical picture of infant-driven household chaos. The framework has three postulations: recurrent daily chaos, overall
entropy growth in household organization, and transient local ordering episodes with switching rules (a volatile Maxwell-demon effect). We illustrate
entropy growth with a two-region toy model (organizer vs. play area), where
entropy production is nonnegative and long-time behavior is typically play-area dominated. We also model toy
diffusion and curiosity-driven behavior, where novelty matters more than punishment in the short term, while gradual learning still occurs.
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Applied Physics
Spoken Digit Recognition and Speaker Classification by Nonlinear Interfered Spin Wave-Based Physical Reservoir Computing
Sota Hikasa, Wataru Namiki, Daiki Nishioka et al. (+4 more)
Recently, artificial-intelligence (AI) technologies have been increasingly utilized in a wide range of real-world applications.
Speech recognition is one of these practical AI tasks and is regarded as a key application for edge AI systems. Consequently,
speech recognition has been widely employed as a representative
benchmark task for assessing the performance of physical reservoir computing (PRC). Although many PRCs have performed this task, the majority of them rely on the frequency-extraction preprocessing method, such as a cochleagram and mel-frequency cepstrum. Especially about the cochleagram, this method enables high-accuracy recognition; however, it requires a substantial computational cost for preprocessing and is unsuitable for edge computing, due to the limited resources. In this study, we employed a nonlinear interfered
spin wave-based PRC, which demonstrated superior computational performance in mathematical tasks. Using this PRC, we evaluated the performance for two types of
speech recognition, spoken digit recognition and speaker classification under four configurations: cochleagram-alone, interfered
spin wave-based PRC with cochleagram, baseline without PRC, and interfered
spin wave-based PRC alone to quantify the contributions of the cochleagram and of the interfered
spin wave-based PRC for each task. As a result, although the cochleagram alone yielded accuracies around 90 % for both tasks, the accuracy reached 85.8 % for speaker classification when only the interfered
spin wave-based PRC was used. These results indicate the potential of the proposed PRC to handle
speech recognition tasks without cochleagram preprocessing.
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All authors Sota Hikasa, Wataru Namiki, Daiki Nishioka, Maki Nishimura, Ryo Iguchi, Kazuya Terabe, Takashi Tsuchiya
Applied Physics
Light-Sculpted Azopolymer Colloids: From Patchy Spheres to Porcupine and Pineapple Morphologies
Sh. Golghasemi Sorkhabi, R. Barille, M. Loumaigne et al. (+3 more)
A simple optical strategy to transform patchy PMMA azopolymer composite nanoparticles into complex, fully three-dimensional morphologies using controlled
laser polarization is presented. The particles consist of a PMMA core decorated with nanoscale azopolymer patches that undergo localized photofluidization upon trans cis isomerization. Linear polarization drives directed mass transport within each patch, producing elongated super-cones that collectively yield porcupine like particles, whereas circular polarization generates isotropic bump deformations reminiscent of sea-pineapple structures. A nonlinear, volume-conserving
geometric model quantitatively reproduces the patch-to-filament transition. Brownian and Jeffery-flow simulations reveal that these photoinduced morphologies dramatically alter hydrodynamic behavior, leading to enhanced anisotropic
diffusion, reduced rotational randomization, and polarization-dependent transport amplification in shear flow. This light-driven, reversible sculpting method provides a versatile route to programmable colloidal shapes and highlights geometry as a powerful control parameter for microscale transport, active materials, and soft-matter physics.
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All authors Sh. Golghasemi Sorkhabi, R. Barille, M. Loumaigne, A. Korbut, S. Zielinska, E. Ortyl
Atomic Physics
Spectroscopy of the $\mathbf{X^2\Sigma^+(v=2) \rightarrow A^2\Pi_{1/2}(v=1)}$ Transition in MgF: Hyperfine Structures and Spectroscopic Constants
Youngju Cho, Yongwoong Lee, Kikyeong Kwon et al. (+3 more)
We report spectroscopic results of the \(X^2\Sigma^+(v=2) \rightarrow A^2\Pi_{1/2}(v=1)\) transition in magnesium monofluoride (MgF). Using Doppler-free
Laser-Induced Fluorescence (LIF) spectroscopy on the \(X^2\Sigma^+(v=2) \rightarrow A^2\Pi_{1/2}(v=1)\) transition, we resolved 47 hyperfine components distributed over 11 transition lines in X and A states. An effective
Hamiltonian – comprising contributions from vibrational, rotational, \(\Lambda\)-doubling, and hyperfine interactions – was presented to model the energy structure of the \(A^2\Pi_{1/2}(v=1)\) state. The spectroscopic parameters, including the rotational constant, the \(\Lambda\)-doubling parameter, and the hyperfine interaction constants, were extracted using a least-square fitting and Markov Chain Monte Carlo (MCMC) procedure. Our study reveals that the spectroscopic constants show subtle changes compared to the \(A^2\Pi_{1/2}(v=0)\) state. These results provide critical spectroscopic
benchmarks for optimizing optical cycling schemes in MgF, thereby advancing optical cycling efficiency in the magneto-optical trapping of MgF.
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All authors Youngju Cho, Yongwoong Lee, Kikyeong Kwon, Seunghwan Roh, Giseok Lee, Eunmi Chae
Fluid Dynamics · Cross-listed from cs.LG
LGFNet: Local-Global Fusion Network with Fidelity Gap Delta Learning for Multi-Source Aerodynamics
Qinye Zhu, Yu Xiang, Jun Zhang et al. (+1 more)
The precise fusion of computational fluid dynamic (CFD) data, wind tunnel tests data, and flight tests data in aerodynamic area is essential for obtaining comprehensive knowledge of both localized flow structures and global aerodynamic trends across the entire flight envelope. However, existing methodologies often struggle to balance high-resolution local fidelity with wide-range global dependency, leading to either a loss of sharp discontinuities or an inability to capture long-range topological correlations. We propose Local-Global Fusion Network (LGFNet) for multi-scale feature decomposition to extract this dual-natured aerodynamic knowledge. To this end, LGFNet combines a spatial perception layer that integrates a sliding window mechanism with a relational
reasoning layer based on self-
attention, simultaneously reinforcing the continuity of fine-grained local features (e.g., shock waves) and capturing long-range flow information. Furthermore, the fidelity gap delta learning (FGDL) strategy is proposed to treat CFD data as a "low-frequency carrier" to explicitly approximate nonlinear discrepancies. This approach prevents unphysical smoothing while inheriting the foundational physical trends from the simulation baseline. Experiments demonstrate that LGFNet achieves state-of-the-art (SOTA) performance in both accuracy and uncertainty reduction across diverse aerodynamic scenarios.
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All authors Qinye Zhu, Yu Xiang, Jun Zhang, Wenyong Wang
Optics · Cross-listed from cond-mat.mtrl-sci
Machine Learning Assisted Reconstruction of Local Electronic Structure of Non-Uniformly Strained MoS2
Soumyadip Hazra, Sraboni Dey, Arijit Kayal et al. (+3 more)
Wrinkles and nanobubbles are an integral and often unavoidable part of integrating 2D van der Waals
semiconductors into actual device architectures. Despite their ubiquitous nature, quantitative correlation between such spatially non-uniform strain and modifications to the local electronic structure remains challenging. Here, density functional theory is combined with a recurrent neural network to reconstruct the local electronic structure of monolayer MoS2 from strain maps derived from atomic force microscopy (AFM) topography and Raman spectral maps. The analysis reveals that biaxial bending induced strain is significantly more effective than both uniaxial bending or in-plane strain in modifying electronic and dielectric properties. A ~ 0.35% strain induced by biaxial bending results in ~ 22% reduction in band gap and ~ 7% increase in dielectric constant, compared to a ~ 5% reduction in band gap and ~ 1% increase in dielectric constant under comparable uniaxial bending. The modified band structure reveals band edge states that concentrate charge in regions of high
curvature or strain. While conductive AFM measurements indicate increased local conductance (carrier density) at wrinkles and nanobubbles, the spatial band gap maps predicted by the model are validated against experimental photoluminescence peak energy maps. The results indicate that strained features like wrinkles and nanobubbles commonly present in real devices influence the band gap, carrier distribution, and dielectric response, which favourably affects electrical transport in such systems. The framework developed here can be readily extended to other 2D materials and
heterostructures, offering a computationally efficient route for studying and exploiting strain effects.
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All authors Soumyadip Hazra, Sraboni Dey, Arijit Kayal, Narendra Shah, Renjith Nadarajan, Joy Mitra
Instrumentation and Detectors
Assessment of the Imaging Performance of the CITIUS High-Resolution Detector for Heavy Charged Particles and Neutrons
Yoshio Kamiya, Haruki Nishino and Takaki Hatsui
We report on the assessment of the imaging performance of CITIUS – a high-speed X-ray detector developed for the large-scale synchrotron radiation facility SPring-8-II – for heavy charged particles and
neutrons. To characterize the detector response, an irradiation experiment was performed using alpha particles from an $^{241}$Am source at four back-bias voltages of 400V, 300 V, 200 V, and 170 V, thereby controlling the amount of charge
diffusion. A Geant4 model of the experiment was constructed, and four model parameters were determined by template fitting to the measured signal cluster shape distributions. The best-fit values are: an intrinsic energy spread of 5% for the source, a gold fraction of 0.4 for the Au-Pd coating, a lateral charge
diffusion spread of 26.5 ${\mu}$m over a drift distance of 650 ${\mu}$m at 400V back-bias, and a per-pixel readout noise of 10000 $e^{-}$ in the medium-gain channel. Using the obtained sensor model, simulations were performed for 4 MeV alpha particles and cold
neutrons to evaluate the expected spatial resolution. In both cases, simulated CITIUS, when operated in a gain-selecting mode between high and medium gains, yields a substantial improvement: at a pixel size of 70 ${\mu}$m for example, the resolution improves from 9.1 ${\mu}$m to 1.2 ${\mu}$m for alpha particles, and from 26 ${\mu}$m to 1.9 ${\mu}$m for cold
neutrons. These results suggest that two key features of CITIUS – its gain-selecting architecture and the substantial charge sharing enabled by the long carrier drift distance – extend its imaging capabilities beyond X-rays to heavy charged particles and
neutrons.
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Physics and Society
Social Amplification Dominates Collective Hazard Response
Xiaolei Chu, Guanren Zhou, Marco Broccardo et al. (+3 more)
Large-scale hazards affect societies not only through direct physical impacts but also through
emotions that spread across populations. Fueled by social amplification and networked communication, collective
emotions often diverge markedly from underlying physical threats, pressuring policymakers toward suboptimal decisions that erode long-term societal resilience and misalign risk governance priorities. Yet when exactly these collective
emotions mirror hazard severity and when they are warped by social dynamics remains poorly understood. We introduce a compact, interpretable model that couples hazard exposure with networked emotional contagion and identifies the transition from proportionate responses to an amplification regime sustained by negativity bias. Applying this framework to the COVID-19 pandemic in the United States, we integrate state-level epidemiological data with large-scale stress signals inferred from Twitter/X activity. Our analysis shows that social influence outweighed direct hazard forcing in over 80% of U.S. states during the study period, and that amplified stress covaries with major economic indices. These findings reveal a measurable regularity in societal hazard response, enabling quantitative anticipation of collective emotional tipping points and supporting community resilience under large-scale hazards.
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All authors Xiaolei Chu, Guanren Zhou, Marco Broccardo, Didier Sornette, Khalid M. Mosalam, Ziqi Wang
Fluid Dynamics · Cross-listed from cs.LG
Lie Generator Networks for Nonlinear Partial Differential Equations
Shafayeth Jamil and Rehan Kapadia
Linear dynamical systems are fully characterized by their eigenspectra, accessible directly from the generator of the dynamics. For nonlinear systems governed by partial differential equations, no equivalent theory exists. We introduce Lie Generator Network-Koopman (LGN-KM), a neural operator that lifts nonlinear dynamics into a linear latent space and learns the continuous-time Koopman generator ($L_k$) through a decomposition $L_k = S - D_k$, where $S$ is skew-symmetric representing conservative inter-modal coupling, and $D_k$ is a positive-definite diagonal encoding modal dissipation. This architectural decomposition enforces stability and enables interpretability through direct spectral access to the learned dynamics. On two-dimensional Navier–Stokes
turbulence, the generator recovers the known dissipation scaling and a complete multi-branch dispersion relation from trajectory data alone with no physics supervision. Independently trained models at different flow regimes recover matched gauge-invariant spectral structure, exposing a gauge freedom in the Koopman lifting. Because the generator is provably stable, it enables guaranteed long-horizon stability, continuous-time evaluation at arbitrary time, and physics-informed cross-viscosity model transfer.
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