Chemical Physics
Eliminating Delocalization Error through Localized Orbital Scaling Correction with Orbital Relaxation from Linear Response
Yichen Fan, Jincheng Yu, Jiayi Du et al. (+1 more)
Despite the great success that Kohn-Sham density functional theory (KS-DFT) has achieved, the delocalization error remains a major challenge for commonly used density functional approximations (DFAs), resulting in systematic errors in ionization energies, electron affinities, band structures, and charge distributions. A recently developed localized orbital scaling correction (LOSC) method, namely linear response LOSC (lrLOSC), addresses these challenges by incorporating a functional correction that includes the screening effect and orbital localization within the LOSC framework. The method has been shown to provide accurate descriptions of bulk systems and core-level binding energies in small molecular systems. In this work, we extend the applicability of lrLOSC to a broader range of molecular systems, spanning various sizes, with a focus on the corrections to valence orbital energies and total energies. To enable the calculation of large chemical systems, we developed an efficient implementation of lrLOSC with computational costs comparable to standard KS-DFT calculations. Numerical results show that, while screening provides modest improvements for small molecules, it becomes critical for achieving high accuracy in larger molecules, from linear to three-dimensional systems. With the screening effect well captured in a unified way, lrLOSC provides accurate descriptions for a wide range of chemical systems, including organic molecular systems of varying sizes and transition-metal
oxide complexes, establishing it as a powerful tool for enhancing the reliability of computational simulations of chemical systems.
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All authors Yichen Fan, Jincheng Yu, Jiayi Du, Weitao Yang
Optics
Wavefront Sensor for Laser Beams Based on Reweighted Amplitude Flow Algorithm
Ondrej Denk, Jan Pilar, Martin Divoky et al. (+2 more)
We present a reference-free computational wavefront sensor based on binary amplitude modulation and phase
retrieval. The method employs Digital Micro-mirror Device as a programmable amplitude modulator and reconstructs the complex optical field from multiple far-field intensity measurements using the Reweighted Amplitude Flow algo-rithm with Optimal Spectral Initialization. Unlike classical pupil-plane wavefront sen-sors, the proposed architecture does not include any wavelength-specific optical elements, enabling straightforward adaptation across a broad spectral range. The achievable spatial resolution of the reconstructed wavefront is scalable with the modulator resolution. We experimentally demonstrate wavefront reconstruction at 650 nm and at 2116 nm, where commercial wavefront sensors are not widely available. The reconstructed wavefront is validated against a commercial lateral shearing interferometer at 650 nm, and the method is further integrated into a closed-loop adaptive optics system using a deformable mirror. The approach is particularly suited for applications requiring high spatial resolution and large dynamic range in slowly varying or quasi-static
laser fields, where computational reconstruction speed is not of the primary concern.
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All authors Ondrej Denk, Jan Pilar, Martin Divoky, Miroslav Cech, Tomas Mocek
Fluid Dynamics
The search for the gust-wing interaction "textbook"
Paolo Olivucci and David E. Rival
We address whether complex physical relations can be investigated through the synergy of automated high-volume experiments and the reduction of large
datasets to a concise, representative subset of canonical examples – a "textbook". To this end, we consider the unsteady aerodynamics of wing-gust interactions, which is characterized by its rich, high-dimensional physics. We take advantage of a purpose-built gust generator to systematically produce over 1,000 distinct random gust events and to measure the unsteady loads induced on a delta wing. We then employ a data summarization procedure to identify representative subsets of increasing size from the large-scale database, which then serve as training data for a machine-learning model of the aerodynamic loads from sparse pressure measurements. An appropriately selected "textbook" of a few events can achieve predictive accuracy comparable to random training sets up to two orders of magnitude larger, capturing the intrinsic diversity of the full-scale data and enhancing modeling efficiency and interpretability. Our methodology evidences the potential of distilling the essential information contained in large amounts of experimental observations.
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Biological Physics · Cross-listed from cond-mat.stat-mech
Fluctuation-Response Design Rules for Nonequilibrium Flows
Ying-Jen Yang and Ken A. Dill
Biological machines like molecular motors and enzymes operate in dynamic cycles representable as
stochastic flows on networks. Current
stochastic dynamics describes such flows on fixed networks. Here, we develop a scalable approach to network design in which local transition rates can be systematically varied to achieve global dynamical objectives. It is based on the fluctuation-response duality in the recent Caliber Force Theory – a path-
entropy variational formalism for nonequilibria. This approach scales efficiently with network complexity and gives new insights, for example revealing the transition from timing- to branching-dominated fluctuations in a kinesin motor model.
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Optics
Non-Hermitian curved space via inverted wave equation
C. Zhang, M. Ikram, Y. Liu et al. (+2 more)
Directly determining graded materials from prescribed wave amplitude and phase is an inverse-design method developed following transformation optics (TO), which enables reflectionless propagation for an incidence wave. However, exiting formulations of this inverted method yields Hermitian media and are thus not applicable to non-Hermitian (NH) photonics. In this Letter, we extend this method to NH media, thereby offering more freedom for manipulating waves of no reflection. Our picture of curved-space powered with spatially distributed gain and loss, is exemplified by three types: amplitude control, phase conversion, and direction shunting. These examples showcase precise wave manipulation in a surprisingly simple manner, which is implementable in photonic platform using similar techniques employed in TO.
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All authors C. Zhang, M. Ikram, Y. Liu, H. Lin, B. Zhou
Atomic Physics
Probe-assisted Depopulation Pumping in Low-pressure Alkali-metal Vapor Cells for Magnetometry
M.E. Limes, J. Smoot, J. Perez et al. (+4 more)
For precision atomic magnetometry, inert buffer gas is included in alkali-metal vapor
cells to significantly broaden hyperfine transitions, which facilitates optical pumping and reduces diffusive relaxation, while also providing non-radiative excited state quenching. We show low-buffer gas pressure (below 50 Torr) alkali vapor
cells with resolved hyperfine
manifolds can also yield high-performance magnetometers. For high polarization in $^{87}$Rb, we optically pump $F=2$ states with narrow linewidth $\sigma_+$ light, while tuning a probe beam to depopulate $F=1$ states ($\Delta\nu = 6.8$ GHz from $F=2$). The probe tuning then also provides $F=2$ detection with high optical rotation and low probe broadening; we demonstrate top-bottom gradiometry, within a single 25 Torr, 0.5 cc
cell, that yields an Earth's field free-precession magnetometer sensitivity of 18 fT/$\sqrt{\text{Hz}}$ with a 1 kHz bandwidth, as well as RF magnetometer sensitivity of 12 fT/$\sqrt{\text{Hz}}$ in a small band about 110 kHz.
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All authors M.E. Limes, J. Smoot, J. Perez, J. Freeman, C. Amano-Dolan, D. Peters, W. Lee
Fluid Dynamics
Critical Reynolds Number as a Topological Phase Transition in Adaptive Fractional Hydrodynamics
Jose I. H. Lopez
We present a theoretical framework that models the laminar-turbulent transition as a topological change in the dissipative operator. The order s of the fractional
Laplacian is promoted from a fixed parameter to a dynamic field, governed by a variational principle that minimizes a regularized free-energy functional. This adaptive formulation continuously interpolates between the local, viscous dissipation of the Navier-Stokes equations and the non-local, anomalous dissipation characteristic of the inertial range in Kolmogorov
turbulence. From this framework, we derive an analytical expression for the critical Reynolds number, Rec, by establishing a spectral balance condition where the effective dissipative capacity of the laminar operator is saturated.
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Optics
Toward quantum-noise-limited interferometric measurements of optical nonlinearity in vacuum
Ali Aras, Adrien E. Kraych, Xavier Sarazin et al. (+3 more)
Quantum Electrodynamics predicts that the
vacuum must behave as a nonlinear optical medium: the
vacuum optical index should increase when it is stressed by intense electromagnetic fields. The DeLLight (Deflection of Light by Light) project aims to measure it by using intense and ultra-short
laser pulses. The experiment uses a Sagnac interferometer to amplify the tiny deflection signal of a low-intensity probe pulse crossing the
vacuum refractive-index gradient produced by an external high-intensity pump pulse. The measurement of the amplified signal by a CCD camera requires a high spatial resolution, which is limited by the ultimate
quantum noise of the CCD. However, interferometric phase noise induced by the mechanical vibrations of the interferometer is also amplified and degrades spatial resolution. To overcome this, we propose a new method named High-Frequency Phase Noise Suppression (HFPNS), based on the addition of a delayed replica (5 ns) of the probe pulse. The delayed pulse, which is not affected by the pump but is subject to the same vibration noise, enables offline subtraction of correlated phase noise. In this work, we present an experimental proof-of-concept on a prototype interferometer operating with a limited amplification factor ($\mathcal{A}\simeq25$), about 10 times smaller than the required value of the final experiment. We have succeeded in reducing phase noise by a factor of 40, resulting in a residual noise level 2.3 times higher than the expected
quantum noise. The residual noise is linked to delay-line instabilities and incident beam pointing fluctuations present during these tests. This result validates HFPNS as a robust method for future
quantum-noise-limited interferometric measurements of
vacuum optical nonlinearity, though additional stabilization and higher interferometric amplification are still needed.
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All authors Ali Aras, Adrien E. Kraych, Xavier Sarazin, Elsa Baynard, François Couchot, Moana Pittman
Chemical Physics
Connection between $GW$ and Extended Coupled Cluster
Johannes Tölle, Marios-Petros Kitsaras, Andreas Irmler et al. (+2 more)
Coupled-cluster (CC) theory and Green's function many-body perturbation theory (MBPT) have long evolved as distinct yet complementary frameworks for describing electronic correlation. While CC methods employ exponential wavefunction parametrizations that guarantee size extensivity and systematic improvability, Green's function approaches such as the $GW$ approximation describe quasiparticle and optical excitations through diagrammatic resummations. Recent analyses have established a formal correspondence between these frameworks: the $GW$ approximation is equivalent to an equation-of-motion (EOM) treatment of the direct-ring coupled-cluster doubles (drCCD) method. Within this context, the extended CC (ECC) ansatz offers a unified framework connecting CC and MBPT. This formulation bridges CC-based and Green's function-based methods, providing novel avenues for incorporating vertex corrections within a CC framework that preserves a sum-over-state representation of the self-energy and lead to potentially systematically improvable Green's function approaches.
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All authors Johannes Tölle, Marios-Petros Kitsaras, Andreas Irmler, Andreas Grüneis, Pierre-François Loos
Atomic Physics · Cross-listed from cond-mat.quant-gas
Experimental study of matter-wave four-wave mixing in $^{39}$K Bose-Einstein condensates with tunable interaction
Yue Zhang, Liangchao Chen, Zekui Wang et al. (+7 more)
We experimentally investigate four-wave mixing (FWM) of matter waves in two
geometric configurations in $^{39}$K Bose-Einstein condensates with the atomic interaction tuned via Feshbach resonances. For one configuration with the single-
spin component, the FWM yield increases with a larger scattering length. For the two-
spin component configuration, we specifically investigate FWM in both the droplet and gas parameter regimes. We find that the FWM yield reaches its maximum near the critical parameter region between the gas and droplet phases. Our research can help to optimize the FWM yield for matter-wave amplification and entangled atom pair generation, making it conducive to applications in
quantum information processing and precision measurement.
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All authors Yue Zhang, Liangchao Chen, Zekui Wang, Yazhou Wang, Pengjun Wang, Lianghui Huang, Zengming Meng, Zhuxiong Ye, Wei Han, Jing Zhang
Plasma Physics · Cross-listed from math-ph
Charged particle motion in a strong magnetic field: The first order expansion
Ugo Boscain and Wadim Gerner
We provide a mathematically rigorous derivation of the first order expansion of the motion of a charged particle in a strong
magnetic field. In contrast to the derivations that can be found in the physics literature we solely assume throughout that the
magnetic field is strong. In particular we do not need to make any structural assumptions on the particle motion, such as the gyroradius being small in comparison to the
magnetic length scale. Instead, some of the additional assumptions which are usually made in the physics literature turn out to be an a posteriori consequence in our approach. Our approach further justifies the utilisation of the guiding centre approximation at "bounce points" within
magnetic mirrors, a situation which violates the usual assumptions which are made in the physics literature when deriving the guiding centre approximation.
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Instrumentation and Detectors
A Helical-Deflector-Based Radio-Frequency Spiral Scanning System for keV Energy Electrons
Simon Zhamkochyan, Vanik Kakoyan, Vardan Bardakhchyan et al. (+21 more)
We present the design, modeling, and experimental validation of a
radio-frequency based time-to-position conversion system for keV electrons incorporating a helical deflector operating in the 400-1000 MHz range. The device performs circular deflection of the electrons when driven by a single RF frequency and enables spiral scanning when two phase-locked RF voltages with slightly different frequencies are applied. The superposition of the two phase-locked RF voltages produces an amplitude-beating field whose slowly varying envelope modulates the deflection radius, transforming the circular scan into a controlled spiral on the detector plane. A detailed theoretical model describing the electron dynamics under two phase-locked RF voltages with different frequencies was derived, yielding analytical expressions for the transverse velocity and radius-vector components at the deflector exit. The experimental studies demonstrated good agreement with the model predictions. Spiral scanning will allow measurements with picosecond resolution in a temporal dynamic range 1-2 orders of magnitude larger than the period of the circular scanning.
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All authors Simon Zhamkochyan, Vanik Kakoyan, Vardan Bardakhchyan, Sergey Abrahamyan, Amur Margaryan, Aram Kakoyan, Hasmik Rostomyan, Anna Safaryan, Gagik Sughyan, Hayk Gevorgyan, Artashes Papyan, Martin Pinamyan, Mikael Ivanyan, Satoshi N. Nakamura, John Annand, Kenneth Livingston, Rachel Montgomery, Patrick Achenbach, Josef Pochodzalla, Dimiter L. Balabanski, Ani Aprahamian, Viatcheslav Sharyy, Dominique Yvon, Hayk Elbakyan
Fluid Dynamics · Cross-listed from math.AP
A fluid-solid interaction problem in porous media
Diego Alonso-Orán and Rafael Granero-Belinchón
In this work, we derive asymptotic interface models for an elastic Muskat free boundary problem describing Darcy flow beneath an elastic membrane. In a weakly nonlinear regime of small interface steepness, we obtain nonlocal
evolution equations that capture the free-boundary dynamics up to quadratic order. In the long-wave thin-film regime, we rewrite the kinematic condition in flux form, flatten the moving domain, and derive a lubrication-type equation. Moreover, we establish well-posedness for these models in suitable Wiener spaces.
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Physics and Society
Detecting and forecasting tipping points from sample variance alone
Naoki Masuda
Anticipating tipping points in complex systems is a fundamental challenge across domains. Traditional early warning signals (EWSs) based on critical slowing down, such as increasing sample variance, are widely used, but their ability to reliably indicate imminent bifurcations and forecast their timing remains limited. Here, we introduce TIPMOC (TIpping via Power-law fits and MOdel Comparison), a parametric framework designed to statistically detect the approach of a bifurcation and estimate its future location using only the sample variance. TIPMOC exploits the mathematical property that variance diverges with a characteristic power-law form near codimension-one bifurcations. By sequentially monitoring system variance as a control parameter changes, TIPMOC statistically adjudicates between linear and power-law divergence at each step. When evidence favors power-law divergence, TIPMOC forecasts the impending tipping point and estimates its position; otherwise, it avoids false positives. Through numerical simulations, we demonstrate TIPMOC's robustness and accuracy in both detection and timing prediction across different types of dynamics and bifurcation, whereas the accuracy of timing prediction is limited. TIPMOC shows low false positive rates and performs well even with uneven sampling and colored noise. This method thus enhances the interpretability and practical utility of classical EWSs, serving as both a transparent add-on and a stand-alone statistical tool for
forecasting regime shifts in diverse complex systems.
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Applied Physics
Establishing the Magnetoelastic Origin of Spin-Wave Routing through Focused Ion Beam Patterning
Felix Naunheimer, Johannes Greil, Valentin Ahrens et al. (+4 more)
Spin waves are promising information carriers for analog and wave-based computing, where functionality relies on compact and precisely engineered scattering landscapes. Focused ion beam (FIB) irradiation enables such control by locally tailoring the
spin-wave dispersion in yttrium iron garnet (YIG). However, a non-monotonic dependence of the
spin-wave wavelength on increasing ion dose hinders predictive landscape design. Here, we present an experimentally validated framework that explains this non-monotonic
spin-wave steering by linking phenomenological strain-induced anisotropy to its magnetoelastic origin. Irradiation-induced
lattice dislocations drive elastic and plastic deformation, which evolve into partial amorphization, each stage contributing distinctly to the dispersion behavior. We combine post-irradiation wet-chemical etching and atomic force microscopy (AFM) to quantify thickness changes, and track the dispersion in etched regions using time-resolved magneto-optical Kerr effect (trMOKE) microscopy. Fitting the data to the Kalinikos–Slavin formalism with an added effective magnetoelastic field isolates contributions from elastic and plastic deformation. Validation is achieved by mapping the deformation
evolution onto a three-phase scenario based on SRIM simulations, reproducing the extracted field trends, and by consistent strain tensor and micromagnetic analyses. These results establish a physical basis for FIB-engineered graded-index (GRIN)
spin-wave landscapes and magnetoelastically programmable magnonic devices.
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All authors Felix Naunheimer, Johannes Greil, Valentin Ahrens, Levente Maucha, Ádám Papp, György Csaba, Markus Becherer
Chemical Physics · Cross-listed from cond-mat.stat-mech
A statistical theory of structure in many-particle systems with local interactions
John Çamk{\i}ran, Fabian Parsch and Glenn D. Hibbard
A theory of structure is formulated for systems of many structureless classical particles with stable local interactions in Euclidean space. Such systems are shown to have their structure in thermodynamic
equilibrium determined exactly by a random field of fine local descriptions and approximately by coarsenings thereof. The degree of order in the local cluster consisting of a particle and its neighbors is identified as a universal source of coarse local descriptions and characterized by expressing the behavior of configurational
entropy in local microscopic terms. A local measure of the angular redundancy in neighboring particle positions is found to satisfy this characterization and thereby established as a valid local order quantifier. A precise relationship between order and
symmetry is obtained by bounding this quantifier sharply from below by a simple function of the local point group and the largest stabilizer under its action on the set of bond pairs. The marginal distribution of the quantifier is given in closed form for highly coordinated particles with broadly distributed bond angles. Applications are made to the ideal gas, perfect
crystal, and simple
liquid.
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Fluid Dynamics
Effect of Reynolds number on triboelectric particle charging in turbulent channel flow
Christoph Wilms and Holger Grosshans
Triboelectric charging in particle-laden flows is a complex interplay of fluid and particle dynamics, collision mechanics, and electrostatics. In this study, we introduce triboFoam, an open-source solver built on the OpenFOAM framework, designed to simulate triboelectric charging in particle-laden turbulent flows. We validate triboFoam using Direct Numerical Simulations (DNS) of a fully developed turbulent channel flow at a friction Reynolds number of $Re_\tau = 180$. The results demonstrate good agreement with DNS data for particle concentration profiles and charge distributions. Then, we investigate the influence of Reynolds number on particle distribution and charging behaviour using Large-Eddy Simulations (LES) at varying friction Reynolds numbers up to $Re_\tau = 550$. Our findings reveal that higher Reynolds numbers lead to increased near-wall particle concentrations and enhanced charging rates, attributed to intensified turbulent fluctuations and elevated impact velocities. Finally, an empirical correlation is proposed to predict the average particle charging rate as a function of Reynolds number and particle diameter. With this work, we provide a tool for simulating triboelectric charging in complex geometries and turbulent flows, advancing the understanding of electrostatic phenomena in particle-laden systems. The empirical correlation offers practical insights for predicting charging behaviour in industrial applications and thus can contribute to improved safety and efficiency in processes involving particulate matter.
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Instrumentation and Detectors
Application of a high-precision distributed uranium source for determining the effective mass and volume of a HPGe detector
A. S. Barabash, S. Evseev, D. Filosofov et al. (+10 more)
A distributed uranium source with the accurately certified activity of 238U has been used to verify the effective mass of the HPGe detector intended for the {\nu}GeN
neutrino experiment. The source, dissolved in nitric acid, provides homogeneous irradiation of the detector
crystal allowing the study of its mass and volume. The experimental spectra obtained with the distributed source have been compared to the detailed Geant4 Monte Carlo simulations. The measured counting rates of several gamma-lines agree with the simulated efficiencies, confirming that the detector mass and volume coincide with the manufacturer specifications. The results demonstrate the applicability of such sources for mass calibration of HPGe detectors.
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All authors A. S. Barabash, S. Evseev, D. Filosofov, V. Kazalov, T. Khussainov, A. Lubashevskiy, N. D. Mokhine, D. Ponomarev, S. Rozov, S. Vasilyev, M. Vorobyeva, E. Yakushev, V. I. Yumatov
History and Philosophy of Physics
Between equilibrium and fluctuation: Einstein's heuristic argument and Boltzmann's principle
Enric Pérez and Antonio Gil
We critically revisit Einstein's 1905 heuristic argument for lightquanta, considering its internal coherence and the scope of its applicability. We argue that Einstein's
reasoning, often celebrated for its originality, is ambiguous because it can be understood as a fluctuation or as a comparison between
equilibrium states. A historical and conceptual analysis of Einstein's use of Boltzmann's principle in those years reveals his evolving stance on its meaning and the role of probability, as well as his persistent doubts about the nature of radiation. We use our analysis to examine the limitations of extending the notion of Einstein's lightquanta across the electromagnetic spectrum: the relevant parameter is not the frequency, but the occupancy number.
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Plasma Physics
Fundamental limit of intensity scaling for harmonic generation on plasma mirrors
Philipp Sikorski, Baptiste Groussin, Aodhan McIlvenny et al. (+12 more)
Plasma mirrors have the potential to considerably boost the intensity of ultra-intense
laser pulses through high-order harmonic generation, offering a promising route to the extreme fields required for probing the strong-field regime of
quantum electrodynamics (SF-QED). This prospect relies on the favorable scaling of harmonic generation with increasing
laser intensity, a longstanding assumption that has remained untested at extreme intensities. Combining the first measurements of Doppler harmonic generation approaching $10^{22}\,\mathrm{W/cm^2}$ with advanced particle-in-
cell modeling, our study reveals fundamental limitations to this scaling. We notably observe a strong reduction of the harmonic yield as the
laser intensity is increased, and show using simulations that this originates from the interaction of the sub-picosecond
laser pedestal with the
plasma mirror. This pedestal drives a rapid
evolution of the
plasma surface, through radiation-pressure compression and surface modulations, which progressively suppress harmonic generation. By extending our simulations up to intensities of $10^{23}\,\mathrm{W/cm^2}$, we show that this
evolution accelerates strongly with increasing intensity, eventually leading to
plasma mirror disruption on the timescale of the main
laser pulse itself, making pulse duration, in addition to temporal contrast, a second key parameter for efficient harmonic generation. These results reveal the fundamental limits of the intensity scaling of harmonic generation from
plasma mirrors and establish the conditions required to preserve efficient harmonic generation at extreme intensities, providing critical guidance for their use as intensity boosters toward the SF-QED regime.
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All authors Philipp Sikorski, Baptiste Groussin, Aodhan McIlvenny, Kosta Oubrerie, Pierre Bartoli, Lieselotte Obst-Huebl, Anthony Vazquez, Lulu Russell, Tirtha Mandal, Kei Nakamura, Anthony J. Gonsalves, Cameron G. R. Geddes, Luca Fedeli, Henri Vincenti, Adrien Leblanc
Atomic Physics
High-voltage generation system for a traveling-wave Stark decelerator
Lucas van Sloten, Leo Huisman and Steven Hoekstra
In this paper we describe the high-voltage generation system we have developed for a traveling-wave Stark decelerator (TWSD). The TWSD can reduce the forward velocity of a molecular beam of heavy neutral polar molecules such as strontium monofluoride (SrF) and barium monofluoride (BaF) from $\sim$ 200 m/s down to $\sim$ 6 m/s. The main motivation for the development of this device is the increased sensitivity from precision spectroscopy of the decelerated molecules to test fundamental physics. The high-voltage generation system can produce eight pulsed sinusoidal waveforms with a maximum amplitude of 10 kV and a linear frequency sweep from 16.7 kHz down to 500 Hz over the span of 40 ms at a repetition rate of 10 Hz. The eight waveforms are phase-offset to each other by 45 degrees. To slow down the heavy molecules, the decelerator is required to have a length of $\sim$ 4 m, which results in a significant capacitive coupling between adjacent channels of $\sim$ 160 pF. As a consequence, the control and stability of the waveforms is extra challenging. We designed a method that compensates for the frequency-dependent coupling between the eight channels. Allowing for amplitude and phase-offsets that do not deviate more than 1% and 2 degrees, respectively, from their design values during the frequency sweep. The system outperforms commercially available options in terms of stability, output voltage amplitude, cost and ease of maintenance. This approach is also relevant for other fields where precise control of high-voltage waveforms is required, such as particle accelerator physics,
plasma physics and mass spectroscopy.
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Atomic Physics
Electron-impact cross sections for dissociation processes of vibrationally excited CH radical
O. Abidi, I. Jendoubi, M. Telmini et al. (+3 more)
This paper presents a theoretical investigation of the cross sections for dissociative electron attachment and dissociative excitation processes in vibrationally excited CH radicals induced by electron impact. Resonant electron-CH collisions are analyzed using the ab-initio R-
matrix method, while
nuclear dynamics are explored within the Local Complex Potential framework. A comprehensive set of vibrationally resolved cross sections and rate coefficients is provided for both the ground and first excited electronic states of the CH molecule. These findings contribute to a better understanding of the kinetics of non-
equilibrium systems containing CH molecules with applications in
plasma technologies for CO2 reduction, combustion processes and various astrophysical contexts.
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All authors O. Abidi, I. Jendoubi, M. Telmini, R. Ghosh, K. Chakrabarti, V. Laporta
Plasma Physics
Fully nonlinear phenomenology of the bump-on-tail (BOT) instability with drag, diffusion and Krook relaxation
Shi-Jie Zhang, Lei Chang, Zhao-Ju Bo et al. (+8 more)
Energetic-particle-driven modes in magnetically confined fusion
plasmas often exhibit nonlinear frequency sweeping, reflecting complex wave-particle interactions near marginal stability. While the bump-on-tail (BOT) instability within the Berk-Breizman framework has served as a canonical model for understanding such phenomena, a unified nonlinear description remains incomplete when drag,
diffusion, and Krook relaxation act simultaneously. In this work, we present a comprehensive numerical investigation of the BOT instability that explicitly retains all three collision operators together with external wave damping. Using a validated characteristic-based BOT code, we systematically scan the multi-dimensional collision parameter space and construct nonlinear regime maps and bifurcation diagrams. To organize the rich dynamics, we introduce a two-level categorization that combines global wave-energy
evolution with chirping subtypes identified from spectral morphology. We find that
diffusion and Krook relaxation regularize the nonlinear dynamics and promote ordered transitions from chaotic behaviors to periodic oscillations and steady saturation as collision strength increases, with the saturation level decreasing approximately exponentially with external damping. In contrast, drag alone does not admit steady solutions and instead drives persistent or chaotic chirping through convective deformation of resonant phase-space structures. When drag is combined with
diffusion or Krook relaxation, clear transition sequences emerge: increasing drag breaks hole-clump
symmetry, broadens the effective resonance region, and drives systematic transitions from transient to intermittent and persistent chirping.
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All authors Shi-Jie Zhang, Lei Chang, Zhao-Ju Bo, Zhi-Song Qu, Ilya Zadiriev, Elena Kralkina, Shogo Isayama, Sin-Jae You, Zi-Chen Kan, Ji-Kai Sun, Jing-Jing Ma
Chemical Physics · Cross-listed from cs.LG
Coarse-Grained Boltzmann Generators
Weilong Chen, Bojun Zhao, Jan Eckwert et al. (+1 more)
Sampling
equilibrium molecular configurations from the Boltzmann distribution is a longstanding challenge. Boltzmann Generators (BGs) address this by combining exact-likelihood generative models with importance sampling, but practical scalability is limited. Meanwhile, coarse-grained surrogates enable the modeling of larger systems by reducing effective dimensionality, yet often lack a reweighting procedure required to ensure asymptotically correct statistics. In this work, we propose Coarse-Grained Boltzmann Generators (CG-BGs), a framework for reduced-order generative modeling with importance sampling in coarse-grained coordinate space. CG-BGs generate samples using a flow-based model and reweight them using a learned potential of mean force (PMF). We show that the PMF can be learned from rapidly converged trajectories via enhanced sampling force matching. Experiments demonstrate that CG-BGs capture solvent-mediated interactions in highly reduced representations while substantially reducing computational cost relative to atomistic BGs, providing a practical route toward
equilibrium sampling of larger molecular systems.
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All authors Weilong Chen, Bojun Zhao, Jan Eckwert, Julija Zavadlav
Chemical Physics · Cross-listed from quant-ph
Projection-Based Memory Kernel Coupling Theory for Quantum Dynamics: A Stable Framework for Non-Markovian Simulations
Wei Liu, Rui-Hao Bi, Yu Su et al. (+4 more)
We present a projection-based, stability-preserving methodology for computing time correlation functions in open
quantum systems governed by generalized
quantum master equations with non-Markovian effects. Building upon the
memory kernel coupling theory framework, our approach transforms the
memory kernel hierarchy into a system of coupled linear differential equations through Mori-Zwanzig projection, followed by spectral projection onto stable eigenmodes to ensure numerical stability. By systematically eliminating unstable modes while preserving the physically relevant dynamics, our method guaranties long-time convergence without introducing artificial damping or ad hoc modifications. The theoretical framework maintains mathematical rigor through orthogonal projection operators and spectral decomposition.
Benchmark calculations on the
spin-
boson model show excellent agreement with exact hierarchical equations of motion results while achieving significant computational efficiency. This approach provides a versatile and reliable framework for simulating non-Markovian dynamics in complex systems.
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All authors Wei Liu, Rui-Hao Bi, Yu Su, Limin Xu, Zhennan Zhou, Yao Wang, Wenjie Dou
Applied Physics · Cross-listed from quant-ph
Practical quantum tokens: challenges and perspectives
Nadezhda P. Kukharchyk, Holger Boche, Christian Deppe et al. (+21 more)
The concept of
quantum tokens dates back alongside
quantum cryptography to Stephen Wiesner's seminal work in 1983[1]. Already this initial work proposes society-relevant applications such as secure
quantum banknotes, which can be exchanged between a bank and a customer. This
quantum currency is based on various physical states that can be easily verified but is protected from being copied by the fundamental
quantum laws. Four decades later, these ideas have flourished in the field of
quantum information, and the concept of
quantum banknotes has not only adopted many varying names, such as
quantum money,
quantum coins,
quantum-digital payments, and
quantum tokens, but also reached its first experimental demonstrations. In this perspective article, we discuss the current state-of-the-art of
quantum tokens in the field of
quantum information, as well as their future perspectives. We present a number of physical realizations of
quantum tokens with integrated
quantum memories and their applicability scenarios in detail. Finally, we discuss how
quantum tokens fit into the information security ecosystem and consider their relationship to post-
quantum cryptography.
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All authors Nadezhda P. Kukharchyk, Holger Boche, Christian Deppe, Kirill G. Fedorov, Martin E. Garcia, Ilja Gerhardt, Rudolf Gross, Thomas Halfmann, Hans Huebl, David Hunger, Wolfgang Kilian, Roman Kolesov, Juliane Krämer, Alexander Kubanek, Kai Müller, Boris Naydenov, Janis Nötzel, Anna P. Ovvyan, Wolfram H. P. Pernice, Gregor Pieplow, Cyril Popov, Tim Schröder, Kilian Singer, Janik Wolters
Computational Physics · Cross-listed from cs.LG
On the Role of Consistency Between Physics and Data in Physics-Informed Neural Networks
Nicolás Becerra-Zuniga, Lucas Lacasa, Eusebio Valero et al. (+1 more)
Physics-informed neural networks (PINNs) have gained significant
attention as a surrogate modeling strategy for partial differential equations (PDEs), particularly in regimes where labeled data are scarce and physical constraints can be leveraged to regularize the learning process. In practice, however, PINNs are frequently trained using experimental or numerical data that are not fully consistent with the governing equations due to measurement noise, discretization errors, or modeling assumptions. The implications of such data-to-PDE inconsistencies on the accuracy and convergence of PINNs remain insufficiently understood. In this work, we systematically analyze how data inconsistency fundamentally limits the attainable accuracy of PINNs. We introduce the concept of a consistency barrier, defined as an intrinsic lower bound on the error that arises from mismatches between the fidelity of the data and the exact enforcement of the PDE residual. To isolate and quantify this effect, we consider the 1D viscous Burgers equation with a manufactured analytical solution, which enables full control over data fidelity and residual errors. PINNs are trained using
datasets of progressively increasing numerical accuracy, as well as perfectly consistent analytical data. Results show that while the inclusion of the PDE residual allows PINNs to partially mitigate low-fidelity data and recover the dominant physical structure, the training process ultimately saturates at an error level dictated by the data inconsistency. When high-fidelity numerical data are employed, PINN solutions become indistinguishable from those trained on analytical data, indicating that the consistency barrier is effectively removed. These findings clarify the interplay between data quality and physics enforcement in PINNs providing practical guidance for the construction and interpretation of physics-informed surrogate models.
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All authors Nicolás Becerra-Zuniga, Lucas Lacasa, Eusebio Valero, Gonzalo Rubio
Instrumentation and Detectors
The high speed analog optical readout system designed for low temperature experiments
Z. Zhou, W. Wu, J. Tang et al. (+5 more)
For low-temperature experiments such as
liquid xenon dark matter detectors, it is crucial to read out detector signals from cryostats. Traditionally, photoelectrical signals are transmitted from the cryogenic region to the outside using coaxial cables through
vacuum feedthroughs on the cryostats. In this paper, we investigate an analog optical transmission method in which the raw electrical signals are converted into optical signals with light intensity linearly proportional to the electrical amplitude, transmitted out of the cryogenic environment through optical fiber, and subsequently converted back into electrical signals by photoelectric devices while preserving the signal waveform. This new approach offers advantages, including low attenuation over long-distance transmission and reduced crosstalk across the feedthroughs. Additionally, the low-temperature optical wavelength multiplexing scheme has been investigated and applied, increasing the transmission capability of a single fiber. At -100 degree Celsius, the proposed analog optical readout system achieves a -3dB bandwidth of larger than 150MHz, a dynamic range of up to 500mV, and a low cryogenic-region power consumption of 70mW per channel, demonstrating its strong potential for low-temperature experiments.
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All authors Z. Zhou, W. Wu, J. Tang, Y. Fu, Y. Guo, Y. Liu, X. Wang, W. Zhi
Biological Physics · Cross-listed from cond-mat.stat-mech
Thermodynamic Optimization of Sensory Adaptation via Game-Theoretic Path Integrals
Gunn Kim
Biological sensory systems, from E.~coli chemotaxis to sensory
neurons in C.~elegans, achieve reliable adaptation over wide dynamic ranges despite operating in strongly noisy and overdamped regimes. Here, we present a field-theoretic framework in which sensory adaptation emerges from a variational free-energy principle, formulated as a
stochastic differential game between an organism and its environment. Using an Onsager–Machlup path-integral formalism, we show that the resulting adaptive dynamics are mathematically equivalent to a class of model reference adaptive control schemes and can be interpreted as a dynamic renormalization of the system's Green's function. Within this framework, the phasic overshoot commonly observed in sensory responses arises naturally from an effective inertia ($m^* \approx \tau \gamma$) generated by
memory-dissipation coupling, rather than from biochemical fine-tuning. Quantitative fits to experimental data across species yield $R^2 > 0.88$, and indicate that adaptive sensory processing operates within a narrow thermodynamically optimal regime bounded by signal-to-noise and stability constraints.
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Medical Physics
Virtual Theranostic Trials: New Approach Methodologies (NAMs) and Precision Radiopharmaceutical Therapies
Carlos F. Uribe, Hamid Abdollahi, Tahir Yusufaly et al. (+7 more)
Radiopharmaceutical therapies are expanding rapidly, but clinical evidence generation is limited by operational constraints and biological heterogeneity in radiopharmaceutical delivery and radiation risk. Virtual theranostic trials can run as companion trials, linking quantitative imaging to patient-specific models to generate evidence for personalized injections and scheduling, accelerate development, and broaden access.
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All authors Carlos F. Uribe, Hamid Abdollahi, Tahir Yusufaly, Taylor J. McColl, Maziar Sabouri, James Fowler, Fereshteh Yousefirizi, Babak Saboury, Pedro L. Esquinas, Arman Rahmim