Medical Physics
LiDRoSIS: An Automated MATLAB-Python Platform for Image Processing and Quantitative Analysis of Lipid Droplets and ROS in Irradiated Cells
Marco Ferreira, Ana Belchior, Teresa Pinheiro et al. (+2 more)
LiDRoSIS is an automated MATLAB-Python software suite for the
segmentation and quantification of lipid droplets (LDs) and reactive oxygen species (ROS) in fluorescence microscopy images of irradiated A549 and MCF7
cells exposed to gold-based nanoparticles. It combines classical image processing
algorithms with statistical post-analysis through a companion Python tool, StatLysis. The platform enables reproducible, high-throughput analysis of morphological and spectral parameters linked to nanoparticle-enhanced radiobiological responses. By bridging imaging and quantitative analytics, LiDRoSIS provides a robust framework for nanomedicine and radiation biology research.
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All authors Marco Ferreira, Ana Belchior, Teresa Pinheiro, Gil Alves, Maria Lopes
Chemical Physics · Cross-listed from cond-mat.quant-gas
Ab initio path-integral Monte Carlo results for the one-particle spectral function of the warm dense electron gas
Paul Hamann, Michael Bonitz, Jan Vorberger et al. (+1 more)
We present quasi-exact ab initio path-integral Monte Carlo results for the Matsubara Green's function of the uniform electron gas (UEG) at finite temperature over a broad range of coupling strengths ($r_s=1,\dots,10)$. We further extract the static self-energy $\Sigma_\infty(p)$ and perform an analytic continuation for spectral function $A(p,\omega)$, conclusively ruling out the possibility of distinct satellite features at these conditions. In addition, our work opens up intriguing avenues to study the single-particle spectrum and density of states of real warm dense matter systems based on first principles.
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All authors Paul Hamann, Michael Bonitz, Jan Vorberger, Tobias Dornheim
Classical Physics
Precise Computation of Forced Response Backbone Curves of Frictional Structures Using Analytical Hessian Tensor of Contact Elements
Wei Wen, Wenkai Qi and Weidong Wen
Predicting the forced vibration response of nonlinear mechanical systems with friction is critical for engineering applications. Accurately determining the backbone curve of resonance peaks is pivotal for the design of friction devices. However, the prediction of these curves is computationally challenging owing to the nonconservative and nonsmooth nature of friction nonlinearity. Although techniques such as damped nonlinear normal modes (dNNMs) and phase resonance methods have been applied, they often suffer from convergence issues, and their computational accuracy is compromised under certain conditions. This study proposes a novel method for computing the forced response backbone curves of structures with frictional contact interfaces. The method accurately tracks the backbone curve through a parameter continuation scheme, formulated via Lagrange multipliers and accelerated by incorporating a derived analytical Hessian Tensor of contact elements. This approach yields highly accurate numerical results and enables numerical singularities on the curve to be identified and robustly traversed. The proposed method is validated using an Euler-Bernoulli beam finite-element model and a lumped-parameter blade-damper-blade model. The results demonstrate superior accuracy compared to conventional dNNMs and phase resonance methods, particularly in cases involving either high structural damping or strong frictional damping. This work provides a robust computational tool and presents a detailed comparative analysis that clarifies the applicability and limitations of the proposed and conventional methods.
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Plasma Physics · Cross-listed from cond-mat.str-el
Dielectric formalism of the 2D uniform electron gas at finite temperatures
Fotios Kalkavouras, Tobias Dornheim, Paul Hamann et al. (+1 more)
We present a comprehensive analysis of the two-dimensional uniform electron gas (2D-UEG or more commonly 2DEG) at finite temperature, spanning a broad range of densities / coupling strengths ($0.01\le{r}_s\le20$) and temperatures / degeneracy parameters ($0.01\le\Theta= k_B T/E_F \le 10$). Within the self-consistent dielectric formalism, we construct two-dimensional versions of the Singwi-Tosi-Land-Sjölander (STLS) and hypernetted-chain (HNC) approximation based schemes. We
benchmark the accuracy of the STLS and the HNC schemes against new state-of-the-art path-integral Monte Carlo data. We also report structural and thermodynamic properties across the full $(r_s,\Theta)$ phase diagram domain studied, identify regimes in which these schemes remain quantitatively reliable, and provide an accurate parametrization of the exchange–correlation free energy of the finite-temperature 2DEG.
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All authors Fotios Kalkavouras, Tobias Dornheim, Paul Hamann, Panagiotis Tolias
Medical Physics
Beyond directions: Symmetry-aware rotation sets for triaxial diffusion encoding by geometric filter optimization
Sune Nørhøj Jespersen and Filip Szczepankiewicz
Purpose: To improve the accuracy of
diffusion-weighted powder average signals for
diffusion encoding with arbitrary b-tensors. Methods: We identify an intrinsic dihedral ($D_2$)
symmetry of
diffusion signals for arbitrary
diffusion encoding, which defines their natural signal space (a quotient of 3D rotations). Based on this, we propose a method to generate optimal rotation sets that are applied to the
diffusion-encoding gradient waveform to yield powder averages with maximal accuracy. The method, termed “
Geometric Filter Optimization” (GFO), amounts to designing a sampling filter that is approximately flat over the relevant part of the associated frequency space. We characterize the filter properties and
benchmark performance in terms of the accuracy and precision of powder averages and higher-order rotational invariants, including comparison with spherical designs and electrostatic-repulsion-based designs defined on the same space. Results: We found that GFO leads to marked improvements in precision and accuracy in powder averaging over
diffusion encoding b-tensors, including axisymmetric and triaxial configurations. For higher-order rotational invariants, the performance was more nuanced, with GFO, electrostatic repulsion, and spherical designs exhibiting different trade-offs in bias and precision depending on $b$ and $N$. Conclusion: A fundamental $D_2$-
symmetry of tensor-valued
diffusion encoding was shown to constrain its rotational structure and guide the design of optimal rotation sets. This yielded GFO, which provides an efficient recipe for obtaining orientations for powder averaging of signals with axisymmetric and triaxial
diffusion encoding. It places no additional demands on gradient system performance and can be used to shorten scan time.
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Optics · Cross-listed from quant-ph
Resonant Excitation Induced Vibronic Mollow Triplets
Devashish Pandey, Corne Koks, Martijn Wubs et al. (+2 more)
The Mollow triplet is the definitive spectral signature of an optically dressed
quantum emitter. We predict that for emitters coupled to localized
phonons, this signature is not confined to the zero-
phonon line. Under a strong resonant drive, we show that Mollow triplets are strikingly replicated on the associated
phonon sidebands -a surprising result, given that
phonon sidebands are typically viewed as incoherent, inelastic scattering pathways. These vibronic Mollow triplets are a direct fingerprint of dynamically generated dressed states that hybridize the emitter's electronic, photonic, and vibrational degrees of freedom. We develop a scalable analytical formalism to model this effect in complex, multi-mode molecular systems, such as dibenzoterrylene. Our work provides the precise driving conditions for observing these novel spectral features, establishing a new signature of coherence in vibronically coupled systems.
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All authors Devashish Pandey, Corne Koks, Martijn Wubs, Nicolas Stenger, Jake Iles-Smith
Physics Education
How to Improve Portuguese Secondary Education
C. J. A. P. Martins
I share some personal thoughts on the status of Portuguese secondary education in general, and of the physics part thereof in particular, drawn from several decades of experience of organizing training activities for students and school teachers, as well as several hundred visits to secondary schools and similar numbers of interviews of secondary school students (from Portugal and elsewhere). I offer various suggestions for improving and modernising our current system.
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Atomic Physics · Cross-listed from cond-mat.mtrl-sci
Bending strain induced thermal conductivity suppression in freestanding BaTiO3 and SrTiO3 membranes
Ziyan Qian, Guangwu Zhang, Weikun Zhou et al. (+2 more)
Freestanding perovskite
oxide membranes provide a novel platform for elastic strain engineering, enabling the manipulation of
phonon transport free from substrate clamping. In this work, we investigate the thermal transport properties of strontium titanate (SrTiO3) and barium titanate (BaTiO3) membranes subjected to self-formed crease induced inhomogeneous strain. By integrating spatially resolved Frequency-Domain Thermoreflectance (FDTR) with micro-Raman spectroscopy, we observe a sharp, localized suppression of thermal conductivity (k) in high-
curvature regions. Specifically, k is reduced from 4.43 to 3.62 W/(m K) in SrTiO3 and from 2.27 to 1.81 W/(m K) in BaTiO3 at the crease centers, directly correlating with the local strain distribution. First-principles calculations reveal that, unlike uniform strain, the
symmetry breaking induced by strain gradients significantly broadens
phonon dispersion and enhances scattering rates. These findings not only elucidate the microscopic mechanisms governing
phonon-strain coupling but also demonstrate the potential of inhomogeneous strain fields as a potent tool for designing dynamic solid-state thermal switches and active thermal management devices.
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All authors Ziyan Qian, Guangwu Zhang, Weikun Zhou, Tsukasa Katayama, Qiye Zheng
Optics
Solution-derived barium titanate waveguides for integrated electro-optic modulation
Virginia Falcone, Eleni Prountzou, Jost Kellner et al. (+2 more)
Metal
oxides with strong nonlinear optical properties and wide transparency window are key materials for the development of compact and efficient photonic integrated
circuits used for electro-optic modulators and entangled
photon sources. Among them, barium titanate (BaTiO$_{3}$) is particularly attractive due to its large Pockels coefficient. However, its use has been limited by challenges in material synthesis and in nanopatterning, owing to its chemical stability and inertness. Here, we demonstrate a monolithic electro-optic modulator entirely based on solution-deposited BaTiO$_{3}$, fabricated through a bottom-up soft nanoimprinting lithography process. Fine-tuning the synthesis and nanofabrication enhances the optical properties of the polycrystalline material. By optimizing the process parameters, we achieve a reduction in propagation losses of two orders of magnitude, enabling efficient electro-optic modulation. This scalable, etch-free approach enables direct patterning of high-quality BaTiO$_{3}$ structures, establishing a new route for low-cost, large-scale integrated electro-optic devices entirely based on
oxide material compatible with a wide range of substrates.
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All authors Virginia Falcone, Eleni Prountzou, Jost Kellner, Ülle-Linda Talts, Rachel Grange
Instrumentation and Detectors
Ring oscillator performance of the ATLAS inner tracker pixel readout chip
Yahya Khwaira, Abdenour Lounis, Maurice Cohen-Solal et al. (+3 more)
This paper presents experimental and simulation data to characterize the Ring Oscillators (RO) produced in 65-nm CMOS technology for the next promising generation of readout chips for the pixel detector in the Inner Tracker (ITk) at the ATLAS experiment at CERN. To enable a better understanding of the RO block embedded in ITkPixV1.1 single chip card (SCC), tests at various temperatures, voltages, accumulated total ionizing dose (TID) with X-ray irradiation, and high-temperature annealing will be presented. The objective of this study is to examine the RO output dependency based on different variable conditions and provide simulation data using Cadence, an electronic design automation (EDA) software to validate the experimental outcomes.
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All authors Yahya Khwaira, Abdenour Lounis, Maurice Cohen-Solal, Mohsine Menouni, Pierre Barrillon, Denis Fougeron
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Modeling the Thermal Behavior of Photopolymers for In-Space Fabrication
Jonathan Ericson, Daniel Widerker, Eytan Stibbe et al. (+15 more)
Future long-duration space missions will require in-situ, on-demand manufacturing of tools and components. Photopolymer-based processes are attractive for this purpose due to their low energy requirements, volume efficiency, and precise control of curing. However, photopolymerization generates significant heat, which is difficult to regulate in microgravity where natural convection is absent, leading to defects such as surface blistering and deformation. In this work, we combine experimental studies and modeling to address these thermal challenges. We report results from International Space Station (ISS) experiments and a dedicated
parabolic flight campaign, which confirm that suppressed convective heat transfer in microgravity exacerbates thermal buildup and defect formation. Building on these observations, we present a predictive thermal model that couples heat transfer, light absorption, and evolving material properties to simulate polymerization and temperature
evolution under terrestrial and microgravity conditions. Laboratory validation demonstrates strong agreement between model predictions and measured temperature profiles. Applying the model to the ISS experiments, we show that the model accurately reproduces experimentally observed blistering in TJ-3704A, a commercial acrylate-based
polymer resin, while also predicting defect-free outcomes for Norland optical adhesives. The model functions as a design tool for defect-free in-space manufacturing, enabling selection of
polymer properties, exposure strategies, and environmental conditions that together inhibit excess thermal buildup, paving the way for scalable, reliable in-situ manufacturing during future missions.
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All authors Jonathan Ericson, Daniel Widerker, Eytan Stibbe, Mor Elgarisi, Yotam Katzman, Omer Luria, Khaled Gommed, Alexey Razin, Amos A. Hari, Israel Gabay, Valeri Frumkin, Hanan Abu Hamad, Ester Segal, Yaron Amouyal, Titus Szobody, Rachel Ticknor, Edward Balaban, Moran Bercovici
Fluid Dynamics
On the testing of grain shape corrections to bedload transport equations with grain-resolved numerical simulations
Yulan Chen, Orencio Durán and Thomas Pähtz
Using grain-resolved LES-DEM simulations, Zhang et al. (J. Geophys. Res. Earth Surf. 130, e2024JF007937, 2025) aimed to validate a grain-shape-corrected bedload transport equation proposed earlier by the same group. It states that grain shape effects are captured through a modified Shields number that depends, among others, on the drag coefficient, $C_{D_\mathrm{settle}}$, determined from the force balance for a grain settling in a fluid at rest. To independently vary $C_{D_\mathrm{settle}}$ in their simulations, the authors changed the boundary conditions on the grains' surfaces: By artificially shifting the locations of the no-slip conditions from the actual grain surface to a virtual surface a distance $l$ into the grain interior, they hoped to well approximate Navier-slip conditions with a slip length $l$. Here, we argue that this approximation is appropriate only if the thickness of the boundary layer that forms around the virtual surface is much larger than $l$, which we demonstrate was not the case for the authors' simulations. In particular, using independent DNS-DEM grain settling simulations for the same hydrodynamic conditions, we directly show that this approximation substantially overestimates the value of $C_{D_\mathrm{settle}}$ of a Navier-slip sphere. This implies that the conditions created with their artificial method do not correspond to physically realistic scenarios and therefore do not support the authors' grain shape correction. To support this conclusion, we demonstrate that their entire numerical data can be alternatively explained by a simple null hypothesis model, without grain shape correction, based on the virtual-grain rather than the actual-grain size.
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Plasma Physics
Piecewise omnigenous magnetohydrodynamic equilibria as fusion reactor candidates
V. Fernández-Pacheco, J.L. Velasco, E. Sánchez et al. (+5 more)
In piecewise omnigenous
magnetic fields, charged particles remain perfectly confined in the abscence of collisions and
turbulence. This concept extends the traditional notion of omnigenity, the theoretical principle upon which most of existing
magnetic fusion reactor designs, including tokamaks, are based. While piecewise omnigenity broadens the range of potentially viable stellarator reactor candidates, it is achieved by relaxing the requirement of continuity in the
magnetic field strength, which could appear to pose significant challenges for the design of magnetohydrodynamic
equilibria. In this work, a stellarator
magnetic configuration is presented that satisfies the ideal magnetohydrodynamic
equilibrium equation and that achieves unprecedented levels of piecewise omnigenity. As a result, it exhibits favorable transport characteristics, including reduced bulk radial (neoclassical and turbulent transport), bootstrap current and fast ion losses. In addition, the configuration displays robust MHD stability across a range of e̱ta} values and possesses a rotational transform profile compatible with an island divertor. Collectively, these features satisfy the standard set of physics criteria required for a viable reactor candidate which, until now, were believed to be attainable only by certain types of omnigenous stellarators.
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All authors V. Fernández-Pacheco, J.L. Velasco, E. Sánchez, R. Gaur, J.M. García-Regaña, J.A. Alonso, I. Calvo, D. Carralero
Optics
Ho3+-doped CALGO crystals for high-power ultrafast 2.1-{\mu}m lasers
Anna Suzuki, Pavel Loiko, Weichao Yao et al. (+8 more)
Ho3+-doped disordered CaAlGdO4 (CALGO)
crystals have recently emerged as a promising gain material platform for next-generation high-power ultrafast 2.1-{\mu}m
laser systems. This
laser gain material offers a unique combination of high-gain, small
quantum defect, inhomogeneously broadened spectra, and good thermal conductivity, enabling ultrashort pulse generation and amplification at high-average power and high pulse energy. Many systems, including mode-locked oscillators and amplifiers with state-of-the-art performance, have been demonstrated in the last few years that promise to meet growing application demands for efficient ultrafast
laser technology in this wavelength region. In this review paper, we summarize recent achievements using this gain material both in oscillators and amplifiers and place these results in the state-of-the-art of 2-{\mu}m ultrafast
laser technology, present detailed spectroscopic characterization of this material, and discuss future perspectives of further performance scaling of Ho:CALGO
lasers.
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All authors Anna Suzuki, Pavel Loiko, Weichao Yao, Parisa Baghery, Martin Hoffmann, Kirill Eremeev, Patrice Camy, Alain Braud, Sergei Tomilov, Yicheng Wang, Clara J. Saraceno
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Non-monotonic hydration dependence of ionic transport in atomically-thin MnO2 sheets
Ata Utku Özkan, Talip Serkan Kas{\i}rga and Aykut Erbaş
The interlamellar space in van der Waals materials has served as a test bed for studies of strongly confined fluid and ion transport. Despite theoretical and experimental progress, it remains unclear how electrostatic correlations arising from interactions between the confined, hydrated ions and the substrate layer can be reconciled with non-
equilibrium ionic transport and the substrate's morphological response. Here, we investigate field-driven ionic conduction in sodium- and water-intercalated layered manganese
oxides ($\mathrm{MnO_2}$), a self-intercalated metal
oxide nanofluidic system, as a model intrinsically-intercalated van der Waals solid, using nonequilibrium all-atom molecular dynamics simulations that explicitly capture ion-water correlations and layer morphology. We demonstrate that electric-field bias induces spontaneous nanoscale segregation of water within the interlayer space, producing coexisting hydrated and weakly hydrated ionic domains coupled to local
lattice distortions. This feedback between hydration and morphology gives rise to heterogeneous transport pathways and leads to a non-monotonic dependence of ionic conductivity on water content. Suppressed conduction arises either from layer collapse at low water levels or from ionic hop blockage by excess water at high water levels. Concurrently, ionic transport exhibits a maximum at intermediate levels of intercalated water, where less hydrated ions can move at the boundaries of strongly hydrated ion clusters. While such non-monotonicity could explain the experimentally observed memristive response of $\mathrm{MnO_2}$ single
crystals, these findings also provide a molecular-level mechanism linking intercalated water levels to ionic metal
oxide nanofluidic systems, suggesting general design principles for robust, water-assisted ionic conductors.
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Plasma Physics
Electric field induced by radial redistribution of the energetic ion pressure in a fusion plasma
Shaojie Wang
It is found by using the gyrokinetic theory that significant radial electric fields, or zonal flows, can be generated by the radial redistribution of energetic ion pressure in a tokamak fusion device. Trapped energetic ions are more effective to generate the radial electric field than the isotropic energetic ions. This suggests that the energetic $\alpha$ particles produced by DT fusion may induce significant radial electric field and thus help to improve the core
plasma confinement in a fusion reactor.
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Atomic Physics
Precision measurement of the ground-state hyperfine constant for $^9Be^+$ in a linear Paul trap via magnetically insensitive hyperfine transitions
Zhi-yuan Ao, Wen-li Bai, Qian-yu Zhang et al. (+2 more)
Direct measurements of the ground-state magnetically insensitive hyperfine transition |F=2,mF=0>->|F=1,mF=0> of $^9Be^+$ ions have been performed using microwave-driven state transfer. The $^9Be^+$ ions are confined and
laser-cooled in a linear Paul trap, forming a Coulomb
crystal. The transition frequencies have been measured over a
magnetic field range of $ \pm 0.5 mT $ centered at zero
magnetic field, and the acquired data were fitted accounting for the high-order Zeeman effect. The hyperfine constant A is determined to be -625.008840(35) MHz, achieving a relative precision of $ 5.6 \times 10^{-8}$.
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All authors Zhi-yuan Ao, Wen-li Bai, Qian-yu Zhang, Wen-cui Peng, Xin Tong
Fluid Dynamics · Cross-listed from math.AP
Couette Taylor instabilities in the small-gap regime
Dongfen Bian, Emmanuel Grenier, Gérard Iooss et al. (+1 more)
The Couette-Taylor instability occurs in a viscous fluid confined between two coaxial rotating cylinders. When the Taylor number surpasses a critical value, the stable Couette flow destabilizes, giving way to steady Taylor
vortices. As the Taylor number increases further, these
vortices themselves become unstable, transitioning into wavy Taylor
vortices. In this article, we focus on the small-gap limit, where the ratio of the cylinder radii approaches unity and the rotation rates of the cylinders are nearly identical. We provide a rigorous proof of the existence of a critical Taylor number $T_c$, at which the Couette flow loses stability. For Taylor numbers just above $T_c$, under fixed axial periodicity, the solutions to the limiting Navier-Stokes system are governed by a Ginzburg-Landau-type partial differential equation. Beyond the classical Taylor
vortex flow, we demonstrate that a two-parameter family of solutions emerges at criticality for $T>T_c$. This family includes not only wavy
vortices but also a variety of other exotic flow patterns, all of which remain steady in the frame rotating at the average angular velocity of the cylinders.
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All authors Dongfen Bian, Emmanuel Grenier, Gérard Iooss, Zhuolun Yang
Instrumentation and Detectors
Introducing Timepix2-Lite: A Miniaturized Readout Interface Enabling Nanosecond-Scale Half-Life Measurement
O. Pavlas, B. Bergmann, M. Holik et al. (+5 more)
This paper presents Timepix2 Lite, a compact readout interface for the Timepix2 hybrid pixel detector, designed to provide high spatial and temporal resolution in a wide range of radiation detection applications. The Timepix2 Lite enables simultaneous energy and precise timing measurements on the nanosecond scale and supports advanced real-time data acquisition and visualization through the TrackLab software framework. Its compact and flexible architecture, enabled by the miniaturized design, allows seamless integration into diverse experimental setups, including
nuclear spectroscopy, stratospheric balloon missions, and nanosecond-scale half-life measurements. As a case study, the half-life of the second excited state in 237Np was determined to be 67.5(7) ns for the 59.5 keV transition, consistent with previously reported results.
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All authors O. Pavlas, B. Bergmann, M. Holik, M. Malich, S. Pospisil, P. Smolyanskiy, V. Vicha, R. Filgas
Instrumentation and Detectors
Efficient and precise Cherenkov-based charged particle timing using SiPMs
M. N. Mazziotta, A. Di Mauro, M. Giliberti et al. (+7 more)
Dedicated R&D efforts are currently underway to couple a thin Cherenkov radiator to Silicon Photomultiplier (SiPM) arrays for precise charged particle Time-of-Flight (ToF) measurements. The
prompt nature of Cherenkov radiation makes it an ideal candidate for achieving ultimate timing performance in a ToF detector. Using a thin radiator with a high refractive index, such as fused silica, enables the generation of a fast signal from charged particles that exceed the Cherenkov threshold. A crucial requirement for approaching the target time resolution is the optimization of both the radiator material and thickness, as well as the optical coupling to the SiPM arrays. In this work, we present the main factors that affect the time resolution and the expected performance achieved through a detailed Monte Carlo simulation and the comparison with beam test results.
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All authors M. N. Mazziotta, A. Di Mauro, M. Giliberti, A. Liguori, L. Lorusso, E. Nappi, N. Nicassio, G. Panzarini, R. Pillera, G. Volpe
Instrumentation and Detectors
A SiPM-Based RICH Detector with Timing Capabilities for Isotope Identification
M. N. Mazziotta, L. Congedo, G. De Robertis et al. (+7 more)
In this work, we present a novel compact particle identification (PID) detector concept based on Silicon Photomultipliers (SiPMs) optimized to perform combined Ring-Imaging Cherenkov (RICH) and Time-of-Flight (TOF) measurements using a common photodetector layer. The system consists of a Cherenkov radiator layer separated from a photosensitive surface equipped with SiPMs by an expansion gap. A thin glass slab, acting as a second Cherenkov radiator, is coupled to the SiPMs to perform Cherenkov-based charged particle timing measurements. We assembled a small-scale prototype instrumented with various Hamamatsu SiPM array sensors with pixel pitches ranging from 2 to 3 mm and coupled with 1 mm thick fused silica window. The RICH radiator consisted of a 2 cm thick aerogel tile with a refractive index of 1.03 at 400 nm. The prototype was successfully tested in beam test campaigns at the CERN PS T10 beam line with pions and
protons. We measured a single-hit angular resolution of about 4 mrad at the Cherenkov angle saturation value and a time resolution better than 50 ps RMS for charged particles with Z = 1. The present technology makes the proposed SiPM-based PID system particularly attractive for space applications due to the limited detector volumes available. In this work, we present beam test results obtained with the detector prototype and we discuss possible configurations optimized for the identification of ions in space applications.
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All authors M. N. Mazziotta, L. Congedo, G. De Robertis, M. Giliberti, F. Licciulli, A. Liguori, L. Lorusso, N. Nicassio, G. Panzarini, R. Pillera
Plasma Physics
Triggers for plasma detachment bifurcation in the edge divertor region of tokamaks
Menglong Zhao, Thomas Rognlien, Ben Zhu et al. (+3 more)
We report the discovery of the trigger for detachment bifurcation phenomenon in tokamak divertors, revealed through steady-state and time-dependent UEDGE simulations: The observed electron temperature cliff at the outer target in DIII-D H-mode
plasmas with ion $B\times \nabla B$ drift driven into the active divertor results from a bifurcation-induced $T_e$ drop above the X-point accompanied by reversal of the $E\times B$ flow pattern in the private flux region. Time-dependent simulations reveal a two-phase transition mechanism: the high-field-side radiation front first extends across the last closed flux surface and stabilizes above the X-point, causing local $T_e$ to drop from $\sim 70\,\mathrm{eV}$ to $\sim 10\,\mathrm{eV}$ and inducing $E\times B$ flow reversal in a thin layer below the X-point, which lasts $< 0.5\,\mathrm{ms}$; Flow reversal below the X-point subsequently triggers the sharp drop in outer target temperature on a timescale of $1-2\,\mathrm{ms}$, establishing deep detachment a few ms thereafter. A bifurcation transition occurs when the high-field-side radiation front crosses the separatrix while the outer divertor remains attached, with the $T_e$ cliff manifesting distinctly when the outer target $T_e \gtrsim 10\,\mathrm{eV}$ prior to the bifurcation. These results demonstrate that the bifurcation is linked to in-out divertor asymmetry and asymmetric radiation front
evolution.
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All authors Menglong Zhao, Thomas Rognlien, Ben Zhu, Filippo Scotti, Xinxing Ma, Adam McLean
Physics and Society
On the existence of Ulanowicz's optimal structural resilience in complex networks
Si-Yao Wei and Wei-Xing Zhou
This study provides a foundational theoretical investigation into the mathematical existence and asymptotic properties of Ulanowicz's structural resilience. While ecological evidence suggests that sustainable systems gravitate toward an optimal efficiency-redundancy balance at $\alpha = 1/\mathrm{e}$, the mathematical attainability of this configuration across broader network
topologies remains unverified. We rigorously prove that while optimal resilience is structurally unattainable in two-node networks, there exists at least one optimal flow configuration within the feasible probability space for any weighted and directed network with the network size $N_\mathcal{V} \geq 3$ and no self-loops. To make the derivations analytically tractable, we introduce a parameterized symmetric network model with uniform marginal distributions. Using this stylized ansatz, our analytical and numerical results reveal that maintaining the optimal state requires distinct asymptotic scaling behaviors as $N_\mathcal{V}$ increases: adjacent primary links scale as $O(N_\mathcal{V}^{-1})$, whereas non-adjacent background links exhibit a steeper quadratic decay of $O(N_\mathcal{V}^{-2})$ with specific logarithmic corrections. Rather than serving as an immediate engineering tool, this work establishes a rigorous mathematical boundary for the optimal resilience framework, demonstrating analytically how an optimally resilient system differentiates into high-throughput primary channels and sparse redundancy pathways.
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Fluid Dynamics
Model-Driven Conditional Fourier Neural Operator for Spectrum-Consistent Synthetic Turbulence Generation
Hongyuan Lin and Shizhao Wang
This short note proposes a model-driven conditional
Fourier neural operator (MD-CFNO) for synthetic
turbulence generation. Spectrum-consistent synthetic
turbulence is essential for inflow boundary construction in computational fluid dynamics and for broadband aeroacoustic noise prediction. Data-driven
turbulence synthesis with neural networks has emerged as a promising direction. However, generating flow fields that match prescribed energy spectra across wide physical regimes remains challenging. Existing data-driven methods typically rely on expensive reliable
datasets with limited generalization and are prone to regression-to-the-mean when trained in the spatial domain. To address these issues, the MD-CFNO is proposed with three components: a model-driven data construction strategy is adopted to improve interpretability and broaden the generalizable parameter regime; conditional
stochastic generation is integrated into the
Fourier neural operator architecture to alleviate regression-to-the-mean effects; and a composite loss is introduced to accelerate convergence and enhance spectral fidelity. Results show that the proposed MD-CFNO generates spectrum-consistent synthetic
turbulence and achieves robust performance under both interpolation and out-of-distribution extrapolation conditions. This study provides a model-driven perspective on synthetic
turbulence, showing the advantages of
Fourier neural operators for conditional generation.
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Atmospheric and Oceanic Physics
The Interdecadal Bipolar Oscillation: An Atmospheric Water Vapor Mode Driving Asynchronous Polar Climate Change
Hongyu Wang, Jingfang Fan, Fei Xie et al. (+5 more)
Climate change is progressing asynchronously between the Arctic and Antarctic, with important implications for global
climate dynamics. While the Arctic has experienced rapid warming and pronounced amplification, the Antarctic has exhibited a delayed and heterogeneous response. Here, we identify an Interdecadal Bipolar Oscillation (IBO) in atmospheric water vapor, a coherent internal mode of variability that connects the two polar regions and helps explain their divergent
climate trajectories over the past eight decades. Using reanalysis data alongside historical and pre-industrial control simulations from CMIP6, we demonstrate that the IBO is a robust internal variability mode with a quasi-period of 60 ~ 80 years. This oscillation modulates the background warming signal, with a phase shift in the late 1980s amplifying moistening and warming in the Arctic while concurrently suppressing changes in the Antarctic. Crucially, model projections suggest a possible phase reversal, which could slow water vapor increases in the Arctic while accelerating them in the Antarctic, potentially marking the start of rapid Antarctic
climate change. While uncertainties remain in how
climate models capture polar water vapor, our findings highlight the IBO as a pivotal driver of polar
climate evolution and a potential contributor to emerging
climate risks in the Southern Hemisphere.
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All authors Hongyu Wang, Jingfang Fan, Fei Xie, Jingyuan Li, Rui Shi, Yan Xia, Deliang Chen, Xiaosong Chen
Optics
Kerr-enhanced amplification of three-wave mixing and emergent masing regimes
Ragheed Alhyder, Rishabh Sahu, Johannes M. Fink et al. (+2 more)
Integrated optical microresonators exploiting either second-order ($\chi^{(2)}$) or third-order ($\chi^{(3)}$) nonlinearities have become key platforms for frequency conversion, low-noise microwave photonics, and
quantum entanglement generation. Here, we present an analytic theory of Kerr-enhanced three-wave mixing amplification in an electro-optic microresonator with both $\chi^{(2)}$ and $\chi^{(3)}$ nonlinearities. We demonstrate that Kerr dressing hybridizes the optical sidebands, renormalizing the $\chi^{(2)}$ couplings and detunings. As a result the system exhibits gain in regions where analogous bare $\chi^{(2)}$ or $\chi^{(3)}$ amplifiers are subthreshold. Time-domain Langevin simulations confirm this threshold reduction, mapping a practical design window for experiments.
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All authors Ragheed Alhyder, Rishabh Sahu, Johannes M. Fink, Mikhail Lemeshko, Georgios M. Koutentakis
Space Physics
Physicochemical properties of lunar regolith simulant for in situ oxygen production
Alyssa Ang De Guzman, Anish Mathai Varghese, Saif Alshalloudi et al. (+3 more)
Permanent lunar settlements will rely on in situ oxygen production from regolith for life support and propulsion. While oxygen is abundant in lunar materials, it is chemically bound within metal
oxides whose extractability depends strongly on regolith composition and processing strategy. In this study, we validate and characterize high-fidelity lunar regolith simulants representative of the lunar highlands and south pole using scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area and pore structure analysis, and hydrogen temperature-programmed reduction. The simulants exhibit strong mineralogical and compositional fidelity to returned Apollo and Chang'e samples, with ilmenite confirmed as the most readily reducible oxygen-bearing phase. However, despite low ilmenite abundance, bulk highland simulants display favorable reduction behavior arising from distributed Fe-bearing silicate and glassy phases, as well as surface and microstructural properties that influence gas-solid interactions. Adsorption experiments with gases (H2, CH4, and CO2) and water indicate that mineralogical heterogeneity and pore accessibility influence their uptake in simulants. These results indicate that oxygen extraction behavior in realistic lunar regolith is governed by whole-regolith response rather than ilmenite content alone, supporting the option of whole-regolith processing strategies for oxygen production in lunar in situ resource utilization architectures.
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All authors Alyssa Ang De Guzman, Anish Mathai Varghese, Saif Alshalloudi, Lance Kosca, Kyriaki Polychronopoulou, Marko Gacesa
Atomic Physics
Light propagation in atomic stratified media: breakdown of the transfer-matrix method at high density
Igor M. Sokolov and William Guerin
The transfer-
matrix method is a standard approach to wave propagation in stratified media. With the advent of cold-atom-based
quantum and photonic technologies, several experiments and many proposals consider light propagation in one-dimensional optical
lattices, using the transfer
matrices as the main tool for the simulation. Here, we study the validity of this method by comparing its results to the microscopic coupled-dipole model, which is exact in the linear-optics regime. We show that the transfer-
matrix method works very well at low density, even for thin disordered slices, and breaks down at high density because the dipole-dipole interaction induces a collective response from the atoms such that the properties of one layer are influenced by the others. We determine the boundary values of atomic densities for which this method is still applicable for describing experiments. Our findings are relevant for experimental realizations using ultra-cold atoms.
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Computational Physics
FEcMD: A multi-physics and multi-scale computational program for dynamic coupling molecular dynamics simulations with transient electric field and heat conduction in metal nanostructures
Bing Xiao, Nan Li, Wenqian Kong et al. (+5 more)
Field emission coupled with molecular dynamics simulation (FEcMD) software package is a computational tool for studying atomic structure
evolution, structural deformation, phase transitions, recrystallization as well as electron emission characteristics of micro- and nano-protrusions and nanowires consisting of elemental metals or multi-component
alloys by means of multi-physics and multi-scale methodology. Current implementations of molecular dynamics simulation coupled with multi-scale electrodynamics (ED) and heat conduction (HC) in FEcMD program are advanced mainly in the two aspects as follows. In electrodynamics, the FEcMD program incorporates the space charge interactions (space charge potential and exchange-correlation effects) in the self-consistent solved Poisson-Schrödinger equation with Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) approximation to evaluate the field emission current density and the related resistive heating process more reliably for nanowires or nano-protrusions especially for nano-gaps between two metal electrodes. Meanwhile, the two-temperature heat conduction model is implemented in electrodynamics coupled with molecular dynamics simulations (ED-MD), providing more dedicated descriptions for the hierarchical electron-
phonon two-channel heat conduction mechanism and the temperature evolutions of electron and
phonon subsystems under the radiofrequency (RF) or pulse electric fields.
Benchmark tests are performed for some key implementations in FEcMD software to validate the numerical results, and also to demonstrate the use of program to study the atomic structure
evolution of metal nano-structures under electric field and heating processes.
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All authors Bing Xiao, Nan Li, Wenqian Kong, Rui Chu, Hongyu Zhang, Guodong Meng, Kai Wu, Yonghong Cheng
Optics · Cross-listed from quant-ph
Scaling Enhancement in Distributed Quantum Sensing via Bidirectional Causal Routing
Binke Xia, Zhaotong Cui, Jingzheng Huang et al. (+2 more)
Sensing networks underpin applications ranging from fundamental physics to real-world engineering. Distributed
quantum sensing (DQS) can improve measurement performance, but existing protocols typically require multipartite
entanglement, which poses substantial challenges for scalable implementation. Here, we introduce a DQS protocol based on bidirectional causal routing in a cyclic network, where a single probe sequentially interrogates M independent sensors along two opposite causal routes. By exploiting the noncommutativity between inter-sensor propagation and local sensing operations, the protocol turns propagation from a passive transport process into a source of sensing information, yielding an asymptotic 1/M^2 scaling of the estimation precision without multipartite
entanglement. We experimentally demonstrate the protocol for distributed beam-tilt sensing in a free-space
quantum optical network comprising up to 9 sensors, achieving picoradian-level precision in estimating the average tilt angle. These results identify propagation dynamics and routing geometry as active metrological resources for scalable distributed
quantum sensing.
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All authors Binke Xia, Zhaotong Cui, Jingzheng Huang, Yuxiang Yang, Guihua Zeng