Geophysics
Crustal and upper mantle model of the Middle East based on full-waveform inversion
R{\i}dvan Örsvuran, Ebru Bozdağ, Daniel Peter et al. (+7 more)
We present MEAD-M20, a new tomographic model of the Middle East and its surrounding regions, including Anatolia, Iran, and the Caucasus. The model is developed within a full-waveform inversion framework, based on 3D wavefield simulations and the adjoint method, after 20 iterations, utilizing an extensive
dataset from permanent and temporary stations available from EarthScope and regional networks. Starting from the global FWI model GLAD-M25 on a 60{\deg}x 60{\deg} regional mesh, we invert 210 regional earthquakes recorded by 1,215 stations to obtain the P- and S-wave model with transverse isotropy in the upper mantle. For the first 12 iterations, we combine multitaper traveltime measurements of 15-50 s body waves and 50-100 s body and surface waves on three components. We use a refined crustal mesh to better sample the crust after the 12th iteration and gradually decrease the minimum surface-wave period to 30 s. MEAD-M20 provides a self-consistent P- and S-wave model ready for seismic wave simulations, which is essential for accurate earthquake location, source parameter estimation, and seismic hazard assessment in the geologically and tectonically complex region. MEAD-M20 reveals several important geodynamical and tectonic features, including local mantle plumes beneath the Arabian Plate, Jordan, and the Levant, characterized by low-velocity anomalies and likely associated with volcanism in the Harrats, Jordan, and the Karacadag regions. In addition to the active subduction and rifting in the area, the model clearly identifies remnants of the Tethys Ocean beneath Eastern Anatolia, which become progressively shallower toward the Makran region in the south, consistent with the subduction history along the Bitlis-Zagros suture zone. We also observe lithospheric-scale low-velocity anomalies associated with the North and East Anatolian faults, extending to depths of approximately 200 km.
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All authors R{\i}dvan Örsvuran, Ebru Bozdağ, Daniel Peter, Daniel Peter, Andrea Chiang, Rengin Gök, Yahya M. Tarabulsi, Ahmed Hosny, Khalid Yousef, Abdullah Mousa
Physics Education
Establishing a national masters̀ programme in high-energy physics: lessons from a Romanian case study
Roxana Zus, Călin Alexa, Paul Grăvilă et al. (+2 more)
The establishment of a joint coordinated national programme for graduate education represents a significant step in strengthening higher education systems and their
alignment with international research environments. This paper examines the creation of the Romanian National Masters̀ Programme in High-Energy Physics, the first initiative of its kind in the country. We outline the motivation for its development, based on the need to prepare students for active participation in large-scale international collaborations such as CERN, while also consolidating domestic expertise. The article describes the programmes̀ design, including its multi-institutional structure, curriculum, and integration of research training, as well as the policy and administrative processes that enabled its implementation. Initial outcomes highlight the programmes̀ contribution to student mobility, research engagement, and capacity building within the Romanian higher education system. Finally, we discuss lessons learned and future perspectives, situating the initiative within broader European efforts to modernise graduate education in the sciences.
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All authors Roxana Zus, Călin Alexa, Paul Grăvilă, Zsolt-Iosif Lázár, Daniel Radu
Plasma Physics
HIR: A collisional-radiative model for hydrogen ionization in plasma with anisotropic fast ions
Sergey Polosatkin
The paper presents the HIR (Hydrogen Ionization Rates) software package developed for calculating the level populations of atomic hydrogen and the dynamics of its ionization in hot
plasma, including the case of fast ions with an anisotropic distribution function. The code is based on a steady-state collisional-radiative model that includes electron and ion impact excitation, de-excitation, ionization, charge exchange, and spontaneous radiative transitions. It is demonstrated that stepwise ionization via excited states contributes up to 20% to the total ionization rate and requires including levels up to the principal
quantum number N=8. For the GDML and GOL-NB mirror trap facilities, the effects of stepwise ionization on the mean free path of fast atoms are analyzed. It is shown that collisions with different
plasma species are non-additive due to stepwise ionization, leading to a reduction in the mean free path by up to 7% at 40 keV. The anisotropy of the fast ion distribution is found to have a negligible effect (less than 1%) on the ionization dynamics in the GDML
plasma. The ionization cost of hydrogen atoms in the GOL-NB
plasma is calculated, demonstrating a strong dependence on
plasma density due to competition between collisional and radiative de-excitation. The HIR package is openly available on GitHub.
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Optics
The Information Rate of Fiber-Wireless Communication Systems Based on Photonic Generation of RF Signals
Long Huang and Jianping Yao
High-capacity fiber-wireless communication systems operating at high frequencies increasingly rely on photonic generation of
radio-frequency (RF) signals. In these systems, optical signals are transmitted over optical fibers and detected by photodetectors, where RF signals are generated at frequencies equal to the difference between the optical carrier frequencies. A major performance-limiting impairment is the phase noise of the generated RF signals, which originates from the phase noise of the optical sources. In this paper, we develop comprehensive probabilistic models for the two principal configurations of fiber-wireless communication systems employing photonic RF generation. Based on these models, we propose an efficient numerical framework for calculating the information rate (IR). Numerical simulations are performed to validate the efficiency of the proposed
algorithm and the results provide design guidelines for high-performance fiber-wireless systems.
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Fluid Dynamics
Foundations of a solved-volatility stochastic turbulence closure: Itô–Hencky kinematics, source-consistent momentum and finite-correlation realisation
Hsieh-Chen Tsai
Most
stochastic closures prescribe a covariance tensor, a noise basis or an eddy-viscosity field. This paper develops a different framework in which the displacement-
volatility field is solved together with the resolved velocity. The starting point is a one-channel Itô configuration map. A local
matrix-logarithm expansion gives distinct material and spatial Hencky increments, their quadratic-variation drifts and the exact pathwise volume constraint. Under constant density, one Brownian channel, pathwise isochoricity and no independent martingale in the resolved Eulerian drift, the material pull-back momentum equation is shown to be the on-shell form of the full
stochastic Reynolds transport balance when the momentum-source covariation is retained. The resulting velocity–
volatility–pressure system has an index-one differential–algebraic structure. Virtual power fixes the mechanical type of the stress impulse and separates work from quadratic covariation. A finite-correlation precursor then gives a Green–Kubo realisation of the solved displacement covariance. State dependence adds a Lyapunov noise-induced drift, while dynamic boundaries add reaction work and active/passive covariance compatibility conditions. The analysis also gives four limits: a non-zero Brownian transport limit cannot retain finite ordinary unresolved kinetic energy; total energy alone does not fix
entropy production; wall tangency limits covariance rank rather than the number of
stochastic modes; and a homogeneous decoupled Helmholtz–Stokes equation has only the trivial periodic solution. The result is a theory-complete, testable closure architecture. Developed turbulent statistics, logarithmic wall scaling and computational-fluid-dynamics validation are deliberately left to the expanded fluid-mechanics study.
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History and Philosophy of Physics
The Development of Detectors of High Energy Neutrinos and Cosmic Rays between 1980 and 2000
A A Watson
The construction of the DUMAND, Lake Baikal and IceCube detectors of high-energy
neutrinos are discussed, with some emphasis on the difficulties encountered. The decade from 1990 marked the period in which the Auger Observatory was conceived and the Collaboration evolved. Again, the difficulties that were overcome to create the Observatory are described. For both IceCube and the Auger Observatory, claims made in the 1980s for the observation of PeV gamma-rays from Cygnus X-3, played a not-insignificant role in their advance.
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Optics
Geometry resolved atomic oxygen risk assessment for very low earth orbit spacecraft
Gun Hi Won, Hyun Jung Kim, SongYi Park et al. (+3 more)
Atomic oxygen (AO) is a major durability concern for spacecraft in very low Earth orbit (VLEO), yet orbit-averaged fluence does not resolve exposure on individual surfaces and internal components. This study develops a geometry-resolved AO assessment by coupling NRLMSISE-00, HWM07, and SYSTEMA ATOMOX. One-year simulations were performed for a 350 km circular Sun-synchronous orbit at LTAN 06:00 and 12:00 using a baseline spacecraft, a wedge-modified body, and two synthetic aperture radar
antenna sub-arrays. The LTAN 12:00 orbit produced 8-10% higher orbit-averaged AO flux than LTAN 06:00. For the baseline geometry, the ram-facing surface accumulated 6.9-7.5 x 10^21 atoms/cm^2, whereas side and zenith/nadir surfaces received only 3-5% of the ram fluence. Material-specific erosion yields changed the component-level risk ranking: the CFRP zenith panel was predicted to erode by 15.1-16.2 um/year despite receiving much lower fluence than the ram-facing multilayer insulation. The wedge generated approximately one order of magnitude spatial variation through local shielding. Housing openings also allowed AO to reach internal printed
circuit boards, with maximum annual fluences of 9.5 x 10^16 and 4.0 x 10^19 atoms/cm^2 in the H- and V-polarized
antenna models, respectively. HWM07 winds produced 10-20% side-panel asymmetry, which decreased below 1% when winds were disabled. Comparison with MISSE-8 reproduced the measured zenith-to-ram ratio of approximately 4% but underpredicted wake exposure, identifying a limitation of ballistic ray tracing. These results demonstrate that VLEO AO durability requires coupled consideration of orbit, atmospheric winds, geometry, and material response.
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All authors Gun Hi Won, Hyun Jung Kim, SongYi Park, ChangWon Seo, Eunji Lee, SeongSik Yoon
Atomic Physics
Experiments with interacting ultracold polar molecules
Philip D. Gregory, Jonathan M. Mortlock, Daniel K. Ruttley et al. (+1 more)
Ultracold polar molecules have emerged as an exciting platform for experiments in
quantum science, with many proposed applications seeking to leverage the existence of long-range dipolar interactions and the rich internal structure of long-lived states. However, the complexity of molecules also presents many experimental challenges. In this chapter, we review the experimental advances over the past two decades that have brought ultracold molecules under full
quantum control. We focus on three key topics: control of ultracold molecular collisions, engineering dipolar interactions and nascent
quantum simulations in optical
lattices.
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All authors Philip D. Gregory, Jonathan M. Mortlock, Daniel K. Ruttley, Simon L. Cornish
Optics
Synthesis of hybrid gold-protein nanobioconjugates with strongly enhanced circular dichroism
Yoann Prado, Victoire Ho, Maud Virolle et al. (+7 more)
Controlling
chiral light-matter interactions with nanophotonics is a powerful strategy for amplifying molecular circular dichroism (CD) beyond its natural limits. Here, we present a plasmonic platform that uses superchiral near fields to amplify the optical activity of biological chromophores. Gold nanoparticles (3.6 nm in diameter) are electrostatically coupled with photosynthetic
proteins which results in stable hybrid nanobioconjugates in aqueous solution. The Q-band absorption spectrum of the
proteins overlaps with the localized surface plasmon resonance of the gold particles. In the visible region, a combination of numerical simulations and normalized CD measurements reveal an enhancement factor of 3 compared to free
proteins. This observation reveals three effects. First, there is a local increase in electromagnetic chirality density in the
protein environment. Second, there is an increase in the absorption of the
proteins. Third, there is plasmon-induced circular dichroism. Our results quantitatively demonstrate that near-field super-chirality directly modulates biomolecular optical activity. These findings open new avenues for chiroptical nanodevices, biosensing platforms, and light-driven asymmetric photochemistry.
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All authors Yoann Prado, Victoire Ho, Maud Virolle, Maria Sanz-Paz, Mathieu Mivelle, Souhir Boujday, Michèle Salmain, Guillaume Demesy, Nicolas Bonod, Bruno Gallas
Plasma Physics
Reconciling chemical models of X-ray Thomson Scattering with the Bethe $f$-sum rule
Maximilian P. Böhme, Paul Hamann, Veronika A. Kruse et al. (+9 more)
X-ray Thomson scattering (XRTS) is a key diagnostic for high-energy-density
plasmas, which can exhibit significant
quantum effects even at elevated temperatures. XRTS experiments are commonly interpreted using the Chihara decomposition, that was derived in the chemical picture and, thus, separates contributions from bound and free electrons. Despite being the de-facto standard for analysing measurements, a well-known shortcoming is that the standard bound-state treatment in the form of the impulse approximation fails to satisfy fundamental theoretical constraints, most notably the Bethe $f$-sum rule (BFSR). The problem arises due to the usage of plane waves in the impulse approximation as well as non-negligible contributions from bound-bound transitions. In this work, we present a minimal analytical extension of the Chihara decomposition of the dynamic structure factor for matter in the ground state, using hydrogenic bound-free and bound-bound transitions. We demonstrate that compliance with the BFSR is only achieved when both bound-bound transitions are explicitly included and an exact treatment of the bound-free contribution is applied. Finally, detector ray-tracing simulations for atomic hydrogen demonstrate experimentally detectable deviations from the standard Chihara model. The model will be made available in the open source XRTS library xDAVE [Bellenbaum et al., Phys.
Plasmas (in print), arxiv:2604.27237].
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All authors Maximilian P. Böhme, Paul Hamann, Veronika A. Kruse, Hannah M. Bellenbaum, Armin Bergermann, David T. Bishel, Thomas Gawne, Dirk O. Gericke, Zhandos A. Moldabekov, Pontus Svensson, Jan Vorberger, Tobias Dornheim
Applied Physics
Stretch-free, shape-induced 3D Island-Bridge Networks for flexible TFTs on Silicon Planar Technology verified through Bending and Scalability to 9x9 Matrix
Daniel Joch, Robert Kammel, Fabian Magerl et al. (+2 more)
This study presents a CMOS-compatible, fully integrated three-dimensional island-bridge concept for flexible electronics on silicon planar technology. By
embedding metal bridges within trenches in a polyimide-passivated island
matrix, the approach localizes mechanical stress to the bridges whereby active components on the islands are protected from mechanical stress, enabling high-performance thin-film transistors (TFTs) on flexible substrates. A concave, arc-shape forming fill in trenches between the islands and backside etching yield freestanding 3D bridges. Numerical simulations to determine the minimum bending radius reveal a characteristic stress distribution in the bridges during bending, with peak stresses at the bridge-island transitions. Variation of trench depth modulates von Mises stress, identifying design parameters for reliability. Experimental validation demonstrates TFT operation under bending, with stable threshold voltage, subthreshold swing, and saturation mobility across a range of bending radii; broader bridges exhibit enhanced mechanical robustness. A 9x9 island-bridge
matrix with addressable integration of TFTs across islands demonstrates the scalability of the concept. Overall, the results verify the manufacturability of stretch-free 3D metal bridges where the three-dimensional shape is defined by the topography of the concave trench filling, with integrated active devices, and confirm the mechanical and electrical functionality of the produced flexible substrates.
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All authors Daniel Joch, Robert Kammel, Fabian Magerl, Mathias Rommel, Michael P.M. Jank
Physics and Society
Coevolution of epidemic dynamics and network topology driven by disease fatality and waning immunity
ThankGod I. S. Ikpe, Takayuki Hiraoka and Naoya Fujiwara
Epidemics on complex networks have been shown to exhibit dynamics that are strongly influenced by the
topology of the network. However, it remains unclear how the
topology of the network is influenced by epidemic properties, such as waning immunity and disease fatality, coupled with demographic changes. To explore the interplay between epidemic dynamics and network
topology, we develop an
agent-based model of a fatal infectious disease with an imperfect immunity on an initially scale-free network that evolves via demographic and epidemic-induced changes. We show that this model undergoes an epidemic transition between a phase in which the disease eventually dies out and a phase in which it becomes endemic. Moreover, the network may lose its scale-free property as a result of the epidemic spreading, giving rise to a topological transition from a power-law to a non-power-law degree distribution. We validate our findings using heterogeneous mean-field approximations of the
agent-based model. These results highlight the importance of accounting for network
evolution in epidemic models and advance our understanding of coevolving dynamical systems, in which disease dynamics and network
topology continuously shape one another.
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Accelerator Physics · Cross-listed from hep-ph
Distinguishing the Axion-Wind and Oscillating-EDM Couplings in Storage-Ring Searches for Axion Dark Matter
V. Hejny and J. Pretz
Resonant
spin-precession experiments in storage rings are sensitive to two distinct
axion and
axion-like particle dark-matter couplings: an oscillating electric dipole moment (EDM) primarily driven by the
axion-
gluon interaction, and the
axion-wind (derivative) coupling acting as an effective pseudomagnetic field on the
spin. Both effects produce a vertical polarization buildup at the same resonance frequency and are therefore degenerate in this standard observable. It is shown that the two couplings enter the vertical build-up and the
spin-precession phase walk as the difference and sum of their resonance strengths, respectively. Measuring both observables simultaneously at fixed energy in a multi-bunch configuration allows the individual coupling strengths to be extracted up to a two-fold sign ambiguity. As a complementary approach, the ratio of electric to
magnetic bending fields in a combined storage ring can be varied while keeping the resonance frequency fixed. This leaves the
axion-wind contribution unchanged while modifying the EDM contribution in a calculable way, enabling a clean separation of the two effects. Both approaches can be used in future storage-ring facilities dedicated to EDM measurements.
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Fluid Dynamics
A universal diffuse interface modeling framework for surfactants
Shahab Mirjalili and Mathieu Bignolles
We propose a universal diffuse-interface modeling framework for surfactant transport in two-phase flows, applicable to all solubility scenarios and to any conservative phase field method. The foundation of our framework is a general three-scalar non-
equilibrium model governing the surfactant concentrations in each bulk phase and at the interface, which builds on our prior consistent scalar transport framework and is locally and globally conservative, leakage-free, Galilean-invariant, and reduction-consistent. Assuming thermochemical
equilibrium, we derive two one-scalar models: one for a surfactant in full
equilibrium between both bulk phases and the interface, and one for a surfactant confined to a single bulk phase and the interface. All models are coupled to the Navier-Stokes equations through a surface tension force that incorporates the Marangoni stress arising from non-uniform interfacial surfactant distributions. While diffuse-interface surfactant models have been developed for the Cahn-Hilliard equation and, more recently, for the conservative Allen-Cahn (CAC) equation, existing models for CAC address only the insoluble and single-phase-soluble cases, leaving the general scenario of partial solubility in both bulk phases unaddressed; furthermore, these models lack Galilean invariance and reduction consistency, and are not applicable beyond the CAC setting. The framework is validated against analytical solutions in one-dimensional transport tests, assessed for convergence in two-dimensional advection-
diffusion simulations, and demonstrated in fully-coupled drop-in-shear flow simulations covering insoluble, soluble, and partially-soluble surfactant scenarios.
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Fluid Dynamics
Accurate wetting dynamics via a conservative Allen-Cahn based lattice Boltzmann approach for multiphase flows
Paolo Bello, Luca Mander, Marco Lauricella et al. (+3 more)
In this work we propose a local
geometric wetting boundary condition for a conservative Allen–Cahn-based
lattice Boltzmann framework. The prescribed contact angle is imposed through ghost phase-field values constructed from a locally reconstructed wall normal and a donor-fluid extrapolation. The ghost-node wetting update is local, geometrically consistent, and compatible with thread-safe large-scale implementations, while phase-field mass is controlled through a separate global volume correction. Validation includes static contact-angle tests, short-time droplet spreading, impact on a hydrophobic surface, and
gravity-driven motion through a sharp-edged orifice. The simulations recover the imposed
equilibrium angles, reproduce contact-angle-dependent spreading exponents between approximately 1/2 and 1/4, and follow the classical W e1/4 maximum-deformation scaling. The model also captures the transition between capture, release, and release with breakup. The proposed approach provides an accurate and scalable framework for wetting-controlled flows in complex geometries.
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All authors Paolo Bello, Luca Mander, Marco Lauricella, Gianmarco Guglielmo, Michele La Rocca, Andrea Montessori
Medical Physics
Liver Metastasis Detection at Reduced Radiation Dose: Diagnostic Evaluation of a Novel Organ-Level Tube Current Modulation Method
Maria Jose Medrano, Sen Wang, Kaylee W. Fang et al. (+8 more)
Objective: To evaluate retroOpt, a novel organ-level tube current modulation (TCM) method that minimizes effective radiation dose while preserving diagnostic image quality for liver metastasis detection. Methods: In this retrospective, IRB-approved study, 22 patients with 68 liver lesions (38 malignant, 30 benign) underwent portal venous phase contrast-enhanced chest-abdomen-pelvis CT. Using projection-domain noise emulation, five series were generated per patient: original full dose (Orig-100), uniform dose reduction to 40% (UD-40) and 60% (UD-60) of the original effective dose, and organ-level TCM at the same levels (Opt-40, Opt-60). Three abdominal radiologists independently detected and classified lesions and rated image quality (5-point Likert). Per-lesion sensitivity was compared by McNemar test. Malignant lesion-size thresholds for 50% and 90% sensitivity (x50, x90) were estimated by logistic regression. Image quality was compared by Wilcoxon signed-rank test. Results: At the 60% level, Opt-60 achieved mean malignant lesion sensitivity comparable to full-dose CT (82% vs 80%) and exceeded uniform reduction (67%). At the 40% level, Opt-40 improved mean sensitivity over UD-40 from 52% to 68%. Mean all-lesion sensitivity rose from 54% (UD-40) to 64% (Opt-40) and from 65% (UD-60) to 77% (Opt-60), remaining comparable to full dose (76%). All optimized-versus-uniform differences were significant (p <= 0.003). Opt-60 lesion-size thresholds closely matched Orig-100 (x50 3.3 vs 3.7 mm; x90 15.7 vs 16.8 mm). Median Opt-60 image quality ranged from 3 to 4.5 across readers. Conclusions: Organ-level TCM preserved liver metastasis detection at 60% of the original effective dose, outperforming uniform dose reduction. Task-specific organ-level dose optimization may enable greater CT dose reduction than uniform strategies for patients requiring repeated metastasis surveillance.
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All authors Maria Jose Medrano, Sen Wang, Kaylee W. Fang, Jennie Cao, Liyan Sun, Luyao Shen, Andy Shon, Luke Yoon, Grant M. Stevens, Adam S. Wang, Justin R. Tse
Fluid Dynamics
Vortex dynamics and air entrainment in dam break wave impacting on vertical walls: A multiphase lattice Boltzmann study
Massimiliano Mustè, Andrea Montessori and Pietro Prestininzi
Air entrainment often plays a crucial role in determining impact loads exerted by free-surface wave flows interacting with structures, yet its modelling is often oversimplified in numerical approaches. In this study a two-phase numerical model, based on the
Lattice Boltzmann Method coupled to a conservative Allen–Cahn interface-capturing equation is employed to perform direct numerical simulations of dam-break waves propagating over a dry bed and impacting on vertical walls. Access to high-resolution simulations enables a detailed assessment of how accurately resolving both air–water and solid–water interfaces affects local and overall dynamics, as well as quantities of extreme engineering interest. Indeed, the magnitudes and locations of the pressure peaks are strongly affected by wave front deflection and local aeration induced by a small corner
vortex. Additionally, comparisons between no-slip and free-slip implementations suggest that the large air cavity formation, commonly observed as trapped inside the reflected jet falling back onto the incoming flow, may be the result of modeling assumptions rather than intrinsic flow physics, again highlighting the key role of near-wall shear in jet breakup dynamics.
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Geophysics
Poroelastic aquifer response drives seasonal vertical land motion in southern Louisiana
Pritom Sarma, Eduardo Arzabala, Carolina Hurtado-Pulido et al. (+4 more)
Coastal Louisiana is sinking, amplifying flooding and land loss, yet the seasonal component of this motion remains difficult to attribute. Satellite geodetic records from Baton Rouge spanning 2004-2024 reveal long-term subsidence of -2.69 +/- 0.69 mm/yr, with a superimposed annual oscillation of 10-15 mm that is in phase with river stage and confined-aquifer hydraulic head. This positive correlation is diagnostic of poroelastic deformation rather than surface loading. A poroelastic model of a semi-confined aquifer driven by hydraulic-head variations reproduces both the long-term and seasonal signals. The seasonal amplitude decreases logarithmically with distance from the intersection of the Baton Rouge Fault and the Mississippi River, as expected for radial pressure
diffusion from a flux source. Fault-river intersections therefore act as seasonal conduits into deep aquifers, representing an underappreciated control on coastal land motion that is likely to strengthen as hydrological extremes intensify.
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All authors Pritom Sarma, Eduardo Arzabala, Carolina Hurtado-Pulido, Einat Aharonov, Renaud Toussaint, Stanislav Parez, Cynthia Ebinger
Classical Physics · Cross-listed from math-ph
Notes on a paper by F. Génot and B. Brogliato on the Painlevé paradox
Stefano Pasquero
We reconsider the analysis of the Classical Painlevé Problem developed by F. Génot and B. Brogliato ([1] New results on Painlevé paradoxes. - European Journal of Mechanics-A/Solids, 18(4):653{677, 1999), focusing on the consistency of their results with Galilean invariance. We show that certain conclusions concerning the dynamical
evolution of the mechanical system are not invariant under changes of Galilean observer and therefore cannot, in their present form, be interpreted as intrinsic properties of the system. In particular, we show that the classi?cation of motion states depends on the observer through the velocity{dependent characterization of the frictional constraint, and we trace the origin of this dependence to the Galilean velocity-addition
theorem. We present and discuss possible reformulations of the model aimed at restoring observer-invariant descriptions of the problem.
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Computational Physics · Cross-listed from cond-mat.mes-hall
Twisted Multilayer Graphene: Superperiodicity and quasicrystals
Pedro Alcázar Guerrero
This thesis investigates how superperiodicity, quasiperiodicity, and disorder shape electronic and
spin transport in
graphene-based systems, with an emphasis on experimentally relevant length scales and realistic atomistic modeling. Using large-scale real-space
quantum-transport methods, it first establishes controlled transport fingerprints that distinguish conventional Bloch propagation in periodic structures from the anomalous dynamics induced by quasiperiodic modulations. Building on this framework, the thesis analyzes magic-angle twisted
bilayer graphene and shows that, within a finite disorder window where flat-band features remain robust, moderate Anderson disorder can counterintuitively enhance the mean free path. This disorder-induced delocalization is further linked to changes in the
quantum metric extracted from optical conductivity, revealing a direct connection between transport, electronic geometry, and the real-space extent of the underlying states. The study then turns to
graphene quasicrystal approximants and hybrid multilayer stacks, identifying sub-ballistic transport and self-similar localization patterns as signatures of quasicrystalline order, while also demonstrating their strong fragility against disorder and interlayer proximity effects. Finally, the thesis addresses
spin transport in suspended monolayer
graphene, showing that atomic-scale corrugations generate short-range fluctuating Rashba fields that can limit
spin lifetimes to the nanosecond range even when charge transport remains close to ballistic. Taken together, these results provide a unified picture of how geometry, disorder, and structural complexity govern transport phenomena in twisted and corrugated
graphene systems.
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Plasma Physics
Polaris: a flexible stellarator demonstration experiment with simple modular coils
Simon P. H. Vincent, Joaquim Loizu, Matthieu Toussaint et al. (+14 more)
We present the design, construction, and first
plasma experiments of Polaris, a new small-scale stellarator experiment (major radius R ~ 0.4 m) located at the Swiss
Plasma Center. Polaris consists of a relatively large
vacuum vessel (~0.5 m^3) predominantly made of glass windows and inside which different sets of
magnetic coils can be installed. A first modular coil configuration has been designed with six identical, circular, water-cooled copper coils toroidally arranged in an optimal way so that they generate a large volume of
magnetic surfaces and rotational transform in
vacuum (iota ~ 0.3). The total current in each coil goes up to ~ 5 kA, producing a
magnetic field on-axis of B ~ 0.03 T. An RF
antenna specifically designed to operate in
vacuum delivers up to 2.5 kW of power to produce
plasma via inductive coupling and electron-impact ionization. We present the engineering solutions adopted for the design of Polaris and illustrate the great experimental flexibility it enables. Time-averaged values and fluctuations of
plasma density, electron temperature, and floating potential are measured at various toroidal locations, providing insights into the
plasma equilibrium, electrostatic
turbulence, and associated transport. The glass
vacuum chamber of Polaris additionally provides unprecedented optical access to the entire
plasma volume. With its original, flexible design, Polaris is a 'stellarator fish-tank', allowing interchangeable coil sets and exploration of various
magnetic configurations. Furthermore, its low-temperature, low-density, high-neutral-pressure
plasmas are relevant to stellarator edge physics, making Polaris a first-of-kind testbed for the fundamental investigation of stellarator edge-relevant physics.
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All authors Simon P. H. Vincent, Joaquim Loizu, Matthieu Toussaint, Rémy Jacquier, Jérémy Salm, Philippe Guittienne, Matias Habib, Idil Sonmez, Christopher B. Smiet, Erol Balkovic, Rogerio Jorge, Alan G. Goodman, Ivo Furno, Christian Moura, William Matthey-Dorey, Steve Couturier, Frédéric Dolizy
Optics
Observation of biased random-flux-induced topological phase transition in gyromagnetic photonic crystals
Hai-Xiao Wang, Chongyang Li, Xianmu Wu et al. (+5 more)
The interplay between disorder and topological states has attracted growing interest. While previous studies have primarily addressed the effects of
geometric or potential randomness, the exploration of topological phase transitions driven by random-flux remains experimentally elusive. Here, we report the first experimental realization of topological phase transitions driven by biased random-flux in gyromagnetic photonic
crystals. By stochastically orienting the magnetization of constituent gyromagnetic rods, we implement a disordered Haldane model in which the sign of the next-nearest-neighbor hopping phases is randomly distributed. We demonstrate that the bulk band gap closes when the densities of positive and negative flux are balanced, i.e, restoring time-reversal
symmetry in a statistical sense, and reopens when a net positive or negative flux is introduced. Microwave near-field measurements directly visualize the reversal of
chiral edge states, confirming a transition between distinct topological phases. Our results establish a unique disorder-driven mechanism for realizing topological phase transitions and deepen our understanding of the interplay between disorder and topological phases in bosonic systems.
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All authors Hai-Xiao Wang, Chongyang Li, Xianmu Wu, Ziyao Wang, Yongmei Wang, Junhui Hu, Shiwei Tang, Zhen Gao
Fluid Dynamics · Cross-listed from cond-mat.soft
Reciprocal theorem for ion-releasing colloidal particles
Evgeny S. Asmolov and Olga I. Vinogradova
We describe a generalization of the reciprocal
theorem for particles suspended in electrolyte solutions and subjected to an electric field that could be either applied or emerged spontaneously.
Attention is focused on catalytic colloids that release ions. The power of the generalization is to capture the effect of formation of a secondary cloud around a catalytic particle, which is equivalent to accounting for an excess charge $Q$ of a system. Our results show that the propulsion speed of catalytic particles has an extra contribution proportional to $Q$ and an external field $E_{\infty}$. The derived equation for $Q$ reveals that its sign is defined by the difference in the ion diffusivity and the magnitude is controlled by the average flux of ions from the surface. We demonstrate the application of the generalized
theorem to electro- and diffusiophoresis of homogeneously releasing ions passive particles, as well as to a self-propulsion of inhomogeneous active particles (microswimmers). It is shown that whilst in some situations the extra term in the reciprocal
theorem vanishes or has a little effect on the particle mobility, in many others it may dramatically change its magnitude, and even sign. In addition, the relevance of our results for microswimmer interactions is discussed briefly.
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Optics
Physics-Informed Neural Operator for Warm-Starting Background-Decomposed and Preconditioned PSFD: Enabling Scalable 3-D EUV Mask Simulation
Doyun Kim and Werner Gillijns
We present a physics-informed neural operator (PINO) trained with pseudo-spectral frequency-domain (PSFD) equations for electromagnetic (EM) scattering problems in EUV lithography. The
Fourier neural operator is factorized into a two-dimensional lateral ($xy$) branch and a one-dimensional axial ($z$) branch and is trained self-consistently with background decomposition. Thus, the full-vector coupling between the mask and the multilayer response is retained without invoking a finite-order Born approximation. In this way, the computational domain size is significantly reduced, thereby lowering the computational cost. The PINO is trained on approximately 16,000 mask designs from the LithoBench library sampled randomly at each training iteration without using precomputed EM field solutions. The PINO surrogate model yields predictions with a mean absolute error of about $7 \times 10^{-3}$ for the scattered intensity of held-out mask patterns relative to the reference PSFD solution. Combined with spectral damping, the PINO warm-start initialization accelerates the background-decomposed PSFD solver on finer discretizations.
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Plasma Physics
Enhanced alpha channeling with spin-polarized fuel
J. F. Parisi, A. Diallo and J. W. S. Cook
The
nuclear spin state of deuterium-tritium (D-T) fuel sets both the D-T fusion cross section and the emission direction of the fusion-born alphas and
neutrons. We show two ways that
spin-polarized fuel (SPF) could enhance alpha channeling, the wave-mediated damping of alpha power onto fuel ions rather than electrons, which is predicted to increase fusion power significantly. First, the enhanced SPF cross section produces more alphas, and second, the perpendicular (to the
magnetic field) bias of the alphas' kinetic energy couples more efficiently to the perpendicular-resonant channeling waves. The birth anisotropy survives slowing-down and appears as a population inversion of the bulk alpha distribution over a broad region of velocity space, so resonant alphas can drive a suitably tuned channeling wave rather than damp it. Without channeling, SPF roughly doubles the fusion power density through the cross-section boost and its temperature feedback on the reactivity, a well-known result. Our velocity-space calculations find the channeling efficiency about 1.5 times higher for vector-aligned fuel than for unpolarized fuel, and channeling raises the fusion power enhancement to three or four times as the channeling efficiency improves, provided the waves do not depolarize the fuel. A transport model of an ARC-class
equilibrium with stiff critical-gradient transport gives an enhancement of 2.2, rising to 3.4 for less stiff transport and to 4.7 in the zero-dimensional model when the critical gradients rise with the hotter ions. Channeling also transports helium quickly to the divertor: at fixed pumping the core helium fraction nearly halves, and a divertor pump several times less selective for helium supports the same core helium dilution.
Spin-polarized fuel thus enhances fusion power through the anisotropic alpha distribution, beyond its increase of the reactivity.
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Atomic Physics
Achieving 100$\,$MHz Instantaneous Bandwidth in a Broadband Rydberg Microwave Sensor
Yuhan Yan, Jinyin Wan, Xuejie Li et al. (+6 more)
Rydberg atoms have attracted considerable
attention in recent years as a novel platform for microwave sensing, owing to their unique physical merits: large transition dipole moments between Rydberg levels and broad frequency coverage. As a critical figure of merit for Rydberg microwave sensors, instantaneous bandwidth serves as a key
benchmark for evaluating their viability in practical applications. Previous studies on instantaneous bandwidth remain limited to single-frequency operation, with typical demonstrated values of only tens of megahertz, a constraint that hampers the real-world deployment of this sensing technology. Here, we experimentally achieve an instantaneous bandwidth of over 100$\,$MHz across a broad frequency range of 2.7-20$\,$GHz and realize a sensitivity in the hundreds of nV$\,$cm$^{-1}\,$Hz$^{-1/2}$ range. The physical mechanism lies in the dressed-state coherence and the interference effect between different transition channels. Our work substantially broadens the instantaneous bandwidth of Rydberg microwave sensors and paves the way for their practical deployment in fields such as radar and wireless communications.
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All authors Yuhan Yan, Jinyin Wan, Xuejie Li, Xing Xia, Haojie Zhao, Binghong Yu, Jianliao Deng, L. Q. Chen, Huadong Cheng
Optics
Resonance-Induced Sign Reversal of Optical Gradient Forces and Three-Dimensional Singularity Trapping
Jinsheng Lu, Soon Wei Daniel Lim and Federico Capasso
In atomic physics, tuning the light frequency across a resonance reverses the trapping force between bright and dark field regions, yet a unified analytical description of this principle applicable to photonic resonators in general has not been established. Here we show that sweeping the incident wavelength through a resonance in the optical response of the particle or device induces a $\pi$ phase shift, reversing the gradient force from attractive to repulsive. A generalized Fano line-shape model captures this quantitatively across physically distinct resonant systems, from plasmonic nanoparticles to high-Q metasurfaces, with full-wave simulations confirming the predictions in every case. Building on this framework, three-dimensional singularity trapping of silicon nanoparticles is demonstrated using counter-propagating vector beams and metasurfaces, with trapping potential depths competitive with conventional bright-field traps. These results establish a platform-independent design principle for controlling optical forces in resonant systems, with broad implications for optical manipulation,
quantum optomechanics, and precision metrology.
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Optics
Real-Time Megapixel Kilohertz Neuromorphic Shack-Hartmann Wavefront Sensor
Yuhan Bao, Chenxin Shao and Kaiwei Wang
Conventional frame-based Shack–Hartmann wavefront sensors (SHWFS) are limited by dynamic range and the intrinsic trade-off between spatial and temporal resolution, while high-bandwidth acquisition poses additional challenges for real-time wavefront reconstruction. This work presents a real-time, megapixel, kilohertz neuromorphic SHWFS to overcome these limitations. In static optical metrology, the proposed pipeline achieves one-shot wavefront acquisition under extreme illumination non-uniformity, reaching a dynamic range of 260 dB at a 20 Hz acquisition frequency. Owing to this high dynamic range and the concomitant high-intensity resolution, wavefront reconstruction errors in dim and bright sub-apertures are reduced by 59% and 70%, respectively, relative to conventional frame-based SHWFS. For dynamic wavefront sensing, the system provides kilohertz-rate centroid tracking over a megapixel field of view with microsecond-scale latency. Centroid localization errors are 0.18 pixels during optical
alignment supervision and 0.26 pixels in high-speed
turbulence observation, verifying the accuracy and reliability of the system across dynamic scenarios. The per-sub-aperture processing throughput reaches 420,737 Hz on a standard CPU, demonstrating high-speed real-time computation without specialized hardware acceleration. Together, these results establish a unified neuromorphic SHWFS framework for high-fidelity one-shot static wavefront reconstruction and real-time high-bandwidth dynamic wavefront sensing.
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Physics and Society · Cross-listed from cs.AI
Many-body Tipping Dynamics of ChatGPT-like AIs
Frank Yingjie Huo and Neil F. Johnson
Why do ChatGPT-like AIs, despite major architectural and training differences, unexpectedly tip to undesirable content (e.g. harmful, misleading, repetitive) even under deterministic greedy decoding? We show that a broad class of such tippings is caused by the many-body interactions between
tokens (
spins) as they cross the finite-layer system. Tipping emerges as a dynamical first passage process between competing output basins.
Attention disorder controls the transport toward, away from, or along the basins' boundary. A few-basin reduction yields a closed finite-layer threshold, whose coarse-grained predictions show good agreement across ChatGPT-like families. These results suggest that a broad class of AI failures represents 'foreseeable engineering risk' rather than inherently unpredictable behavior, with important implications for legal and societal assessments of AI harm.
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Optics
Monolithic Multifocal Diamond Metalens for High-Power Laser Systems
Xiaoxuan Li, Xiaoyu Sun, Ce Li et al. (+6 more)
High-power
laser systems increasingly rely on multi-beam processing to enhance manufacturing throughput. However, conventional multifocal systems remain constrained by bulky architectures, stringent
alignment requirements, and susceptibility to
laser-induced degradation under intense irradiation. Here, we demonstrate a monolithic multifocal diamond metalens with a 7.2 mm aperture that maintains exceptional thermal stability and power tolerance. The device employs high-aspect-ratio truncated-cone diamond nanopillars to generate two focal spots separated by 200 {\mu}m at a focal length of 4 mm. Under sustained 25 W pulsed-
laser irradiation for 1 h, the diamond metalens exhibits a focal shift of only 25.5 {\mu}m, resulting in a maximum processing-depth variation of 33.2 {\mu}m during 4H silicon carbide (SiC)
laser scribing, far below the 319.1 {\mu}m deviation observed for a commercial objective lens combined with a beam-splitting diffractive optical element (DOE). Even under extreme optical loading, the metalens withstands continuous-wave
laser irradiation up to 8.25 kW for 30 s without structural degradation, while complementary pulsed testing yields a
laser-induced damage threshold (LIDT) of 2.45 J/(cm^2) for diamond. This work broadens the operating envelope of transmissive meta-optics to extreme optical loads, opening new opportunities across high-power photonic systems.
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All authors Xiaoxuan Li, Xiaoyu Sun, Ce Li, Zhiqiang Xie, Fengjiang Liu, Boqu Chen, Ding Zhao, Kaikai Du, Min Qiu