Plasma Physics
First-Principles Explanation of the Drift Configuration Dependence of the Radial Electric Field and High-Confinement Access in Tokamaks
B. J. Frei, R. Bilato, O. Grover et al. (+6 more)
The origin of the difference in the high-confinement (H-mode) power threshold between favorable and unfavorable drift configurations in tokamaks, experimentally linked to a deeper radial electric field (Er) well in the former, remains unresolved. Using first-principles gyrokinetic simulations of edge and scrape-off-layer
turbulence in ASDEX Upgrade, we show that
turbulence-driven poloidal flows generate this deeper Er well in the favorable configuration through enhanced nonlinear
turbulence-mean flow energy transfer. This transfer is significantly weaker in the unfavorable case, yielding a shallower Er well, while
turbulence intensity is simultaneously higher. Within the
turbulence-flow shear suppression paradigm, the combination of stronger shear and reduced
turbulence facilitates H-mode access in the favorable configuration. These results provide the first validated, self-consistent full-f gyrokinetic explanation of how drift configuration controls the nonlinear dynamics of profiles, Er, flows, and
turbulence, thereby setting the H-mode power threshold.
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All authors B. J. Frei, R. Bilato, O. Grover, W. Zholobenko, C. Angioni, M. Bergmann, P. Ulbl, F. Jenko, the ASDEX Upgrade Team
Applied Physics · Cross-listed from cond-mat.soft
Nonlinear Wave Propagation in 1D Polycatenated Ring Chains
Xiaoxiao Xiong, Reo Yanagi, Tingtao Zhou et al. (+1 more)
We study the nonlinear wave dynamics of one-dimensional chains of polycatenated rings. These interlocked structures support amplitude-dependent nonlinear wave propagation driven by tensile activation and internal structural flexibility, unlike traditional granular
crystals. Through dynamic impact experiments, finite-element modeling, and discrete-particle simulations of vertical chains pretensioned by
gravity, we observe and explain nonlinear waves characterized by a compact leading wavefront followed by persistent trailing oscillations, which arise from energy partitioning into the rings' internal bending modes. Further, we demonstrate that the system's nonlinearity is not a fixed material constant. By altering the rings'
geometric aspect ratio and contact angles, we can tune the effective contact exponent and the amplitude scaling of the wave speed. This work builds upon nonlinear wave propagation in classical granular
crystals and establishes polycatenated systems as a highly tunable and designable platform to study and control nonlinear dynamics.
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All authors Xiaoxiao Xiong, Reo Yanagi, Tingtao Zhou, Chiara Daraio
Chemical Physics
Drift-React: One-step Generation of Reaction Pathways via SE(3) Drifting Fields
Rémi Schlama and Philippe Schwaller
Mapping reaction pathways and transition states (TS) is fundamental to chemistry but computationally expensive at scale. The minimum energy pathway (MEP) dictates reaction rates and mechanisms, yet recovering it via electronic-structure methods requires thousands of costly force evaluations. Recent generative models accelerate TS identification but rely on iterative inference and only predict isolated saddle-point snapshots, missing the continuous reaction trajectory. We introduce Drift-React, an $\mathrm{SE}(3)$-equivariant generative framework that predicts complete reaction pathways in a single forward pass from only reactant and product geometries. By shifting distribution
evolution to training via a Sinkhorn-weighted drifting field, Drift-React eliminates both the iterative force evaluations of NEB-style methods and the sequential ODE/SDE integration of
diffusion and flow matching models. Evaluated on the Transition1x and
Halo8
datasets, our one-step model generates physically consistent MEPs that accurately capture energetic bottlenecks and enable arbitrary-resolution sampling along the reaction coordinate. For isolated TS prediction, Drift-React matches the sub-Ångström accuracy of state-of-the-art iterative models while delivering orders-of-magnitude acceleration, clearing a major computational bottleneck for large-scale reaction network exploration.
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Fluid Dynamics
Transient and asymptotic Taylor–Aris dispersion of Brownian rods in arbitrary regular-polygonal ducts
Jingsen Feng and Xu Chu
Taylor–Aris dispersion of Brownian rods in non-circular ducts is governed by a coupling absent from passive-scalar theory. Pressure-driven shear aligns the rods and makes translational
diffusion tensorial, while duct geometry determines how this tensor is sampled across the cross-section. We formulate this problem for dilute rods in regular-polygonal ducts of arbitrary side number. At each cross-sectional point, a local shear-aligned Jeffery–Brownian closure gives four transport fields, namely two transverse diffusivities, a direct axial diffusivity and a signed shear–axial cross coefficient. Because the shear frame rotates through a polygon, these fields enter a conservative two-dimensional transverse operator rather than a radial scalar-
diffusion problem. Its zero mode is a non-uniform invariant density, which replaces the area measure in the Taylor–Aris reduction and reduces, in the circular-pipe limit, to a weighting proportional to the inverse shear-direction diffusivity. The resulting
cell problem separates the effects of rod
alignment on streamline sampling and transverse relaxation.
Alignment produces only a small, non-monotone shift in mean speed, but gives a larger enhancement of the Taylor coefficient by reducing transverse mixing. Normalization by the same-geometry spherical coefficient removes most passive shape dependence and exposes the approach to the fully aligned transverse-mixing limit. Finite regular polygons converge smoothly to the circular-pipe branch, whereas low-sided polygons retain distinct shear-sampling signatures. A biorthogonal spectral formulation resolves finite-time releases. Localized, multi-peaked and broad injections excite different non-zero transverse modes and exhibit different pre-asymptotic variance growth, but modal decay selects the common long-time Taylor–Aris coefficient given by the
cell problem.
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Chemical Physics · Cross-listed from quant-ph
Absorbing Many-Body Correlations into Core-Optimized Orbitals
Hao Zhang and Matthew Otten
The cost of simulating
quantum many-body systems - on classical or
quantum hardware - scales with the number of variational parameters, so progress at fixed computational budget hinges on more parameter-efficient ansätze. Configuration Interaction (CI) is widely dismissed as parameter-heavy; we show this verdict is an artifact of the orbital basis. Co-optimizing the orbital basis with a sparse CI wavefunction - a method we call Core-Optimized Orbitals (COO) - absorbs a large fraction of the dynamical correlation directly into the single-particle basis, cutting the determinant count by several orders of magnitude beyond the already compact TrimCI ansatz on which it builds. On [Fe$_4$S$_4$] (54e, 36o), a billion-determinant TrimCI+COO wavefunction reaches accuracy that would require $3\!\times\!10^{14}$ determinants in a localized basis. At matched accuracy, it is $8\times$ more compact than the largest unrestricted-DMRG
benchmark ($25\times$ with PT2). Across the iron-sulfur series - from [Fe$_2$S$_2$] (30e,20o) to the P-cluster (114e,73o) - TrimCI+COO is $10$-$100\times$ more compact than SU(2)-adapted DMRG with
entanglement-minimized orbitals at matched accuracy. A tunable Hubbard-on-graph model factorizes the advantage into an orbital-basis gain and an ansatz gain, the latter capturing multi-center
entanglement that resists MPS localization. COO therefore changes the picture of CI efficiency: sparse CI with optimized orbitals can outperform state-of-the-art tensor networks on strongly correlated multi-center systems.
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Plasma Physics
Gyrokinetic Simulations for Spherical Tokamak Divertor Design
Akash Shukla
Nuclear fusion is an attractive source of energy because the fuel is abundant and it produces low levels of carbon emissions. The tokamak, which confines a
plasma using
magnetic fields, is the most mature
nuclear fusion reactor concept. Maximizing energy confinement by minimizing turbulent heat loss while also minimizing damage to the reactor is essential for producing efficient, commercially viable fusion reactors. Heat exhaust methods used in the scrape-off layer (SOL) of the tokamak greatly influence performance. Conventional heat exhaust methods focus on minimizing reactor damage rather than maximizing confinement. The low-recycling regime, a newer approach, focuses on maximizing energy confinement. Studying the low-recycling regime, which features a high temperature and low density SOL, requires new modeling tools. We have developed the gyrokinetic code Gkeyll into an appropriate tool, and we use it to demonstrate the viability of the low-recycling regime with simulations of the Spherical Tokamak for Energy Production (STEP). Our work addresses several key issues with low recycling. Our simulation results indicate that a high SOL temperature and low SOL density could be achieved without using a lithium divertor plate. This is an important step because lithium divertor plates evaporate when exposed to large heat fluxes, which lowers the SOL temperature, counteracting the desired regime. Our simulation results also indicate that kinetic effects can lower the peak heat flux on the divertor plate, which would improve reactor survivability, and confine sputtered
impurities to the divertor region, which would prevent core contamination and performance degradation.
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Classical Physics · Cross-listed from cond-mat.stat-mech
Emergent heavy-tailed distributions from a Markovian random walk
Henrique S. Lima and Evaldo M. F. Curado
The emergence of heavy-tailed statistics in complex systems is conventionally attributed to non-local
stochastic jumps or non-Markovian
memory. Here, we present a one-dimensional random walk where power-law behaviors arise instead from a strictly local, discrete-time Markovian mechanism. The step length is governed by a deterministic function of the walker's position, establishing a positive feedback loop that induces strong effective correlations along the trajectories. Through analytical derivations in the continuum limit and extensive numerical simulations, we show that this rule yields a robust, non-Gaussian stationary state. The exact analytical solution is obtained in the closed form of a symmetric, Lorentz-like distribution, $\rho_{\text{st}}(x) \propto (|x|/l+r\Delta x)^{-2}$, confirming asymptotic power-law tails that decay as $|x|^{-2}$ over six decades. Furthermore, by employing the Onsager-Machlup path-integral formalism, we demonstrate that effective velocity and acceleration acquire physical meaning along the shortest fluctuation trajectories. Crucially, we find that a non-zero initial acceleration acts as the fundamental mechanism driving the walker away from the origin, ensuring both the emergence of scale-free statistics and the normalizability of the stationary distribution. This minimal pathway provides a new microscopic foundation for the widespread $-2$ power law observed across multidisciplinary complex systems.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Weak wave turbulence as a precursor to universal coarsening in a homogeneous Bose gas
Simon M. Fischer, Martin Gazo, Sebastian J. Morris et al. (+6 more)
Relaxation and condensation of an isolated low-energy Bose gas provide an ideal setting for the study of the universal features of far-from-
equilibrium many-body dynamics and the emergence of long-range order. Conceptually, the emergence of such order involves two steps: the formation of local coherence, on a system-specific microscopic lengthscale, and the spreading of coherence, over lengthscales much larger than any microscopic scale. The latter is understood in terms of universal phase-ordering kinetics, or coarsening, characterized by an algebraic growth of the coherence length. Here, for a homogeneous Bose gas with tunable interactions, we show that the former also has a universal description, within the framework of weak wave
turbulence (WWT). Specifically, the initial transport of particles to low momenta corresponds to an inverse turbulent cascade that is, in agreement with the WWT theory, characterized by a power-law momentum distribution, with exponent $\gamma = 2.4(1)$, and transport times ${\propto} (na)^{-2}$, where $n$ is the gas density and $a$ the $s$-wave scattering length.
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All authors Simon M. Fischer, Martin Gazo, Sebastian J. Morris, Nikolai Maslov, Haoyu Zhang, Jiří Etrych, Gevorg Martirosyan, Christoph Eigen, Zoran Hadzibabic
Atmospheric and Oceanic Physics · Cross-listed from astro-ph.EP
Variation of Venusian Gravity Wave Absolute Momentum Fluxes and Drag as Retrieved from the Akatsuki Mission
Erdal Yiğit and Emilia Sloan
Using temperature
retrievals from Akatsuki
radio occultation measurements, we characterize
gravity wave activity as a function of vertical wavenumber and altitude and, for the first time, estimate the absolute horizontal momentum fluxes and the magnitude of the associated
gravity wave drag (i.e., wave acceleration), which quantify the potential effects of these waves in the Venusian middle atmosphere between 40–95 km. Observed temperature perturbations, which are indicative of atmospheric
gravity wave activity, reach amplitudes of approximately $\pm$10 K, and significant momentum flux (10–30 m$^2$ s$^{-2}$) and wave drag (0.003–0.03 m s$^{-2}$) are detected across all analyzed profiles. The inferred wave drag represents a lower bound on the total
gravity wave-induced drag in the Venusian atmosphere. Momentum flux tends to increase exponentially with altitude below approximately 50–60 km, then peaks and attenuates at higher altitudes. Wave drag becomes prominent where momentum flux begins to decrease, which is a consequence of wave dissipation. Both quantities exhibit multiple altitude-localized maxima, which is consistent with upward wave propagation followed by dissipation at different altitudes for different vertical wavelengths. Damping due to
gravity wave nonlinear interactions is likely to play the major role in limiting the growth of wave amplitudes and fluxes with height. These features are observed across a range of latitudes and local times. Overall, the results provide observational constraints on
gravity wave momentum transport and dissipation in the Venusian middle atmosphere and could guide numerical models in their effort to quantify wave-mean flow interactions in Venus's atmosphere.
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Optics
Extreme Optical Field Confinement and Enhancement in a Plasmonic Picopatch within a Nanoparticle-on-Mirror Resonator
Jinna He, Mario Zapata-Herrera, Xabier Arrieta et al. (+4 more)
Plasmonic resonances in metallic nanogaps can confine light into nanometric regions, but reaching modes of volume $\approx 1$ nm$^3$ remains challenging. We present a detailed theoretical analysis of the optical modes of an experimentally-motivated nanoresonator configuration that contains a picopatch formed by the lifting of a few gold atoms in the gap of a Nanoparticle-on-Mirror (NPoM) structure. Classical simulations indicate that the plasmonic modes associated with the picopatch geometry can confine light to extremely small regions and are highly sensitive to the picopatch size and shape, enabling broad tunability. Furthermore, these modes can couple strongly with other nanocavity modes of the structure, as identified from a clear anti-crossing behavior of the polaritonic resonances. Remarkably, up to $\approx 2000$-fold electric field enhancement inside the picopatch and tiny effective mode volumes approaching $\approx 1$ nm$^3$ are obtained. Further, changing the morphology of the picopatch does not modify the qualitative findings, and increasing the absorption losses in the classical simulations, to mimic
quantum (non-local) effects in the metal permittivity, decreases the electric field enhancement only moderately. Compared to the standard picocavities formed by single-atom protrusions, picopatches are an intriguing alternative to reach extreme optical field confinement and enhancement in plasmonic cavities.
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All authors Jinna He, Mario Zapata-Herrera, Xabier Arrieta, Mingli Wan, Yuan Zhang, Javier Aizpurua, Ruben Esteban
Optics
Magnon-mediated microwave to optical time dynamics
Rajkumar Jadhav, Xinglin Zeng, Cedric Traub et al. (+6 more)
Optomagnonic modulation techniques are an emerging platform for information transfer from the microwave to the optical domain. However, these techniques focus largely on the spectral domain of the transduced signal. Given the potential of the field to bridge the gap between microwave and optical signals, analyzing and studying the interactions real-time in temporal domain becomes equally essential. In this work, we exploit the optomagnonic modulation in a YIG microsphere to demonstrate and study microwave to optical real-time dynamic transfer on a time scale comparable to the decay of
magnons. We inductively excite
magnons in the microwave domain and use
magnon-based Brillouin light scattering to transduce the signature of excited magnonic waveforms to the optical domain. The square type modulation of the
magnons is retrieved in the corresponding optical sidebands. Our work enables real-time measurement of the magnonic dynamics and therefore direct access to lifetime measurements of the magnonic mode. Providing insight into the temporal dynamics of
magnons, this work can open up new promising research directions such as in
magnon coupled superconducting
qubits or
magnon-based Brillouin
memory.
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All authors Rajkumar Jadhav, Xinglin Zeng, Cedric Traub, Fabian Engelhardt, Abdullah Alabbadi, Arghadeep Pal, Pascal Del'Haye, Silvia Viola Kusminskiy, Birgit Stiller
Plasma Physics · Cross-listed from astro-ph.HE
Polarized 3D Synthetic Turbulence I: Magnetic Field Line Random Walk
Matthieu Bouchet, Yoann Génolini, Silvio S. Cerri et al. (+2 more)
The behavior of
magnetic field lines in a turbulent
plasma is a key property of the medium, with important consequences for
plasma dynamics and charged-particle transport. We study the
diffusion properties of
magnetic field lines in synthetic
turbulence featuring different polarization configurations for the
magnetic perturbations, as prescribed by the existing magnetohydrodynamic modes (namely, Alfvénic and magnetosonic). These turbulent field realizations are then compared with the isotropic (or, random) polarization case, which is the one typically adopted in the literature. We construct polarized synthetic
turbulence simulations and study the properties of field lines through the running
diffusion coefficient. Our key findings can be summarized as follow: (i) field line wandering is strongly dependent on polarization configurations, (ii) we unveil that the sub-diffusive phase of field line is highly dependent on the polarization and is well reproduced by theoretical predictions based on Corrsin's hypothesis in the low
turbulence level regime, (iii) in particular the scaling of the asymptotic
diffusion coefficient in magnetosonic-like polarization is $(\delta B/B)^4$ at odd with the $(\delta B/B)^2$ scaling found in the quasi-linear regime for random polarization, (iv) interestingly we note that the subdiffusive phase of field line transport in the magnetosonic-like polarization follows closely the one observed in recent high resolution MHD
turbulence simulations, we end giving a word of caution when FL transport is investigated in such simulations.
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All authors Matthieu Bouchet, Yoann Génolini, Silvio S. Cerri, Alexandre Marcowith, Philipp Mertsch
Plasma Physics
Dynamics of fast magnetosonic wave turbulence
Nicolás Pablo Müller and Sébastien Galtier
Fast magnetosonic waves are among the fundamental oscillation modes of astrophysical
plasmas. To study their dynamics, we carry out numerical simulations of the wave
turbulence kinetic equation, which describes the
evolution of the energy spectrum of a set of weakly nonlinear fast magnetosonic waves. This kinetic equation, which involves three-wave interactions, has recently been derived from compressible magnetohydrodynamics in the low-$\beta$ limit (Galtier 2023). It has an exact stationary solution, the Kolmogorov-Zakharov spectrum, corresponding to a direct energy cascade. Here we perform free decay simulations of the kinetic equation for which we propose a Kolmogorov-type phenomenology to explain the temporal decay laws of energy and integral length scale. In the forced simulations, we show that the cascade is in fact composed of a mixture of a forward cascade for counter-propagating waves, and a backward cascade for co-propagating waves, with the former being stronger than the latter. The Kolmogorov-Zakharov energy spectrum in $k^{-3/2}$ is found in the radial direction with an anisotropy due to the amplitude that depends on the angle relative to the strong mean
magnetic field. We give the analytical expression of the Kolmogorov-Zakharov constant, which is numerically verified in the high Reynolds number limit. Our study provides a theoretical explanation for certain observations in the
solar wind
plasma (Zhao et al. 2022), where a regime of weak
turbulence has been identified for fast magnetosonic waves, alongside a critical balance regime for strong Alfvén wave
turbulence.
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Optics
All-band photonic integrated optical parametric amplification
Nikolai Kuznetsov, Zihan Li and Tobias J. Kippenberg
Optical amplifiers are ubiquitous in science and technology and are the workhorse of modern communications. Currently, virtually all amplifiers rely on atomic resonances, such as rare-earth-doped fibers, or are based on III-V
semiconductors. Fueled by emerging applications, there is increased demand for amplifiers that are high-gain, broadband, low-noise, and deliver high output power outside traditional wavelength ranges. Over the past few decades, it has been shown that optical parametric amplifiers (OPAs) can address this challenge. Pioneering works on highly nonlinear optical fibers or bulk
crystals have demonstrated their potential, but high pump powers and long fiber length limited their practical use. Recently, a renaissance of OPAs has occurred with the demonstration of photonic integrated
circuits, which exhibit higher effective nonlinearity and enable wider bandwidths. Yet they require ultra-low loss, highly precise dispersion engineering, and large chip footprints, limiting OPA performance to date. Here, we overcome these limitations and, using periodically poled thin-film lithium tantalate (PPLT) photonic integrated
circuits, we demonstrate continuous-wave optical parametric gain up to 23.5 dB, with a flat-top profile spanning across an 850 nm-wide optical wavelength window, corresponding to 100 THz and covering all communication bands. Moreover, on-chip output signal power as large as 313 mW in the optical O-band is achieved. We further realize all-optical inter-band modulation transfer between the C- and O-bands. Our approach uses cascaded second-order nonlinear processes that provide high effective third-order nonlinearities while preserving the wide material bandgap. These results establish PPLT integrated photonic
circuits as a scalable platform for broadband optical amplification and frequency conversion across wavelengths where rare-earth doped amplifiers are absent.
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Data Analysis and Statistics · Cross-listed from astro-ph.EP
Follow the wobble: Statistical methods to detect astrometric binary asteroids in Gaia FPR
Luana Liberato, Paolo Tanga, David Mary et al. (+7 more)
In a previous article, we obtained the first-ever list of astrometric binary asteroid candidates. Some of these candidates have now been confirmed. In that previous work, however, the details of the statistical methods were not provided. Our first aim is to provide methodological details and performance evaluation of the approach used for detecting binaries. Our second aim is to establish an updated list of binary asteroid candidates from
Gaia FPR astrometric residuals exploration, where we account for the statistical properties of FPR data. We account for the astrometric uncertainties from FPR and we refine the statistical model of the data, which we use in MC simulation to evaluate the strength of the individual detections; we set up a trend detection method in the residuals and apply a dedicated period search
algorithm; we update the statistical selection process to build the list of candidates; we set up a method for detecting objects in multiple windows of consecutive observation; we refine the method for confidence interval estimation of these parameters and we better constrain the physical parameter selection. We detect 343 binary asteroid candidates corresponding to 410 windows of consecutive observations in the astrometric data. We show that in noise-only control simulations, the typical number of detections is 88% lower than in the FPR data. We also detect 9 known binaries, 25 candidates overlapping with the Pan-STARSS survey and 99 overlapping with our previous binary search in DR3. Finally, we report the detection of 45 objects with trends in residuals suggestive of wide binary systems. Our results and analyses demonstrate that although detecting binary asteroids is a difficult problem due to their low signal level, the proposed method is likely to provide a reliable list of detections, including systems poorly accessible to conventional techniques.
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All authors Luana Liberato, Paolo Tanga, David Mary, Raphael Lallemand, Ziyu Liu, Benoit Carry, Josselin Desmars, Daniel Hestroffer, Kate Minker, Alexandros Siakas
Physics and Society
An Analytics Framework for Modeling Residential Photovoltaic Adoption and Decision Dynamics
Canigó Callau-Boix, Raúl Toral and Pere Colet
Photovoltaic generation plays a central role in the energy transition, yet understanding its adoption dynamics requires robust analytical frameworks that capture both temporal and spatial patterns of decision behavior. This study applies a data-driven decision analytics approach to examine residential self-consumption photovoltaic installations in Catalonia within an innovation
diffusion framework. The temporal
evolution of adoption is modeled using a logistic growth function, providing evidence that imitation effects are a primary driver of adoption decisions. To extend the analysis, a quantitative methodology is developed to estimate the influence of external factors on adoption behavior, revealing that social perception exerts a stronger impact than regulatory and socioeconomic variables when considered independently. In addition, a spatial analytics component is incorporated to assess territorial heterogeneity, identifying correlations between adoption patterns and demographic and socioeconomic characteristics. The findings contribute to predictive and diagnostic analytics by offering a structured framework to model technology
diffusion and inform policy and investment decisions aimed at accelerating sustainable energy adoption.
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Chemical Physics
Machine Learning Interatomic Potentials: Advancing Open-Source Software for Efficient and Scalable Molecular Simulation
Christoph Brunken, Titouan Cormier, Lucien Walewski et al. (+15 more)
Machine learning interatomic potentials (MLIPs) enable atomistic simulations with near ab initio accuracy at significantly reduced computational cost, but their broader adoption is often limited by fragmented tooling, limited scalability, and inflexible software design. We present mlip v2, a new generation of the mlip library that advances efficient and scalable molecular simulation through a unified and extensible framework. The new release features a targeted API redesign with improved modularity and control, enabling flexible customization of training, data processing, and simulation workflows. It further integrates a new high-performance backend for equivariant operations, e3j, significantly accelerating model inference and simulations. In addition, the framework introduces a range of entirely new capabilities, including the eSEN architecture with a Mixture-of-Experts formulation for scalable training on large and diverse
datasets, improved handling of electrostatics through more physically grounded charge modeling and long-range interaction treatment, and advanced simulation features such as NPT ensembles and nudged elastic band methods. Together, these extensions significantly broaden the scope of MLIP applications, enabling efficient modeling of complex, reactive, and out-of-
equilibrium systems, and bridging the gap between ML research and practical molecular simulation applications. The library is available on GitHub and on PyPI under the Apache license 2.0.
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All authors Christoph Brunken, Titouan Cormier, Lucien Walewski, Marco Carobene, Yessine Khanfir, Zachary Weller-Davies, Miguel Bragança, Armand Picard, Adrien Pichard, Leon Wehrhan, Heloise Chomet, Eszter Varga-Umbrich, Marie Bluntzer, Massimo Bortone, Valentin Heyraud, Silvia Acosta-Gutiérrez, Jules Tilly, Olivier Peltre
Atomic Physics
X-ray and extreme-ultraviolet spectra from collisions of Ar$^{18+}$ and O$^{8+}$ ions with neutrals
Stepan Dobrodey, Chintan Shah, Sonja Bernitt et al. (+4 more)
We present measurements of K-shell x-ray emission following charge exchange of fully ionized argon with various neutral gaseous targets at small collision energies inside an electron beam ion trap. We also resolve the principal
quantum number of electron capture in extreme-ultraviolet spectra from initially bare and hydrogen-like oxygen ions held in the same trap. We analyze discrepancies between these as well as previous measurements with theoretical models based on the multichannel Landau-Zener approach.
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All authors Stepan Dobrodey, Chintan Shah, Sonja Bernitt, Ming Feng Gu, Liyi Gu, Thomas Pfeifer, José R. Crespo López-Urrutia
Plasma Physics
Second stability region for gyrokinetics and the L-H transition
R.J.J. Mackenbach, A. Zocco and P. Helander
Using a simple circular tokamak geometry, we show the well-known `second stability region' of MHD-ballooning modes exists for linear gyrokinetics too – whether electrostatic or electromagnetic – and we suggest that the
plasma enters this region in H-mode as a consequence of the bootstrap current and Shafranov shift altering the
magnetic field, which may occur if the normalised pressure gradient is $\alpha_{\rm MHD} \simgt 1$ and collisionality is low. By performing simulations in more realistic
magnetic geometries, we demonstrate a large reduction in collisionless, electrostatic turbulent transport when going from density and temperature profiles typical of L- and H-mode, respectively. This reduction is shown to be a consequence of both the bootstrap current lowering the global
magnetic shear, and the pressure gradient altering the local
magnetic shear, pushing the
plasma towards the second-stability region. A path connecting the L- and H-mode
equilibria is constructed, along which the energy and particle fluxes exhibit non-monotonic behaviour as a function of the pressure gradient.
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Fluid Dynamics
Experimental investigation of twin pulsed jets in a hemispheric elastic cavity
L. S. Merlo, L. Kadem, W. Saleh et al. (+2 more)
This study experimentally examines the impact of spacing between two pulsed jets and their strengths on the fluid dynamics within an elastic hemispherical cavity. Such interactions between multiple pulsed jets are observed in various natural and industrial contexts, including cardiovascular flows, where they occur naturally within the atria or result from medical interventions (e.g., mitral valve repair, mechanical heart valves, paravalvular leaks) or diseases (e.g., aortic or pulmonary valve regurgitation). Fundamentally, these flows usually feature two or more pulsed jets interacting in an expanding, elastic environment. In this investigation, the experimental setup features two parallel pulsed jets entering the cavity, with jet strength varied across five formation times (1, 2, 3, 4, 5) and four spacing ratios (1.5, 2.0, 2.5, 3.0). Time-resolved particle image velocimetry is used to capture the instantaneous velocity fields. The results reveal three distinct flow regimes: short-time decay, decay at the wall, and wall rebound with or without the formation of secondary
vortices. These findings uncover rare aspects of twin
vortex ring behavior, including
symmetry breaking, trajectory shifts, and wall-induced rebound mechanisms, with direct relevance to cardiac fluid dynamics in both healthy and pathological conditions.
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All authors L. S. Merlo, L. Kadem, W. Saleh, H. D. Ng, G. Di Labbio
Optics
Agentic metasurface design with self-correcting language-model systems
Bei Wu, Bo Xiong, Haiyao Luo et al. (+5 more)
Automated metasurface design is increasingly important, and recent advances in
language-model systems are opening a route toward agentic optical design. Yet modern metasurface applications, from metalenses and holography to optical computing, require long design chains spanning modeling, simulation, coding, optimization and evaluation. These chains are error-prone, whereas existing
language-model-based metasurface tools remain largely limited to simple objectives, predefined pipelines or
language-to-layout generation. Here we introduce MetaDesigner, a self-correcting
language-model system for agentic metasurface design. From a natural-
language optical objective, MetaDesigner plans the design route, retrieves domain knowledge, invokes simulation and optimization tools, generates missing tool code and identifies errors through a dedicated Verifier. We demonstrate three tasks of increasing complexity: an RGB metalens with three independent focal spots, a six-plane full-color hologram with an average structural similarity index measure (SSIM) of 0.97, and an optoelectronic hybrid neural network for image style transfer. These tasks require 74, 136 and 90
reasoning steps, respectively, and the system self-corrects errors in frequency mapping, numerical aperture estimation, network-parameter counting and loss-function description. These results establish MetaDesigner as a self-correcting route to agentic metasurface design, where
language-model systems can not only execute optical design tasks but also extend, inspect and repair the design process itself.
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All authors Bei Wu, Bo Xiong, Haiyao Luo, Yaqi Li, Li Zhang, Qiaolu Chen, Hongsheng Chen, Yihao Yang
Physics and Society · Cross-listed from cond-mat.dis-nn
Directed extended-range percolation
Wenbo Liu, Yiwen Zeng, Xueming Liu et al. (+1 more)
While for standard percolation directionality is known to increase the combinatorial complexity of percolation, here we show that when connectivity is ensured by paths of length $R\geq 2$, network directionality, impeding backtracking, can significantly reduce the complexity of percolation. To illustrate this finding, we introduce Directed Extended-Range Percolation (DERP), defined directed networks with non-reciprocal edges, motivated by applications in
quantum communication. In this framework, message transmission is enabled between trusted nodes separated by a directed path of length at most $R$. Using a message-passing approach, we show that directionality enables an exact determination of the percolation threshold and the anomalous critical indices on locally tree-like structures. On random directed networks we find that the critical behavior of DERP depends sensitively on degree correlations. These analytical predictions are corroborated by extensive Monte Carlo simulations, highlighting the profound impact of directionality and correlations on long-range connectivity in complex networks.
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All authors Wenbo Liu, Yiwen Zeng, Xueming Liu, Ginestra Bianconi
Plasma Physics · Cross-listed from nlin.PS
On the Riemann problem for the Adlam-Allen model
Su Yang, Marco Calabrese, Vassilis Koukouloyannis et al. (+1 more)
In the present work, we revisit the Adlam-Allen (AA) model in order to investigate its numerically observed rarefaction and dispersive shock waves that arise in numerical simulations of the Riemann problem associated with the model. On the one hand, we perform a direct analysis of the rarefaction and dispersive shock waves of the AA model via examining its corresponding dispersionless system and leveraging the DSW-fitting method to obtain theoretical predictions on various edge features of the dispersive shock waves. On the other hand, we review the KdV reduction of the AA model and utilize the KdV dispersive shock wave to approximate that of the AA model. Relevant numerical comparisons demonstrate the good performance of not only the direct analysis on the AA dispersive shock wave, but also of the approximation via the KdV DSW. These methodologies provide a systematic toolbox for analyzing the outcome of Riemann problems in not only this fundamental setting of cold
plasmas but also potentially in related
plasma-physics problems.
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All authors Su Yang, Marco Calabrese, Vassilis Koukouloyannis, Panayotis G.Kevrekidis
Classical Physics
Dielectric insulated transmission lines in receiving antenna operation
Reuven Ianconescu and Vladimir Vulfin
This work derives exact expressions for the voltage induced into a two conductors dielectrically isolated transmission line by a monochromatic incident plane wave from an arbitrary direction, at a given polarization. The transmission line cross section, consisting of the conductors and the dielectric material, may be of any shape, provided the cross section size is much smaller than the wavelength, so that the waves in radiation mode satisfy the quasi TEM condition. We calculate analytically the voltage along the transmission line for given end loads and compare the results with ANSYS HFSS simulation results. Our calculations are based on the knowledge of the radiation from such a transmission line, derived elsewhere and the radiation-absorption reciprocity.
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Physics and Society
Endogenous drivers of gender disparity in online dating
Huaiyu Tan, Chenyu Li, Taha Yasseri et al. (+2 more)
In its early days, online dating was heralded as a great equalizer, removing biases built into the structures of heterosexuality courtship. However, as repeatedly observed, that prophecy was never fulfilled, and some biases have even become exacerbated. In this paper, we identify a general endogenous mechanism that drives the widening of the gender gap in first-contact rates of heterosexual dating. This mechanism relies on assumptions about the participants' expectations of new contacts and their time constraints. We formulate this
symmetry-breaking mechanism as a system of differential equations and analyze its fixed points and their stability.
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All authors Huaiyu Tan, Chenyu Li, Taha Yasseri, Lei Shi, Petter Holme
Chemical Physics · Cross-listed from math.NA
On the Regularity and Interpolation of Coupled Cluster Amplitudes in Canonical Orbital Basis
Jonas Beck and Benjamin Stamm
Arguably the most widely used approaches for obtaining highly accurate molecular ground-state energies are coupled cluster methods. Despite introducing two layers of approximation, a linear and a nonlinear one, coupled cluster methods remain computationally intensive, with the complexity scaling as $O(poly(N))$, where $N$ is the number of electrons. Moreover, this method must be applied over a large set of different
nuclear coordinates in order to study certain chemical phenomena. Therefore, in this work, we investigate the regularity of single-reference coupled cluster amplitudes with respect to
nuclear coordinate displacements, with the aim of enabling interpolation or extrapolation approaches that rely on only a limited number of reference geometries. We show that, in theory, under certain non-degeneracy assumptions on the Hartree-Fock level of theory, and the coupled cluster level of theory the amplitudes behave real analytic. Furthermore, we analyze the artifacts that arise in practical calculations that use canonical orbitals, which hinder this high degree of regularity, and suggest strategies to mitigate these issues. Finally, we validate our findings through numerical experiments by interpolating the amplitudes and comparing the performance of the interpolants with that of the exact amplitudes.
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Optics
A Non-Volatile Heterogeneous Quantum Dot III-V/Si DFB Laser with Optical Memristive Behavior
Stanley Cheung, Bassem Tossoun, Di Liang et al. (+5 more)
In this work, we introduce a non-volatile heterogeneous
quantum dot (QD) III-V/Al2O3/Si distributed feedback (DFB)
laser exhibiting optical memristive behavior. The device operates in the O-band (~1300 nm) with a threshold current density of 234 A/cm2 and a side-mode suppression ratio exceeding 48 dB. Co-integrated Al2O3-based memristors produce bipolar resistive switching, yielding non-volatile wavelength shifts of ~ 46 pm and ~ 17 dB peak power contrast with zero static holding power. The III-V/Al2O3/Si heterojunction memristor I-V hysteresis is also modeled. This new device enables simultaneous coherent light generation and persistent optical state storage, establishing a new class of active photonic
memory for neuromorphic and reconfigurable WDM applications.
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All authors Stanley Cheung, Bassem Tossoun, Di Liang, Yuan Yuan, Yingtao Hu, Geza Kurczveil, Xucheng Yang, Raymond Beausoleil
Space Physics
C-SWIM: A Coupled Space Weather Impact Model for Satellite Fleet Vulnerability and Economic Loss Under a 1-in-100-Year Solar Energetic Particle Event
D. Bor, E. J. Oughton, R. S. Weigel et al. (+4 more)
Modern economies depend critically on satellite infrastructure, yet the aggregate economic consequences of extreme
solar energetic particle (SEP) events have not been rigorously assessed. This study develops an integrated framework linking SEP hazard characterization, dynamic geomagnetic cutoff
rigidity modeling, radiation dose transport, and fleet-wide failure probability estimation to macroeconomic impact analysis. Using extreme-value analysis of 160 SEP events over 27.4 years (1996-2025), failure probability is estimated for ~10,650 US operational satellites under orbital regime-dependent shielding assumptions. The assessment reveals that ~100 satellites (1.0%) are at Critical risk, concentrated in high-altitude low Earth orbit and highly elliptical orbit, while medium Earth orbit and geosynchronous orbit satellites fall in the Negligible class (P_fail < 10^-9) under the assumed radiation-hardened components and shielding. The expected capital loss across the ~$254B fleet totals ~$5.2B. Three failure scenarios, expanding from Critical satellites only (P_fail > 10^-2), to Critical and Elevated (P_fail > 10^-3), and to all satellites with non-negligible risk (P_fail > 10^-6), yield daily economic impacts of ~$70M, ~$270M, and ~$1.3B, respectively. Earth observation suffers up to 95.6% capacity loss in the worst case, while military services experience 16.1-20.4% disruption across scenarios. Results are first-order estimates: hardware failure counts are conservative because only total ionizing dose is modeled, and daily economic impacts represent upper bounds because operator response and recovery are not included.
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All authors D. Bor, E. J. Oughton, R. S. Weigel, R. Yang, T. Clower, M. J. Wiltberger, R. Linares
Instrumentation and Detectors
Identification and mitigation of memory block timing issue in ITk ABCStar during ASIC production
B. Ashmanskas, J. Botte, J.R. Dandoy et al. (+15 more)
The ABCStar is a mixed-signal front-end readout ASIC for the strips sensor portion of the ATLAS ITk detector being developed as part of the High-Luminosity LHC upgrade. In pre-production testing, a subtle design flaw was uncovered in the ABCStar that was reducing wafer yields in some manufactured lots from the expected 90% to as low as 2%. The root cause was determined to be a timing issue in the logic synthesized to control previously silicon proven
memory blocks re-used for this ASIC. The solutions proposed included manufacturing process changes by the wafer foundry, changes to the operating parameters for the ABCStar in the detector, and the possibility that a redesign might be required. The two mitigation efforts were undertaken in parallel, with the process modification route a less desirable solution since already manufactured wafers would need to be scrapped in favour of the new ones. Based on a knowledge of the existing process, and testing done on the worst performing wafers, it was proposed that raising the core operating voltage of the ABCStar from 1.20V to 1.25V could address the timing issue by sufficiently speeding up its transistors. An extensive testing program that included the effects of temperature and radiation expected over the lifetime of the ITk detector was conducted to validate that approach. Those tests and studies proved that even the worst performing wafers would have yields over 80% with the 1.25V core voltage, and neither the modified process nor redesign would be required for ensuring reliable operation of the ITk. Based on testing, a further timing mitigation was implemented to provide an additional margin of reliability by increasing the duty cycle of the clock to the ABCStar. Testing of all ABCStar wafers has been completed and the production of the detector modules using these ASICs is now well underway as a result of the efforts detailed herein.
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All authors B. Ashmanskas, J. Botte, J.R. Dandoy, J. Dopke, N. Dressnandt, B.J. Gallop, J.J. John, P.T. Keener, T. Koffas, J. Kroll, R.P. McGovern, F.M. Newcomer, B.J. Norman, P.W. Phillips, C. Sawyer, R. Scouten, P. Vicente Leitao, M. Warren
Atomic Physics
Simulation of Rydberg Ionization in Atomic Beams for FIB Optimization
Clelia Bastelica, Azer Trimeche, Colin Lopez et al. (+4 more)
This study explores the excitation and ionization of an atomic beam as a pathway to optimize focused ion beams (FIBs) for high-precision applications. Leveraging the unique advantages of Rydberg excitation followed by field ionization – specifically its ability to minimize velocity and position dispersions – we present a method to generate ion beams with good performance at low energies. A custom Lua program, integrated into the SIMION simulation platform, models the intricate processes of particle distributions,
laser excitation, and Rydberg ionization. This integrated approach incorporates essential parameters such as excitation and ionization rates, Stark shifts, Doppler effects, and electric fields, enabling a detailed analysis of ion beam properties. Our simulations demonstrate the influence of critical factors such as the chosen Rydberg state, ionization region characteristics, and velocity dispersions on the final ion beam quality. By optimizing these parameters, we achieve significant reduction of the axial energy spread and the longitudinal extent of the ionization region. This framework bridges theoretical modeling and experimental validation, offering a comprehensive toolkit for the development of next-generation ion sources and advancing FIB technologies across various scientific domains.
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All authors Clelia Bastelica, Azer Trimeche, Colin Lopez, Matthieu Viteau, Patrick Cheinet, Daniel Comparat, Yan J. Picard