Fluid Dynamics
A physics-constrained machine-learning sub-grid-scale modeling approach for turbulent premixed flames
Seung Won Suh, Jonathan F. MacArt, Luke N. Olson et al. (+1 more)
A physics-embedded training framework is used to close the sub-grid-scale dynamics of turbulent premixed flames. The trained model augments the resolved flow equations and is trained to match its predicted flow field to trusted data. An end-to-end optimization of the coupled resolved equations and embedded model leads to a model that is robust and effective for a freely propagating premixed flame in
turbulence, modeled by a single-species, single-step, and irreversible chemical reaction. Important constraints are built into the training formulation for conservation, scalar boundedness, and equivariance. The model is scaled based on the residual of the resolved flow equations to focus its influence where the closure is needed. It outperforms other cases considered — no-model, dynamic closure, and the same machine learning model trained directly to fit the residual data — for a long-time simulation, correcting the
turbulence dissipation and flame kinematics. Finally, it is shown how the prediction-based training better informs the model than the precise residual data.
Read the full abstract ▾
All authors Seung Won Suh, Jonathan F. MacArt, Luke N. Olson, Jonathan B. Freund
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Modifying van der Waals Materials via Cavity Vacuum Fluctuations
Mohammad Hassan, Cankut Tasci, Leon Orlov-Sullivan et al. (+2 more)
In the field of cavity
quantum materials,
vacuum fluctuations of optical cavities are used for modifying ground-state properties of
quantum materials without external driving. Here, one example is the van der Waals (vdW)/dispersion interaction in layered 2D vdW materials, where non-additive long-range correlations can dominate the interlayer binding. While cavity-induced changes of such interactions have been predicted and described using ab initio methods for molecular systems, no efficient description exists yet for extended materials. In this Letter, we close this gap by introducing a periodic formulation of the
photon many-body dispersion (pMBD) functional within
quantum electrodynamical density-functional theory (QEDFT). Applying this method with efficient $\textbf{q}$-point sampling to
bilayer hBN and
graphene, we predict cavity-modified stacking, increased
equilibrium interlayer distances, and softened layer breathing modes with increasing light-matter coupling strength. Our results establish cavity
vacuum fluctuations as a tuning knob for the structural properties of vdW materials.
Read the full abstract ▾
All authors Mohammad Hassan, Cankut Tasci, Leon Orlov-Sullivan, Leonardo A. Cunha, Johannes Flick
Applied Physics · Cross-listed from quant-ph
Beyond sensitivity: mechanism-resolved error budgets for designing quantum sensors
Nima Leclerc, Marco Capelli, Kevin James Rietwyk et al. (+14 more)
Quantum sensors are specified by a headline sensitivity, yet applications also demand accuracy and reliability. The dominant limiter of one metric is often known, but no method resolves how interacting mechanisms combine into a signed, per-mechanism budget for each metric. We introduce a framework that computes a sensor's sensitivity, accuracy, and robustness from one open-system simulation and attributes each to its limiting mechanism. For a nitrogen-vacancy diamond ensemble the attribution inverts across metrics: dephasing limits sensitivity, the thermal ground-state shift limits accuracy, and optical leakage limits robustness. At identical sensitivity the recovered-field bias spans $8$ to $1500$\,nT, so tuning to sensitivity alone can miss the accuracy target by two orders of magnitude. The same modeling transfers to a cesium optically pumped magnetometer recording a human magnetocardiogram. As a digital twin, it predicts the gain from addressing each limiter, so sensors can be designed to the required metrics.
Read the full abstract ▾
All authors Nima Leclerc, Marco Capelli, Kevin James Rietwyk, Mark Dong, Dmitry Lyakh, Geoffrey Iwata, Brandon Rodenburg, Sean Oliver, Benedikt Kloss, Jin-Sung Kim, Stefan Bogdanovic, Yunheng Chen, Meysam Sharifzadeh Mirshekarloo, Cedric Weber, Marcus Doherty, Ethan Pratt, Joseph Hagmann
Chemical Physics
A reaction volume bias Monte Carlo trial for sampling chemisorption in confinement
Samiha Sharlin, Harold W. Hatch, Daniel W. Siderius et al. (+1 more)
Molecular modeling of chemisorption with Monte Carlo requires the development of new trial moves to efficiently sample complex fluids such as water in Bronsted acid zeolites. Here, we develop a reaction volume bias (RxVB) Monte Carlo trial for modeling chemisorption by combining identity-switch and aggregation-volume-bias (AVB) moves. This method aims to promote the sampling of reactions by choosing reactive pairs that are within an arbitrarily specified reaction volume. The RxVB move achieves up to a 90-fold increase in accepted reaction events over unbiased moves in a single-site slit-pore model, corresponding to a 70-fold gain in statistical efficiency after accounting for computational overhead. But when the same move is applied to water in a Bronsted acid zeolite without orientational bias, there is no measurable speedup for a single MFI unit
cell. We demonstrate a simple expression that predicts the maximum efficiency increase in the simplest case where selecting reactants that are near each other is the major sampling bottleneck. Dense water systems may require additional configuration-bias or orientational bias to improve sampling of the hydrogen bond network in order to increase acceptance. This new RxVB trial was made available with examples in the open-source Free Energy and Advanced Sampling Simulation Toolkit (FEASST) simulation package.
Read the full abstract ▾
All authors Samiha Sharlin, Harold W. Hatch, Daniel W. Siderius, Tyler R. Josephson
Optics · Cross-listed from quant-ph
Langevin Theory of Non-Markovian Quantum Dynamics: Application to Delayed Coherent Feedback and the Laser Linewidth
Marc Cuenca-Laràs, Ming Li, Carlos Navarrete-Benlloch et al. (+1 more)
Phase-space methods are powerful tools for the treatment of Markovian open
quantum systems: they map the reduced dynamics of a system S, in interaction with an environment E, exactly onto Langevin equations for c-number
stochastic variables, as opposed to Heisenberg-Langevin equations for operators. Langevin equations provide analytical insight in key regimes and excel at handling strong nonlinearities and couplings, where other methods often falter. Extending phase-space methods to non-Markovian dynamics, however, has remained a long-standing challenge. Here we address this gap by applying phase-space representations to the full S+E system; integrating out the environmental degrees of freedom then yields a general Langevin framework for S that incorporates both deterministic and
stochastic contributions from E. Normally ordered representations, such as the Glauber-Sudarshan P representation and its positive variant due to Drummond and Gardiner, lead to Langevin equations in which (i) non-Markovian effects emerge exclusively in the deterministic terms, via a
memory kernel, and (ii) noise contributions vanish when E is initially in the
vacuum state. To demonstrate the power of this framework, we address the paradigmatic problem of delayed coherent feedback, in which the system is driven by its own past state, and study its impact on the
laser linewidth: we recover the narrowing observed well above threshold and predict an enhanced narrowing just above it. Crucially, the number of
stochastic variables scales linearly with the system size, making the framework suitable for problems ranging from a few degrees of freedom to genuinely many-body systems. This opens the way to the systematic study of non-Markovian driven-dissipative
quantum systems using the same analytical and numerical tools that have long made phase-space methods so successful in the Markovian regime.
Read the full abstract ▾
All authors Marc Cuenca-Laràs, Ming Li, Carlos Navarrete-Benlloch, Germán J. de Valcárcel
Classical Physics
Casimir-electrostatic pull-in in nanoelectromechanical actuators: Differentiable design sensitivities and the damping-dependent collapse boundary
N. S. Akintsov, A. P. Nevecheria, S. N. Andreev et al. (+1 more)
Nanoelectromechanical actuators operating at sub-100-nm gaps collapse through a pull-in instability set by competing electrostatic and Casimir forces. The quasi-static fold that bounds their safe operating range has been known in closed form for three decades, together with the Casimir ceiling above which no static
equilibrium survives, which fixes the smallest gap a given stiffness and area can hold open against the
quantum vacuum. That fold does not give the threshold reached from rest, its dependence on damping, or the design sensitivities of either. We train a physics-informed neural network in a rapidity coordinate that maps the movable pull-in pole to infinity, which keeps the residual bounded across the collapse threshold where fixed-step Runge-Kutta integration steps into unphysical states. Differentiating the trained surrogate returns pull-in-voltage sensitivities that match the closed-form fold to a relative error of $3\times10^{-6}$ and inverts a device specification to a gap of 97.036 nm at a target actuation voltage. Applied to the from-rest boundary, which carries no closed form once the damping is finite, it supplies the same sensitivities where no analytic root exists. We prove that this boundary is bracketed by two closed-form curves, that it is nondecreasing in the damping ratio, that it merges with the fold once the damping ratio exceeds $2^{-1/4}$, and that the gap closes as $(\tau_*-\tau)^{2/5}$. Numerically the merger already occurs at $0.396$, and the growth of the collapse time changes there from logarithmic to inverse square root. The classical-limit bound on the thermal Lifshitz derating is at the percent level, and the physical shift at these gaps lies orders of magnitude below it.
Read the full abstract ▾
All authors N. S. Akintsov, A. P. Nevecheria, S. N. Andreev, Qing-Hua Qin
Atomic Physics
Photoelectron interferometry with spectrally shaped polychromatic infrared pulses
E. A. Boati, G. Arvidsson, M. Ammitzböll et al. (+19 more)
Laser-assisted photoelectron interferometry is a cornerstone of attosecond science, first used to characterize attosecond pulse trains and later to study photoionization dynamics. Extending this method to spectrally shaped polychromatic infrared probe fields enables encoding of information across multiple interferometric pathways within the photoelectron spectrum. Here, we experimentally demonstrate
laser-assisted photoelectron interferometry using a spectrally shaped polychromatic infrared probe field composed of five distinct spectral components forming a Golomb ruler in the frequency domain. The measured interferograms exhibit multiple beating frequencies that agree with theoretical calculations, demonstrating the simultaneous encoding of multiple
laser-assisted
quantum beats in a single measurement. A quantitative analysis of the beating amplitudes shows that the strongly modulated temporal profile of the polychromatic probe introduces intensity- and delay-dependent distortions of the
quantum beats that cannot be explained by second-order perturbation theory. These results establish the conditions required for the quantitative interpretation of polychromatic photoelectron interferometry and highlight the opportunities offered by spectro-temporal engineering of the probe field for future developments in attosecond science.
Read the full abstract ▾
All authors E. A. Boati, G. Arvidsson, M. Ammitzböll, P. K. Maroju, C. Lévêque, R. Weissenbilder, V. Shiriaeva, H. Laurell, M. Li, H. Wang, C. Dittel, M. Canhota, C. Guo, R. Taïeb, J. Caillat, R. J. Squibb, R. Feifel, M. Gisselbrecht, C. L. Arnold, S. Luo, A. L'Huillier, D. Busto
Computational Physics
Modelling platelet dynamics in blood flow: an unresolved DEM approach
Francesca Zucchelli, Carmine Porcaro, Mahdi Saeedipour et al. (+2 more)
Computational models of blood flow are caught between fully resolved
cell-based methods, which faithfully reproduce the dynamics of individual
cells but are computationally prohibitive at vessel scale, and continuum models, scalable yet blind to particle motion. We present an unresolved, mesoscale computational fluid dynamics-discrete element method (CFD-DEM) model of platelet dynamics that bridges this gap and, coupled with an existing unresolved description of deformable red blood
cells, moves closer to a scalable model of whole blood. Within this framework, implemented on the open source OpenFOAM-LIGGGHTS coupling, platelets are represented as rigid oblate particles advanced by orientation dependent drag, lift and hydrodynamic torque closures. The model is first validated against resolved simulations and experiments in cylindrical microvessels of diameter $100-200\,\mu m$, across wall shear rates $\dot{\gamma}=150-1650\,s^{-1}$ and hematocrit Ht $=10-20\%$ then used to characterize platelet margination. The model quantifies
diffusion coefficient, CFL formation and their dependence on shear rate, Ht and channel size. In particular, platelet diffusivity grows with vessel size and shear rate, while remaining insensitive to Ht, whereas CFL thickens with shear rate and thins with Ht. We further show that even at this mesoscale level, the model remains sensitive to platelet shape: oblate platelets marginate faster and diffuse nearly an order of magnitude more than their spherical surrogates, reaching a comparable steady state distribution but along markedly different temporal paths. Together these results demonstrate that shape driven platelet dynamics can be recovered at a fraction of the cost of fully resolved methods.
Read the full abstract ▾
All authors Francesca Zucchelli, Carmine Porcaro, Mahdi Saeedipour, Bastien Chopard, Jonas Latt
Optics · Cross-listed from quant-ph
Input-Output Analysis of Quantum Dot SUPER Excitation
Johannes Kerber, Christoph Hotter, Helmut Ritsch et al. (+1 more)
The Swing-UP of the
quantum EmitteR population (SUPER) two-color pulsed excitation scheme allows for robust and close to 100% excitation of a two-level
quantum emitter using only red detuned light. We analyze the underlying counterintuitive dynamics using a full
quantum input-output description of the in- and outgoing light pulses for the case of two coherent free-space input pulses at realistic
photon numbers. At the microscopic level, the SUPER mechanism exhibits its nonlinear three-
photon Raman-type character, leading to a net
photon-number change of $-2$ in one mode and $+1$ in the other, as was first guessed from cavity-enhanced model descriptions at low
photon numbers. We confirm that in free space, a sufficiently high pulse
photon number, much larger than one, is required to achieve high-fidelity inversion. To treat the large coherent-state amplitudes (
photon numbers) relevant for SUPER, we extend the
quantum input-output formalism to include a cumulant expansion approach. With an interaction-picture formulation, the few exchanged
photons that govern the nontrivial dynamics enable direct full-
quantum calculations in truncated
Hilbert spaces, including treatments in a displacement frame and for initial Fock-state pulses.
Read the full abstract ▾
All authors Johannes Kerber, Christoph Hotter, Helmut Ritsch, Klaus Mølmer
Plasma Physics
Real-time virtual circuits for plasma shape control via neural network emulators: experimental demonstration on MAST Upgrade
Nicola C. Amorisco, Kamran Pentland, Adriano Agnello et al. (+12 more)
Conventional
plasma shape control in tokamaks relies on virtual
circuits (VCs) that are computed offline from linearisations around a small, tailored number of reference
equilibria, and deployed as expertly prepared schedules during the discharge. Here, we report on the first experimental deployment of real-time VCs. We replace pre-set look up tables with VCs updated in real time using surrogates of the
plasma response. Both the existing control architecture and the interpretability of VC-based control are retained. Previous work showed that neural network emulators can produce accurate VCs, and validated their performance in closed-loop shape control simulations. Here, we report their first experimental validation on MAST Upgrade (MAST-U). Dedicated experiments spanning different scenarios, including prescribed shape perturbations, feedback-driven divertor-leg motion, and strongly evolving
plasma configurations, show that real-time VCs can realise
plasma shape control tasks within the MAST-U
plasma control system. These results establish the experimental feasibility of real-time linearisations as a practical extension of conventional
plasma shape control in tokamaks. The present implementation demonstrates a central step towards a simpler control workflow, in which manually constructed, phased VC schedules are replaced by VCs generated automatically online from a trained surrogate model, without scenario-specific retraining.
Read the full abstract ▾
All authors Nicola C. Amorisco, Kamran Pentland, Adriano Agnello, George K. Holt, Alasdair Ross, Matthew J. Marshall, Edward Jones, Graham J. McArdle, Charles Vincent, Timothy Nunn, Martin Kochan, Pedro Cavestany, Aran Garrod, Stanislas Pamela, James Buchanan
Applied Physics
Synergy between laser linewidth and frequency chirp in mesospheric magnetometry based on the sodium laser guide star
Yucheng Yang, Chunyang Lei, Kai Guo et al. (+1 more)
Mesospheric sodium magnetometry with a
laser guide
star measures the geomagnetic field near 90~km. Its sensitivity hinges on
laser linewidth and chirp, yet prior work optimized these two parameters only separately. We use velocity-resolved density-
matrix simulations of Larmor-synchronous pulsed Na D$_2$ pumping to scan both parameters jointly. Linewidth and chirp exhibit a synergy: when chirping carries the
recoil-mitigation role, the return flux stays within 1% of its peak across linewidths of 2–10~MHz. The flux-optimal chirp is $0.19~\mathrm{MHz/\upmu s}$, one fifth of the continuous-wave rate; this synergy guides high-sensitivity mesospheric magnetometer design.
Read the full abstract ▾
All authors Yucheng Yang, Chunyang Lei, Kai Guo, Shuai Wang
Optics
Correlation Swapping: a correlator for independent thermal light sources
Wanting Hou, Jilun Zhao, Zhiyuan Ye et al. (+4 more)
Optical intensity correlation is a fundamental property of light and an essential resource for numerous optical applications. In this work, we introduce the concept of classical correlation swapping, a classical analogue of
quantum entanglement swapping, to generate all-purpose spatial correlations between two independent thermal light sources. Using a spatially unresolved Mach-Zehnder interferometer and a medium variable, we theoretically and experimentally demonstrate the feasibility of the correlator with two distinct schemes for independent pseudo-thermal light beams. Notably, the resulting
photon correlations can be readily tailored to exhibit either bunching (peak) or anti-correlated (dip) characteristics, with a significantly reduced number of post-selection measurements. Leveraging this classical correlator, we further demonstrate the first classical ghost imaging experiment using uncorrelated or unknown light. Numerical simulations also confirm that the correlator can not only operate well in other spatial degrees of freedom (e.g., orbital angular momentum) but also be used to establish specific spatial correlations between pseudo-thermal light sources possessing distinct correlation properties. This work opens a new avenue for harnessing uncorrelated classical light in correlation-based optical applications.
Read the full abstract ▾
All authors Wanting Hou, Jilun Zhao, Zhiyuan Ye, Hong-Chao Liu, Hai-Bo Wang, Jun Xiong, Kaige Wang
Computational Physics · Cross-listed from cs.LG
Euclidean Fourier Neural Operators
Nathanael Bosch, Niklas Frederik Schmitz and Michael F. Herbst
Fourier neural operators (FNOs) provide an efficient framework for learning mappings between function spaces as they are, by construction, independent of the grid resolution at which they are trained and evaluated. However, FNOs are not independent of the periodic domain they are applied to: their discrete spectral weights are indexed by integer
Fourier mode numbers, which correspond to physical wavevectors. When applied to a different domain, the same trained weights act at different wavevectors, and the FNO silently represents a different operator. This makes FNOs unsuitable for tasks where transfer across domains is crucial. We propose Euclidean
Fourier neural operators~(EFNOs) as a domain-independent alternative to FNOs. By parameterizing the spectral kernel as a continuous function of the physical wavevector, the EFNO can learn operators that act consistently across periodic domains of varying shape and size. We evaluate the EFNO on a simple heat equation and on a practically relevant materials science task of learning exchange-correlation potentials across different
crystal structures, and demonstrate that the EFNO is able to generalize to unseen grid sizes and domains.
Read the full abstract ▾
Chemical Physics
Third-order Algebraic Diagrammatic Construction Renormalized by Particle-Particle Ladders
Arno Förster
The algebraic diagrammatic construction (ADC) of the electronic self-energy is based on Moller-Plesset perturbation theory. Its vertices contain bare energy denominators that do not capture renormalization of Hartree-Fock excitations through excited-state correlations. As we show here, Epstein-Nesbet (EN) partitioning of the electronic
Hamiltonian overcomes this deficiency at zero extra cost by introducing dressed denominators that resum to infinite order the diagonal elements of ladder diagrams described by the pair propagator in the particle-particle $T$-
matrix approximation. Third-order ADC with EN-dressed denominators leads to an almost fourfold increase in accuracy compared to standard ADC(3) on a challenging
benchmark set for IPs of closed-shell molecules, reaching an accuracy between EOM-CCSD and EOM-CCSDT. For open-shell systems, the gains in accuracy are more modest, but standard ADC is nevertheless outperformed.
Read the full abstract ▾
Optics
High-performance silicon-metal laser welding resisting extreme conditions
Jiawei Yin, Markus Blothe, Hagen P. Kohl et al. (+3 more)
Reliable material joining is essential for countless industrial applications. While femtosecond
laser welding provides a route beyond conventional bonding methods, demonstrations of silicon-metal joints are rare due to nonlinear propagation effects and have so far been limited to shear joining strengths of a few MPa. Here, we demonstrate high-strength silicon-Kovar
laser welding using sub-nanosecond pulses. By optimizing the focal position, the welding pattern, the
laser polarization, and the metal roughness, remarkable shear joining strengths up to 15.8 MPa are achieved. The silicon-metal joints withstand temperatures of up to 500 {\deg}C and are hermetically sealed. Together with the remarkable strength values, the resistance to harsh environments underpins the applicability of silicon-metal welding in various fields including aerospace,
nuclear science, and metallurgy.
Read the full abstract ▾
All authors Jiawei Yin, Markus Blothe, Hagen P. Kohl, Christina Schütze, Stefan Nolte, Maxime Chambonneau
Atomic Physics · Cross-listed from quant-ph
Optomechanical inertial reference for atom interferometry
A. Rajagopalan, K. Stolzenberg, D. Thomas et al. (+5 more)
Atom interferometers are among the most sensitive inertial sensors, yet deployment outside the laboratory is limited by vibration noise, conventionally mitigated by external sensors or bulky isolation. Here we demonstrate a hybrid inertial sensor which fuses an optomechanical resonator and an atom interferometer by exploiting the resonator's test mass as the interferometer's reference mirror. This allows for better correlation than with two separate sensors, whose unknown transfer function is replaced by the static response of one mechanical element. The resonator achieves a displacement sensitivity of $8.6\cdot 10^{-15}$ m/$\sqrt{\mathrm{Hz}}$ with suppressed 1/f noise and yields a minimum acceleration sensitivity of $1.1\cdot10^{-6}$ m/s$^2$/$\sqrt{\mathrm{Hz}}$ over a bandwidth extending from sub-Hertz to 2.5 kHz. Under ambient laboratory conditions the integrated system removes vibration-induced phase ambiguity for accelerations up to $50\cdot 10^{-3}$ m/s$^2$ and reaches the interferometer's technical noise limit, which a commercial force-balance accelerometer does not. Because the resonance-tracking readout is largely independent of the mechanical design, the architecture transfers directly to other precision sensing platforms.
Read the full abstract ▾
All authors A. Rajagopalan, K. Stolzenberg, D. Thomas, A. Herbst, S. Abend, E. M. Rasel, F. Guzmán, D. Schlippert
Data Analysis and Statistics · Cross-listed from stat.ML
Localizing Global Discrepancies: Marginal Contributions and Contextual Anomaly Detection
Tommaso dorigo
Global goodness-of-fit and discrepancy statistics can establish that a sample departs from a reference distribution without identifying which observations drive the departure. We develop a framework for this localization problem by assigning to each observation its conditional or marginal contribution across random statistical contexts. This connects resampling diagnostics and data valuation to projection theory and event-level anomaly detection. For symmetric statistics, fixed-size replacement is exactly equivalent to centered conditional localization. For U-statistics, the addition score equals the first Hoeffding/Hájek contribution; for smooth distributional functionals it is related at leading order to the influence function; and for unbiased known-background MMD it reduces exactly to the MMD witness. This viewpoint also yields more efficient
estimators. Matched-context subtraction removes fluctuations unrelated to the observation, while for pairwise MMD the event-containing terms give a simple localizer. On the LHC Olympics anomaly-detection
benchmark, the pair
estimator converges to the direct empirical MMD witness with the predicted 1/(Rm^2) scaling, where m is batch size and R the number of batches. At m=1000 and R=5x106 it reaches correlation 0.9993 with essentially identical AUC. We also ask when context contains information beyond an event's own features. In a shared-latent toy model, the full single-event signal and background distributions are identical by construction, forcing isolated-event AUC=0.5. Discriminating information survives only in cross-event dependence induced by the shared latent parameter; the ensemble recovers this information, whereas an independent-latent control does not. This separates two roles of context: efficient localization of a global discrepancy and genuinely additional class information when the alternative contains shared structure.
Read the full abstract ▾
Plasma Physics · Cross-listed from astro-ph.SR
A high-frequency type II radio burst associated with an X2.3 class flare
Divya Paliwal, Anshu Kumari, Vishwa Vijay Singh et al. (+3 more)
Radio observations provide a powerful diagnostic of the
solar corona, enabling investigations of dynamic phenomena associated with
solar flares, coronal mass ejections (CMEs), and shock waves. We present a multiwavelength analysis of a rare high-frequency type II
radio burst (starting frequency of $\sim$750 MHz and frequency drift rate of $\sim$0.5 MHz s$^{-1}$) associated with the X2.3-class
solar flare that occurred on 6 November 2024. A propagating EUV disturbance was observed shortly after the
flare onset in the SDO/AIA field of view, while
radio spectrographs recorded the type II burst between 13:46 and 13:56 UT over a frequency range of $\sim$750 to 45 MHz.
Radio imaging observations from the Nançay Radioheliograph (NRH) show that the
radio sources propagate southward during the event. X-ray spectroscopy from HEL1OS onboard Aditya-L1 and imaging observations from STIX onboard
Solar Orbiter reveal signatures of efficient non-thermal electron acceleration associated with the
flare. An NLFFF extrapolation identifies a pre-eruptive
magnetic flux rope in the source region, while white-light coronagraph observations obtained during the event show no detectable large-scale CME. The speed of the erupting flux rope, derived from stereoscopic EUV observations, is consistent, within measurement uncertainties, with the shock speed inferred from the
radio dynamic spectrum. Together, these observations suggest that compact flux rope eruptions, even in the absence of a detectable white-light CME, can generate low-coronal shocks capable of producing high-frequency type II
radio emission.
Read the full abstract ▾
All authors Divya Paliwal, Anshu Kumari, Vishwa Vijay Singh, Dinesh Mishra, Pritam Das, Nadiya K
Plasma Physics
Electromagnetic pressure-gradient-driven instabilities with moderate high mode numbers in tokamak plasmas
Yann Narbutt, Ksenia Aleynikova, Matthias Borchardt et al. (+6 more)
Pressure gradient-driven instabilities are investigated in tokamak
plasmas using the global gyrokinetic code EUTERPE emphasizing the role of moderate high mode numbers. As the normalized
plasma pressure $\beta$ is increased, there is a well-known, sudden transition from ion-temperature-gradient (ITG) instabilities to kinetic ballooning modes (KBM), if the magnetohydrodynamic (MHD) geometry is held fixed. However, if the
equilibrium field is recomputed for each value of $\beta$, so that the
equilibrium is consistent with the stability calculation, the transition can disappear. In a number of cases, we are only able to find an ITG-KBM transition if inconsistent
equilibria are used. In the MHD unstable regime, gyrokinetic simulations and MHD stability calculations show good agreement for moderate ratios of ion temperature gradient to density gradient and small values of the ion gyro-radius. Otherwise, non-MHD contributions are important, such as the diamagnetic stabilization and ion wave–particle resonant effects.
Read the full abstract ▾
All authors Yann Narbutt, Ksenia Aleynikova, Matthias Borchardt, Thomas Hayward-Schneider, Ralf Kleiber, Axel Könies, Alexey Mishchenko, Carolin Nührenberg, Edilberto Sánchez
Computational Physics
Real-Time Monitoring of MHD Liquid Metal Flows with Shallow Recurrent Decoders
Claudio Scardino, Stefano Riva, Carolina Introini et al. (+4 more)
State estimation in magnetohydrodynamic flows is critical for real-time monitoring of
liquid metal blankets in tokamak fusion reactors. Due to the multiphysics nature of these phenomena, high-fidelity simulations are computationally prohibitive for real-time applications. This work investigates a data- driven Reduced Order Model framework: the Shallow Recurrent Decoder (SHRED) coupled with Principal Component Analysis, to map sparse temperature measurements to the full thermo-hydraulic system's state. The major contribution of this work lies in the two-parameter analysis of a fully three-dimensional domain representative of the DEMO breeding blanket configuration. Here, the flow is subjected to an external
magnetic field varying in direction and intensity and is hindered by two cylinders acting as a water-cooling system, which impose a temperature boundary condition on their surfaces. This double-parametric
magnetic variation induces nonlinear transitions in the flow dynamics, ranging from chaotic behavior at low
magnetic field intensities to laminarized regimes at high intensities, characterized by the formation of asymmetric side layers at an inclination angle of 30 degrees. SHRED reconstruction maintains a mean relative error of approximately 5% for the temperature, pressure, and velocity fields. This accuracy is maintained across both weak and strong
magnetic fields, ranging from 0.075 T to 0.300 T, and for inclination angles from 5 to 30 degrees, reflecting its dominant toroidal component. These errors are only slightly larger than the lower error bound dictated by low-rank truncation. The results establish SHRED as a reliable state
estimator for complex and realistic engineering applications involving completely unseen parametric scenarios and validate it as an accurate real-time state estimation technique suitable for online monitoring and control of real facilities.
Read the full abstract ▾
All authors Claudio Scardino, Stefano Riva, Carolina Introini, Matteo Lo Verso, Eric Cervi, Antonio Cammi, Laura Savoldi
Computational Physics · Cross-listed from quant-ph
Variationally Optimized Imaginary-time Polynomial Filters for Ground State Projection
Bahman Seifi, Ibsal Assi and J. P. F. LeBlanc
In this work, we develop a variational imaginary-time
evolution (ITE) framework based on
polynomial filtering, derived from an operator-level action principle, which yields an optimized non-
unitary projector expressed as a
polynomial in the
Hamiltonian. Starting from a single-ancilla, first-order imaginary-time update defined by a Taylor expansion and Trotter-Suzuki (TS) decompositions, we show that replacing these approximations with alternative variational formulas substantially improves both accuracy and stability at larger time steps, leading to up to an order-of-magnitude enhancement in the final success probability. We further derive rigorous error bounds that depend only on static properties of the
Hamiltonian, providing practical guidance for selecting the simulation time step.
Benchmarks on the transverse-field Ising model demonstrate faster convergence to the ground-state energy and improved robustness compared to standard TS–Taylor ITE, highlighting variational
polynomial filtering as a practical route to higher-fidelity ground-state preparation on near-term
quantum devices.
Read the full abstract ▾
Instrumentation and Detectors
Development of a high-granularity, high-precision timing readout electronics system for large-area MRPC detectors
J.N.Tang, W.H.Wu, Y.Q.Tan et al. (+4 more)
Multi-gap Resistive Plate Chamber (MRPC) detectors offer excellent time resolution and detection efficiency, creating a strong demand for high-precision, highly scalable timing readout systems. In this work, a readout electronics system is designed for a large-area 100*100 cm MRPC detector containing 2400 high-granularity 2*2 cm pad channels. The system consists of two Front-End Boards (FEBs), a central clock distribution module, and a back-end DAQ aggregator. Each FEB is equipped with 40 32-channel PETIROC2B ASICs mounted directly behind the sensing pads. An automated S-curve calibration procedure equalizes the baseline dispersion across all 2400 channels, reducing the FWHM of the baseline voltage distribution from 50 mV to 12 mV and establishing a uniform triggering threshold. Signal-injection measurements confirm an intrinsic single-channel electronic time resolution of 33 ps RMS, alongside inter-chip and inter-board time resolutions of 43 ps RMS and 45 ps RMS, respectively. This high-granularity, high-precision timing readout system can be widely applied to Time-of-Flight systems,
cosmic-ray
muon imaging, as well as other fast-timing detector systems.
Read the full abstract ▾
All authors J.N.Tang, W.H.Wu, Y.Q.Tan, W.Zhi, H.J.Yang, Imad Laktineh, Q.P.Shen
Optics · Cross-listed from cond-mat.mes-hall
Crystal-phase quantum dots in AlGaAs nanowires
Rohan Radhakrishnan, Rodion Reznik, Gilles Patriarche et al. (+6 more)
Crystal-phase
quantum dots (CPQDs)$\unicode{x2014}$
quantum dots in nanowires defined by
crystal structure rather than material composition$\unicode{x2014}$constitute the only platform capable of fabricating
quantum-dot arrays with the ultimate precision of a single atomic layer. This intrinsic control yields perfectly aligned
quantum dots with atomically sharp interfaces, providing a unique pathway toward scalable
quantum-dot-based photonic
quantum technologies. To date, CPQDs have been studied primarily in binary
semiconductors, such as InP and GaAs, where their emission linewidths are typically in the meV range, thereby limiting their technological potential. Here, we report, for the first time, CPQDs in AlGaAs nanowires and show bright single-
photon emission with linewidths as narrow as 61 $\mu eV$ and low background emission, demonstrating optical quality well beyond typical CPQDs. We attribute this performance to a type-I band
alignment, as suggested by an
exciton lifetime of 1 ns, significantly shorter than that typically observed in type-II CPQDs. Additionally, we observe an
exciton fine-structure splitting and a Zeeman splitting, as commonly observed in standard type-I self-assembled
quantum dots.
Read the full abstract ▾
All authors Rohan Radhakrishnan, Rodion Reznik, Gilles Patriarche, Lorenzo Leandro, Igor Ilkiv, Anna Andreeva, Artem Khrebtov, George Cirlin, Nika Akopian
Optics
Structural perturbation theory for bound states in the continuum via bifurcation of zeros and extrema of the dispersion relation
Lijun Yuan and Ya Yan Lu
In a lossless periodic structure, a bound state in the continuum (BIC) corresponds to a real zero and a local maximum of the imaginary part of a complex dispersion relation $k = k(\beta)$, where $\beta$ is the Bloch wave number. A perturbation of the structure deforms the dispersion curve and may destroy, move or split the BIC, as demonstrated in existing studies involving lossless
symmetry-preserving perturbations,
symmetry-breaking perturbations and dissipative perturbations. We present a comprehensive perturbation theory, emphasizing the
evolution of the real zeros and extreme points of $\mathrm{Im}[k(\beta)]$ under various structural perturbations. In particular, our theory reveals the existence of lasing threshold modes (LTMs), which are also zeros of $\mathrm{Im}[k(\beta)]$ when the perturbation involves gain with or without balanced loss. Using local Taylor expansions and Puiseux series, we determine the number, locations, and leading-order scaling of real zeros and extreme points for various types of BICs under different types of structural perturbations. The theory recovers known results and predicts new behavior for super-BICs under $\mathcal{PT}$-symmetric perturbations. Specifically, a propagating super-BIC corresponding to a fourth-order zero of $\mathrm{Im}[k(\beta)]$ splits into two real zeros representing either two BICs or two LTMs, and a symmetric standing wave splits into two BIC-LTM pairs. Our theory provides a general framework for studying BICs and nearby resonant modes in both lossless and non-Hermitian periodic structures.
Read the full abstract ▾
Physics and Society
Early warning signals for synchronization transitions from partial observations
Yusuke Kato and Naoki Masuda
Anticipating the onset of collective synchronization is important in many networked systems, yet observing every oscillator is often impractical. We investigate whether synchronization transitions can be detected from a small set of monitored, or sentinel, nodes. Using a
stochastic Kuramoto model on networks, we numerically compare three early warning signals: the local order parameter, its temporal variance, and the variance of individual oscillator phases after removing their mean rotational trends. We also compare sentinel-selection strategies based on node dynamics, degree, and random sampling. We show that, under partial observation, the local order parameter and the variance of detrended phases provide substantially stronger warning signals than the variance of the local order parameter. Selecting nodes according to their dynamical behavior near the transition consistently improves performance over other sentinel-selection methods. With only $\lfloor\ln N\rfloor$ dynamically selected sentinels, two success indicators approach the performance obtained by observing all $N$ nodes. These results demonstrate that synchronization transitions can be anticipated from sparse observations when the warning signal and monitored nodes are chosen appropriately.
Read the full abstract ▾
Data Analysis and Statistics · Cross-listed from hep-ex
Vertex reconstruction for a search for neutron-antineutron conversions with HIBEAM
Alexander Burgman, Sze Chun Yiu, Yamna Shaikh et al. (+13 more)
The HIBEAM/NNBAR programme (incorporated into the FINESSE/NNBAR programme) at the European Spallation Source is proposed to search for
neutrons converting to antineutrons. An important observable is the reconstructed vertex arising from charged particles produced by an antineutron annihilating on a thin target foil and which pass through a time projection chamber. This paper studies track clustering and foil-plane vertex reconstruction for this
topology. Both non-machine-learning methods and graph-neural-network methods are tested and compared with each other, including deterministic clustering, trackless projection and a hybrid clustering/graph-neural-network chain with track classification and vertex refinement. We conclude that, for the geometrically simple events in the HIBEAM TPC, classical reconstruction methods perform on-par with machine-learning based methods in terms of vertex coordinate reconstruction. Custom machine-learning based methods can, however, deliver event-shape information that may be important in downstream analyses.
Read the full abstract ▾
All authors Alexander Burgman, Sze Chun Yiu, Yamna Shaikh, David Milstead, Eily Merjy, Lucas Åstrand, Kenneth Österberg, Fredrik Oljemark, Bernhard Meirose, Matthias Holl, Valentina Santoro, Jorge Amaral, Ernesto Kemp, André Nepomuceno, Tiago Quirino, Joshua L. Barrow
Space Physics
Solar Magnetic Configuration Control over Radiation Belt Electrons
Ahmad Lalti, Jonathan Rae, Clare Watt et al. (+2 more)
Earth is surrounded by two highly dynamic concentric belts of particle radiation. The outer radiation belt exhibits coherent variability at
solar-cycle, seasonal, and 27-day (Carrington) timescales. While the
solar-cycle and Carrington variations have been attributed to the recurrence of coronal hole
solar wind, the seasonal variation has long been explained by local
geometric effects that modulate the
solar wind-magnetosphere coupling. Here, we challenge this paradigm by showing that the periodic recurrence of coronal hole
solar wind likewise drives the seasonal variation. We further demonstrate that the Alfvénic nature of this
solar wind is responsible for the observed electron flux enhancement in the outer radiation belt. These findings provide a unifying framework linking
solar magnetic topology,
solar wind properties, and magnetospheric dynamics across multiple timescales at Earth and beyond.
Read the full abstract ▾
All authors Ahmad Lalti, Jonathan Rae, Clare Watt, Stephanie Yardley, Savvas Raptis
Accelerator Physics
Wakefield-Dressed Relativistic Vortex Electrons in Plasma Accelerators
Zhigang Bu, Lingang Zhang and Liangliang Ji
Plasma wakefield acceleration is usually regarded as a classical mechanism for producing high- energy charged-particle beams. Here we show that an axisymmetric
plasma wakefield can also act as a moving
quantum structure that supports relativistic
vortex electron states. Starting from the Dirac equation, we derive the electron spinor eigenstates with definite total angular momentum in an ideal bubble-regime wakefield. The transverse focusing field confines and quantizes the electron transverse motion into Laguerre-Gaussian
vortex modes, while the longitudinal electric field acceler- ates the electron without destroying the
symmetry-protected angular momenta. We further analyze the localized and off-axis
vortex electron wave-packets, and non-ideal wakefield perturbations, and identify the conditions for preserving electron-
vortex-state purity. These results suggest
plasma wakefield as a route toward high-energy
vortex electrons and extend
plasma-based acceleration from classical beam dynamics to
quantum-state control of relativistic particles.
Read the full abstract ▾
Fluid Dynamics
LES of iron-powder combustion in a jet-in-hot-coflow burner - Insights on flame structure and ignition characteristics
Shyam Hemamalini and XiaoCheng Mi
Micron-sized iron powders are a rapidly advancing novel energy storage technology. In order to improve the design of real-world iron-powder combustors, adequate understanding of the ignition behavior in such settings is necessary. In this work, a jet-in-hot-coflow (JHC) burner designed by Hameete et al. (2024) to test ignition of iron particles in lab-scale turbulent flames is modeled numerically using LES and Lagrangian point-particles. The JHC burner is simulated in two different modes–an open flame and an enclosed flame–similar to the experimental reference. Two iron-oxidation-rate models–the first-order model and
oxide-layer model–are used to examine the effect on capturing the ignition behavior. For the radiative heat transfer between the two phases, a simplified Stefan-Boltzmann approximation model and the P1 model are considered, similar to Ramaekers et al. (2025). Analysis of flame structure indicates ignition in the circumference of the jet, aided by the break-up of the coflow. At higher $T_\mathrm{coflow}$, ignition onset and oxidation completion is earlier prior to jet break-up. Minimum coflow temperature for particle ignition with the
oxide layer model is $1125\mathrm{K}$ with complete oxidation at $1250\mathrm{K}$, and for the first-order model at $800\mathrm{K}$ and $900\mathrm{K}$, respectively. Both of these results do not match the experimental results of Hameete. Oxidation degree is predictably higher for enclosed flames. For the chosen particle distribution, the P1 model exhibits higher radiative heat loss and results in a slightly lower oxidation degree. Analysis on particle ensembles with partial oxidation shows that the overall oxidation degree at a sufficient height above the nozzle reflects particle ignition probability. Further analysis in regards to particle size shows ignition failure is more prevalent in larger particles.
Read the full abstract ▾
Instrumentation and Detectors · Cross-listed from astro-ph.IM
Development, Configuration and Performance Characterization of a Scalable BETA ASIC-Based Readout System for Multi-Channel SiPM Detectors
Giulio Lucchetta, Keerthana Rajan Lathika, Benjamin Nobre Hauptmann et al. (+17 more)
We present the design, configuration, and performance characterization of a scalable readout system based on the BETA application-specific integrated
circuit (ASIC), developed to meet stringent requirements on noise, linearity, dynamic range, and power consumption for multi-channel silicon photomultiplier (SiPM) detectors in spaceborne instrumentation. The readout electronics consists of modular interface boards (FIBs) hosting multiple BETA ASICs and controlled by a field-programmable gate array (FPGA), which provides configuration, data acquisition, and global trigger generation. Multiple BETA FIBs were tested in a dedicated optical setup enabling simultaneous readout of a large number of channels. The system performance was evaluated using three S13552-10 SiPM arrays manufactured by Hamamatsu for the FIT detector, a scintillating-fiber tracker developed for charged
cosmic-ray particle tracking and charge measurement in the HERD mission. We describe the configuration procedures and performance measurements of the readout system, including gain calibration, linearity characterization, and threshold response. In addition, we present the development of a global internal trigger logic for the identification of ionizing particles in the FIT detector. The results demonstrate the stability, scalability, and suitability of the developed BETA-based readout system for large-scale multi-channel SiPM detector applications in space experiments.
Read the full abstract ▾
All authors Giulio Lucchetta, Keerthana Rajan Lathika, Benjamin Nobre Hauptmann, Philipp Azzarello, Oscar Blanch, Juan Boix, Laia Cardiel, Arturo Castaño Gallardo, Albert Espinya, Jennifer Maria Frieden, David Gascon, Daniel Gubermann, Kimberly Sarah Keyser, Manel Martinez, Joan Mauricio, Marina Orta-Terré, Chiara Perrina, Javier Rico, Andreu Sanuy, Monong Yu