Chemical Physics · Cross-listed from cond-mat.stat-mech
Correlation between the first-reaction time and the acquired boundary local time
Yilin Ye and Denis S. Grebenkov
We investigate the statistical correlation between the first-reaction time of a diffusing particle and its boundary local time accumulated until the reaction event. Since the reaction event occurs after multiple encounters of the particle with a partially reactive boundary, the boundary local time as a proxy for the number of such encounters is not independent of, but intrinsically linked to, the first-reaction time. We propose a universal theoretical framework to derive their joint probability density and, in particular, the correlation coefficient. To illustrate the dependence of these correlations on the boundary reactivity and shape, we obtain explicit analytical solutions for several basic domains. The analytical results are complemented by Monte Carlo simulations, which we employ to examine the role of interior obstacles on correlations in disordered media. Applications of these statistical results in chemical physics are discussed
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Applied Physics
Polymer-inspired mechanical metamaterials
Zhenyang Gao, Pengyuan Ren, Yifeng Dong et al. (+18 more)
Metamaterials benefit from unique architected patterns to achieve lightweight with exceptional mechanical properties inaccessible to conventional materials. Typical mechanical metamaterials are inspired by
crystal-like
lattice structures, whose closely packed frameworks often exhibit a rigid mechanical nature. Here, we present
polymer-inspired metamaterials (PIMs) by programming deformation and strengthening mechanisms that mimic the mechanical roles of key constituent elements in
polymer networks. By combining metamaterial programmability with
polymer-inspired structures, we design crosslinking, proto-crystalline order, and
entanglement in PIMs to enable macroscale strengthening mechanisms inspired by crosslink, molecular-density, and pre-stretch strengthening in
polymers, expanding the metamaterial structure-property design space. This macroscale
polymer-inspired programmability also suggests that PIMs could serve as a design platform incorporating the programmability strategies to achieve desired deformation and strengthening responses, holding a potential for applications in soft robotic joints and compliant connectors.
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All authors Zhenyang Gao, Pengyuan Ren, Yifeng Dong, Gengchen Zheng, Min-Son Pham, Xiao Shang, Shaojia Wang, Shuo Yang, Zijue Tang, Yongbing Li, Hua Sun, Yi Wua, Hongjian Jiang, Lan Zhang, Tobin Filleter, Lingyu Kong, Kun Zhou, Haowei Wanga, Yang Lu, Yu Zou, Hongze Wang
Optics
Intrinsic temporal and spectral mixing in time-resolved terahertz spectroscopy
Benjamin J. Dringoli and David G. Cooke
In an ultrafast optical-pump terahertz-probe measurement, the photoinduced material response can be modulated on a timescale shorter than the extent of the THz pulse. In this situation, the measured time-frequency response deviates from a simple time-dependent linear response. When full two-dimensional time-frequency maps are measured, this yields complex features that can be incorrectly assigned to a photoexcited coherent response. We investigate this experimentally via the measured response of photoexcited SnSe, whereby photoinduced phase change dynamics lead to ultrafast changes of the charge carrier and
lattice optical conductivity response. Two-dimensional time-frequency THz transmission maps subsequently show unexpected time-frequency features at early pump-probe delay times. These features are reproduced in both finite-difference time-domain simulations of the THz experiment and in an extension of non-
equilibrium response function theory, demonstrating their systematic origin. This work improves the understanding of systematic effects in high time resolution optical-pump THz-probe spectroscopy, and explores the conditions in which they are likely to appear.
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Physics and Society
Inequality traps detected in sustainable development goals data
Juan C. Rocha, Maike Hamann, Jiangxiao Qiu et al. (+9 more)
The relationship between inequality and the biosphere has been hypothesized to mutual dependecies and feedbacks. If that is true, such feedbacks may give rise to inequality regimes and potential tipping points between them. Here we explore synergies and trade-offs between inequality and biosphere-related sustainable development goals. We used the openly available SDG
datasets by the World Bank (WB) and United Nations (UN) and applied ordination methods to distill interactions between economic inequality and the environmental impact across countries. Our results confirm the existence of inequality regimes, and we find preliminary evidence that corruption may be a candidate driver of tipping between regimes.
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All authors Juan C. Rocha, Maike Hamann, Jiangxiao Qiu, Tong Wu, Tomas Chaigneau, Emilie Lindkvist, Caroline Schill, Alon Shepon, Andrew R. Tilman, Geraldine D. Verkleij, Anne-Sophie Crépin, Carl Folke
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
How accurate are foundational machine learning interatomic potentials for heterogeneous catalysis?
Luuk H. E. Kempen, Raffaele Cheula and Mie Andersen
Foundational machine learning interatomic potentials (MLIPs) are being developed at a rapid pace, promising closer and closer approximation to ab initio accuracy. This unlocks the possibility to simulate much larger length and time scales. However,
benchmarks for these MLIPs are usually limited to ordered, crystalline and bulk materials. Hence, reported performance does not necessarily accurately reflect MLIP performance in real applications such as heterogeneous catalysis. Here, we systematically analyze zero-shot performance of 80 different MLIPs, evaluating tasks typical for heterogeneous catalysis across a range of different data sets, including adsorption and reaction on surfaces of alloyed metals,
oxides, and metal-
oxide interfacial systems. We demonstrate that current-generation foundational MLIPs can already perform at high accuracy for applications such as predicting vacancy formation energies of perovskite
oxides or zero-point energies of supported nanoclusters. However, limitations also exist. We find that many MLIPs catastrophically fail when applied to
magnetic materials, and structure relaxation in the MLIP generally increases the energy prediction error compared to single-point evaluation of a previously optimized structure. Comparing low-cost task-specific models to foundational MLIPs, we highlight some core differences between these model approaches and show that – if considering only accuracy – these models can compete with the current generation of best-performing MLIPs. Furthermore, we show that no single MLIP universally performs best, requiring users to investigate MLIP suitability for their desired application.
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Applied Physics
Fabrication Optimization of Suspended Stencil Mask Lithography for Multi-Terminal Josephson Junctions
Justus Teller, Abdur Rehman Jalil, Florian Lentz et al. (+2 more)
Stencil mask lithography is an advanced technique for fully in-situ fabricating Josephson junctions, which is increasingly being used for multi-terminal Josephson junctions. This study provides information on the optimal mask design and mask reliability. For this, 270 mask designs were systematically fabricated and investigated under scanning electron microscope. Reliable statements are made about mask yield, minimal dimensions, and systematic dependencies on the number of superconducting terminals. We find that stencil mask lithography can be used reliably for fabricating multi-terminal Josephson junctions, enabling lateral mask dimensions down to 40$\,$nm on average.
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All authors Justus Teller, Abdur Rehman Jalil, Florian Lentz, Detlev Grützmacher, Thomas Schäpers
Plasma Physics
CARONTE: a Physics-Informed Extreme Learning Machine-Based Algorithm for Plasma Boundary Reconstruction in Magnetically Confined Fusion Devices
Federico Fiorenza, Sara Dubbioso, Gianmaria De Tommasi et al. (+1 more)
In this work, we propose a novel physics informed neural network based
algorithm for real time
plasma boundary reconstruction in tokamak devices. The approach is based on a single Extreme Learning Machine network used to solve the homogeneous Grad Shafranov equation, which is required to identify the
plasma boundary. This architecture enables the real time training of the network parameters using the available
magnetic sensor data and, consequently, dynamically adapting the network output to the evolving
plasma equilibrium. We demonstrate that, the network performs accurate
plasma boundary reconstruction for complex configurations, outperforming well established methods, such as the
algorithm used for decades at the Joint European
Torus, the world's largest tokamak, until it ceased operation in 2023. Indeed, compared to the latter, the proposed solution better generalizes the poloidal flux function, without requiring
algorithm retuning across different
plasma equilibria. The proposed neural network reconstructor demonstrates also greater robustness with respect to noise on the
magnetic measurements. Moreover, this method takes advantage of the generalization power of neural networks but without the need for extensive, time consuming training based on a huge amount of experimental data, making its implementation on existing devices straightforward.
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All authors Federico Fiorenza, Sara Dubbioso, Gianmaria De Tommasi, Alfredo Pironti
Chemical Physics
QMCkl: A Kernel Library for Quantum Monte Carlo Applications
Emiel Slootman, Vijay Gopal Chilkuri, Aurelien Delval et al. (+16 more)
Quantum Monte Carlo (QMC) methods deliver highly accurate electronic structure calculations but are computationally intensive. The
quantum Monte Carlo kernel library (QMCkl) provides a modular, portable collection of high-performance kernels implementing the core building blocks of QMC calculations. It offers a C-compatible API, supports the TREXIO standard for input, and covers essential QMC kernels including atomic and molecular orbitals, cusp corrections, Jastrow factor, and the necessary derivatives also to perform variational and structural optimization. QMCkl separates algorithmic development from hardware-specific tuning by combining human-readable reference implementations with performance-optimized kernels that produce identical numerical results. The library enables consistent, efficient, and reproducible simulations across different QMC codes and architectures, and achieves substantial speedups in the evaluation of the energy and its derivatives. Beyond QMC, QMCkl can accelerate deterministic
quantum chemistry workflows and visualization tools, promoting cross-code interoperability and simplifying high-performance scientific software development.
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All authors Emiel Slootman, Vijay Gopal Chilkuri, Aurelien Delval, Max Hoffer, Tommaso Gorni, François Coppens, Joris van de Nes, Ramón L. Panadés-Barrueta, Evgeny Posenitskiy, Abdallah Ammar, Edgar Josué Landinez Borda, Kevin Camus, Oto Kohulàk, Emmanuel Giner, Pablo de Oliveira Castro, Cedric Valensi, William Jalby, Claudia Filippi, Anthony Scemama
Applied Physics
Acoustic scattering singularities via quasi-Bound states in the continuum
Anis Maddi, Mourad Oudich, Aurelien Merkel et al. (+2 more)
Non-Hermitian systems enable advanced control of wave propagation by exploiting engineered losses. This introduces an additional degree of freedom that permits the emergence of exceptional points (EPs). In this letter, we theoretically and experimentally demonstrate the control of scattering singularities in a non-Hermitian acoustic system using quasibound states in the continuum (qBICs). Through Friedrich Wintgen interference, the losses of a two port cavity are tuned until achieving critical coupling, yielding narrowband coherent perfect absorption (CPA) with a quality factor of 140. Additionally, by coupling two distinct resonators, we observe the emergence of an EP, where both
eigenvalues simultaneously coalesce and vanish, resulting in narrowband unidirectional absorption. Our results establish a connection between qBICs and scattering singularities, and offer a route toward acoustic devices featuring narrowband resonances and tunable radiative losses.
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All authors Anis Maddi, Mourad Oudich, Aurelien Merkel, Julio A. Iglesias Martínez, Badreddine Assouar
Geophysics
Self-Affine Scaling of Earth's Islands
Matthew Oline, Jeremy Hoskins, David Seekell et al. (+2 more)
Earth's relief is approximately self-affine, meaning a zoom-in on a small region looks statistically similar to a large region upon rescaling. Fractional Brownian surfaces give an idealized self-affine model of Earth's relief with one parameter, the Hurst exponent $H$, characterizing the roughness of the surface. We compile a large
dataset of topographic profiles of islands (N=131,063 with the range of areas covering 8+ orders of magnitude) and obtain four estimates for the Hurst exponent of Earth's surface by fitting four statistical laws from the theory of self-affine surfaces concerning islands: (i) distribution of areas, (ii) volume-area relationship, (iii) perimeter-area relationship, and (iv) maximum height-area relationship. The estimated Hurst exponents indicate different fractal scaling behavior for different
geometric features, and are sorted in order of increasing expected influence of coastal processes. This sheds light on the impact of coastal erosion and sedimentation on island geomorphology.
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All authors Matthew Oline, Jeremy Hoskins, David Seekell, Mary Silber, B.B. Cael
Optics · Cross-listed from quant-ph
Non-markovian reservoir profile effects on dynamics of light within a single waveguide
J. R. Silva and C. Antunis B. S. Santos
In this work, we investigate how different reservoir
memory profiles influence the dynamical
evolution of a single waveguide coupled to an external environment. We compare three representative
memory kernels: Lorentzian, Gaussian and Uniform, highlighting their distinct spatial correlations and their impact on system behavior. We compute the transmission amplitude, transparency properties, as well as long-time behavior of the system under each
memory model. To quantify deviations from Markovian dynamics, we employ a non-Markovianity measure based on information backflow, allowing a direct comparison between the structured reservoirs and the Markovian limit. Our results reveal clear signatures of memoryless-induced modifications in the transmission spectrum and demonstrate how specific reservoir profiles enhance or suppress non-Markovian effects.
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Optics
Subspace tracking: a novel measurement method to test the standard phase noise model of optical frequency combs
Darko Zibar, Holger Heebøll, Jasper Riebesehl et al. (+3 more)
The introduction of digital signal processing (DSP) assisted coherent detection has been a cornerstone of modern fiber-optic communication systems. The ability to digitally, i.e. after analogue-to-digital converter, compensate for chromatic dispersion, polarization mode dispersion, and phase noise has rendered traditional analog feedback loops largely obsolete. While analog techniques remain prevalent for phase noise characterization of single-frequency
lasers, the phase noise characterization of optical frequency combs presents a greater challenge. This complexity arises from different number of phase noise sources affecting an optical frequency comb. Here, we show how a phase noise measurement techniques method based on multi-heterodyne coherent detection and DSP-based subspace tracking can be used to identify, measure and quantify various phase noise sources associated with an optical frequency comb.
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All authors Darko Zibar, Holger Heebøll, Jasper Riebesehl, Michael Galili, Francesco Da Ros, Aleksandr Razumov
Instrumentation and Detectors
Temperature dependence of the long-term annealing behavior of neutron irradiated diodes from 8-inch p-type silicon wafers
Leena Diehl, Oliwia Kaluzinska, Marie Mühlnikel et al. (+7 more)
To face the higher levels of radiation due to the 10-fold increase in integrated luminosity during the High-Luminosity LHC, the CMS detector will replace the current Calorimeter Endcap (CE) using the High-Granularity Calorimeter (HGCAL) concept. The high-radiation regions of the the CE, where fluences between $1\cdot10^{14}~n_{eq}/cm^{2}$ and $1\cdot10^{16}~n_{eq}/cm^{2}$ and doses of up to 2\,MGy are expected considering an integrated luminosity of $3\,ab^{-1}$, will be equipped with silicon pad sensors. This includes the entire electromagnetic as well as parts of the hadronic section of the CE. The silicon sensors are processed on 8-inch p-type wafers with an active thickness of 300\,\textmu m, 200\,\textmu m and 120\,\textmu m and cut into hexagonal shapes for optimal use of the full wafer area and tiling. With each main sensor, several small test structures (e.g. pad diodes) are hosted on the wafers, used for quality assurance and radiation hardness tests. In order to investigate the radiation-induced bulk damage, these diodes have been irradiated with reactor
neutrons at JSI (Jozef Stefan Institute, Ljubljana, Slovenia) to fluences between $5\cdot10^{14}~n_{eq}/cm^{2}$ and $1.5\cdot10^{16}~n_{eq}/cm^{2}$. This study focuses on the isothermal annealing behavior of the bulk material at different temperatures between 5.5{\deg}C and 60{\deg}C using electrical characterization and charge collection measurements. The results are used to extract the annealing time constants for this material and fluence range based on the Hamburg model approach to allow an estimation of the expected annealing effects in silicon sensors during the year-end technical stops and the long HL-LHC shutdowns. The annealing parameters found will make it possible to model the annealing behavior of p-type silicon detector projects at HL-LHC fluence ranges better than the existing Hamburg model.
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All authors Leena Diehl, Oliwia Kaluzinska, Marie Mühlnikel, Max Andersson, Natalya Gerassyova, Jenan Amer, Eva Sicking, Dana Groner, Jan Kieseler, Matteo Defranchis
Geophysics
Direct inversion of data-space Hessian for efficient time-domain extended-source waveform inversion using the multiplier method
Mahdi Sonbolestan and Ali Gholami
The augmented Lagrangian (AL) method has been successfully applied for solving the full waveform inversion (FWI) problem. In AL-based FWI, the Lagrange multipliers serve as source extensions, offering several advantages to the inversion, such as improved robustness to cycle skipping, faster convergence, and simplified penalty parameter tuning. Time-domain applications of this method have been enabled by reformulating the optimization problem in the data space, significantly reducing
memory requirements by projecting source-side multipliers into the data space. These data-side multipliers act as data extensions, effectively expanding the data space. A key challenge in these methods lies in computing the data-side multipliers, which involves solving a linear system to deblur the data residuals using the data-space Hessian
matrix before it serves as the adjoint source. This Hessian
matrix is prohibitively large to construct and invert explicitly. Iterative Krylov methods can be applied to solve this system as inner iterations, but they require two PDE solves per inner iteration per source, leading to significant computational costs. In this work, we present a key improvement to extended waveform inversion based on multiplier methods. We propose a novel approach that significantly reduces the computational cost of Hessian inversion. The method computes receiver-side Green functions in the time domain and directly constructs frequency-domain Hessian
matrices for all required frequencies. These Hessian
matrices, with dimensions equal to the number of receivers, can be computed, inverted, and stored in
memory. Once constructed, they can be used simultaneously for all sources, further enhancing efficiency. Numerical experiments demonstrate the substantial computational gains achieved by the proposed method, highlighting its effectiveness for extended-source FWI in the time domain.
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Optics · Cross-listed from cond-mat.mes-hall
Wigner polarons reveal Wigner crystal dynamics in a monolayer semiconductor
Lifu Zhang, Liuxin Gu, Haydn S. Adlong et al. (+12 more)
Wigner
crystals,
lattices made purely of electrons, are a quintessential paradigm of studying correlation-driven
quantum phase transitions. Despite decades of research, the internal dynamics of Wigner
crystals has remained extremely challenging to access, with most experiments probing only static order or collective motion. Here, we establish monolayer WSe2 as a new materials platform to host zero-field Wigner
crystals and then demonstrate that
exciton spectroscopy provides a direct means to probe both static and dynamic properties of these electron
lattices. We uncover striking optical resonances that we identify as Wigner polarons, quasiparticles formed when the electron
lattice is locally distorted by
exciton-Wigner
crystal coupling. We further achieve all-optical control of
spins in the Wigner
crystal, directly probing valley-dependent Wigner polaron scattering well above the
magnetic ordering temperature and in the absence of any external
magnetic field. Finally, we demonstrate optical melting of the Wigner
crystal and observe intriguingly different responses of the umklapp (static) and Wigner polaron (dynamic) resonances to optical excitation. Our results open up exciting new avenues for elucidating electron dynamics and achieving ultrafast optical control of interaction-driven
quantum phase transitions in strongly correlated electron systems.
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All authors Lifu Zhang, Liuxin Gu, Haydn S. Adlong, Arthur Christianen, Eugen Dizer, Ruihao Ni, Rundong Ma, Suji Park, Houk Jang, Takashi Taniguchi, Kenji Watanabe, Ilya Esterlis, Richard Schmidt, Atac Imamoglu, You Zhou
Plasma Physics
Photon Accelerator in Magnetized Electron-Ion Plasma
Sergei Bulanov, Stepan Bulanov, Timur Esirkepov et al. (+6 more)
Strong
magnetic fields and
plasmas are intrinsically linked in both terrestrial laboratory experiments and in space phenomena. One of the most profound consequences of that is the change in relationship between the frequency and the wave number of electromagnetic waves propagating in
plasma in the presence of such
magnetic fields when compared to the case without these fields. Furthermore,
magnetic fields alter electromagnetic wave interaction with relativistic
plasma waves, resulting in different outcomes for particle and radiation generation. For a relativistic
plasma wave-based
photon acceleration this leads to an increased frequency gain, and, thus, potentially to higher efficiency. The influence of a
magnetic field leads to quantitative and qualitative change in the properties of
photon acceleration, amplifying the increase in the electromagnetic wave frequency.
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All authors Sergei Bulanov, Stepan Bulanov, Timur Esirkepov, Gianluca Gregori, Gabriele Grittani, Marcel Lamač, Brandon Russell, Alec Thomas, Petr Valenta
Applied Physics · Cross-listed from cond-mat.mes-hall
Controlling Spin-Waves by Inhomogeneous Spin-Transfer Torques
Lorenzo Gnoatto, Jean F. O. da Silva, Artim L. Bassant et al. (+4 more)
We investigate the interplay between
spin currents and
spin waves in nanofabricated Permalloy waveguides with geometrical constrictions. Using propagating
spin-wave spectroscopy, micromagnetic simulations, and analytical modeling, we provide experimental evidence that
spin-wave phase can be modulated by inhomogeneous
spin-transfer torques generated by current-density gradients shaped by the constriction geometry. Narrower constrictions enhance these gradients and modify the internal field for Damon-Eshbach
spin waves, resulting in pronounced changes in
spin-wave group velocity and phase. To our knowledge, this constitutes the first demonstration of deterministic phase modulation via engineered nonuniform
spin-transfer torques. Beyond enabling a scalable route to magnonic interferometry - a building block for
spin-wave-based computing - our findings establish a platform to control
spin-wave dynamics in spatially varying current landscapes, relevant for analogue-
gravity experiments in condensed matter systems.
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All authors Lorenzo Gnoatto, Jean F. O. da Silva, Artim L. Bassant, Rai M. Menezes, Rembert A. Duine, Milorad V. Milossevic, Reinoud Lavrijsen
Applied Physics
Hypervelocity Impact Debris Cloud Trajectory-Planning based on Additive Manufactured Lattice Structures
Bilin Zheng, Xiao Kang, Xiaoyu Zhang et al. (+3 more)
Space debris and micrometeoroid (MMOD) impacts pose a serious threat to the safe operation of spacecraft. However, traditional protective structures typically suffer from limitations such as excessive thickness and inadequate load-bearing capacity. Guided by the design concepts of debris-cloud deflection and hierarchical energy dissipation, this study proposes a trajectory-planning
lattice protective structure. First, the
lattice parameters and geometry were designed according to the functional relationship between the incident angle and the transmitted/ricochet trajectory angles. Subsequently, multi-angle hypervelocity impact experiments were carried out to evaluate the proposed
lattice protection structure. In combination with post-impact CT three-dimensional reconstruction and smoothed particle hydrodynamics (SPH) numerical simulations, the protective mechanisms of the
lattice structure were systematically characterized and clarified. The results demonstrate that, for three oblique incidence conditions, the
lattice structure remained intact and significantly deflected the debris-cloud momentum direction while effectively dissipating its kinetic energy. The angled plates with gradient designs enabled continuous changes in the momentum direction and stepwise kinetic energy dissipation through multiple cycles of debrisation, dispersion, and trajectory deflection. This research presents a novel, engineering-ready approach for spacecraft MMOD protection and validates the potential of trajectory-planning
lattice structures for hypervelocity impact defense.
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All authors Bilin Zheng, Xiao Kang, Xiaoyu Zhang, Hao Zhou, Mengchuan Xu, Chang Liu
Space Physics
Angular dependence of third-order law in anisotropic MHD turbulence
Bin Jiang, Zhuoran Gao, Yan Yang et al. (+6 more)
In
solar wind
turbulence, the energy transfer/dissipation rate is typically estimated using MHD third-order structure functions calculated using spacecraft observations. However, the inherent anisotropy of
solar wind
turbulence leads to significant variations in structure functions along different observational directions, thereby affecting the accuracy of energy-dissipation rate estimation. An unresolved issue is how to optimise the selection of observation angles under limited directional sampling to improve estimation precision. We conduct a series of MHD
turbulence simulations with different mean
magnetic field strengths, $ B_0 $. Our analysis of the third-order structure functions reveals that the global energy dissipation rate estimated around a polar angle of $ \theta = 60^\circ$ agrees reasonably with the exact one for $ 0 \le B_0/b_{rms} \le 5 $, where $b_{rms}$ denotes the root-mean-square
magnetic field fluctuation. The speciality of $60^\circ$ polar angle can be understood by the Mean Value
Theorem of Integrals, since the spherical integral of the polar-angle component ($\widetilde{T_\theta}$) of the divergence of Yaglom flux is zero, and $\widetilde{T_\theta}$ changes sign around 60$^\circ$. Existing theory on the energy flux vector as a function of the polar angle is assessed, and supports the speciality of $60^\circ$ polar angle. The angular dependence of the third-order structure functions is further assessed with virtual spacecraft data analysis. The present results can be applied to measure the turbulent dissipation rates of energy in the
solar wind, which are of potential importance to other areas in which
turbulence takes place, such as laboratory
plasmas and astrophysics.
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All authors Bin Jiang, Zhuoran Gao, Yan Yang, Francesco Pecora, Kai Gao, Cheng Li, Sean Oughton, William Matthaeus, Minping Wan
Physics and Society
Resilience of coupled systems under deep uncertainty and dynamic complexity: An integrative literature review
Jannie Coenen, Vítor Vasconcelos, Heiman Wertheim et al. (+8 more)
Resilience in coupled systems is increasingly critical in addressing global challenges such as
climate change and pandemics. These systems show unpredictable behaviour due to dynamic complexity and deep uncertainty across spatiotemporal scales. Despite growing interest, few studies systematically integrate both concepts when assessing resilience. This paper conducts an integrative review of 102 English-
language publications to identify gaps in current approaches. Findings reveal that most papers address lower levels of uncertainty and rarely consider dynamic complexity and deep uncertainty simultaneously, which limits the effectiveness of resilience strategies. To advance systems research, we propose a conceptual framework and practical tools to support researchers and decision-makers in evaluating and improving resilience. The paper also outlines future research directions for more robust, adaptive, and integrative resilience assessments.
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All authors Jannie Coenen, Vítor Vasconcelos, Heiman Wertheim, Marcel Olde Rikkert, Sophie Hadjisotiriou, Vittorio Nespeca, Tom Oreel, Rick Quax, Etiënne Rouwette, Vincent Marchau, Hubert Korzilius
Computational Physics · Cross-listed from stat.ML
Boltzmann generators for amorphous particle systems
Louis Grenioux, Leonardo Galliano, Ludovic Berthier et al. (+2 more)
Sampling configurations in thermodynamic
equilibrium is a long-standing challenge in statistical physics. Boltzmann generators address this problem by employing generative models to propose independent configurations, which are then reweighted via importance sampling using exact likelihood evaluations. Recent Boltzmann Generators based on continuous normalizing flows and flow matching have achieved significant success for particle systems and biomolecules. However, these approaches have not been extended to amorphous materials (glasses), for which
equilibrium sampling is notoriously slow. Because of their disordered structure, the invariances and geometrical constraints of amorphous materials differ from those of
crystals and biomolecules, preventing the direct use of existing generative models. Here, we develop Boltzmann Generators tailored to amorphous materials by building the required equivariances directly into Riemannian
stochastic interpolants. Our framework incorporates periodic boundary conditions and particle
symmetries using equivariant graph neural networks. Numerical experiments demonstrate that enforcing physical
symmetries significantly improves the accuracy of Boltzmann Generators, but also reveal an intrinsic limitation of the continuous-flow formulation: accumulated numerical errors during likelihood integration break time-reversibility, compromising exact thermodynamic reweighting. These results reveal a fundamental challenge for continuous-flow generative models in statistical mechanics and call for alternative approaches that preserve exact thermodynamic consistency.
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All authors Louis Grenioux, Leonardo Galliano, Ludovic Berthier, Giulio Biroli, Marylou Gabrié
Plasma Physics
Disruption Modelling for Engineering and Physics Design of Tokamak Energy ST-E1 Fusion Power Plant
M. Scarpari, X. Zhang, K. Borowiec et al. (+14 more)
Plasma disruptions represent a critical challenge for high-performance tokamak operations, as they can compromise machine integrity and reduce operational availability. Although future fusion devices essentially need to incorporate strategies to minimise disruption occurrence, complete avoidance remains unattainable. Consequently, assessing and characterising unmitigated disruption consequences is fundamental for the design and qualification of next-generation fusion power plants. This work supports the pre-conceptual design of ST-E1, a low aspect-ratio Tokamak Fusion Power Plant developed by Tokamak Energy Ltd., by presenting a comprehensive disruption modelling approach applied across different design stages. The methodology integrates both physics and engineering considerations to evaluate the impact of disruptions on machine performance and structural integrity. From an engineering perspective, several ST-E1 layout options were analysed to investigate the electromagnetic response of key components under disruption-induced loads, enabling comparison between alternative design solutions. On the physics side, a broad set of disruption scenarios was explored, scanning operational space parameters,
plasma-material interactions, and associated thermal loads. Furthermore, the study examined variations in disruption behaviour arising from different reference
equilibria, focusing on a range starting from Double Null to Single Null configurations, reflecting the increasing up-down asymmetry consequences. The results reveal significant contrasts in
plasma dynamics and structures electromagnetic behaviour between configurations, highlighting the importance of disruption modelling in guiding design choices. These analyses have proven instrumental in shaping ST-E1 development, offering critical insights for mitigating risks and optimising future fusion reactor designs.
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All authors M. Scarpari, X. Zhang, K. Borowiec, P. F. Buxton, G. Calabro, S. Carusotti, A. Ciula, V. Godhani, J. D. Lore, E. N. J. Maartensson, S. A. M. McNamara, J. H. Nichols, M. Notazio, M. Robinson, M. Romanelli, J. Willis, ST-E1 Team
Atomic Physics
Self-consistent bounds on Beyond the Standard Model bosons from spectroscopy of muonic atoms with magic nuclei
K. A. Beyer and N. S. Oreshkina
Spectroscopy of muonic atoms is, to date, the most accurate technique to extract parameters of the
nuclear charge density. The same reasons for their heightened sensitivity to
nuclear parameters, a large overlap of the muonic wavefunction with the
nucleus, makes them attractive systems to test Beyond the Standard Model (BSM) Physics. This raises concerns of self-consistency as the same data are used to, first, extract
nuclear parameters, and second, check the consistency with BSM models. We combine the two steps and self-consistently extract the
nuclear and BSM parameters. We show that the data are consistent with vanishing BSM coupling and extract robust exclusion bounds. We further note that the
nuclear parameters change under the influence of those BSM couplings on the parameter fits and compare with the fit solely based on
quantum electrodynamics (QED).
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Optics
Octave-spanning, deterministic single soliton generation in 4H-silicon carbide-on-insulator microring resonators
Yi Zheng, Liping Zhou, Chengli Wang et al. (+5 more)
The miniaturization of self-referencing frequency comb systems enables emerging applications in metrology and spectroscopy. One major challenge in realizing the chip-scale self-referencing function is to generate octave-spanning
soliton microcombs with low operation power. Accessing
soliton states is also not trivial due to the thermal effect. Though an auxiliary
laser was utilized to compensate for the thermal effect, deterministic single
soliton generation is still elusive, especially for broadband operation. In this work, dispersion management is performed for a 4H-silicon carbide-on-
insulator (SiCOI) multi-mode microring resonator, benefiting from the submicron-confinement waveguide layout. The fundamental transverse electric (TE) mode is engineered to anomalous dispersion for two dispersive waves generation over an octave span. While a higher order TE mode is engineered to normal dispersion to accommodate the auxiliary light for thermal compensation. The normal dispersion prevents modulation-instability Kerr comb generation, allowing for a large
soliton existence range. We achieve microring resonators with Q up to 5.8 million and sub-milli-watt-threshold Kerr comb generation. Combining the dispersion-managed design and high Q device, we demonstrate the deterministic generation of a single
soliton comb spanning beyond an octave with a low on-chip power of 60 mW. Our demonstration paves the way to realize chip-scale, turn-key, self-referenced frequency combs.
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All authors Yi Zheng, Liping Zhou, Chengli Wang, Yanjing Zhao, Ailun Yi, Kresten Yvind, Xin Ou, Minhao Pu
Applied Physics · Cross-listed from cond-mat.mes-hall
Current-Induced Modulation of Spin-Wave Propagation in a Y-Junction via Transverse Spin-Transfer Torque
Lorenzo Gnoatto, Rai M. Menezes, Artim L. Bassant et al. (+3 more)
We report the transverse control of
spin-wave propagation in the configuration where the
spin-wave wavevector k is perpendicular to the charge-current density J. Building on theoretical predictions of
spin-wave refraction by nonuniform
spin-polarized currents, and guided by micromagnetic simulations used to optimize the device geometry and current distribution, we experimentally explore a Y-shaped Permalloy structure in which a locally injected current perturbs the
spin-wave dispersion. Measurements reveal current-dependent amplitude differences between the two output branches, providing initial experimental indications consistent with transverse,
spin-transfer-torque-driven deflection. Although the magnitude of the effect is modest and accompanied by significant uncertainties, the observed trends qualitatively follow expectations from the simulations. These results demonstrate the feasibility of influencing
spin-wave routing through local current injection and establish a proof-of-concept basis for current-controlled manipulation of
spin-wave propagation in reconfigurable magnonic
circuits.
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All authors Lorenzo Gnoatto, Rai M. Menezes, Artim L. Bassant, Rembert A. Duine, Milorad V. Milosevic, Reinoud Lavrijsen
Atomic and Molecular Clusters
Decoding Molecular Geometries in Coulomb Explosion Imaging via Physics-Informed Deep Neural Network
Xingyu Guo, Enliang Wang, Wenguang Wu et al. (+8 more)
Determining the absolute configuration of gas-phase molecules in position-space has long been a fundamental challenge in molecular physics. While strong-field-induced Coulomb explosion imaging (CEI) has emerged as a powerful tool for probing molecular stereochemistry in momentum-space, reconstructing the original three-dimensional structure of polyatomic molecules remains a long-standing challenge due to the inherent complexity of multidimensional inversion. Here, we introduce a deep learning framework that bridges this gap by directly recovering position-space molecular structures from Coulomb explosion momentum patterns. Our approach combines CEI simulations with a neural network trained to establish the mapping between momentum-space Newton plots and real-space geometries. The trained model demonstrates high fidelity in reconstructing the structure of CHF$_3$ from experimental CEI data. This generalizable framework can not only be extended to other molecular systems but also opens avenues for time-resolved structural analysis of molecular dynamics.
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All authors Xingyu Guo, Enliang Wang, Wenguang Wu, Zhaopeng Xing, Tuo Liu, Chunkai Xu, Xu Shan, Artem Rudenko, Daniel Rolles, Jing Chen, Xiangjun Chen
Plasma Physics
SCOPE: Simple Coil Optimization for Plasma and Engineering
Nathan Welch and Chris Marsden
Designing superconducting coils for a tokamak fusion device is a highly coupled, non-linear design problem. The coils have many disparate engineering requirements from structural to power electronics, as well strict limits placed on the system by the high temperature superconducting (HTS) cables. Simultaneously, the coils must be able to contain multiple
plasma scenarios from inception, through ramp up, to flat top, and ramp down, all whilst applying a large, controlled, inductive voltage to drive current. In addition, we wish to optimize divertor separatrices to increase the likelihood of designing a suitable divertor strikepoint. Lastly, the physical limits of the entire tokamak must be taken into account and space reserved for support structures, access for maintenance schemes, and installation limits. The method outlined here uses a combined simulated annealing method to find optimal coil sizes and positions with a constrained quadratic or quartic optimization for the coil currents. The method is designed to optimize coils for multiple scenarios simultaneously, including ramp-ups, to avoid over optimization of a single design point. A key enabler is the efficient implementation that allows millions of evaluations to be performed in a few hours with modest computational power. This optimization method is part of a larger, iterative workflow which enables further, detailed design work to feedback on the optimization.
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Optics
Spatiotemporal topological phase transitions in photonic spacetime crystals
Zebin Zhu, Bolun Huang, Siqi Xu et al. (+5 more)
Topological phase transitions have played a central role in topological physics. However, such transitions have so far been restricted to spatial or temporal
crystals. Here, we transcend this conventional framework and report, for the first time, spatiotemporal topological phase transitions in photonic spacetime
crystals - structures that are periodically modulated in both space and time. In a genuine photonic spacetime
crystal composed of a dynamically modulated transmission-line metamaterial, we theoretically propose and experimentally demonstrate complete spatiotemporal topological phase transitions, characterized by the closing and reopening of both energy and momentum band gaps, along with changes in spatiotemporal topological invariants and topological phases. Furthermore, we directly observe a spatiotemporal, topologically localized state that exhibits causality-governed excitation and robustness to spatiotemporal disorders. Our findings reveal the interplay among space, time, and
topology, establishing a unified framework that provides a comprehensive picture of the emerging topological spacetime physics and opening new avenues for robust spatiotemporal topological wave manipulations.
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All authors Zebin Zhu, Bolun Huang, Siqi Xu, Jingming Chen, Yan Meng, Zhenxiao Zhu, Xiang Xi, Zhen Gao
Medical Physics
Endorsing Titanium-Scandium Radionuclide Generator for PET and Positronium Imaging
Paweł Moskal, Aleksander Khreptak, Jarosław Choiński et al. (+7 more)
The development of PET and positronium imaging techniques is strictly related to the availability of suitable radionuclides and robust radiochemistry platforms. Among the emerging candidates, $^{44}$Sc has attracted significant interest due to its favourable physical properties, including a half-life of $\sim$4 hours, a pure $\beta^{+}$ emission profile, and the additional
prompt $\gamma$-emission that enables advanced triple-
photon detection schemes. These characteristics make $^{44}$Sc particularly promising for highresolution imaging and novel quantitative methodologies. However, routine clinical and preclinical implementation requires a practical, sustainable, and cost-efficient production route. In this context, we propose a titanium-scandium radionuclide generator as an optimal solution. This study focuses on optimising the synthesis of the long-lived parent isotope, $^{44}$Ti ($T_{1/2}$ = 59.1 years), from which $^{44}$Sc can be selectively eluted in a chemically pure form when needed. An analysis of various production pathways was conducted, including
proton and deuteron reactions on scandium, as well as $\alpha$-particle and lithium-induced reactions on calcium, to determine the most efficient reaction parameters, target design, and expected yield. Furthermore, we identify some existing cyclotron facilities suitable for implementing this technology. Results indicate that efficient $^{44}$Ti production is achievable using
proton beams in the 20-30 MeV range under extended irradiation conditions. The proposed generator system would enable routine and decentralised $^{44}$Sc supply. Its integration with the novel J-PET scanner may significantly reduce diagnostic costs and improve access to advanced PET imaging in regions with limited medical imaging infrastructure.
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All authors Paweł Moskal, Aleksander Khreptak, Jarosław Choiński, Pete Jones, Ihor Kadenko, Agnieszka Majkowska-Pilip, Rudrajyoti Palit, Anna Stolarz, Rafał Walczak, Ewa Stępień
Fluid Dynamics · Cross-listed from gr-qc
Cosmology with non-linear barotropic Israel-Stewart fluid with causal relaxation time
Vishnu A Pai and Titus K Mathew
We derive an extended expression for the relaxation time of a barotropic Israel-Stewart (IS) fluid using the non-linear causality constraint, and propose a new formulation for modeling causal viscous dissipation in barotropic fluids. With this generalized relaxation time, the non-linear IS equation simplifies to a first-order non-linear expression connecting bulk viscous pressure and energy density, which remains valid in any homogeneous and isotropic spacetime. In the case of spatially flat Friedmann universe, adopting this extended relation in the generalized non-linear IS theory, provides new class of analytical solutions in both, the linear, and the non-linear regimes. We also find that, the resulting effective equation of state in the linear regime naturally reproduces the generalized polytropic form which is often introduced phenomenologically in literature. Resulting dynamical implications are investigated and the constraints necessary for ensuring an acceptable evolutionary behavior for the fluid are determined. A detailed dynamical system analysis of the coupled Einstein-Israel-Stewart (EIS) system is also performed. Finally, we solve the coupled EIS equations numerically, and show that the model can support a transient Hubble slow-roll expansion phase with a smooth exit to a radiation-dominated universe, which is challenging to obtain in standard inflationary models.
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