Optics
Geometrical optical activity induced by a continuous distribution of screw dislocations
Humberto Belich and Edilberto O. Silva
We study light propagation in a medium with uniform torsion, modeled as a continuum of screw dislocations within the
geometric theory of defects. By solving Maxwell's equations in covariant form, we show that torsion induces intrinsic chirality and circular birefringence: right- and left-circular polarizations acquire different wavenumbers, leading to a purely
geometric optical activity. The polarization plane of a linearly polarized beam rotates according to the simple law $\Delta\theta = \Omega\rho L$, linear in the dislocation density $\Omega$, propagation length $L$, and transverse coordinate $\rho$. This can be recast as an effective birefringence $\Delta n = 2c\Omega\rho/\omega$, providing
geometric design rules for torsion-induced rotatory power. Using parameters from dislocated
semiconductors, we obtain millidegree rotations over millimetre-scale paths, within reach of modern polarimetric techniques and amenable to enhancement in metamaterial platforms. We also show that the same spiral geometry implements a broadband
geometric phase gate for polarization
qubits and has an electronic analogue on the surface of cylindrical topological
insulators, where torsion shears the Dirac cone, establishing a unified
geometric link between torsion, optical activity, and topological electronic responses.
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Instrumentation and Detectors
A Neutron Microscope Using a Nested Wolter-I Condenser and a Bank of Diffractive-Refractive Achromatic Objectives
Henning Friis Poulsen, Cæcilie Andersen, Nolan Ravinet et al. (+10 more)
We propose a nested Wolter-I mirror design for a
neutron condenser, which is based on established X-ray
telescope technology. We demonstrate through simulations that it can increase the flux density at the ESS imaging instrument ODIN by up to two orders of magnitude. Experimental measurements of reflectivity and figure errors on a prototype mirror element confirm the technical feasibility of the approach. Then, we discuss design strategies for an imaging objective to fully exploit the condenser specifications while achieving spatial resolutions comparable to those of X-ray micro-CT instruments. Analytically, we show that for monochromatic beams suitable solutions exist employing arrays of hundreds of identical objectives, realized either as compound refractive lenses (CRLs) or Fresnel zone plates (FZPs). To mitigate the inherent chromatic aberration of these optics, each individual objective could be replaced by an achromatic FZP/CRL combination. Key optical properties of the resulting microscope are estimated. This novel full-field microscopy concept for highly divergent, polychromatic
neutron beams has the potential to improve temporal and spatial resolution for large samples and sample environments and to enable the simultaneous acquisition of hundreds of projections in
neutron tomography.
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All authors Henning Friis Poulsen, Cæcilie Andersen, Nolan Ravinet, Joan Vila-Comamala, Mano Raj Dhanalakshmi Veeraraj, Erik Bergbäck Knudsen, Peter Kjær Willendrup, Sonny Massahi, Finn Erland Christensen, Desiree Della Monica Ferreira, Markus Strobl, Christian David, Luise Theil Kuhn
Applied Physics
Supercritical Snapping and Controlled Launching via Dual Latch Gels
Xiaona M. Xu, Nolan A. Miller, Gregory M. Grason et al. (+1 more)
Natural organisms have evolved integrated Latch-Mediated Spring Actuation systems (LaMSA) that consist of multiple latches and springs to enhance power output and adapt to diverse environmental conditions. Similar designs are appealing yet largely unexplored in engineered materials due to the complexity of integrating multiple components into a single material platform. Here, we report a dual-latched magneto-elastic shell device capable of selectively activating the latches to regulate snapping pathways and energy output based on specific actuation requirements. Differential deswelling across the thickness acts as the motor to load the elastic energy into the shell, which is then released via the snap-through instability once the loading reaches the critical threshold, constituting an intrinsic mechanical latch. Activation of the external
magnetic latch delays snapping onset beyond the threshold of the intrinsic latch, leading to a power-amplified supercritical snap-through instability as well as a bifurcation instability. The combined function of both latches allows for flexible control over energy storage and release. Additionally, this integrated LaMSA system possesses an untethered anchoring mechanism, enabling the device to launch in arbitrary directions from the substrate, driven by the energy released during snapping. We envision that the design principles of dual-latched LaMSA systems will create opportunities for power-dense actuation in engineered materials and robotic devices.
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All authors Xiaona M. Xu, Nolan A. Miller, Gregory M. Grason, Alfred J. Crosby
Chemical Physics
Chemically decisive benchmarks on the path to quantum utility
Srivathsan Poyyapakkam Sundar, Vibin Abraham, Bo Peng et al. (+1 more)
Progress towards
quantum utility in chemistry requires not only algorithmic advances, but also the identification of chemically meaningful problems whose electronic structure fundamentally challenges classical methods. Here, we introduce a curated hierarchy of chemically decisive
benchmark systems designed to probe distinct regimes of electronic correlation relevant to molecular, bioinorganic, and heavy-element chemistry. Moving beyond minimal toy models, our
benchmark set spans multireference bond breaking (N$_2$), high-
spin transition-metal chemistry (FeS), biologically relevant iron-sulfur clusters ([2Fe-2S]), and actinide-actinide bonding (U$_2$), which exhibits extreme sensitivity to active-space choice, relativistic treatment, and correlation hierarchy even within advanced multireference frameworks. As a concrete realization, we
benchmark a recently developed automated and adaptive
quantum algorithm based on generator-coordinate-inspired subspace expansion,ADAPT-GCIM, using a black-box workflow that integrates
entropy-based active-space selection via the ActiveSpaceFinder tool. Across this chemically diverse problem set, ADAPT-GCIM achieves high accuracy in challenging correlation regimes. Equally importantly, these
benchmarks expose general failure modes and design constraints-independent of any specific
algorithm-highlighting the necessity of problem-aware and correlation-specific strategies for treating strongly correlated chemistry on
quantum computers. To support systematic benchmarking and reproducible comparisons, the
Hamiltonians for all systems studied are made openly available.
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All authors Srivathsan Poyyapakkam Sundar, Vibin Abraham, Bo Peng, Ayush Asthana
Instrumentation and Detectors
Charge-Carrier Mobility in Diamond: Review, Data Compilation, and Modelling for Detector Simulations
Faiz Rahman Ishaqzai, Muhammed Deniz, Kevin Kröninger et al. (+1 more)
Reported electron and hole mobilities and saturation velocities in diamond vary widely across the literature. We provide a consolidated review of first-principles predicted and experimentally measured mobility and saturation-velocity values in diamond, alongside a focused assessment of the semi-empirical mobility models used to extract low-field mobilities and high-field saturation velocities. We attribute the dispersion primarily to (i) the electric-field window probed in TCT measurements, (ii) the choice of mobility model, and (iii) the excitation source ($\alpha$,
laser, or electron). Using an aggregated literature
dataset, we
benchmark the Trofimenkoff and Caughey–Thomas parameterizations together with a new piecewise model for both conduction- and valence-band transport. For electrons, the piecewise model provides the best global description over a broad electric-field range. It can be interpreted as the room-temperature limit of a more general superposition framework that explicitly incorporates intervalley repopulation in the conduction band. For holes, the Caughey–Thomas model remains the statistically preferred description, consistent with the absence of a repopulation signature in the accessible data. Furthermore, we demonstrate a systematic source dependence ($\alpha$ versus
laser) and quantify its impact on fitted mobility and saturation-velocity values. We provide temperature scalings over narrow intervals around room temperature to support Jacoboni–Canali-type parameterization for diamond. Together, these results reconcile much of the apparent inconsistency in the literature and offer guidance for model selection, experimental design, and device-level simulation of charge transport in intrinsic diamond.
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All authors Faiz Rahman Ishaqzai, Muhammed Deniz, Kevin Kröninger, Jens Weingarten
Instrumentation and Detectors · Cross-listed from cs.LG
Towards Tensor Network Models for Low-Latency Jet Tagging on FPGAs
Alberto Coppi, Ema Puljak, Lorenzo Borella et al. (+6 more)
We present a systematic study of Tensor Network (TN) models $\unicode{x2013}$
Matrix Product States (MPS) and Tree Tensor Networks (TTN) $\unicode{x2013}$ for real-time jet tagging in high-energy physics, with a focus on low-latency deployment on Field Programmable Gate Arrays (FPGAs). Motivated by the strict requirements of the HL-LHC Level-1 trigger system, we explore TNs as compact and interpretable alternatives to deep neural networks. Using low-level jet constituent features, our models achieve competitive performance compared to state-of-the-art deep learning classifiers. We investigate post-training quantization to enable hardware-efficient implementations without degrading classification performance or latency. The best-performing models are synthesized to estimate FPGA resource usage, latency, and
memory occupancy, demonstrating sub-microsecond latency and supporting the feasibility of online deployment in real-time trigger systems. Overall, this study highlights the potential of TN-based models for fast and resource-efficient inference in low-latency environments.
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All authors Alberto Coppi, Ema Puljak, Lorenzo Borella, Daniel Jaschke, Enrique Rico, Maurizio Pierini, Jacopo Pazzini, Andrea Triossi, Simone Montangero
Instrumentation and Detectors
The BigBite Calorimeter for the Super Bigbite Spectrometer Program at Jefferson Lab
Provakar Datta, Katherine Evans, Jason Bane et al. (+24 more)
We report features of the design, construction, installation, and performance of the BigBite Calorimeter (BBCal), a lead-glass electromagnetic calorimeter constructed as part of the BigBite Spectrometer (BBS), which served as the electron arm for the Super Bigbite Spectrometer (SBS) program of high-precision
neutron electromagnetic form factor measurements in
Hall A at Jefferson Lab. As a total-absorption calorimeter, BBCal provided the primary electron trigger for BBS, detecting (quasi-) elastically scattered electrons in the 1-4 GeV energy range with an energy resolution of approximately 6.2%, position resolution of 1.2 cm, and timing resolution of 0.5 ns.
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All authors Provakar Datta, Katherine Evans, Jason Bane, Hem Bhatt, Bhesha Devkota, Eric Fuchey, Tyler Hague, Douglas Higinbotham, Amanda Hoebel, Mark Jones, Abishek Karki, Mikhail Kubantsev, Shujie Li, Michael Nycz, Roman Pomatsalyuk, Andrew Puckett, Igor Rachek, Seamus Riordan, Brad Sawatzky, Sebastian Seeds, Albert Shahinyan, Yuri Shestakov, Arun Tadepalli, Vladimir Verebryusov, Hakob Voskanyan, Bogdan Wojtsekhowski, Ashley Yoon
Chemical Physics
OmniMol: Transferring Particle Physics Knowledge to Molecular Dynamics with Point-Edge Transformers
Ibrahim Elsharkawy, Vinicius Mikuni, Wahid Bhimji et al. (+1 more)
We present OmniMol, a state-of-the-art all-to-all
transformer-based small molecule machine-learned interatomic potential (MLIP). OmniMol is built by adapting Omnilearned, a foundation model for particle jets found in high-energy physics (HEP) experiments such as at the Large
Hadron Collider (LHC). Omnilearned is built with a Point-Edge-
Transformer (PET) and pre-trained using a diverse set of one billion particle jets. It includes an interaction-
matrix attention bias that injects pairwise sub-
nuclear (HEP) or atomic (molecular-dynamics) physics directly into the
transformer's
attention logits, steering the network toward physically meaningful neighborhoods without sacrificing expressivity. We demonstrate OmniMol using the oMol
dataset and find excellent performance even with relatively few examples for fine-tuning. Further, due to architectural transfer from Omnilearned, we demonstrate uniquely fast inference. This study lays the foundation for building interdisciplinary connections given
datasets represented as collections of point clouds.
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All authors Ibrahim Elsharkawy, Vinicius Mikuni, Wahid Bhimji, Benjamin Nachman
Classical Physics
Nonlinear Scalar Interactions in the EMDrive: Petiau's Elliptic-Function Approach
Mario J. Pinheiro
The EMDrive, a controversial electromagnetic propulsion concept, challenges momentum conservation in standard Maxwell electrodynamics. We propose a beyond-Maxwell framework by coupling the electromagnetic field to a light scalar field, inspired by
axion-like particle models and effective field theory. Using Guy Petiau's 1958
elliptic-function solutions for nonlinear wave equations, we construct exact cavity modes and combine them via Jacobi addition
theorems. These nonlinear modes produce an asymmetric momentum flux, suggesting a theoretical pathway for EMDrive thrust. We compute the stress-tensor asymmetry numerically and show that while standard
axion-like particles yield negligible effects, light scalars beyond current constraints could produce measurable thrust. The framework provides testable predictions connecting EMDrive physics to dark matter searches.
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Fluid Dynamics
Quantum geometry of the rotating shallow water model
Sriram Ganeshan and Alan T. Dorsey
The rotating shallow water equations (RSWE) are a mainstay of atmospheric and oceanic modeling, and their wave dynamics has close analogues in settings ranging from two-dimensional electron gases to active-matter fluids. While recent work has emphasized the topological character of RSWE wave bands, here we develop a complementary
quantum-
geometric description by computing the full
quantum geometric tensor (QGT) for the linearized RSWE on an $f$-plane. The QGT unifies two pieces of band geometry: its real part defines a metric that quantifies how rapidly wave polarization changes with parameters, while its imaginary part is the Berry
curvature that controls
geometric phases and topological invariants. We obtain compact,
symmetry-guided expressions for all three bands, highlighting the transverse structure of the metric and the monopole-like Berry
curvature that yields Chern numbers for the Poincaré bands. Finally, we describe a feasible route to probing this geometry in rotating-tank experiments via weak, time-periodic parametric driving.
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Accelerator Physics
Increasing the opening speed of the plasma opening switch on an direct action accelerator with an inductive energy storage device
D.V. Vinnikov, O.M. Ozerov, V.V. Katrechko et al. (+3 more)
To increase the voltage multiplication factor in a small-sized direct-acting electron accelerator DIN-2K with an inductive energy storage and a
plasma opening switch, it is necessary to ensure an increase in the rate of change of the current and its amplitude during the POS opening for the purpose of obtaining an explosive electron emission with the formation of an electron beam and a virtual cathode. However, the opening process depends on many electrical parameters of the plant, and it re-quires determining their joint and individual effect on its dynamics. The purpose of this research is to study and determine the effects of electrical parameters, including those of the discharge voltages of the entire electrical
circuit of the accelerator on the dynamics of the
plasma opening switch, in particular opening speed, current amplitudes, and opening time, as well as to give recommendations on optimizing the operation of accelerators of this type and highlight possible ways to increase the voltage multiplication factor. Methodology. A method for determining the induced voltage according to experimental current oscillograms has been proposed. The methodology was verified by the coincidence of its data with the results of measurements by a capacitive voltage divider with the data spread of less than 20%. Scientific novelty. The rates of change in the current at the
plasma switch opening stage were determined depending on the main electrical parameters of the DIN-2K accelerator. The diagnostics of the voltage induced during the POS opening were provided using no capacitive voltage divider in the internal volume of the accelerator, which enabled the removal of some diagnostic tools from the working volume of the chamber. Practical significance.
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All authors D.V. Vinnikov, O.M. Ozerov, V.V. Katrechko, V.I. Tkachov, O.V. Manuilenko, I.N. Onishchenko
Optics · Cross-listed from quant-ph
Mitigating nonlinear transduction noise in high-cooperativity cavity optomechanics
Daniel Allepuz-Requena, Zohran Ali, Dennis Høj et al. (+4 more)
Coupling mechanical motion to an optical resonator enables displacement measurements approaching the standard
quantum limit (SQL). However, increasing the optomechanical coupling strength will inevitably lead to probing of the nonlinear response of the optical resonator. Thermal intermodulation noise (TIN) arising from the nonlinear mixing of thermomechanical motion can further increase the imprecision well above the SQL and has hitherto been canceled up to second order of nonlinearity via operation at the "magic detuning". In this work, we record the output of a membrane-in-the-middle microcavity system operating at room temperature and achieving high cooperativity, $C>n_\text{th}$, and apply a nonlinear transform that removes all orders of TIN, improving the mechanical signal-to-noise ratio by nearly 10 dB. Our results can be applied to experiments affected by third-order TIN, which we expect to be the dominating intrinsic source of noise in high-cooperativity room-temperature cavity optomechanical systems.
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All authors Daniel Allepuz-Requena, Zohran Ali, Dennis Høj, Yingxuan Chen, Luiz Couto Correa Pinto Filho, Alexander Huck, Ulrik L. Andersen
Optics
Optimal universal bounds for waves with varied coherence based on supremum and infimum coherence spectra
Shiyu Li and Cheng Guo
We establish a majorization-based theory for bounding observables of waves with varied coherence. For any measurement, exact bounds are attained by the maximal and minimal elements in the set of input coherence spectra. The set's supremum and infimum, which may lie outside the set, provide optimal universal bounds: any alternative spectrum yielding universal bounds produces weaker constraints. We present an
algorithm to compute the supremum and infimum, and prove that they lie either at singular boundary points or strictly outside the set of coherence spectra.
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Fluid Dynamics
Boundary treatment algorithms for meshfree RANS turbulence modeling
Mohan Padmanabha, Jörg Kuhnert, Nicolas R. Gauger et al. (+1 more)
In this paper, we propose improved wall-treatment strategies for meshfree methods applied to turbulent flows. The goal is to enhance wall-function handling in simulations of high-Reynolds-number turbulent flows and to understand the performance of
turbulence models within these frameworks. While wall-function techniques are well established for mesh-based methods, their implementation in meshfree methods faces unique challenges. The main difficulties arise from scattered point distributions and dynamic point movement in Lagrangian frameworks. To address these issues, we evaluate a baseline closest-neighbor approach alongside two novel techniques: the nearest-band neighbor (NBN) method and the shifted boundary (SB) method. The NBN method enforces wall functions on a band of interior points, helping to maintain uniform point selection. On the other hand, the SB method virtually moves boundary points to a fixed wall-normal distance, eliminating the spatial noise associated with point movement. We evaluate these methods using
turbulence closures: Spalart–Allmaras, $k-\varepsilon$, and $k-\omega$
turbulence models. These methods are validated on 1D Couette flow, a turbulent flat plate, and a 3D NACA 0012 airfoil at high Reynolds numbers. Results demonstrate that both novel methods outperform the standard closest-neighbor approach on flat geometries. For flat plates, the SB method provides stability and perfectly smooth $y^+$ distributions. However, when applied to a curved NACA 0012 profile, the NBN method proves to be robust and flexible. In contrast, the SB method exhibits setbacks in numerical
diffusion and premature flow separation on curved geometries. This is due to uncorrected normal-vector shifting and adverse pressure gradients. This work establishes the NBN method as a reliable, robust foundation for simulating turbulent flows over practical geometries using meshfree methods.
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All authors Mohan Padmanabha, Jörg Kuhnert, Nicolas R. Gauger, Pratik Suchde
Atomic Physics · Cross-listed from quant-ph
Counterdiabatic driving for random-gap Landau-Zener transitions
Georgios Theologou, Mikkel F. Andersen and Sandro Wimberger
The Landau–Zener (LZ) model describes a two-level
quantum system that undergoes an avoided crossing. In the adiabatic limit, the transition probability vanishes. An auxiliary control field $H_\text{CD}$ can be reverse-engineered so that the full
Hamiltonian $H_0 + H_\text{CD}$ reproduces adiabaticity for all parameter values. Our aim is to construct a single control field $H_1$ that drives an ensemble of LZ-type
Hamiltonians with a distribution of energy gaps. $H_1$ works best statistically, minimizing the average transition probability. We restrict our
attention to a special class of $H_1$ controls, motivated by $H_\text{CD}$. We found a systematic trade-off between instantaneous adiabaticity and the final transition probability. Certain limiting cases with a linear sweep can be treated analytically; one of them being the LZ system with Dirac $\delta(t)$ function. Comprehensive and systematic numerical simulations support and extend the analytic results.
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Physics and Society
Transforming Crises into Opportunities: From Chaos to Urban Antifragility
Joseph Uguet, Nicola Tollin and Jordi Morato
Urban crises - floods, pandemics, economic shocks, and conflicts - function as accelerators of urban change, exposing structural vulnerabilities while creating windows for reinvention. Building on a prior theoretical contribution that identified fifteen principles of urban antifragility, this paper tests and operationalizes the framework through an empirical assessment of 26 cities selected for their post-crisis adaptation trajectories. Using a tailored diagnostic methodology, we
benchmark cities' Stress Response Strategies (SRS) and then evaluate Urban Development Trajectories (UDT) across four weighted dimensions, positioning each case along a fragility-robustness-resilience-antifragility continuum and applying a balanced-threshold rule to confirm antifragile status. Results show that "resilience enhanced by innovation and technology" is the most effective response typology (86.9/100), and that six cities meet the antifragile trajectory criteria. By mapping best practices to activated principles and analysing co-activations, the study identifies a robust "hard core" of principles - Sustainable Resilience (O), Strategic Diversity (F), Proactive Innovation (I), and Active Prevention (N) - supplemented by operational enablers (e.g., anticipation, mobilization, shock absorption). The paper concludes by proposing an evidence-based, SDG-aligned operational model that links high-impact principle pairings to measurable indicators, offering a practical roadmap for cities seeking to convert crises into sustained transformation. Keywords: Post-crisis strategies, Urban antifragility, Sustainable cities and communities, Disaster resilience and urban regeneration, Risk governance and Black Swan adaptation.
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Atmospheric and Oceanic Physics
On the geometry of aggregate snowflakes
Axel Seifert, Christoph Siewert, Fabian Jakub et al. (+2 more)
Snowflakes play a crucial role in weather and
climate. A significant portion of precipitation that reaches the surface originates as ice, even when it ultimately falls as rain. Contrary to the popular image of symmetric, dendritic
crystals, most large snowflakes are irregular aggregates formed through the collision of primary ice
crystals, such as hexagonal plates, columns, and dendrites. These aggregates exhibit complex, fractal-like structures, particularly at large sizes. Despite this structural complexity, each aggregate snowflake is unique, with properties that vary significantly around the mean - variability that is typically neglected in weather and
climate models. Using a physically based aggregation model, we generate millions of synthetic snowflakes to investigate their
geometric properties. The resulting
dataset reveals that, for a given monomer number (cluster size) and mass, the maximum dimension follows approximately a lognormal distribution. We present a parameterization of aggregate geometry that captures key statistical properties, including maximum dimension, aspect ratio, cross-sectional area, and their joint correlations. This formulation enables a
stochastic representation of aggregate snowflakes in Lagrangian particle models. Incorporating this variability improves the realism of simulated fall velocities, enhances growth rates by aggregation, and broadens Doppler radar spectra in closer agreement with observations.
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All authors Axel Seifert, Christoph Siewert, Fabian Jakub, Leonie von Terzi, Stefan Kneifel
Biological Physics · Cross-listed from quant-ph
Searching for Quantum Effects in the Brain: A Bell-Type Test for Nonclassical Latent Representations in Autoencoders
I. K. Kominis, C. Xie, S. Li et al. (+2 more)
Whether neural information processing is entirely classical or involves
quantum-mechanical elements remains an open question. Here we propose a model-agnostic, information-theoretic test of nonclassicality that bypasses microscopic assumptions and instead probes the structure of neural representations themselves. Using autoencoders as a transparent model system, we introduce a Bell-type consistency test in latent space, and ask whether decoding statistics obtained under multiple readout contexts can be jointly explained by a single positive latent-variable distribution. By shifting the search for
quantum-like signatures in neural systems from microscopic dynamics to experimentally testable constraints on information processing, this work opens a new route for probing the fundamental physics of neural computation. The proposed test identifies violations of classical latent-variable consistency at the level of statistical representations, without assuming a specific underlying physical mechanism.
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All authors I. K. Kominis, C. Xie, S. Li, M. Skotiniotis, G. P. Tsironis
Atomic Physics
Electro-optic frequency comb Doppler thermometry
Sean M. Bresler, Erin M. Adkins, Stephen P. Eckel et al. (+4 more)
We demonstrate a Doppler thermometer based on direct optical frequency comb spectroscopy of an $^{85}$Rb vapor with a chirped electro-optic frequency comb (EOFC). The direct EOFC Doppler thermometer is accurate to within its approximately 1 K statistical uncertainty. We experimentally compare direct EOFC spectroscopy with conventional Doppler spectroscopy using a single-frequency, step-scanned
laser probe. Our results show that direct EOFC spectroscopy mitigates transit-induced optical pumping distortion of the atomic lineshape, which is the dominant systematic temperature shift in alkali atom Doppler thermometry. Optical Bloch equation simulations of conventional and direct EOFC Doppler spectroscopy confirm that EOFC spectroscopy can use higher optical power to reduce statistical noise without optical pumping distortion. Our results indicate that EOFC Doppler thermometry is a promising approach to realizing a primary thermometer with size and measurement rate sufficient for applications including pharmaceutical manufacturing and
nuclear waste monitoring.
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All authors Sean M. Bresler, Erin M. Adkins, Stephen P. Eckel, Tobias K. Herman, David A. Long, Benjamin J. Reschovsky, Daniel S. Barker
Accelerator Physics
Corrections for systematic errors in slit-profiler transverse phase space measurements
C. Richard, M. Krasilnikov, N. Aftab et al. (+8 more)
In photo injectors, the transverse emittance is one of the key measures of beam quality as it defines the possible performance of the whole facility. As such it is important to measure the emittance in photo injectors and ensure the accuracy of these measurements. While there are many different methods of measuring the emittance, this paper focuses on quantifying the systematic errors present in transverse phase space measurements taken with slit-profiler methods, i.e. scanning a narrow slit over the beam and continually measuring the passed beamlets' divergence with a downstream profiler. The measurement errors include effects of the slit size, beamlet imaging, and residual space charge. While these effects are generally small, they can have significant impact on the measured emittance when the 2D phase space is strongly coupled. The systematic effects studied and corrections are demonstrated with simulations and measurements from the Photo Injector Test facility at DESY in Zeuthen (PITZ) using a slit-screen emittance scanner.
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All authors C. Richard, M. Krasilnikov, N. Aftab, Z. Amirkhanyan, D. Dmytriiev, A. Hoffmann, X.-K. Li, Z. Lotfi, F. Stephan, G. Vashchenko, S. Zeeshan
Plasma Physics
Canonical Vorticity Perspective on Magnetogenesis: Unifying Weibel, Biermann, and Beyond
Modhuchandra Laishram and Young Dae Yoon
We briefly review the current status of magnetogenesis, a cross-disciplinary field that bridges cosmology and
plasma physics, studying the origin of
magnetic fields in the universe. We formulate a canonical vorticity framework to investigate kinetic
plasma physics-based magnetogenesis processes in a collisionless
plasma. By considering canonical vorticity, a weighted sum of the fluid vorticity and the
magnetic field as the canonical variable, this framework unifies several magnetogenesis processes, including the Biermann battery, the Weibel instability, and predicts several new pressure tensorial configurations as the fundamental source of self-generated
magnetic field and vorticity in
plasma. The framework is further extended to relativistic regime where an additional source of canonical vorticity, termed as kineclinicity effect, is identified. The theoretical predictions are systematically validated using particle-in-
cell simulations, highlighting their implications for laboratory and astrophysical
plasma environments.
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Computational Physics · Cross-listed from math.NA
Chebyshev Accelerated Subspace Eigensolver for Pseudo-hermitian Hamiltonians
Edoardo Di Napoli, Clément Richefort and Xinzhe Wu
Studying the optoelectronic structure of materials can require the computation of several thousands of the smallest positive eigenpairs of a pseudo-hermitian
Hamiltonian. Iterative eigensolvers may be preferred over direct methods for this task since their complexity is a function of the desired fraction of the spectrum. In addition, they generally rely on highly optimized and scalable kernels such as
matrix-vector multiplications that leverage the massive parallelism and the computational power of modern exascale systems. The Chebyshev Accelerated Subspace iteration Eigensolver (ChASE) is able to compute several thousands of the most extreme eigenpairs of dense hermitian
matrices with proven scalability over massive parallel accelerated clusters. This work presents an extension of ChASE to solve for a portion of the smallest positive eigenpairs of pseudo-hermitian
Hamiltonians as they appear in the treatment of excitonic materials. By exploiting the numerical structure and spectral properties of the
Hamiltonian matrix, we preserve the characteristic positive-negative
symmetry in the treatment of the eigenvectors and propose an oblique variant of Rayleigh-Ritz projection that features quadratic convergence of the Ritz values with no explicit construction of the dual basis. Additionally, we introduce a parallel implementation of the recursive
matrix-product operation appearing in the Chebyshev filter with limited amount of global communications. Our development is supported by a full numerical analysis and experimental tests.
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Optics
Spatio-spectrally tailored multimode metasurface lasers in the visible range
Ayesheh Bashiri, Aleksandr Vaskin, Katsuya Tanaka et al. (+3 more)
Spectrally engineered multifrequency nanolasers are highly desirable for on-chip photonics, multiplexed biosensing, and display technologies; yet, achieving them within a single compact platform remains challenging. Here, we demonstrate multimode lasing from
symmetry-broken TiO2 metasurfaces integrated with an SU8 slab waveguide containing Rhodamine 6G. By co-engineering guided-mode resonances, surface
lattice resonances near Rayleigh anomalies, and quasi-bound states in the continuum, we realize complementary high-Q feedback pathways that overlap with the gain spectrum. The direction of the lasing emission is tailored through outcoupling via second-order Bragg diffraction and Rayleigh anomaly conditions, supporting both normal and oblique emission. Experiments reveal discrete lasing outputs across ~100 nm bandwidth (548-648 nm), spanning nearly the full Rhodamine 6G emission band, with thresholds as low as ~7 nJ per pulse (35.7 uJ/cm^2) and up to four concurrent lasing peaks from a single device. These results establish a metasurface-dye platform for multifrequency and angle-selective lasing, opening new opportunities for compact, multifunctional nanophotonic sources.
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All authors Ayesheh Bashiri, Aleksandr Vaskin, Katsuya Tanaka, Muyi Yang, Thomas Pertsch, Isabelle Staude
Physics and Society
Nested hyperedges promote the onset of collective transitions but suppress explosive behavior
Federico Malizia, Andrés Guzmán, Federico Battiston et al. (+1 more)
Higher-order interactions can induce abrupt collective transitions, yet the microscopic mechanisms controlling macroscopic critical behavior remain unclear. Here we show that nested hyperedges generate a dual effect on dynamical processes: they promote the onset of collective behavior while suppressing the explosive transitions driven by higher-order feedback. To uncover the mechanism, we develop an analytically tractable theory of contagion on hypergraphs that explicitly tracks nestedness between groups of different sizes, allowing us to identify the microscopic mechanism responsible for this dual behavior. By disentangling contagion pathways, we find that nestedness redirects transmission from external links to internal, group-embedded routes – boosting early activation but making dyadic and triadic channels increasingly redundant. This loss of structural independence quenches the nonlinear amplification required for bistability, progressively smoothing the transition as hyperedges become nested. The phenomenology holds for groups of any size, and is not specific to spreading dynamics but also emerges in higher-order Ising and Kuramoto dynamics. Overall, our results identify nestedness between group interactions as a general structural mechanism governing critical transitions in complex systems.
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All authors Federico Malizia, Andrés Guzmán, Federico Battiston, István Z. Kiss
Plasma Physics
Reply to "Comment on Nuclear Fusion 66, 016012 (2026) by Richard Fitzpatrick, A Simple Model of Current Ramp-Up and Ramp-Down in Tokamaks" by A.H. Boozer
Richard Fitzpatrick
This report is a follow up to my paper "A simple model of current ramp-up and ramp-down in tokamaks" [Nucl. Fusion 66, 016012 (2026)] in the light of comments on the paper recently made by Dr. A.H. Boozer (arXiv:2601.05977).
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Comprehensive parameter and electrochemical dataset for a 1 Ah graphite/LNMO battery cell for physical modelling as a blueprint for data reporting in battery research
Christina Schmitt, August Johansson, Xavier Raynaud et al. (+9 more)
While current technology has enabled their widespread use, further improvements are needed for stationary, portable, and mobile applications, for example by the development of novel cathode materials. Digitalization of battery development, combining both experimental and modelling efforts is extremely valuable in this development. This is addressed in the present paper, where the authors present a comprehensive
dataset for a graphite/LNMO 1 Ah pouch
cell, including material, design, and electrochemical data. The
dataset, validated through the BattMo modelling framework, supports physical modelling and aims to benefit the battery modelling community by offering a comprehensive resource for future studies. Both the
dataset and the accompanying software for numerical validation is openly available and processed in such a way that it can serve as blueprint for reporting of comparable research data.
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All authors Christina Schmitt, August Johansson, Xavier Raynaud, Eibar Joel Flores Cedeño, John Mugisa, Dane Sotta, Agathe Martin, Nicolas Schaeffer, Cédric Debruyne, Yvan Reynier, Simon Clark, Dennis Kopljar
Plasma Physics
From Weibel seeds to collisionless dynamos beyond pair-plasmas
Lise Hanebring, James Juno, Ammar Hakim et al. (+2 more)
Bridging the spatiotemporal scales of
magnetic seed field generation and subsequent dynamo amplification in the weakly collisional intracluster medium presents an extreme numerical challenge. We perform collisionless
turbulence simulations with initially unmagnetized electrons that capture both
magnetic seed generation via the electron Weibel instability and the ensuing dynamo amplification. Going beyond existing pair-
plasma studies, we use an ion-to-electron mass ratio of 100 for which we find electron and ion dynamics are sufficiently decoupled. These simulations are enabled by the 10-moment collisionless fluid solver of Gkeyll, which evolves the full pressure tensor for all species. The electron heat-flux closure regulates pressure isotropization and effectively sets the
magnetic Reynolds number. We investigate how the strength of the closure influences the transition between a regime reminiscent of previous kinetic pair-
plasma simulations and a regime exhibiting dynamo behavior qualitatively similar to magnetohydrodynamics.
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All authors Lise Hanebring, James Juno, Ammar Hakim, Jason M. TenBarge, Istvan Pusztai
Computational Physics · Cross-listed from cs.SD
Stable Differentiable Modal Synthesis for Learning Nonlinear Dynamics
Victor Zheleznov, Stefan Bilbao, Alec Wright et al. (+1 more)
Modal methods are a long-standing approach to physical modelling synthesis. Extensions to nonlinear problems are possible, leading to coupled nonlinear systems of ordinary differential equations. Recent work in scalar auxiliary variable techniques has enabled construction of explicit and stable numerical solvers for such systems. On the other hand, neural ordinary differential equations have been successful in modelling nonlinear systems from data. In this work, we examine how scalar auxiliary variable techniques can be combined with neural ordinary differential equations to yield a stable differentiable model capable of learning nonlinear dynamics. The proposed approach leverages the analytical solution for linear vibration of the system's modes so that physical parameters of a system remain easily accessible after the training without the need for a parameter encoder in the model architecture. Compared to our previous work that used multilayer perceptrons to parametrise nonlinear dynamics, we employ gradient networks that allow an interpretation in terms of a closed-form and non-negative potential required by scalar auxiliary variable techniques. As a proof of concept, we generate synthetic data for the nonlinear transverse vibration of a string and show that the model can be trained to reproduce the nonlinear dynamics of the system. Sound examples are presented.
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All authors Victor Zheleznov, Stefan Bilbao, Alec Wright, Simon King
Fluid Dynamics
Submesoscale and boundary layer turbulence under mesoscale forcing in the upper ocean
S. Peng, S. Silvestri and A. Bodner
The interaction among quasi-geostrophic mesoscale eddies, submesoscale fronts, and boundary layer
turbulence (BLT) is a central problem in upper ocean dynamics. We investigate these multiscale dynamics using a novel large-eddy simulation on a \qty{100}{\kilo\meter}-scale domain with meter-scale resolution. The simulation resolves BLT energized by uniform surface wind and convective forcing. A front interacts with BLT within a prescribed, spatially inhomogeneous mesoscale eddy field, representing a canonical eddy quadrupole. Using a triple flow decomposition, we analyze the dynamic coupling and kinetic energy budgets among the large-scale field, submesoscale field, and the resolved BLT. Our analysis reveals significant heterogeneity in the structure and intensity of submesoscales and BLT under varying mesoscale forcing. Turbulent kinetic energy and production rates can vary by an order of magnitude along the front, creating distinct turbulent hotspots whose locations are tied to the underlying large-scale flow. The region under stronger mesoscale convergence holds stronger horizontal and vertical geostrophic shear productions for BLT, and stronger self-production and BLT-destruction for submesoscales. In contrast, the region under dominant mesoscale divergence holds dramatic distortion of the front isotherm, along with dominant submesoscale vertical buoyancy production and self-destruction. Within this idealized framework, these results provide a controlled process-level characterization of how prescribed mesoscale heterogeneity modulates BLT and submesoscales in the ocean mixed layer, which can inform future parameterization developments.
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Computational Physics · Cross-listed from cond-mat.mtrl-sci
The transformation mechanisms among cuboctahedra, Ino's decahedra and icosahedra structures of magic-size gold nanoclusters
Ehsan Rahmatizad Khajehpasha, Mohammad Ismaeil Safa, Nasrin Eyvazi et al. (+2 more)
Gold nanoclusters possess multiple competing structural motifs with small energy differences, enabling structural coexistence and interconversion. Using a high-accuracy machine learned potential trained on some 20'000 density functional theory reference data points, we investigate transformation pathways connecting both high-
symmetry and amorphous cuboctahedra, Ino's decahedra and icosahedra for Au55, Au147, Au309 and Au561 nanoclusters. Our saddle point searches reveal that high-
symmetry transformations from cuboctahedra and Ino's decahedra to icosahedra proceed through a single barrier and represent soft-mode-driven jitterbug-type and slip-dislocation motions. In addition, we identify lower-barrier asymmetric transformation pathways that drive the system into disordered, Jahn-Teller-stabilized amorphous icosahedra. Minima Hopping sampling further uncovers, in this context, many such low-
symmetry minima. Some of the newly identified global minima for Au309 and Au561 have energies that are up to 2.8 eV lower than the previously reported global minima. Hence, both the shapes and the transformation pathways studied in previous investigations are not the physically relevant ones. In contrast to the previously studied pathways, our transformation pathways give reasonable transformation times that are in rough agreement with experiments.
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All authors Ehsan Rahmatizad Khajehpasha, Mohammad Ismaeil Safa, Nasrin Eyvazi, Marco Krummenacher, Stefan Goedecker