Chemical Physics
$\Delta$-ML Ensembles for Selecting Quantum Chemistry Methods to Compute Intermolecular Interactions
Austin M. Wallace, C. David Sherrill and Giri P. Krishnan
Ab initio
quantum chemical methods for accurately computing interactions between molecules have a wide range of applications but are often computationally expensive. Hence, selecting an appropriate method based on accuracy and computational cost remains a significant challenge due to varying performance of methods. In this work, we propose a framework based on an ensemble of $\Delta$-ML models trained on features extracted from a pre-trained atom-pairwise neural network to predict the error of each method relative to all other methods including the “gold standard” coupled cluster with single, double, and perturbative triple excitations at the estimated complete basis set limit [CCSD(T)/CBS]. Our proposed approach provides error estimates across various levels of theories and identifies the computationally efficient approach for a given error range utilizing only a subset of the
dataset. Further, this approach allows comparison between various theories. We demonstrate the effectiveness of our approach using an extended BioFragment
dataset, which includes the interaction energies for common biomolecular fragments and small organic dimers. Our results show that the proposed framework achieves very small mean-absolute-errors below 0.1 kcal/mol regardless of the given method. Furthermore, by analyzing all-to-all $\Delta$-ML models for present levels of theory, we identify method groupings that align with theoretical hypotheses, providing evidence that $\Delta$-ML models can easily learn corrections from any level of theory to any other level of theory.
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Chemical Physics · Cross-listed from quant-ph
Entanglement Witnesses of Condensation for Enhanced Quantum Sensing
Lillian I. Payne Torres, Irma Avdic, Anna O. Schouten et al. (+3 more)
Quantum phenomena such as
entanglement provide powerful resources for enhancing classical sensing. Here, we theoretically show that collective
entanglement of
spin qubits, arising from a condensation of particle-hole pairs, can strongly amplify transitions between ground and excited
spin states, potentially improving signal contrast in optically detected
magnetic resonance. This collective state exhibits an $\mathcal{O}(\sqrt{N})$ enhancement of the transition amplitude with respect to an applied microwave field, where $N$ is the number of entangled
spin qubits. We computationally realize this amplification using an ensemble of $N$ triplet
spins with
magnetic dipole interactions, where the largest transition amplitudes occur at geometries for which the condensation of particle-hole pairs is strongest. This effect, robust to noise, originates from the concentration of
entanglement into a single collective mode, reflected in a large
eigenvalue of the particle-hole reduced density
matrix – an
entanglement witness of condensation analogous to off-diagonal long-range order, though realized here in a finite system. These results offer a design principle for
quantum sensors that exploit condensation-inspired
entanglement to boost sensitivity in
spin-based platforms.
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All authors Lillian I. Payne Torres, Irma Avdic, Anna O. Schouten, Olivia C. Wedig, Gregory S. Engel, David A. Mazziotti
Optics
Graphene and thin graphite films for ultrafast optical Kerr gating at 1 GHz repetition rate under focused illumination
Amr Farrag, Assegid M. Flatae and Mario Agio
The ability to address sub-picosecond events of weak optical signals is essential for progress in
quantum science, nonlinear optics, and ultrafast spectroscopy. While up-conversion and optical Kerr gating (OKG) offer femtosecond resolution, they are generally limited to ensemble measurements, making ultrafast detection in nano-optics challenging. OKG, with its broadband response and high throughput without phase-matching, is especially promising when used at high repetition rates under focused illumination. Here, we demonstrate an ultrafast detection scheme using the third-order nonlinearity of
graphene and thin graphite films, operating at 1 GHz with sub-nanojoule pulses and achieving 141 fs temporal resolution. Their exceptionally large nonlinear refractive index, orders of magnitude higher than conventional Kerr media, enhances detection efficiency at smaller thicknesses, enables sub-picosecond response, and supports broadband operation. Their atomic-scale thickness minimizes dispersion and simplifies integration with microscopy platforms, optical fibers, and nanophotonic
circuits, making them a compact, practical material platform for nano-optical and on-chip ultrafast Kerr gating.
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Plasma Physics · Cross-listed from astro-ph.HE
Entity – Hardware-agnostic Particle-in-Cell Code for Plasma Astrophysics. I: Curvilinear Special Relativistic Module
Hayk Hakobyan, Ludwig M. Böss, Yangyang Cai et al. (+8 more)
Entity is a new-generation, fully open-source particle-in-
cell (PIC) code developed to overcome key limitations in astrophysical
plasma modeling, particularly the extreme separation of scales and the performance challenges associated with evolving, GPU-centric computing infrastructures. It achieves hardware-agnostic performance portability across various GPU and CPU architectures using the Kokkos library. Crucially, Entity maintains a high standard for usability, clarity, and customizability, offering a robust and easy-to-use framework for developing new
algorithms and grid geometries, which allows extensive control without requiring edits to the core source code. This paper details the core general-coordinate special-relativistic module. Entity is the first PIC code designed to solve the Vlasov-Maxwell system in general coordinates, enabling a coordinate-agnostic framework that provides the foundational structure for straightforward extension to arbitrary coordinate geometries. The core methodology achieves numerical stability by solving particle equations of motion in the global orthonormal Cartesian basis, despite using generalized coordinates like Cartesian, axisymmetric spherical, and quasi-spherical grids. Charge conservation is ensured via a specialized current deposition technique using conformal currents. The code exhibits robust scalability and performance portability on major GPU platforms (AMD MI250X, NVIDIA A100, and Intel Max Series), with the 3D particle pusher and the current deposition operating efficiently at about 2 nanoseconds per particle per timestep. Functionality is validated through a comprehensive suite of standard Cartesian
plasma tests and the accurate modeling of relativistic magnetospheres in curvilinear axisymmetric geometries.
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All authors Hayk Hakobyan, Ludwig M. Böss, Yangyang Cai, Alexander Chernoglazov, Alisa Galishnikova, Evgeny A. Gorbunov, Jens F. Mahlmann, Alexander Philippov, Siddhant Solanki, Arno Vanthieghem, Muni Zhou
History and Philosophy of Physics
Quantum Spacetime: Echoes of basho
Fedele Lizzi
I will discuss how the concept of basho, introduced by Nishida Kitaro nearly a century ago, can give an interesting insight to understand the concept of a point in modern
quantum gravity. A
quantum spacetime, necessary for the quantization of
gravity, requires a whole rethinking of geometry, starting from the primitive concepts, like that of a point. I argue that the local
vision of what becomes of classical points in
quantum gravity, and in particular in noncommutative geometry, shows several similarities with Nishida's basho.
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Data Analysis and Statistics · Cross-listed from cond-mat.stat-mech
On the uniqueness of the coupled entropy
Kenric P. Nelson
The coupled
entropy, $H_\kappa,$ is proven to uniquely satisfy the requirement that a generalized
entropy be a measure of the uncertainty at the scale, $\sigma,$ for a class of non-exponential distributions. The coupled stretched exponential distributions, including the generalized Pareto and Student's t distributions, are uniquely parameterized to quantify linear uncertainty with the scale and nonlinear uncertainty with the tail shape for a broad class of complex systems. Thereby, the coupled
entropy optimizes the representation of the uncertainty due to linear sources. Lemmas for the composability and extensivity of the coupled
entropy are proven. The uniqueness of the coupled
entropy is further supported by demonstrating consistent thermodynamic relationships, which correspond to a model used for the momentum of high-energy particle collisions. Applications of the coupled
entropy in measuring statistical complexity, training variational inference
algorithms, and designing communication channels are reviewed.
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Optics
Ultrafast optical Kerr Gate at 1 GHz repetition rate by focusing on BBS glass
Amr Farrag, Assegid M. Flatae, Lenorah M. Stott et al. (+4 more)
Efficient detection of ultrafast phenomena is central to modern optical sciences, driving advances in
quantum science and technology, physical chemistry, and nanophotonics. When processes occur on sub-picosecond timescales, time-resolved methods such as transient absorption, up-conversion, and optical Kerr gating (OKG) can be utilized to probe these dynamics, though they are typically applied to ensembles rather than single emitters. The OKG technique offers high detection efficiency over a broad spectral range, making it particularly promising for ultrafast single-
photon detection at high-repetition-rates. Here, we present an ultrafast scheme based on the third-order nonlinearity of bismuth borosilicate (BBS) glass, operating at a 1 GHz repetition rate with less than 1 nJ pulse energy under focusing, and achieving a time resolution down to 175 fs. BBS glass was selected for its high nonlinear coefficient, which enhances detection efficiency, sub-ps response time, and its compatibility with standard microscopy platforms.
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All authors Amr Farrag, Assegid M. Flatae, Lenorah M. Stott, Alessandro Jagatti, Andrea Lapini, Doris Möncke, Mario Agio
Geophysics
Structure-Function Coherent Coarsening for Cross-Resolution Ecohydrological Modeling
Long Jiang, Yang Yang, Morgan Thornwell et al. (+5 more)
Ecohydrological models are increasingly applied in regional scenario-based studies, yet their cross-resolution application remains constrained by high computational costs of fine-resolution simulations and by structural inconsistencies introduced during scale transfer. We propose a Structure-Function Coherent Coarsening (SFCC) framework that improves the preservation of hydrological structure and functional heterogeneity during model input coarsening. Using the VELMA model in 24 subbasins of the Salish Sea Basin, USA, we evaluate coarsening strategies for three input types: (i) DEMs coarsened with a Hydro-Aware approach that better preserves drainage
topology; (ii) land cover and soil type
datasets coarsened with function-preserving methods (Auto-Weight and Auto-Reassign) that retain small but process-dominant classes; and (iii) initial conditions coarsened with Hydro-Aware, Landcover-Aware, and Soil-Aware strategies to improve temporal stability. Results show that the Hydro-Aware method better preserves watershed morphology and yields more consistent runoff and nitrate loss predictions across resolutions than mean-based coarsening. For categorical inputs, the function-preserving methods can reduce the dominant-class bias of majority aggregation, particularly in basins where small, high-impact patches drive nitrogen export. Long-term simulations show that hydrological variables stabilize quickly, whereas biogeochemical variables stabilize more slowly. In both cases, differences caused by coarsening decrease over time and eventually level off. This suggests that preserving both structural consistency and functional heterogeneity can help maintain stable model behavior over time.
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All authors Long Jiang, Yang Yang, Morgan Thornwell, Robert McKane, Sonali Chokshi, Huanfeng Duan, Tiantian Yang, Hoshin Vijai Gupta
Fluid Dynamics
Addressing A Posteriori Performance Degradation in Neural Network Subgrid Stress Models
Andy Wu and Sanjiva K. Lele
Neural network subgrid stress models often have a priori performance that is far better than the a posteriori performance, leading to neural network models that look very promising a priori completely failing in a posteriori Large Eddy Simulations (LES). This performance gap can be decreased by combining two different methods, training data augmentation and reducing input complexity to the neural network. Augmenting the training data with two different filters before training the neural networks has no performance degradation a priori as compared to a neural network trained with one filter. A posteriori, neural networks trained with two different filters are far more robust across two different LES codes with different numerical schemes. In addition, by ablating away the higher order terms input into the neural network, the a priori versus a posteriori performance changes become less apparent. When combined, neural networks that use both training data augmentation and a less complex set of inputs have a posteriori performance far more reflective of their a priori evaluation.
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Applied Physics
Residual Stress Anisotropy In Thin-Film Lithium Niobate For Stress-Managed MEMS
Byeongjin Kim, Ian Anderson, Tzu-Hsuan Hsu et al. (+4 more)
In this work, we present the first experimental study of residual stress and post-release beam deflection in 128-degree Y-cut thin-film lithium niobate (TFLN) on Si, revealing pronounced stress anisotropy with in-plane orientation. Using optical profilometry with
curvature fitting, we extract the stress gradient (sigma1) and generate orientation-resolved stress maps across multiple film thicknesses (100 nm, 220 nm, and 460 nm). For films in the 220 to 460 nm range, we identify stress-free in-plane orientations near approximately 55 degrees and 125 degrees, enabling extremely flat suspended beams. In contrast, ultra-thin 100 nm films exhibit shifted stress-free orientations near approximately 20 degrees and 160 degrees. Leveraging these orientations, we demonstrate very long suspended beams up to 2 cm in length, 10 micrometers in width, and 460 nm in thickness without collapse. These results establish in-plane stress anisotropy and thickness selection in TFLN as practical design levers for mechanically stable, scalable, and stress-managed microelectromechanical systems (MEMS).
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All authors Byeongjin Kim, Ian Anderson, Tzu-Hsuan Hsu, Ziqian Yao, Mihir Chaudhari, Sinwoo Cho, Ruochen Lu
Atmospheric and Oceanic Physics
Cold Pools Reduce the Impacts of Deforestation on Convection Initiation
Nicholas M. Falk, Gabrielle R. Leung, Leah D. Grant et al. (+1 more)
The individual and synergistic impacts of cold pools and land surface heterogeneity on convection initiation are investigated. Idealized large eddy simulations of deep convection over the Amazon rainforest are conducted. Simulations test realistic and homogenized vegetation, along with realistic and suppressed low-level evaporation which eliminates cold pools. Updrafts are tracked to determine convection initiation locations. The aggregation of initiation locations is quantified with an organization index. Initiation locations are randomly distributed over homogeneous vegetation, with or without cold pools, demonstrating that cold pools have minimal impacts on initiation locations over homogeneous vegetation. With realistic vegetation, convection initiation is more frequent over forested than deforested areas due to favorable thermodynamics. Heterogeneous vegetation effectively aggregates initiation locations and precipitation compared to homogeneous vegetation, whereas cold pools disaggregate initiation locations and precipitation by propagating into deforested regions and initiating convection. Thus, cold pools partially counteract the effects of anthropogenically driven land surface heterogeneity.
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All authors Nicholas M. Falk, Gabrielle R. Leung, Leah D. Grant, Susan C. van den Heever
Fluid Dynamics
Laminar and Turbulent Flow in Wavy Pipes under Strong Wall Modulations
Ismail El Mellas, Juan J. Hidalgo and Marco Dentz
We study laminar, transitional and turbulent flow in wavy pipes using direct numerical simulations for bulk Reynolds numbers between 1-5300. Flow behaviors are analyzed in terms of the friction factor f and mean velocity statistics for strong sinusoidal wall fluctuations in axial direction. Depending on the wall amplitude k, flow reversal may appear at bulk Reynolds numbers as small as 25, inducing local recirculation zones significantly increasing friction in the laminar regime. These effects are not captured by classical models based on bulk
geometric parameters, but require the definition of an effective hydraulic radius Rh as a hydrodynamic concept. Furthermore, wall modulations trigger subcritical transitions to
turbulence in a Reynolds range between 500 and 1000, well below the classical threshold for smooth pipes. The DNS data suggest an upper bound for laminar persistence with a critical Reynolds number that scales as a power-law with the wall amplitude, consistent with finite amplitude transition scenarios. In the turbulent regime, flow is found to be fully rough, dominated by inertial separation and wall-induced disturbances independent of Re. Using the hydraulic radius as the characteristic length scale, the wall amplitude provides a robust
estimator for the equivalent sandgrain roughness, also a hydrodynamic concept. The impact of strong wall fluctuations on laminar and turbulent friction laws, as quantified by hydraulic radius and sandgrain roughness , and the amplitude dependence of critical Reynolds number, emphasise the limitations of the Moody diagram for the flow quantification in conduits with strong wall fluctuations across all flow regimes.
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Physics and Society
Circulation of Elites in an Adaptive Network Model
Alexander Jochim and Stefan Bornholdt
Societies experience politically stable and unstable phases along history, whereas political power is usually passed to new elite groups by these changes. Structural dynamics of the elites in a society have been proposed to be one of the core drivers shaping long term behavior. As current models and data are rather macroscopic, the emergence of macroscopic behavior from microscopic dynamics is largely unclear. Here, we introduce an adaptive network model of directed links representing political power and competing political ideas, based on local dynamical rules, only. The model is based on two socially motivated behaviors: the cumulative advantage effect of political power and intra-elite conflict. We observe punctuated
equilibria as an emergent behavior and find a phase transition towards a disordered phase. We define an advance warning measure for elite collapse and find that the states of only a few largest nodes are suitable as a proxy with predictive information.
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Applied Physics
Radial Mode Lithium Niobate Rosen Transformer
Ziqian Yao, Heather Chang, Eric Stolt et al. (+4 more)
In this work, we demonstrate the first two-port radial-mode Rosen
transformer based on 36$^{\circ}$Y-cut lithium niobate (LN) for piezoelectric power conversion. The device achieves a high transformation ratio (TF) of 16, a high electromechanical coupling factor ($k^2$) of 16.8% and a quality factor ($Q$) of 2500, yielding an outstanding figure of merit (FoM = $Q \cdot k^2$) of 420. The fabricated
transformer features a large effective turns ratio of 16 and delivers an open-
circuit voltage gain of 45.56 (unloaded) and 40.57 with a load of 1 M$\Omega$ in parallel with 0.1 pF, validating its ability to provide efficient passive voltage amplification. An equivalent
circuit model was developed to accurately fit both finite-element-simulated and measured admittance spectra, enabling reliable parameter extraction. These results establish LN radial-mode resonators as a promising high-performance,
magnetic-less
transformer platform.
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All authors Ziqian Yao, Heather Chang, Eric Stolt, Clarissa Daniel, Tzu-Hsuan Hsu, Juan Rivas-Davila, Ruochen Lu
Plasma Physics
Investigating the growth cycles of titania and carbonaceous nano dusty plasmas
Bhavesh Ramkorun
Solid nanoparticles which range in size from 1 to 500 nm can spontaneously grow from reactive gaseous precursors in nonthermal
plasmas. This dissertation studies the particle size, and growth time with and without a background
magnetic field in the
plasma. Traditionally, studies have focused on the growth of either carbonaceous or silicate
dust from either acetylene or silane, respectively. However, recently, there have been a shift towards studying new kinds of
dust. For example, recent studies have grown
polymers and metallic
dust. This dissertation first introduces and studies the growth of titanium dioxide
dust from the metal-organic vapor precursor of titanium tetraisopropoxide. The as-grown materials are amorphous but high temperature annealing crystallizes the samples into anatase and subsequently rutile. Then, the growth of titania dusty
plasma is and compared to the growth of carbonaceous
dust from acetylene, in argon
plasma. They are grown during the presence and absence of weak
magnetic fields of 500 Gauss. Both kinds of
dust growth exhibit a growth cycle, which had already been shown for various nano dusty
plasma. This occurs because once the
dust accumulates a critical radius and mass, they move away from the central region of the
plasma, allowing a new generation of growth begins. Ultimately, the new generation of growth also moves away leading to a continuous cycle of particle formation and transport as long as the
plasma is on. However, with the presence of the
magnetic field, the cycle time decreases, and the spatial distribution of the
dust cloud appears differently. Finally, we focus on the growth cycle time of carbonaceous
dust and how it decreases with a gradual increase in
magnetic field, varying from 20 - 1000 Gauss. We particularly noticed a minimum at 330 Gauss, which coincides with electron magnetization.
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Optics · Cross-listed from cond-mat.dis-nn
Non-Hermitian impurity problem
E. T. Kokkinakis, I. Komis, K. G. Makris et al. (+1 more)
The problem of a single Hermitian
impurity has long served as a cornerstone in condensed matter physics, offering fundamental insights into the mechanisms of Anderson localization. Yet, despite the increased interest in the spectral and localization properties of non-Hermitian
lattices with defects, the non-Hermitian extension of the single
impurity problem remains largely unexplored. In this work, we investigate the role of a single complex
impurity in one-, two-, and three-dimensional infinite tight-binding
lattices. Our study reveals a series of counterintuitive phenomena, including regions where localization vanishes and re-emerges as the
impurity strength varies. Next, we study the corresponding finite-sized
lattices, which are highly relevant to experimental realizations in readily accessible photonic platforms, revealing a variety of exotic features, such as scale-free localized states, exceptional points, and peculiar cross-shaped localized eigenstates, whose profiles deviate from the conventional exponential localization. This work paves the way for future studies on transport phenomena in non-Hermitian disordered
lattices.
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All authors E. T. Kokkinakis, I. Komis, K. G. Makris, E. N. Economou
Fluid Dynamics · Cross-listed from cond-mat.soft
DoS Dos and Don'ts
Lucas Warwaruk, Konstantinos Zinelis, Randy H. Ewoldt et al. (+2 more)
Dripping-onto-Substrate (DoS) rheometry is a well-established method for measuring the extensional rheology of low-viscosity
liquids. However, clear guidelines on the capabilities and limitations of the technique are lacking. In the present work, we define operational limits for measuring a transient extensional viscosity directly from observation of the rate of filament thinning, as well as model-based bounds on calculating a viscosity $\eta$ and extensional relaxation time $\tau_E$ of a
liquid using DoS. Dilute solutions of polyethylene
oxide (PEO) and polyacrylamide (PAM) are used to probe the lower limit of measurable $\tau_E$, demonstrating that values as low as 0.1 ms can be resolved, provided (a) the intrinsic Deborah number (based on the ratio of the relaxation time and the Rayleigh breakup time scale) is $De \geq \mathcal{O}(0.1)$ and (b) an instrumental constraint related to spatial and temporal resolution is satisfied. This instrumental constraint is quantified through a new metric we define as the filament capture rate, a “figure of merit” (expressed in Hz) that can be used to quantify the number of data points within the elasto-capillary regime that are available for extraction of $\tau_E$. We also investigate the sensitivity to other experimental parameters including variations in nozzle radius and Bond number ($Bo$). Across the tested range ($0.2 < Bo < 0.7$), extensional relaxation times for the same fluid vary by less than $\pm16$ %; however, experiments with low viscosity fluids at $Bo > 0.5$ exhibit damped gravitational oscillations that affect early-time dynamics. Collectively, these results provide a quantitative roadmap for reliable DoS rheometry and affirm its use for measuring sub-millisecond relaxation times in weakly elastic fluids.
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All authors Lucas Warwaruk, Konstantinos Zinelis, Randy H. Ewoldt, Christopher W. Macosko, Gareth H. McKinley
Optics · Cross-listed from eess.IV
Learning Latent Transmission and Glare Maps for Lens Veiling Glare Removal
Xiaolong Qian, Qi Jiang, Lei Sun et al. (+8 more)
Beyond the commonly recognized optical aberrations, the imaging performance of simplified optical systems–including single-lens and metalens designs–is often further degraded by veiling glare caused by stray-light scattering from non-ideal optical surfaces and coatings, particularly in complex real-world environments. This compound degradation undermines traditional lens aberration correction yet remains underexplored. A major challenge is that conventional scattering models (e.g., for dehazing) fail to fit veiling glare due to its spatial-varying and depth-independent nature. Consequently, paired high-quality data are difficult to prepare via simulation, hindering application of data-driven veiling glare removal models. To this end, we propose VeilGen, a generative model that learns to simulate veiling glare by estimating its underlying optical transmission and glare maps in an unsupervised manner from target images, regularized by Stable
Diffusion (SD)-based priors. VeilGen enables paired
dataset generation with realistic compound degradation of optical aberrations and veiling glare, while also providing the estimated latent optical transmission and glare maps to guide the veiling glare removal process. We further introduce DeVeiler, a restoration network trained with a reversibility constraint, which utilizes the predicted latent maps to guide an inverse process of the learned scattering model. Extensive experiments on challenging simplified optical systems demonstrate that our approach delivers superior restoration quality and physical fidelity compared with existing methods. These suggest that VeilGen reliably synthesizes realistic veiling glare, and its learned latent maps effectively guide the restoration process in DeVeiler. All code and
datasets will be publicly released at https://github.com/XiaolongQian/DeVeiler.
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All authors Xiaolong Qian, Qi Jiang, Lei Sun, Zongxi Yu, Kailun Yang, Peixuan Wu, Jiacheng Zhou, Yao Gao, Yaoguang Ma, Ming-Hsuan Yang, Kaiwei Wang
Optics
High system efficiency nonlinear frequency conversion on thin-film lithium niobate
Philipp Lohmann, Daniel Wendland, Francesco Lenzini et al. (+1 more)
Integrated photonic platforms can greatly enhance the efficiency of nonlinear frequency conversion processes by tightly confining light on a sub-micron scale. However, this advantage is often reduced by large fiber-to-chip coupling losses which drastically reduce the overall performance. Here we demonstrate a highly efficient thin-film lithium niobate frequency converter based on periodically poled waveguides combined with direct
laser written out-of-plane couplers. Including on-chip and fiber-to-chip losses we obtain a conversion efficiency of 152 %/W, thus demonstrating a promising approach for future scalable integrated devices.
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All authors Philipp Lohmann, Daniel Wendland, Francesco Lenzini, Wolfram H.P. Pernice
Instrumentation and Detectors
First operation of poly(ethylene naphthalate) enclosures for high-purity germanium detectors in liquid argon for $^{42}$K/$^{42}$Ar mitigation
Christoph Vogl, Tommaso Comellato, Konstantin Gusev et al. (+10 more)
Commercial argon contains cosmogenic $^{42}$Ar whose progeny $^{42}$K is a critical background component for the Large Enriched Germanium Experiment for Neutrinoless $\beta \beta$ Decay (LEGEND). LEGEND operates High-Purity Germanium (HPGe) detectors bare in
liquid argon. $^{42}$K is attracted by the HPGe detectors' electric fields, and drifts toward the germanium surface, where it undergoes beta decay. LEGEND-1000 will mitigate $^{42}$K-induced background by using underground-sourced argon, depleted in cosmogenic isotopes. If underground argon is not available, mitigation techniques must be employed. Poly(ethylene naphthalate) (PEN) enclosures were proposed to hinder the ion drift, decrease the beta-particle's energy, and produce scintillation light. In this paper, we report on operating two HPGe detectors, both bare and PEN-enclosed, in $^{42}$Ar-enriched
liquid argon, and find no evidence for deterioration of energy stability or resolution due to the enclosures. We monitor the beta and gamma rates of $^{42}$K, find complex time-dependencies extending to roughly 30 days after applying the HPGe detectors' high-voltage, and qualitatively demonstrate the $^{42}$K suppression capabilities of enclosures.
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All authors Christoph Vogl, Tommaso Comellato, Konstantin Gusev, Brennan Hackett, Patrick Krause, Andreas Leonhardt, Bela Majorovits, Niko N. P. N. Lay, Moritz Neuberger, Nadezda Rumyantseva, Mario Schwarz, Michael Willers, Stefan Schönert
Applied Physics · Cross-listed from cs.RO
FORWARD: Dataset of a forwarder operating in rough terrain
Mikael Lundbäck, Erik Wallin, Carola Häggström et al. (+8 more)
We present FORWARD, a high-resolution
multimodal dataset of a cut-to-length forwarder operating in rough terrain on two harvest sites in the middle part of Sweden. The forwarder is a large Komatsu model equipped with vehicle telematics sensors, including global positioning via satellite
navigation, movement sensors, accelerometers, and engine sensors. The forwarder was additionally equipped with cameras, operator vibration sensors, and multiple IMUs. The data includes event time logs recorded at 5 Hz of driving speed, fuel consumption, machine position with centimeter accuracy, and crane use while the forwarder operates in forest areas, aerially
laser-scanned with a resolution of around 1500 points per square meter. Production log files (Stanford standard) with time-stamped machine events, extensive
video material, and terrain data in various formats are included as well. About 18 hours of regular wood extraction work during three days is annotated from 360-
video material into individual work elements and included in the
dataset. We also include scenario specifications of conducted experiments on forest roads and in terrain. Scenarios include repeatedly driving the same routes with and without steel tracks, different load weights, and different target driving speeds. The
dataset is intended for developing models and
algorithms for trafficability, perception, and autonomous control of forest machines using artificial intelligence, simulation, and experiments on physical testbeds. In part, we focus on forwarders traversing terrain, avoiding or handling obstacles, and loading or unloading logs, with consideration for efficiency, fuel consumption, safety, and environmental impact. Other benefits of the open
dataset include the ability to explore auto-generation and calibration of forestry machine simulators and automation scenario descriptions using the data recorded in the field.
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All authors Mikael Lundbäck, Erik Wallin, Carola Häggström, Mattias Nyström, Andreas Grönlund, Mats Richardson, Petrus Jönsson, William Arnvik, Lucas Hedström, Arvid Fälldin, Martin Servin
Optics
Aspects of quantum geometry in photonic time crystals
Karthik Subramaniam Eswaran, Ali Emami Kopaei and Krzysztof Sacha
We develop a
geometric description of
quantum light in photonic time
crystals on the SU(1,1) coherent-state
manifold. In a projective picture, the
evolution of each mode appears as a Möbius isometry on the Poincaré disk, where
topologies of trajectories distinguish stable, unstable, and critical regimes. The
geometric phase is related to the
hyperbolic area enclosed by cyclic paths in the complex projective
Hilbert space. This framework offers an intuitive view of stability and
topology in
quantum photonic time
crystals.
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Accelerator Physics
Characterisation and mitigation of RF knockout during beam stacking
Carl Jolly, David Kelliher, Jean-Baptiste Lagrange et al. (+5 more)
Beam stacking allows a Fixed Field alternating gradient Accelerator (FFA) to increase the extracted beam current whilst also allowing for a flexible time structure making FFAs a promising candidate for future spallation
neutron sources and high beam intensity applications. For successful beam stacking, beam loss caused by RF knockout must be avoided. RF knockout can occur during beam stacking because of the finite dispersion function at the RF cavity location, which is unavoidable in a scaling FFA. In this work, the RF knockout resonance is characterised and through a series of experiments at the ISIS
Neutron and
Muon Source, we show that it is possible to suppress the loss from RF knockout.
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All authors Carl Jolly, David Kelliher, Jean-Baptiste Lagrange, Alan Letchford, Shinji Machida, David Posthuma de Boer, Chris Rogers, Andrew Seville
Plasma Physics
Efficient calculation of magnetic fields from ferromagnetic materials near strong electromagnets, and application to stellarator coil optimization
Matt Landreman, Humberto Torreblanca and Antoine Cerfon
In fusion reactor design, steels under consideration for the blanket are
ferromagnetic, so the steel's effect on the
plasma physics must be examined. For efficient calculation of these fields, we can exploit the fact that the
magnetic material gives a small perturbation relative to the fields from the electromagnetic coils and
plasma. Moreover the magnetization is saturated due to the strong fields in typical fusion systems. These approximations significantly reduce the nonlinearity of the problem, so the
magnetic materials can be described by an array of point dipoles of known magnitude, oriented in the direction of the coil and
plasma field. The approach is verified by comparison to finite-element calculations with commercial software and shown to be accurate. As no linear or nonlinear solve is required, only evaluation of Biot-Savart-type integrals, the method here is significantly simpler to implement than other methods, and extremely fast. The method is compatible with arbitrary CAD geometry, and also allows rapid computation of the
magnetic forces. We demonstrate adding the
ferromagnetic effects to free-boundary MHD
equilibrium calculations, assessing the effect on
plasma properties such as confinement and stability. Moreover, it is straightforward to differentiate through the model to get the derivative of the field with respect to the electromagnet parameters. We thereby demonstrate gradient-based coil optimization for a quasi-isodynamic stellarator in which the field contribution from a
ferromagnetic blanket is included. Even a significant steel volume is found to have little impact on the
plasma physics properties, with the main effects being a slight destabilization of ballooning modes and a radial shift of the edge islands due to decrease in rotational transform. Both issues are corrected by minor reoptimization of the coil shapes to account for the field from the steel.
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Data Analysis and Statistics · Cross-listed from hep-ex
A First Full Physics Benchmark for Highly Granular Calorimeter Surrogates
Thorsten Buss, Henry Day-Hall, Frank Gaede et al. (+5 more)
The physics programs of current and future
collider experiments necessitate the development of surrogate simulators for calorimeter showers. While much progress has been made in the development of generative models for this task, they have typically been evaluated in simplified scenarios and for single particles. This is particularly true for the challenging task of highly granular calorimeter simulation. For the first time, this work studies the use of highly granular generative calorimeter surrogates in a realistic simulation application. We introduce DDML, a generic library which enables the combination of generative calorimeter surrogates with realistic detectors implemented using the DD4hep toolkit. We compare two different generative models - one operating on a regular grid representation, and the other using a less common point cloud approach. In order to disentangle methodological details from model performance, we provide comparisons to idealized simulators which directly sample representations of different resolutions from the full simulation ground-truth. We then systematically evaluate model performance on post-reconstruction
benchmarks for electromagnetic shower simulation. Beginning with a typical single particle study, we introduce a first multi-particle
benchmark based on di-
photon separations, before studying a first full-physics
benchmark based on hadronic decays of the tau
lepton. Our results indicate that models operating on a point cloud can achieve a favorable balance between speed and accuracy for highly granular calorimeter simulation compared to those which operate on a regular grid representation.
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All authors Thorsten Buss, Henry Day-Hall, Frank Gaede, Gregor Kasieczka, Katja Krüger, Anatolii Korol, Thomas Madlener, Peter McKeown
Accelerator Physics
The impact of ionising collisions on channeling and radiation emission for high-energy electrons and positrons
Andrei V. Korol and Andrey V. Solov'yov
This paper presents a quantitative analysis of the impact of inelastic collisions with atoms in a crystalline environment on the channeling efficiency and intensity of the channeling radiation for high-energy electrons and positrons passing through oriented crystalline targets. This analysis is based on numerical simulations of the channeling process, which were performed using the MBN Explorer software package. Ionising collisions are considered random, fast and local events, and are incorporated into the classical relativistic molecular dynamics framework according to the previously described
algorithm. The case studies presented refer to 10 GeV electrons and positrons incident on single
crystals of diamond and silicon, oriented along the (110) and (111) planes, with thicknesses of up to 1 mm for electrons and 6 mm for positrons. To elucidate the role of ionising collisions, simulations were performed with and without accounting for them. It is shown that, for electrons, both approaches lead to similar results with regard to both the channelling efficiency and the radiation intensity. In practical terms, this means that numerical simulations can be carried out without accounting for ionising collisions, which are much faster yet produce similar results. For positrons, the ionising collisions reduce significantly the channeling efficiency. However, their impact on the radiation intensity strongly depends on the opening angle of the cone within which the radiation emission is collected. A quantitative analysis of this feature is presented in the paper.
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Computational Physics
A DSMC method for the space homogeneous multispecies Landau equation
Andrea Medaglia
We present a Direct Simulation Monte Carlo (DSMC) method for the spatially homogeneous multispecies Landau-Fokker-Planck equation. The scheme is derived from a first-order approximation of the multispecies Boltzmann operator in the grazing collision limit and employs a regularized, easy-to-sample scattering kernel that removes the need for iterative solvers while preserving the fundamental invariants of the Landau dynamics. The method is fully mesh-free – being a Monte Carlo particle
algorithm – which makes it naturally scalable to high-dimensional velocity spaces and straightforward to couple with particle-in-
cell (PIC) solvers via operator splitting. A notable feature of our approach is its ability to treat realistic mass ratios: we show accurate simulations up to the physical
proton-electron ($p$-$e$) mass ratio $m_p/m_e \approx 1836$. We validate the method against the multispecies BKW
benchmark for Maxwellian interactions and study collisional relaxation for Coulomb interactions, showing conservation of mass, momentum, and energy, and the expected trend towards Maxwellian
equilibria.
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Chemical Physics · Cross-listed from quant-ph
Enhancing Infrared Laser Dissociation of Molecules with the Electromagnetic Vacuum
Johan F. Triana and Felipe Herrera
Controlling bond breaking is a long-standing goal in molecular physics. Infrared nanocavities are currently being developed for reaching exotic coupling regimes of cavity QED with a few molecules, but it is not well understood how chemical reactions would proceed in such systems. To address this, we study infrared
laser photodissociation of a single CS$_{2}$ molecule with a stretching mode that strongly interacts with a resonant infrared
vacuum, subject to a strong
laser field that either resonantly drives the molecule at its fundamental vibration frequency or injects
photons at the cavity resonance. We show that the intensities required for photodissociation are significantly lower inside the cavity than in free space, with a strong dependence on the type of driving condition. By directly injecting
photons into the cavity, the molecule dissociates with two orders of magnitude less
laser energy than by directly driving the vibrational mode. This photodissociation enhancement is a purely
quantum mechanical effect that cannot be captured semi-classically. The intracavity ladder climbing dynamics is substantially modified relative to free space due to
vacuum-induced admixing a large number of vibrational
quantum numbers and the cavity field acting as a surrogate molecular mode that strongly interacts with the dissociative vibrational motion. Our work provides fundamental mechanistic understanding of chemical dynamics that can be used for designing new types of nanophotonics experiments that probe single-molecule chemistry.
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Instrumentation and Detectors
Performance of the front-end electronics of the CMS electromagnetic calorimeter barrel for the High-Luminosity LHC
The CMS Electromagnetic Calorimeter Group
The performance of the CMS electromagnetic calorimeter upgraded readout electronics, developed for the High-Luminosity phase of the LHC, is discussed. Data collected in two beam test campaigns conducted in 2018 and 2021 at the H4 and H2 beam lines of the CERN SPS are analyzed. Time and energy resolutions are measured on a $5\times 5$
matrix of lead tungstate
crystals equipped with prototypes of the new front end readout electronics, using electron and pion beams of energies spanning from 25 to 250 GeV. In both campaigns the constant term of the energy resolution is measured to be better than 0.6% and the time resolution for electrons with energies above 50 GeV is measured to be better than 30 ps, fulfilling the design requirements.
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Fluid Dynamics · Cross-listed from cond-mat.soft
Molecular insight on ultra-confined ionic transport in wetting films: the key role of friction
Aymeric Allemand, Anne-Laure Biance, Christophe Ybert et al. (+1 more)
Nanofluidic transport is ubiquitous in natural systems from extra-cellular communication in biology to geological phenomena, and promotes the emergence of new technologies such as energy harvesting and water desalination. While experimental access to ultraconfined fluids has advanced rapidly, their behavior challenges conventional theoretical descriptions based on Poisson-Boltzmann theory or the Stokes equation whose possible extension remains an open question. In this work, we use molecular dynamics simulations to investigate ionic transport within wetting films of water confined on silica surfaces down to the sub-nanometer scale. We then analyze these results using a simple one-dimensional theoretical framework. Remarkably, we show that this model remains valid even at confinement close to the molecular scale. Our results reveal that the dynamic of ion plays a key role in ionic transport, through ion adsorption at the water-silica interface. Adsorbed cations do not participate in ionic conduction, but instead generate molecular-scale roughness and transmit additional frictional forces to the substrate. This mechanism produces an apparent viscosity increase in electrostatically driven flows, reaching up to four times the bulk value in the case of potassium. Our findings highlight the critical role of interfacial ion adsorption in nanoscale hydrodynamics and provide new insights for interpreting experiments and designing nanofluidic systems.
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All authors Aymeric Allemand, Anne-Laure Biance, Christophe Ybert, Laurent Joly