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Physics Physics

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Thursday 11 December

Biological Physics · Cross-listed from quant-ph

Single-molecule Scale Nuclear Magnetic Resonance Spectroscopy using a Robust Near-Infrared Spin Sensor

Nuclear magnetic resonance (NMR) at the single-molecule level with atomic resolution holds transformative potential for structural biology and surface chemistry. Near-surface solid-state spin sensors with optical readout ability offer a promising pathway toward this goal. However, their extreme proximity to target molecules demands exceptional robustness against surface-induced perturbations. Furthermore, life science applications require these sensors to operate in biocompatible spectral ranges that minimize photodamage. In this work, we demonstrate that the PL6 quantum defect in 4H silicon carbide (4H-SiC) can serve as a robust near-infrared spin sensor. This sensor operates at tissue-transparent wavelengths and exhibits exceptional near-surface stability even at depth of 2 nm. Using shallow PL6 centers, we achieve nanoscale NMR detection of proton ($\mathrm{^{1}H}$) spins in immersion oil and fluorine ($\mathrm{^{19}F}$) spins in Fomblin, attaining a detection volume of $\mathrm{(3~nm)^3}$ and a sensitivity reaching the requirement for single-proton spin detection. This work establishes 4H-SiC quantum sensors as a compelling platform for nanoscale magnetic resonance, with promising applications in probing low-dimensional water phases, protein folding dynamics, and molecular interactions.
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All authors Yu Chen, Qi Zhang, Yuanhong Teng, Chihang Luo, Zhijie Li, Jinpeng Liu, Ya Wang, Fazhan Shi, Jiangfeng Du

Biological Physics · Cross-listed from quant-ph

Quantum relaxometry for detecting biomolecular interactions with single NV centers

The investigation of biomolecular interactions at the single-molecule level has emerged as a pivotal research area in life science, particularly through optical, mechanical, and electrochemical approaches. Spins existing widely in biological systems, offer a unique degree of freedom for detecting such interactions. However, most previous studies have been largely confined to ensemble-level detection in the spin degree. Here, we developed a molecular interaction analysis method approaching single-molecule level based on relaxometry using the quantum sensor, nitrogen-vacancy (NV) center in diamond. Experiments utilized an optimized diamond surface functionalized with a polyethylenimine nanogel layer, achieving $\sim$10 nm average protein distance and mitigating interfacial steric hindrance. Then we measured the strong interaction between streptavidin and spin-labeled biotin complexes, as well as the weak interaction between bovine serum albumin and biotin complexes, at both the micrometer scale and nanoscale. For the micrometer-scale measurements using ensemble NV centers, we re-examined the often-neglected fast relaxation component and proposed a relaxation rate evaluation method, substantially enhancing the measurement sensitivity. Furthermore, we achieved nanoscale detection approaching single-molecule level using single NV centers. This methodology holds promise for applications in molecular screening, identification and kinetic studies at the single-molecule level, offering critical insights into molecular function and activity mechanisms.
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All authors Min Li, Qi Zhang, Xi Kong, Sheng Zhao, Bin-Bin Pan, Ziting Sun, Pei Yu, Zhecheng Wang, Mengqi Wang, Wentao Ji, Fei Kong, Guanglei Cheng, Si Wu, Ya Wang, Sanyou Chen, Xun-Cheng Su, Fazhan Shi

Physics Education · Cross-listed from cs.DL

Balancing the Byline: Exploring Gender and Authorship Patterns in Canadian Science Publishing Journals

Canada is internationally recognized for its leadership in science and its commitment to equity, diversity, and inclusion (EDI) in STEM (science, technology, engineering, and math) fields. Despite this leadership, limited research has examined gender disparities in scientific publishing within the Canadian context. This study analyzes over 67,000 articles published in 24 Canadian Science Publishing (CSP) journals between 2010 and 2021 to better understand patterns of gender representation. Findings show that women accounted for less than one-third of published authors across CSP journals. Representation varied by discipline, with higher proportions of women in biomedical sciences and lower proportions of women in engineering - trends that mirror broader national and global patterns. Notably, the proportion of women submitting manuscripts closely matched those published, suggesting that broader workforce disparities may play a larger role than publication bias. Women were less likely to be solo authors or to hold prominent authorship positions, such as first or last author - roles typically associated with research leadership and career advancement. These findings point to the need for a two-fold response: continued efforts to address systemic barriers to women's participation in science, and a review of publishing practices to ensure equitable access, recognition, and inclusion for all researchers.
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All authors Eden J. Hennessey, Amanda Desnoyers, Margaret Christ, Adrianna Tassone, Skye Hennessey, Bianca Dreyer, Alex Jay, Patricia Sanchez, Shohini Ghose

Plasma Physics

A DC discharge plasma experiment for undergraduate laboratories

Plasma physics offers a wide range of fundamental phenomena, making it an excellent subject for undergraduate laboratory instruction. In this work, we present the design, construction, and characterization of a DC glow-discharge plasma chamber developed for the junior-level curriculum, a project carried out by two undergraduate students. The apparatus consists of a 1-meter-long quartz tube with a movable electrode, enabling systematic exploration of plasma behavior under varying pressure, voltage, and geometry. Using this platform, we characterized the Paschen breakdown relation and the voltage-current characteristics of the plasma. We then developed Langmuir probes to map spatial distributions of electron temperature and density, and used Boltzmann plot spectroscopy to measure excitation temperatures across different plasma regions. Finally, with custom Helmholtz coils, we demonstrated magnetic focusing of electrons. We performed Runge-Kutta simulations of particle trajectories and analyzed the electron drift velocity by comparing the focal lengths. Overall, this plasma chamber provides a versatile platform for investigating fundamental plasma phenomena and offers potential for future studies, including microwave-plasma interactions and other student-driven investigations.
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Atomic Physics

Search for a solar-bound axion halo using the Global Network of Optical Magnetometers for Exotic physics searches

We report on a search for a gravitationally bound solar axion halo using data from the Global Network of Optical Magnetometers for Exotic physics searches (GNOME), a worldwide array of magnetically shielded atomic magnetometers with sensitivity to exotic spin couplings. Motivated by recent theoretical work suggesting that self-interacting ultralight axions can be captured by the Sun's gravitational field and thermalize into the ground state, we develop a signal model for the pseudo-magnetic fields generated by axion-proton gradient couplings in such a halo. The analysis focuses on the fifth GNOME Science Run (69 days, 12 stations), employing a cross-correlation pipeline with time-shifted daily modulation templates to search for the global, direction-dependent, monochromatic signal expected from a solar axion halo. No statistically significant candidate signals are observed. We set 95% confidence-level upper limits on the amplitude of the axion-induced pseudo-magnetic field over the frequency range $\approx 0.05-20$ Hz, translating to constraints on the linear and quadratic axion-proton couplings for halo densities predicted by gravitational capture models and for the maximum overdensities allowed by planetary ephemerides. In the quadratic coupling case, our limits surpass existing astrophysical bounds by over two orders of magnitude across much of the accessible parameter space.
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All authors Tatum Z. Wilson, Derek F. Jackson Kimball, Samer Afach, Jiexiao Bi, B. C. Buchler, Dmitry Budker, Kaleb Cervantes, Joshua Eby, Nataniel L. Figueroa, Ron Folman, Jiawei Gao, Daniel Gavilán-Martín, Menachem Givon, Zoran D. Grujić, Hong Guo, Paul Hamilton, M. P. Hedges, Zhejun Huang, Dongok Kim, Younggeun Kim, Sami S. Khamis, Emmanuel Klinger, Abaz Kryemadhi, Nina Kukowski, Jianjun Li, Grzegorz Lukasiewicz, Hector Masia-Roig, Tafai Muck, Michal Padniuk, Christopher A. Palm, Chaitanya Paranjape, Sun Yool Park, Xiang Peng, Gilad Perez, Rayshaun Preston, Szymon Pustelny, Wolfram Ratzinger, Yossi Rosenzweig, Ophir M. Ruimi, Amy Saputo, Theo Scholtes, P. C. Segura, Yannis K. Semertzidis, Yun Chang Shin, Jason E. Stalnaker, Ibrahim Sulai, Dhruv Tandon, Rayshaun Thompson, Ken Vu, Arne Wickenbrock, Teng Wu, Yucheng Yang, Yixin Zhao

Computational Physics

Flow-priority optimization of additively manufactured variable-TPMS lattice heat exchanger based on macroscopic analysis

Heat exchangers incorporating triply periodic minimal surface (TPMS) lattice structures have attracted considerable research interest because they promote uniform flow distribution, disrupt boundary layers, and improve convective heat-transfer performance. However, from the perspective of forming a macroscopic flow pattern optimized for heat-exchange efficiency, a uniform lattice is not necessarily the optimal configuration. This study initially presents a macroscopic modeling approach for a two-fluid heat exchanger equipped with a TPMS Primitive lattice. The macroscopic flow analysis is conducted based on the Darcy–Forchheimer theory. Under the assumption that heat is transferred solely at the interface between the fluid and the TPMS walls, a macroscopic heat-transfer model is developed using a volumetric heat-transfer coefficient, which serves as an artificial property characterizing the unit-volume heat-transfer capability. To regulate the relative dominance of the hot and cold flows-effectively, the channel widths-within the heat exchanger, we adopt the isosurface threshold of the Primitive lattice as the design variable and construct an optimization scheme for the lattice distribution using the previously described macroscopic model. The optimization is subsequently carried out for a planar heat exchanger where the hot and cold fluids each follow U-shaped flow trajectories. The optimal solution was verified, and its validity was examined through detailed geometric analysis and experiments conducted using metal LPBF. The optimal solution derived from the macroscopic model also demonstrated a clear performance advantage over the uniform lattice in the experimental results. The optimal solution obtained from the macroscopic model also demonstrated a clear performance improvement over the uniform lattice, with an average enhancement of 28.7% in the experimental results.
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All authors Kazutaka Yanagihara, Jun Iwasaki, Kiyoto Saso, Taichi Yamashita, Shomu Murakoshi, Akihiro Takezawa

Optics · Cross-listed from quant-ph

Photorefractive-based on-chip optical power limiter against light-injection attacks in quantum key distribution

Light-injection attacks pose critical security threats to quantum key distribution (QKD) systems. Conventional countermeasures, such as isolators, filters, and optical power monitoring, suffer from limited on-chip compatibility and inherent security vulnerabilities. To overcome these limitations, we propose and experimentally demonstrate an integrated attack sensing and automatic response unit utilizing the photorefractive effect in a thin-film lithium niobate microring resonator. The unit provides a rejection ratio exceeding 25 dB against non-resonant injected light. Under resonant attacks with power levels above tens of microwatts, the unit autonomously attenuates the signal transmission, with 14 dB attenuation measured at the maximum tested attack power of 10 dBm, leading to a significant suppression of the secure key rate. We further verify its response to pulsed light injection and incorporate possible residual leakage associated with finite response time into the key-rate analysis. This work provides a highly sensitive, broadband, and fully on-chip defense mechanism that significantly enhances the physical-layer security of QKD systems against light-injection attacks.
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All authors Min Chen, Hong-Yan Song, Jia-Lin Chen, Peng Ye, Guo-Wei Zhang, Fang-Xiang Wang, Li Zhang, Shuang Wang, De-Yong He, Zhen-qiang Yin, Guang-Can Guo, Wei Chen, Zheng-Fu Han

Optics

Heteronuclear and Homonuclear Vector Solitons in Lasers

Vector solitons (VSs), being observed across various fields from optics to Bose-Einstein condensates, are localized structures composed of orthogonal modes bound by nonlinear couplings. Nevertheless, the influence of intermodal linear coupling on the physical properties of this bimodal structure remains to be decently revealed and harnessed. Utilizing an ultrafast fiber laser as a platform, we predict and demonstrate that the linear mode coupling (LMC) induces the deformable VS in terms of the temporal and spectral structures. Weak LMC supports heteronuclear vector solitons built of dissimilar polarization modes, i.e., a single pulse coupled to an orthogonal damped pulse chain. On the other hand, strong LMC facilitates the homonuclear VS composed of polarization modes with similar structures, in the form of soliton compounds featuring caterpillar motions. Our findings reveal new patterns of VSs and open an effective avenue for versatile ultrafast optical sources.
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All authors Du Yueqing, Zhang Zhenzhu, Zhang Heze, Xue Jia, Zeng Chao, Cui Yudong, Mao Dong, Malomed Boris, Zhao Jianlin

Wednesday 10 December

Computational Physics

BattMo – Battery Modelling Toolbox

This paper presents the Battery Modelling Toolbox (BattMo), a flexible finite volume continuum modelling framework in MATLAB\textsuperscript{\textregistered} (\citeproc{ref-MATLAB}{The MathWorks Inc., 2025}) for simulating the performance of electro-chemical cells. BattMo can quickly setup and solve models for a variety of battery chemistries, even considering 3D designs such as cylindrical and prismatic cells. The simulation input parameters, including the material parameters and geometric descriptions, are specified through JSON schemas. In this respect, we follow the guidelines of the Battery Interface Ontology (BattINFO) to support semantic interoperability in accordance with the FAIR principles (\citeproc{ref-fair}{Wilkinson et al., 2016}). The Doyle-Fuller-Newman (DFN) (\citeproc{ref-Doyle1993ModelingCell}{Doyle et al., 1993}) approach is used as a base model. We include fully coupled thermal simulations. It is possible to include degradation mechanisms such as SEI layer growth, and the use of composite material, such as a mixture of Silicon and graphite. The models are setup in a hierarchical way, for clarity and modularity. Each model corresponds to a computational graph, which introduces a set of variables (the nodes) and functional relationship (the edges). This design enables the flexibility for changing and designing new models. The solver in BattMo uses automatic differentiation and support adjoint computation. We can therefore compute the derivative of objective functions with respect to all parameters efficiently. Gradient-based optimization routines can be used to calibrate parameters from experimental data.
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All authors Xavier Raynaud, Halvor Møll Nilsen, August Johansson, Eibar Flores, Lorena Hendrix, Francesca Watson, Sridevi Krishnamurthi, Olav Møyner, Simon Clark

Biological Physics

Subcellular Metabolic Tracking Using Fluorescent Nanodiamonds Relaxometry

Fluorescent nanodiamonds (FNDs) relaxometry holds promising future for advancement of high spatiotemporal resolution metabolic imaging technology. In this study, we demonstrate a simultaneous integration of spatial position tracking with FND relaxometry to characterize the temporal dynamics of metabolic processes, thereby enhancing the capability to monitor cellular activities over time. To enable targeted metabolic probing in living cells, FNDs were surface-functionalized to achieve specific localization within key organelles, including the nucleus and mitochondria. This strategy not only facilitates subcellular-level metabolic monitoring but also allows for direct comparison between intra- and extranuclear microenvironments within the same living cell, offering substantial potential for elucidating the spatial and functional heterogeneity of cellular metabolism.
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All authors Jia Su, Linyu Zeng, Pengyu Chen, Zenghao Kong, Fazhan Shi

General Physics

Matter-free gravitational collapse and the equivalence principle

The dynamics of a degenerate spherically symmetric wormhole in a vacuum is considered. An extension of the equivalence principle to matter free objects that are the source of a gravitational field is proposed. Using the Klinkhamer metric as an example, it is shown that a degenerate wormhole is precisely such an object. Application of the extended equivalence principle reduces the radial dynamics of the Klinkhamer wormhole to the dynamics of the radial fall of a test particle in a Schwarzschild gravitational field. It is proven that any bound state of the traversable Klinkhamer wormhole eventually collapses into a nontraversable Einstein-Rosen wormhole. An estimate is presented showing that the traversable Klinkhamer wormhole, although nonstationary, is a longlived state.
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Physics and Society

Language, participation and inclusivity in the urban planning process in Mzuzu City

Participation in urban planning is championed for entrenching democracy and development. Malawi passed the Local Government Act (1998) and Decentralization Policy (1998) to facilitate community participation in decision-making processes. Several studies have been conducted on decentralization and local governance on community participation. Little attention has been paid to examining the impact of the language used in planning processes on democracy and inclusivity envisaged in the law and policy. Using communicative action theory, the study examined challenges posed by language used in planning processes on inclusivity in the approval processes of urban plans. Data were collected through semi-structured interviews, focus group discussions, observations and document review and analyzed using thematic and discourse analysis. The findings show that while there is high participation at community planning levels, because planners communicate using local languages, participation is compromised in the service committees at city level where final planning decisions are made due to language barrier. Specifically, lack of sincerity, truthfulness, comprehensibility and therefore legitimacy are apparent. Planners are reluctant to simplify written language and translate planning jargon into local languages for councillors to understand. The study concludes that community participation in the urban planning process in Mzuzu fails to entrench democracy due to lack of inclusiveness owing to the language barrier at city level where final planning decisions are made. The study proposes a framework for inclusive participation in urban planning including the motivation, conditions for effective participation and outcomes of participation.
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Physics and Society

Topological Dirac cluster synchronization on directed hypergraphs

Topological higher-order synchronization reveals collective phenomena demonstrating how topology shapes dynamics, yet providing a general theoretical framework for designing and controlling dynamical states on higher-order networks remains a challenge of the field. Here we propose a dynamical systems framework for topological cluster synchronization on directed hypergraphs that can be used to design synchronization patterns on nodes and hyperedges of directed hypergraphs. By encoding oriented hyperedges into the hypergraph topological Dirac Hamiltonian, we obtain a spectrum whose isolated eigenstates correspond to distinct topological synchronization cluster states defined jointly on nodes and hyperedges. By selecting any isolated eigenstate, the system can be driven toward the associated dynamical state reflecting a specific partition of the hypergraph without modifying the underlying hypergraph structure. We numerically demonstrate the ability to design different topological cluster synchronization states on directed-hypergraph block models and empirical systems-including higher-order contact networks and the ABIDE functional brain network. Our results establish a general and interpretable route for controlling collective dynamics in directed higher-order systems.
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All authors Yupeng Guo, Ahmed A. A. Zaid, Xueming Liu, Ginestra Bianconi

Fluid Dynamics

Reduced-Order Hydrodynamic Modelling of a Sphere Near a Wall Using Sparse Regression and Neural Networks

This work presents an interpretable parametric surrogate model motivated by the need to identify a hydrodynamic model for resolving the trajectory of an object in real-time. The surrogate is formulated as a reduced-order model for a canonical configuration in which a one-degree-of-freedom heaving sphere operates near a vertical wall. High-fidelity CFD simulations are used to generate a parametric dataset of heave-decay responses over varying wall distances (WD) and drop heights (DH). Sparse Identification of Nonlinear Dynamics (SINDy) is then applied to each CFD trajectory to identify a low-order nonlinear ordinary differential equation (ODE) with polynomial terms representing effective hydrostatic restoring and radiation damping, and the harmonic terms representing the wave-induced excitation forces. The SINDy identified coefficients are then used as a prior constraint in a neural operator network (ONet) that learns a smooth mapping from wall distance and drop height to the ODE coefficients, yielding a surrogate capable of predicting dynamics at arbitrary points in the input space without rerunning expensive CFD calculations. The resulting surrogate reproduces CFD heave-decay responses with near-optimal accuracy given the limiting assumptions while being capable of running in real time. The approach provides a practical pathway toward real-time, physics-informed surrogate modelling for launch-and-recovery operations.
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All authors Zev Hoffman, Sara Vahaji, Arpan Das, Micheal Candon, Daniel Sgarioto, Jayarathne Nirman, Pier Marzocca

Optics

Solid-state Laser Cooling

Since the first proof-of-concept demonstrations of photoluminescence-based optical refrigeration, solid-state laser cooling has developed into a credible competitor to conventional cryogenic technologies. Solid-state laser cooling continues to advance as new materials push cooling limits. These developments have created a need to consolidate progress made to date as well as standardize critical experimental considerations needed for reliable and verifiable cooling measurements. This primer therefore outlines essential concepts and requirements, which underpin solid-state laser cooling. The primer summarizes key milestones achieved with cooling-grade, rare-earth-doped glasses and crystals as well as with semiconductors. It additionally highlights emerging applications of solid-state optical refrigeration. To strengthen the consistency and reproducibility of cooling results going forward, two reporting checklists are introduced. They cover materials, cooling metrics, and thermometry. This primer is intended to serve as both a tutorial and a practical reference for incoming and existing researchers involved in solid-state laser-cooling.
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All authors Yang Ding, Shenghao Zhang, Alexander R. Albrecht, Zhaojie Feng, Lars Forberger, Hiroki Tanaka, Markus P. Hehlen, Galina Nemova, Peter J. Pauzauskie, Denis V. Seletskiy, Masaru Kuno

Optics

Momentum-space non-Hermitian skin effect in an exciton-polariton system

Localization of a macroscopic number of eigenstates on a real-space boundary, known as the non-Hermitian skin effect, is one of the striking topological features emerging from non-Hermiticity. Realizing this effect typically requires periodic (lattice) systems with asymmetry of intersite coupling, which is not readily available in many physical platforms. Instead, it is meticulously engineered, e.g., in photonics, which results in complex structures requiring precise fabrication steps. Here, we propose a simpler mechanism: introducing an asymmetric, purely imaginary potential in a topologically trivial system induces momentum-space localization akin to the skin effect. We experimentally demonstrate this localization using exciton polaritons, hybrid light-matter quasi-particles in a simple engineered `round box' trap, pumped by a laser pump offset from the trap center. The effect disappears if the pump is concentric with the trap. The localization persists and becomes stronger at higher densities of polaritons, when a non-equilibrium Bose-Einstein condensate is formed and the system becomes nonlinear. Our approach offers a new route to realizing skin effects in continuous, non-periodic systems and exploring the interplay of non-Hermiticity, topology, and nonlinearity in macroscopic quantum states.
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All authors Yow-Ming Hu, Mateusz Król, Daria A. Smirnova, Lev A. Smirnov, Bianca Rae Fabricante, Karol Winkler, Martin Kamp, Christian Schneider, Sven Höfling, Timothy C. H. Liew, Andrew G. Truscott, Elena A. Ostrovskaya, Eliezer Estrecho

Optics · Cross-listed from cond-mat.mes-hall

Harnessing Vacuum Fluctuations to Shape Electronic and Photonic Behavior

Vacuum quantum fluctuations are an inescapable and fundamental feature of modern physics. By integrating cavity-enhanced or surface-modified vacuum quantum fluctuations with low-dimensional materials, a new paradigm-vacuumronics-emerges, enabling unprecedented control over both material properties and photonic responses at the micro- and nanoscale. This synergy opens novel pathways for engineering quantum light-matter interactions, advancing applications in quantum photonics, nanoscale optoelectronics, and quantum material design.
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Instrumentation and Detectors

{\mu}RWELL-PICOSEC: Precision Timing with Resistive Micro-Well Detector

The PICOSEC detector concept uses a micro-pattern gaseous detector (MPGD) amplification structure combined with a Cerenkov radiator coated with a semi-transparent photocathode to provide below tens of picosecond-level precision timing capabilities with minimum ionizing particles. PICOSEC has triggered interest in the development of time-of-flight detectors for particle identification and timing detectors for track reconstruction in the high rate environment of future nuclear and high energy physics experiments. The PICOSEC Micromegas (or PICOSEC-MM) detector, developed by the CERN-based PICOSEC collaboration, use the Micromegas structure for gaseous amplification and achieve below 20 ps timing resolution. A new type of PICOSEC detector, the {\mu}RWELL-PICOSEC based on {\mu}RWELL amplification structure, is being investigated at Thomas Jefferson National Accelerator Facility (Jefferson Lab) alongside PICOSEC-MM R&D efforts in Europe. Preliminary results from the two 2024 beam test campaigns at CERN demonstrate a timing performance better than 24 ps is achievable with a single-channel {\mu}RWELL-PICOSEC prototype. A vigorous R&D effort is ongoing to improve the timing performance, robustness and operational stability of {\mu}RWELL-PICOSEC detectors. Development of a large size {\mu}RWELL-PICOSEC is also under consideration for applications in large scale experiments.
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Computational Physics

Generative Modeling of Entangled Polymers with a Distance-Based Variational Autoencoder

We present a variational autoencoder framework for learning and generating configurations of structured polymer globules from distance matrices. We used coarse-grained molecular dynamics to sample polyethylene structures, which we used as the training set for our deep learning model. By combining convolution and attention layers, the model encodes the structural patterns of distance matrices into an organized and roto-translationally invariant latent space of lower dimensionality. The generative capability of the variational autoencoder, coupled with a post-processing pipeline based on multidimensional scaling and short molecular dynamics, enables the recovery of physically meaningful configurations. The reconstructed and generated samples reproduce key observables, including energy, size, and entanglement, despite minor discrepancies in the raw decoder output.
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All authors Pietro Chiarantoni, Oscar Serra, Mohammad Erfan Mowlaei, Venkata Surya Kumar Choutipalli, Mark DelloStritto, Xinghua Shi, Micheal L. Klein, Vincenzo Carnevale

Computational Physics

A Model-Guided Neural Network Method for the Inverse Scattering Problem

Inverse medium scattering is an ill-posed, nonlinear wave-based imaging problem arising in medical imaging, remote sensing, and non-destructive testing. Machine learning (ML) methods offer increased inference speed and flexibility in capturing prior knowledge of imaging targets relative to classical optimization-based approaches; however, they perform poorly in regimes where the scattering behavior is highly nonlinear. A key limitation is that ML methods struggle to incorporate the physics governing the scattering process, which are typically inferred implicitly from the training data or loosely enforced via architectural design. In this paper, we present a method that endows a machine learning framework with explicit knowledge of problem physics, in the form of a differentiable solver representing the forward model. The proposed method progressively refines reconstructions of the scattering potential using measurements at increasing wave frequencies, following a classical strategy to stabilize recovery. Empirically, we find that our method provides high-quality reconstructions at a fraction of the computational or sampling costs of competing approaches.
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All authors Olivia Tsang, Owen Melia, Vasileios Charisopoulos, Jeremy Hoskins, Yuehaw Khoo, Rebecca Willett

Instrumentation and Detectors

A Computational Procedure for Assessing I$_c$($\varepsilon$) in Nb$_3$Sn/Bi-2212 Hybrid Magnets

The critical current of superconductors is commonly measured by testing unloaded wires under an external magnetic field. While stressed by intense Lorentz forces, the existing HTS/LTS superconductors are prone to a reduction in critical current before reaching their structural mechanical limit. In this work, the magnetic and mechanical analysis of the FNAL 4-layer Bi-2212/Nb$_3$Sn hybrid dipole magnet is reported, aimed at predicting the critical current degradation for both the superconductors during powering at 16 T. All the Rutherford cables in the coils of the hybrid magnet were modeled at the strand level in Ansys APDL with the heterogeneous cable model. Utilizing this detailed geometry, it was possible to evaluate the effects of strain on the critical current degradation for both the Nb$_3$Sn and Bi-2212 superconductors under the intense Lorentz forces. The analysis presented in this paper integrates strain-dependent critical current laws, with parameters derived from experimental data, to simulate the hybrid magnet's performance for all possible current-powering configurations. The proposed methodology enables a detailed assessment of conductor integrity and I$_C$($\varepsilon$) reduction in existing hybrid magnet designs, providing a versatile and rigorous framework for optimizing future high-field hybrid magnets.
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All authors A. D'Agliano, A. V. Zlobin, I. Novitski, G. Vallone, P. Ferracin, E. Barzi, S. Donati, V. Giusti

Biological Physics

Unifying Theories in High-Dimensional Biology: Approaches, Challenges and Opportunities

Across biological subdisciplines, the last decade has seen an explosion of high-dimensional datasets, including datasets for cells, species, immune systems, neurons and behaviour. At the ICTS workshop 'Unifying Theories in High-Dimensional Biophysics' we discussed whether this high dimensionality poses a challenge or opportunity for describing, understanding and predicting biological systems theoretically. We discussed methods, models and frameworks that can help with addressing empirical observations based on these high-dimensional datasets. We summarize the challenges and opportunities that emerged in discussions according to individual participants below.
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All authors Marianne Bauer, Akshit Goyal, Sidhartha Goyal, Gautam Reddy, Shaon Chakrabarti, Michael M Desai, William Gilpin, Jacopo Grilli, Kabir Husain, Sanjay Jain, Mohit Kumar Jolly, Kyogo Kawaguchi, Aneta Koseska, Milo Lin, Leelavati Narlikar, Simone Pigolotti, Archishman Raju, Krishna Shrinivas, Rahul Siddharthan, Greg J Stephens, Andreas Tiffeau-Mayer, Suriyanarayanan Vaikuntanathan

Applied Physics

Investigation of Real-Space Transfer Noise in InP Quantum Wells

Indium phosphide (InP) high electron-mobility transistors (HEMTs) are widely used in many fields such as quantum computing because of their unparalleled microwave noise performance. Achieving improved noise performance requires a physical understanding of the noise mechanisms. Here, we experimentally test a theoretical proposal for drain (output) noise as originating in part from real-space transfer (RST) by characterizing the microwave noise temperature of transfer-length method structures with the same channel composition but two different barrier compositions. This choice was made to alter the confining potential of electrons in the channel, thereby affecting the RST mechanism, while avoiding changes to the channel transport properties. We observe trends of noise temperature with physical temperature and source-drain voltage which are compatible with the predictions of RST noise theory. This finding supports the hypothesis that RST contributes to drain noise in HEMTs.
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All authors Jiayin Zhang, Anthony J. Ardizzi, Kieran A. Cleary, Austin J. Minnich

Instrumentation and Detectors · Cross-listed from hep-ex

Enabling searches for long-lived particles at a future 10 TeV Muon Collider

Muon Colliders offer fantastic opportunities to explore new phenomena at the energy frontier. However, beam-induced-backgrounds from muon decays pose significant challenges for detector design, readout, and reconstruction. Previous detector studies have employed stringent hit-timing requirements to reduce occupancy to manageable levels with negligible efficiency loss for prompt Standard Model particles. In the spirit of maximizing discovery potential, we investigate the capability of detecting meta-stable charged long-lived particles at a 10 TeV Muon Collider. As a benchmark, we consider a Gauge Mediated Supersymmetry Breaking (GMSB) model in which the stau is long-lived and can be identified as a high momentum, slowly moving track. We find that nominal hit-timing selections are too restrictive, and investigate the impact of looser requirements. We demonstrate that it is possible to recover sensitivity to particles with masses close to $\sqrt{s}/2$ by expanding time acceptance, and provide recommendations to further improve tracker design and track reconstruction.
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All authors Mira Littmann, Mark Larson, Kate Wandrisco, Benjamin Rosser, Tate Flicker, Kane Huang, Leo Rozanov, Karri Folan Di Petrillo

Optics

Generation of Perfectly Achromatic Optical Vortices Using a Compensated Tandem Twisted Nematic Cell

The generation of white optical vortices is currently constrained by intrinsic trade-offs between spectral bandwidth, conversion efficiency, and temporal pulse integrity in conventional diffractive and geometric-phase approaches. In this work, we theoretically investigate a compensated tandem crossed twisted nematic (TN) liquid crystal architecture that overcomes these fundamental limitations. By developing a rigorous Jones matrix model and defining specific figures of merit for chromatic fidelity, we analyze the impact of manufacturing imperfections and non-adiabatic waveguiding (deviations from the Mauguin regime) on the device performance. We propose and evaluate three distinct compensation strategies, ranging from optimized passive designs for specific manufacturing tolerances to a robust active compensation scheme utilizing a tunable retarder. Our analysis demonstrates that the active approach effectively nullifies parasitic amplitude modulation, enabling the generation of perfectly achromatic vortices with high phase purity across an arbitrary bandwidth. This establishes the compensated tandem TN cell as a superior and versatile platform for high-fidelity white-light singular optics.
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Computational Physics · Cross-listed from math.NA

Efficient Boys function evaluation using minimax approximation

We present an algorithm for efficient evaluation of Boys functions $F_0,\dots,F_{k_\mathrm{max}}$ tailored to modern computing architectures, in particular graphical processing units (GPUs), where maximum throughput is high and data movement is costly. The method combines rational minimax approximations with upward and downward recurrence relations. The non-negative real axis is partitioned into three regions, $[0,\infty\rangle = A\cup B\cup C$, where regions $A$ and $B$ are treated using rational minimax approximations and region $C$ by an asymptotic approximation. This formulation avoids lookup tables and irregular memory access, making it well suited hardware with high maximum throughput and low latency. The rational minimax coefficients are generated using the rational Remez algorithm. For a target maximum absolute error of $\varepsilon_\mathrm{tol} = 5\cdot10^{-14}$, the corresponding approximation regions and coefficients for Boys functions $F_0,\dots,F_{32}$ are provided in the appendix.
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Data Analysis and Statistics · Cross-listed from stat.ME

A Primer on Bayesian Parameter Estimation and Model Selection for Battery Simulators

Physics-based battery modelling has emerged to accelerate battery materials discovery and performance assessment. Its success, however, is still hindered by difficulties in aligning models to experimental data. Bayesian approaches are a valuable tool to overcome these challenges, since they enable prior assumptions and observations to be combined in a principled manner that improves numerical conditioning. Here we introduce two new algorithms to the battery community, SOBER and BASQ, that greatly speed up Bayesian inference for parameterisation and model comparison. We showcase how Bayesian model selection allows us to tackle data observability, model identifiability, and data-informed model development together. We propose this approach for the search for battery models of novel materials.
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All authors Yannick Kuhn, Masaki Adachi, Micha Philipp, David A. Howey, Birger Horstmann

Data Analysis and Statistics · Cross-listed from cs.LG

Detailed balance in large language model-driven agents

Large language model (LLM)-driven agents are emerging as a powerful new paradigm for solving complex problems. Despite the empirical success of these practices, a theoretical framework to understand and unify their macroscopic dynamics remains lacking. This paper proposes a method based on the least action principle to estimate the underlying generative directionality of LLMs embedded within agents. By experimentally measuring the transition probabilities between LLM-generated states, we report evidence consistent with a tendency toward detailed balance in LLM-generated transitions, indicating that LLM generation may not be achieved by generally learning rule sets and strategies, but rather by implicitly learning a class of underlying potential functions that may transcend different LLM architectures and prompt templates. To our knowledge, this provides an effective macroscopic description of LLM generative dynamics that does not depend on specific model details. This work is an attempt to establish a macroscopic dynamics theory of complex AI systems, aiming to elevate the study of AI agents from a collection of engineering practices to a science built on effective measurements that are predictable and quantifiable.
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All authors Zhuo-Yang Song, Qing-Hong Cao, Ming-xing Luo, Hua Xing Zhu

Applied Physics · Cross-listed from quant-ph

Broadband Spatio-Spectral Mode Conversion via Four-Wave Mixing

We introduce a framework for scalable and broadband free-space phase-matched four-wave mixing in ring resonators. This method for four-wave mixing reduces the complexity of coupling an emitter to a quantum network by combining the spatial and spectral interfaces between them into one nonlinear optical process. The device is compliant with current heterogeneous integration capabilities and has a bandwidth of 165 nm for efficient spatio-spectral conversion. We outline a fabrication-ready diamond-on-insulator pathway towards modular unit cells that natively bridge visible color centers to the infrared spectrum for scalable quantum networks. We also present and analyze an end-to-end framework for considering single-photon coupling efficiency from a color center to a quantum network. This framework represents a step forwards in analyzing and reducing system-scale losses in a spin-photon interface.
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All authors Helaman Flores, Mahmoud Jalali Mehrabad, Siavash Mirzaei-Ghormish, Ryan M. Camacho, Dirk Englund

Instrumentation and Detectors

Identifying Neutron Sources using Recoil and Time-of-Flight Spectroscopy

Neutron-source identification is central to nuclear physics and its applications, from planetary science to nuclear security, yet direct source discrimination from measured neutron spectra remains fundamentally elusive. Here, we introduce a Bayesian protocol that directly infers source ensembles from measured neutron spectra by combining full-spectrum template matching with probabilistic evidence evaluation. Applying this protocol to recoil and time-of-flight spectroscopy, we recover single- and two-source configurations with strong statistical significance ($>\!\!4\sigma$) at event counts as low as $\sim\!\!10^{3}$. These results demonstrate that neutron spectral signatures can be leveraged for robust source identification, opening a new observational window for both fundamental research and operationally driven applications.
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All authors David Breitenmoser, Ricardo Lopez, Shaun D. Clarke, Sara A. Pozzi