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Physics Physics

physics Watch Physics

Tuesday 24 March

Atomic Physics

Very sensitive vapor-cell quasi-DC atomic E-field sensor

Amy Damitz, George Burns and Yuan-Yu Jau

We report several technical approaches that significantly improve the performance of a vapor-cell atomic electrometer operating in the quasi-DC frequency domain ($\ll$ 1 kHz). With a very small active volume of approximately 11 mm$^3$ inside the vapor cell, we demonstrated a noise floor for electric field (E-field) sensitivity ranging from 0.2 to 7.7 mV/m$\sqrt{\rm Hz}$ for a frequency band of 1–100 Hz. Our work utilizes only a bare vapor cell for electrometry, without any metal parts or electrodes, to ensure minimal distortion of the measured E-field and to minimize the effective sensing volume for high spatial resolution. The E-field-sensitive atomic state (Rydberg state) is excited and read out optically, maximizing the simplicity of the system design and enabling the miniaturization of quasi-DC E-field sensors for potential applications, such as diagnostics of electronics without physical contact, communications in and below the super-low frequency (SLF) band, proximity detection, remote activity surveillance, tracing charge signatures, and research in bioscience and geoscience.
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Optics

On Sub-Sevenfold Symmetries in LH2 Stacked Ring Scaffolds: A Quantum Optical Perspective

Arpita Pal

For highly efficient light-harvesting, purple photosynthetic bacteria rely on light-harvesting 2 (LH2) complexes featuring ninefold, eightfold, and sevenfold rotational symmetries; however, sub-sevenfold scaffolds have not yet been observed in nature. To investigate this absence, we utilize a closed coupled-dipole model that neglects dissipative effects, which remains valid for a temporal window shorter than the interlayer excitation energy transfer time (on the picosecond scale) in an LH2 scaffold. We examine collective eigenmodes across $C_n$ stacked model ring geometries for $n=9,8,7,6$. Our results demonstrate that the minimum energy separation between specific collective bands occurs at the angular-momentum modes $m=\pm 1$ for known geometries, effectively predicting the photoactive absorption wavelengths of the lower bacteriochlorophyll (BChl) ring. Specifically, we predict peaks at 851, 848, and 825 nm for ninefold, eightfold, and sevenfold symmetries, respectively, which agree well with experimental observations. Applying this analysis to a hypothetical sixfold geometry, we predict a significant blue shift in the photoactive wavelength of the lower BChl ring, suggesting inefficient harvesting of the available solar spectrum and offering a quantum optical perspective on the evolutionary absence of sub-sevenfold scaffolds in LH2 complexes. Our study demonstrates that quantum cooperative models can elucidate specific aspects of biological LH systems.
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Medical Physics

Spatial Sampling of Hemispherical Arrays for Three-Dimensional Photoacoustic Computed Tomography

Wanqing Zhang, Hengyue Zhu and Yide Zhang

Three-dimensional (3D) photoacoustic computed tomography (PACT) is a powerful noninvasive biomedical imaging modality that provides volumetric data for structural and functional assessment in vivo. To maximize angular coverage and mitigate limited-view artifacts, modern 3D PACT systems frequently employ hemispherical transducer arrays. While substantial effort has been devoted to improving image quality through post-processing algorithms, the intrinsic impact of the hardware array layout on the baseline image quality remains underexplored. In this study, we systematically investigate how the spatial sampling characteristics of hemispherical array distributions affect imaging performance under fixed hardware constraints. We propose a uniform-spacing sampling criterion to generate three representative array distributions and evaluate their performance using quantitative metrics across static, noise-perturbed, reduced-element, and rotational acquisition scenarios. Across these diverse testing regimes, the Fibonacci distribution consistently demonstrates superior structural robustness and more globally balanced reconstruction quality, a result we attribute to its highly isotropic sampling properties. These findings demonstrate that an optimal hardware-level sampling strategy is critical for maintaining global reconstruction stability. Ultimately, this framework establishes a rigorous quantitative methodology for benchmarking hemispherical array distributions and provides practical design guidance for the future development of 3D PACT systems.
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Atmospheric and Oceanic Physics · Cross-listed from eess.SP

End-to-End Optical Propagation Modeling for Water-to-Air Channels under Sea Surface and UAV Effects

Mohamed Nennouche, Mohammad-Ali Khalighi, Alexis Alfredo Dowhuszko et al. (+1 more)

Underwater observatories have recently emerged as an efficient solution for marine biodiversity monitoring. The primary objective of this work is to enable efficient and cost-effective data muling from underwater sensors by investigating the use of optical wireless communications to transmit data from the underwater sensors to an aerial node close to the water surface, such as an unmanned aerial vehicle (UAV). More specifically, we utilize a direct water-to-air (W2A) optical communication link between the sensor node equipped with an LED emitter and the UAV equipped with an ultra-sensitive receiver, i.e., a silicon photo-multiplier. As a main contribution, we develop a comprehensive Monte Carlo-based ray-tracing algorithm to characterize this complex channel. This framework rigorously incorporates the impact of air bubbles modeled through the Mie scattering theory, a realistic sea surface representation derived from the JONSWAP spectrum, and an analytical derivation of the channel loss resulting from UAV instability under wind-induced perturbations. Furthermore, we conduct a comprehensive analysis of the W2A channel, examining the influence of key parameters such as wind speed, transmitter configurations, and receiver characteristics. The end-to-end performance evaluation demonstrates the practical feasibility of the proposed approach, achieving a bit-error rate of $10^{-3}$ at a data rate of 1 Mbps for a transmitter depth of 47 m and wind speeds up to 13 m/s.
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All authors Mohamed Nennouche, Mohammad-Ali Khalighi, Alexis Alfredo Dowhuszko, Djamal Merad

Instrumentation and Detectors

Long-term scintillation light performance, calibrations, and triggering efficiency in the MicroBooNE detector

MicroBooNE collaboration: P. Abratenko, D. Andrade Aldana, L. Arellano et al. (+190 more)

A detailed understanding of scintillation light in liquid argon time projection chambers (LArTPCs) is essential for the robust extraction of physics measurements from their data. This article presents the long-term performance of scintillation light production and detection using five years of data from the MicroBooNE LArTPC neutrino detector. We describe the MicroBooNE light simulation and light-based triggering schemes, and present the photomultiplier tube gain calibration and stability, light response stability, and light-based systematic uncertainties over the course of five years of data collection. We also make an in-situ measurement of the scintillation light triggering efficiency down to 30 MeV of visible energy. Finally, we discuss two notable observations in MicroBooNE's data, both reported here for the first time: an approximately 50% decline in MicroBooNE's light yield over time, concentrated in the first two years of running; and a higher than expected O(200 kHz) rate of single photoelectrons (SPE). We present the first measurements of the dependence of the SPE rate on the TPC electric field strength and polarity. Together, the results presented in this article provide an important benchmark for the long-term performance of scintillation light systems in LArTPCs and their use in particle physics measurements.
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All authors MicroBooNE collaboration: P. Abratenko, D. Andrade Aldana, L. Arellano, J. Asaadi, A. Ashkenazi, S. Balasubramanian, B. Baller, A. Barnard, G. Barr, D. Barrow, J. Barrow, V. Basque, J. Bateman, B. Behera, O. Benevides Rodrigues, S. Berkman, A. Bhat, M. Bhattacharya, V. Bhelande, A. Binau, M. Bishai, A. Blake, B. Bogart, T. Bolton, M.B. Brunetti, L. Camilleri, D. Caratelli, F. Cavanna, G. Cerati, A. Chappell, Y. Chen, J.M. Conrad, M. Convery, L. Cooper-Troendle, J.I. Crespo-Anadon, R. Cross, M. Del Tutto, S.R. Dennis, P. Detje, R. Diurba, Z. Djurcic, K. Duffy, S. Dytman, B. Eberly, P. Englezos, A. Ereditato, J.J. Evans, C. Fang, B.T. Fleming, W. Foreman, D. Franco, A.P. Furmanski, F. Gao, D. Garcia-Gamez, S. Gardiner, G. Ge, S. Gollapinni, E. Gramellini, P. Green, H. Greenlee, L. Gu, W. Gu, R. Guenette, L. Hagaman, M. D. Handley, O. Hen, A. Hergenhan, M. Harrison, S. Hawkins, C. Hilgenberg, G.A. Horton-Smith, A. Hussain, B. Irwin, M.S. Ismail, C. James, X. Ji, J.H. Jo, A. Johnson, R.A. Johnson, D. Kalra, G. Karagiorgi, W. Ketchum, A. Kelly, M. Kirby, T. Kobilarcik, K. Kumar, N. Lane, J.-Y. Li, Y. Li, K. Lin, B.R. Littlejohn, L. Liu, S. Liu, W.C. Louis, X. Luo, T. Mahmud, N. Majeed, C. Mariani, J. Marshall, D.A. Martinez Caicedo, F. Martinez Lopez, M. G. Manuel Alves, S. Martynenko, A. Mastbaum, I. Mawby, N. McConkey, B. McConnell, L. Mellet, J. Mendez, J. Micallef, T. Mohayai, A. Mogan, M. Mooney, A.F. Moor, C.D. Moore, L. Mora Lepin, M. A. Hernandez Morquecho, M.M. Moudgalya, S. Mulleria Babu, D. Naples, A. Navrer-Agasson, N. Nayak, M. Nebot-Guinot, C. Nguyen, L. Nguyen, J. Nowak, N. Oza, O. Palamara, N. Pallat, V. Paolone, A. Papadopoulou, V. Papavassiliou, H. Parkinson, S.F. Pate, N. Patel, Z. Pavlovic, E. Piasetzky, K. Pletcher, I. Pophale, X. Qian, J.L. Raaf, V. Radeka, A. Rafique, R. Raymond, M. Reggiani-Guzzo, J. Rodriguez Rondon, M. Rosenberg, M. Ross-Lonergan, I. Safa, C. Sauer, D.W. Schmitz, A. Schukraft, W. Seligman, M.H. Shaevitz, R. Sharankova, J. Shi, L. Silva, E.L. Snider, S. Soldner-Rembold, J. Spitz, M. Stancari, J. St. John, T. Strauss, A.M. Szelc, N. Taniuchi, K. Terao, C.Thorpe, D. Torbunov, D. Totani, M. Toups, A. Trettin, Y.-T. Tsai, J. Tyler, M.A. Uchida, T. Usher, B. Viren, J. Wang, L. Wang, M. Weber, H. Wei, A.J. White, S. Wolbers, T. Wongjirad, K. Wresilo, W. Wu, E. Yandel, T. Yang, L.E. Yates, H.W. Yu, G.P. Zeller, J. Zennamo, C. Zhang, Y. Zhang

Applied Physics · Cross-listed from cs.RO

Quadrature Oscillation System for Coordinated Motion in Crawling Origami Robot

Sean Liu, Ankur Mehta and Wenzhong Yan

Origami-inspired robots offer rapid, accessible design and manufacture with diverse functionalities. In particular, origami robots without conventional electronics have the unique advantage of functioning in extreme environments such as ones with high radiation or large magnetic fields. However, the absence of sophisticated control systems limits these robots to simple autonomous behaviors. In our previous studies, we developed a printable, electronics-free, and self-sustained oscillator that generates simple complementary square-wave signals. Our study presents a quadrature oscillation system capable of generating four square-wave signals a quarter-cycle out of phase, enabling four distinct states. Such control signals are important in various engineering and robotics applications, such as orchestrating limb movements in bio-inspired robots. We demonstrate the practicality and value of this oscillation system by designing and constructing an origami crawling robot that utilizes the quadrature oscillator to achieve coordinated locomotion. Together, the oscillator and robot illustrate the potential for more complex control and functions in origami robotics, paving the way for more electronics-free, rapid-design origami robots with advanced autonomous behaviors.
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Data Analysis and Statistics · Cross-listed from hep-ex

Searching for Anomalies with Foundation Models

Vinicius Mikuni and Benjamin Nachman

Foundation models have the potential to extend the discovery reach for anomaly detection searches. When studying the large OmniLearned foundation model on data from the CMS experiment, unexpected behavior was observed in a mass sideband. The purpose of this paper is to perform a full analysis, including a complete background estimate, on the phase space picked out by the large model. We find that the background estimation describes the data well in validation regions, but is unable to accurately model the signal region. We invite further scrutiny of these events and our methods.
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Computational Physics · Cross-listed from cs.LG

Residual Attention Physics-Informed Neural Networks for Robust Multiphysics Simulation of Steady-State Electrothermal Energy Systems

Yuqing Zhou, Ze Tao and Fujun Liu

Efficient thermal management and precise field prediction are critical for the design of advanced energy systems, including electrohydrodynamic transport, microfluidic energy harvesters, and electrically driven thermal regulators. However, the steady-state simulation of these electrothermal coupled multiphysics systems remains challenging for physics-informed neural computation due to strong nonlinear field coupling, temperature-dependent coefficient variability, and complex interface dynamics. This study proposes a Residual Attention Physics-Informed Neural Network (RA-PINN) framework for the unified solution of coupled velocity, pressure, electric-potential, and temperature fields. By integrating a unified five-field operator formulation with residual-connected feature propagation and attention-guided channel modulation, the proposed architecture effectively captures localized coupling structures and steep gradients. We evaluate RA-PINN across four representative energy-relevant benchmarks: constant-coefficient coupling, indirect pressure-gauge constraints, temperature-dependent transport, and oblique-interface consistency. Comparative analysis against Pure-MLP, LSTM-PINN, and pLSTM-PINN demonstrates that RA-PINN achieves superior accuracy, yielding the lowest MSE, RMSE, and relative $L_2$ errors across all scenarios. Notably, RA-PINN maintains high structural fidelity in interface-dominated and variable-coefficient settings where conventional PINN backbones often fail. These results establish RA-PINN as a robust and accurate computational framework for the high-fidelity modeling and optimization of complex electrothermal multiphysics in sustainable energy applications.
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Data Analysis and Statistics

Beyond the Central Limit: Universality of the Gamma Distribution from Padé-Enhanced Large Deviations

Mario Castro and José A. Cuesta

The central limit theorem provides the theoretical foundation for the universality of the normal distribution: under broad conditions, the asymptotic distribution of a sum of independent random variables approaches a Gaussian. Yet, physical systems described by positive random variable – from earthquakes to microbial growth to epidemic spreading – consistently exhibit gamma rather than Gaussian statistics – what leads to field-specific mechanistic explanations that are non robust to small changes in the model details. We show that gamma distributions emerge naturally from large deviation theory when Padé approximants replace polynomial expansions of the derivative of the scaled cumulant generating function, respecting positivity constraints that the central limit theorem violates. Gamma universality thus emerges as the constrained analog of Gaussian universality, providing a mechanism-free explanation for its pervasive appearance across different disciplines.
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History and Philosophy of Physics

Mars in the Australian Press, 1875-1899. 1. Interpretation, Authority and Planetary Science

Richard de Grijs

[Abridged] In the late nineteenth century, Mars emerged as one of the most intensively reported astronomical objects in the popular press, driven by favourable oppositions, improved telescopic capabilities and growing speculation regarding planetary habitability. I examine how Mars was interpreted in Australian newspapers between the 1870s and 1899, focusing on the ways in which astronomical knowledge was framed, contextualised and debated within a colonial media environment. Drawing on a large collection of digitised newspaper articles, I analyse how observational authority, instrumental credibility and individual expertise were harnessed in press reporting. The paper situates Australian Mars coverage within a global network of scientific communication dominated by metropolitan centres in Europe and North America, while highlighting the distinctive role played by southern-hemisphere visibility. Australian observatories and observers were frequently positioned as contributors of confirmatory observation rather than interpretive leadership, reinforcing a pattern of locally grounded but internationally oriented scientific engagement. The analysis traces a shift from early emphasis on disciplined observation and measurement to later periods characterised by contested interpretations, particularly surrounding the so-called Martian "canals" and the speculative claims advanced by personalities such as Percival Lowell in the USA. By examining how newspapers mediated between observational astronomy, engineering analogies and popular imagination, this study contributes to a broader understanding of how planetary science entered public discourse beyond metropolitan centres. In doing so, it underscores the active role of colonial newspapers in shaping scientific meaning and situates Australian Mars reporting within the wider history of nineteenth-century astronomical culture.
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Biological Physics · Cross-listed from cond-mat.soft

Thickness effects in the electromechanical stability of charged biological membranes

Sirui Ning, Yannick A. D. Omar, Karthik Shekhar et al. (+1 more)

Understanding how electric fields destabilize biological membranes is important for electroporation-based technologies and bioelectronic interfaces. However, theoretical descriptions of this phenomenon remain fragmented. Existing theories treat either electrostatics in membranes of finite thickness or electrohydrodynamic flows at idealized zero-thickness interfaces, leaving unresolved a unified description that simultaneously incorporates finite membrane thickness, surface charge, and bulk electrohydrodynamics. Here, we apply a recently-developed, dimension-reduction framework that captures the coupled electrohydrodynamic and mechanical effects governing height fluctuations of a charged lipid bilayer of thickness $\delta$ in an electrolyte characterized by Debye screening length $\lambda$. We derive voltage- and charge-dependent renormalizations of the effective surface tension and bending rigidity, along with a dispersion relation governing undulatory instabilities. A wide range of prior theoretical results arise as limiting cases of our more general theory when finite-thickness effects are neglected or screening is asymptotically strong. The key new contribution arises from traction moments generated across the finite membrane thickness, which are absent in zero-thickness descriptions. Under physiological screening ($\delta/\lambda\sim 4$), these contributions account for more than $>70\%$ of the total electrostatic correction to both surface tension and bending rigidity. The theory further reveals that surface charges can stabilize the membrane at physiological ionic strengths, increasing the effective tension and shifting electroporation thresholds in a manner that depends on charge asymmetry between the leaflets.
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All authors Sirui Ning, Yannick A. D. Omar, Karthik Shekhar, Kranthi K. Mandadapu

Applied Physics · Cross-listed from eess.SY

High-Fidelity Transcranial Ultrasound Multi-focal Stimulation via Physics-Aware Hologram Technique

Moon Hwan Lee, Mohd. Afzal Khan, Akm Ashiquzzaman et al. (+5 more)

Transcranial ultrasound stimulation (TUS) offers non-invasive deep-brain neuromodulation with high spatial precision, but reliably generating complex multi-target acoustic fields through the skull remains challenging. Here, we introduce a physics-aware hologram technique that directly generates fabrication-ready holographic implementations while preserving consistency between numerical field synthesis and physical acoustic realization. The method enables single-, dual-, and tri-focal transcranial stimulation patterns and was validated through in silico simulations, ex vivo skull measurements, and in vivo experiments. Compared with representative state-of-the-art methods, the proposed approach improved focal reconstruction and energy confinement at intended targets while reducing off-target acoustic leakage. In a neuropathic-pain mouse model, simultaneous bilateral stimulation of thalamic nuclei reduced c-Fos expression and showed preliminary improvements in pain-related behavioral responses. These findings support the use of fabrication-consistent holographic design for spatially localized and reproducible multi-target transcranial neuromodulation.
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All authors Moon Hwan Lee, Mohd. Afzal Khan, Akm Ashiquzzaman, Eunbin Lee, Jonghun Lee, Euiheon Chung, Hyuk-Sang Kwon, Jae Youn Hwang

Chemical Physics

COACH: Toward the performance limit of traditional hybrid density functionals for molecular chemistry

Jiashu Liang and Martin Head-Gordon

Density functional theory (DFT) offers an exceptional balance between accuracy and efficiency, but practical density functional approximations face an unavoidable trade-off among simplicity, accuracy, and transferability. Here we present a systematic functional-development protocol that combines constraint enforcement, flexible functional forms, and modern optimization within a predefined application domain and functional class. Applying this strategy to the range-separated hybrid (RSH) meta-GGA framework, we obtain the carefully optimized and appropriately constrained hybrid (COACH) functional. Across broad molecular benchmarks, COACH improves both accuracy and transferability relative to leading RSH meta-GGAs, including \(\omega\)B97M-V, while retaining the computational practicality of its rung. These results suggest that COACH comes closer to the performance limit of traditional hybrid meta-GGA functionals for general molecular ground-state chemistry. Further substantial progress will likely require richer nonlocal or orbital-dependent information than is available from semilocal density ingredients combined with simple exact-exchange mixing.
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Chemical Physics

A unified variational framework for the inverse Kohn-Sham problem

Nan Sheng

The inverse Kohn-Sham (KS) problem seeks a local effective potential whose noninteracting ground state reproduces a prescribed electron density. Although many inversion formulations and schemes have been developed, they are often formulated in disparate languages, including reduced variational optimization, penalty regularization, response-based iteration, and PDE-constrained optimization. In this work, we develop a unified framework for inverse KS theory in two steps. First, we identify the fixed-density noninteracting constrained search and its density-potential duality as the natural variational anchor of the inverse KS problem. In this setting, the KS potential appears as the variational dual object associated with density reproduction, reducing to the familiar multiplier picture in regular regimes. Second, building on this anchor, we classify major inversion formulations according to how the KS state equations and density-reproduction condition are treated within the optimization architecture, with orbital orthonormality retained as an additional structural constraint. Within this framework, the Wu-Yang formulation appears as a potential-space reduced multiplier formulation, the Zhao-Morrison-Parr construction as a quadratic-penalty relaxation, and PDE-constrained approaches as explicit state-constraint formulations at the orbital level. Rather than comparing inversion formulations primarily at the level of implemented algorithms, the present work develops an optimization-theoretic formulation map. This viewpoint identifies where additive-constant ambiguity, asymptotic normalization, nonsmooth variational structure, metric choice, and weak-gap instability enter different inversion architectures, and it makes explicit how major inversion approaches are connected and where algorithmic design choices arise.
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Atomic Physics

A multi-ion optical clock with $\mathbf{5 \times 10^{-19}}$ uncertainty

Melina Filzinger, Martin R. Steinel, Jian Jiang et al. (+4 more)

Today's most accurate clocks are based on laser spectroscopy of electronic transitions in single trapped ions and feature fractional frequency uncertainties below $1\times10^{-18}$. Scaling these systems to multiple, simultaneously interrogated ions reduces measurement times, driving recent advances in multi-ion clocks. However, maintaining state-of-the-art systematic uncertainties while increasing the number of ions remains a central challenge. Here, we report on a multi-ion optical atomic clock with a fractional frequency uncertainty of $5.3\times10^{-19}$ and up to 10 \Sr ions. Ion-resolved state detection enables minimization of position-dependent shifts, with residual effects suppressed below the $10^{-20}$-level. Clock operation with eight to ten ions reduces the measurement time by a factor of 4.8 compared to single-ion operation. A comparison with an established \Yb single-ion clock yields an unperturbed frequency ratio of $0.6926711632159660405(20)$, with a statistical uncertainty of $0.9\times10^{-18}$ and a combined uncertainty of $2.9\times 10^{-18}$. These results demonstrate robust multi-ion clock operation with reduced averaging time and state-of-the-art accuracy.
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All authors Melina Filzinger, Martin R. Steinel, Jian Jiang, Daniel Bennett, Tanja E. Mehlstäubler, Ekkehard Peik, Nils Huntemann

Plasma Physics

Frequency Chirping of Energetic-Particle-Driven Geodesic Acoustic Modes in Tokamaks

R. Wu, A. Biancalani, M. V. Falessi et al. (+5 more)

A suprathermal population of ions is present in tokamak plasmas due to external heating mechanisms and fusion reactions. These energetic particles (EPs) can drive waves unstable, via inverse Landau damping. An example is the energetic-particle-induced geodesic acoustic mode (EGAMs). In this work, investigate the nonlinear dynamics of EGAMs by means of global gyrokinetic simulations with the particle-in-cell code ORB5. In particular, we study the nonlinear evolution of the frequency, known as "frequency chirping". To investigate the underlying phase-space dynamics, Phase Space Zonal Structure (PSZS) diagnostics are employed. By identifying the resonance energy from the phase-space distribution and reconstructing the corresponding mode frequency, an independent estimate of the frequency evolution is obtained. The reconstructed frequencies show good agreement with those extracted directly from continuous wavelet transform analysis of the electric-field signal, establishing a direct correspondence between observable frequency chirping and the nonlinear evolution of resonant energetic particles in phase space.
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All authors R. Wu, A. Biancalani, M. V. Falessi, D. Gossard, R. Ivanov, P. Lauber, X. Wang, F. Zonca

Chemical Physics

Elucidating the Synergetic Interplay between Average Intermolecular Coupling and Coupling Disorder in Short-Time Exciton Transfer

Siwei Wang, Guangming Liu and Hsing-Ta Chen

Exciton transport in molecular aggregates is a fundamental process governing the performance of organic optoelectronics and light-harvesting systems. While most theoretical studies have emphasized long-time transport behavior, recent advances in ultrafast spectroscopy have brought into focus the short-time regime, in which exciton motion remains ballistic on femtosecond-to-picosecond timescales. In this work, we develop an analytical framework for short-time exciton dynamics in a one-dimensional lattice subject to both on-site energetic (diagonal) disorder and intermolecular coupling (off-diagonal) fluctuations. Utilizing the reciprocal-space analysis, we derive closed-form expressions for the first and second spatial moments considering both localized excitation and moving Gaussian initial conditions. Our analytical and numerical results show that, while the long-time dynamics are influenced by diagonal disorder, the short-time ballistic expansion is governed primarily by off-diagonal disorder. Crucially, we reveal a synergistic interplay between the average intermolecular coupling and the off-diagonal coupling disorder strength, demonstrating that they contribute equivalently to short-time exciton transport. Moreover, we integrate this generic disorder model with a realistic molecular system within the framework of macroscopic quantum electrodynamics, thereby providing a theoretical foundation for characterizing and optimizing ultrafast energy flow of disordered molecular aggregates in complex dielectric media.
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Medical Physics

Exact analytical PGSE signal for diffusion confined to a cylindrical surface using a spectral Laplacian formalism

Erick J Canales-Rodríguez, Chantal M.W. Tax, Juan Manuel Górriz et al. (+3 more)

Objective. To derive an exact analytical expression for the diffusion MRI signal arising from diffusion confined to a cylindrical surface under finite rectangular pulsed-gradient spin-echo (PGSE) gradients, and to develop computationally efficient strategies for repeated model evaluations. Approach. The Bloch-Torrey equation was solved using a spectral matrix formalism of the Laplace operator in the eigenbasis of the cylindrical surface. The resulting signal is expressed as a product of non-commuting matrix exponentials and is valid for arbitrary rectangular gradient durations and separations, without approximations to the diffusion propagator or spin phase distribution. A reduced real spectral basis was introduced to decrease the dimensionality of the problem. Accelerated implementations based on Strang splitting and Gauss-Legendre quadrature were developed for repeated signal evaluations and computation of the spherical mean. The analytical signal was validated against Monte Carlo diffusion simulations. Main results. The exact formulation showed excellent agreement with Monte Carlo simulations over a wide range of cylinder radii and acquisition parameters. The spectral expansion converged rapidly with mode order, and the reduced basis substantially decreased computational cost without loss of accuracy. The accelerated implementations provided large additional speed-ups while retaining controllable errors relative to the exact solution. Significance. The proposed framework extends exact finite-pulse solutions of the Bloch-Torrey equation to diffusion confined to cylindrical surfaces and provides practical implementations for directional and orientationally averaged diffusion MRI signals. It therefore offers an approximation-free reference for assessing faster signal approximations and for applications requiring large numbers of model evaluations.
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All authors Erick J Canales-Rodríguez, Chantal M.W. Tax, Juan Manuel Górriz, Derek K. Jones, Jean-Philippe Thiran, Jonathan Rafael-Patiño

History and Philosophy of Physics

Henri Poincare Saint Louis Lecture of 1904: Publication, Dissemination, and Historiographical Implications

Hector Giacomini

Henri Poincare Saint Louis lecture of 1904 occupies an important place in the prehistory of relativity. In it, Poincare formulated the principle of relativity in general terms and presented it as one of the guiding principles of mathematical physics, together with the principles of least action and energy conservation. This article reconstructs the early publication and international dissemination of the lecture before the end of June 1905, through La Revue des idees, the Bulletin des sciences mathématiques, The Monist, and La valeur de la science. Drawing on library records, accession data, booksellers' advertisements, press notices, and correspondence, it shows that Poincare text circulated rapidly through scholarly, commercial, and institutional channels in Europe and North America. The significance of this circulation is not merely bibliographical. It bears directly on the documentary landscape within which Einstein 1905 relativity paper should be historically situated. The early availability of Poincare lecture and of La valeur de la science shifts attention toward the concrete conditions under which texts, concepts, and problems circulated in the months and weeks preceding Einstein's June 1905 paper. Evidence from Einstein Bern milieu further supports this view. Joseph Sauter later testimony and the possibility of redating the Habicht letter to 1 June 1905, on the basis of several converging chronological and documentary arguments, suggest that the intellectual environment of 1905 was denser than simplified narratives of solitary discovery imply. Availability is not influence; but without reconstructing availability, the historical problem of Einstein relation to Poincaré and Lorentz remains ill posed.
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Physics and Society

Near-optimal solutions for carbon capture, conversion, storage, and removal strategies

Sina Kalweit, Ricardo Fernandes, Alberto Alamia et al. (+1 more)

Achieving climate neutrality in Europe requires rapid electrification alongside carbon management strategies for residual emissions. Existing analyses of the European energy system often focus on collocated carbon capture and geological sequestration, with limited attention to the interactions among carbon capture and utilization, transport, sequestration, and diverse carbon dioxide removal (CDR) options. Moreover, existing literature focuses on discussing the optimal, neglecting that near-optimal solutions might provide very different system configurations at a marginal higher cost. Here, we integrate afforestation, biochar, enhanced rock weathering, and perennialization into a sector-coupled European energy system model (PyPSA-Eur) clustered to 39 nodes with 750 aggregated time steps. We explore their contributions using a Modelling to Generate Alternatives (MGA) approach. The approach combines minimization, maximization, and random vectors to explore the near-optimal solution space for up to 5% increased total system costs. Our results show that, in a carbon-neutral system, multiple configurations of carbon management options can achieve net-zero emissions with only marginal cost increases. We find that a 5% total system cost increase is sufficient to accommodate the full spectrum from zero to full deployment of the individual CDR options, as well as a wide range of synthetic fuel use across different fuel types. Increased reliance on CDR options offers no clear cost advantage compared to greater utilization of synthetic fuels.
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All authors Sina Kalweit, Ricardo Fernandes, Alberto Alamia, Marta Victoria

Chemical Physics

Exact density-functional theory as parallel ensemble variational hierarchies: from Lieb's formulation to Kohn-Sham theory

Nan Sheng

Exact density-functional theory is recast here as two parallel exact ensemble variational hierarchies: an interacting hierarchy rooted in Lieb's ensemble formulation and a noninteracting hierarchy rooted in exact noninteracting ensemble theory. In optimization terms, $N$-representability is primal feasibility, Legendre-Fenchel duality equates the primal and dual values, $v$-representability is dual attainment, and the Hohenberg-Kohn theorem gives uniqueness, modulo constants, of an attained local potential. The Kohn-Sham construction couples the interacting density-space optimality condition to a compatible noninteracting dual realization on their common $N$-representable density domain. State-class restrictions yield the Levy-Lieb and single-determinant branches, while fractional particle number and fractional occupations lead naturally to piecewise linearity, one-sided chemical potentials, Janak-type relations, and the derivative discontinuity. This organization locates the exactness of Kohn-Sham theory in the preservation of the interacting density-space optimization together with its compatible noninteracting realization, without implying a general many-body spectral interpretation of Kohn-Sham eigenvalues.
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Fluid Dynamics · Cross-listed from math-ph

Interfacial instability as a trigger for dryout inception in two-phase CO2 flow

G. Cantini, G. Arnone, F. Capone et al. (+2 more)

Progress in particle physic leads to increasing in detector luminosity and a consequent increasing overheating induced by Joule effect. An effective cooling strategy is the exploitation of CO\textsubscript{2} heat latency in phase-change. An additional challenge, relevant to detectors for High Energy Particles, is the consequent geometrical constrain due to the limited space avialable for the cooling system within the detector arrangement, leading to the implementation of cooling system by means of millichannels. In this context, at relative high vapour quality the liquid phase exhibits annular flow, anticipating the dryout. Dryout is a critical condition where the heat transfer coefficient dramatically drops and dangerous temperature levels can be reached, potentially leading to catastrophic consequences. Experimental evidences reveal that its behavior in two-phase annular flows differs from conventional refrigerants and the fundamental inception-mechanism is not yet understood. This study aims at investigating the key new idea whereby dryout inception is triggered by instability of the liquid-vapour interface. A mathematical model for two-phase annular flow is presented and the stability of the interface between the two fluids is studied through the linear theory. The stability analysis reduces to solving a coupled forth-order differential eigenvalue problem that is treated numerically with an in-house code based on the Chebyshev-$\tau$ method. Numerical investigations identify a critical value for the vapour quality, named $x_{dry}$, that leads to interface instability. The resulting predictions on $x_{dry}$ are confirmed by experimental data collected from two independent experimental campaigns, validating the hypothesis that dryout inception is governed by interfacial instabilities.
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All authors G. Cantini, G. Arnone, F. Capone, J.A. Gianfrani, M. Carnevale

Applied Physics

Laser-Enhanced Contact Optimization in Silicon Photovoltaics: Mechanisms, Reliability, and Predictive Process Design

Donald Intal and Abasifreke U. Ebong

Laser-enhanced contact optimization (LECO) has emerged as an important method for simultaneously reducing contact resistivity and metallization-induced recombination in advanced crystalline silicon solar cells, thereby enabling concurrent gains in fill factor and open-circuit voltage, particularly in TOPCon devices. However, broader industrial transferability remains constrained by the need to preserve these gains within a narrow process window and by unresolved, architecture-dependent questions regarding the kinetic stability of some LECO-modified interfaces. LECO is therefore examined in this review as a coupled multiphysics process that links localized electrothermal activation and microstructural evolution to device-level electrical signatures through an instantaneous regime map and a reliability classification based on time-dependent drift. A predictive workflow is outlined that couples transient electrothermal modeling with reduced state metrics, including effective diffusion depth and local areal energy density, and propagates calibrated thresholds across the recipe space. The framework separates stable optimization from marginal activation and latent damage, while explaining why fine-line scaling and copper-containing contact stacks can tighten stability margins through current localization and diffusion-barrier constraints. These insights provide a basis for reliability-aware process-window design and future digital-twin-assisted optimization of LECO for scalable, high-efficiency silicon photovoltaics.
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Atomic Physics · Cross-listed from hep-ph

Dark Matter Detection through Rydberg Atom Transducer

J. F. Chen, Haokun Fu, Christina Gao et al. (+5 more)

Ultralight bosonic dark matter with masses in the meV range, corresponding to terahertz (THz) Compton frequencies, remains largely unexplored due to the difficulty of achieving both efficient signal conversion and single-photon-sensitive detection at THz frequencies. We propose a hybrid detection architecture that integrates a dielectric haloscope, Rydberg-atom transducer, and superconducting nanowire single-photon detection within a unified cryogenic platform operating at $\lesssim 1\,\text{K}$. The dielectric haloscope converts dark matter into THz photons via phase-matched resonant enhancement, achieving form factors $C \sim 0.4$ and loaded quality factors $Q_L \sim 10^4$. A cold $^{87}$Rb ensemble then coherently up-converts the THz signal to the optical domain through six-wave mixing among Rydberg states. The intrinsic directionality and narrow bandwidth ($\Delta\nu_{\mathrm{atomic}} \sim 1\,\text{MHz}$) of this process provide extra suppression of isotropic thermal backgrounds. With 10 days of integration at $0.3\,\text{K}$, we project sensitivity to the axion-photon coupling $g_{a\gamma\gamma} \sim 10^{-13}\,\mathrm{GeV}^{-1}$ at $m_a \sim 0.4\,\text{meV}$, reaching the QCD axion band and opening the THz window for searches of both axion and dark photon dark matter.
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All authors J. F. Chen, Haokun Fu, Christina Gao, Jing Shu, Geng-Bo Wu, Peiran Yin, Yi-Ming Zhong, Ying Zuo

Chemical Physics

Vectorial Imaging of the Photodissociation of 2-Bromobutane Oriented via Hexapolar State Selection

Masaaki Nakamura, Po-Yu Tsai, Shiun-Jr Yang et al. (+6 more)

Molecular orientation techniques are becoming available in the study of elementary chemical processes, in order to highlight those structural and dynamical properties that would be concealed by random rotational motions. Recently successful orientation was achieved for asymmetric-top and chiral molecules of much larger complexity than hitherto. In this work, we report and discuss the correlation between the vectors photofragment recoil velocity v, transition dipole moment {\mu}, and permanent dipole moment d in a dissociation experiment on hexapole oriented 2-bromobutane, photoinitiated by a linearly polarized laser. The sliced ion images of the Br* (2P1/2) and Br (2P3/2) photofragment were acquired at 234.0 and 254.1 nm, respectively, by (2+1) resonance-enhanced multiphoton ionization technique. A detailed analysis of the sliced ion images obtained at a tilting angle 45o of the laser polarization provides the information on correlation of the three vectors, which are confined by two polar angles {\alpha}, ḩi} and one azimuthal angle {\phi}{\mu}d in the recoil frame. The sliced ion images of Br fragments eliminated individually from the enantiomers at 254.1 nm yield the asymmetric factor close to zero; for this reason the photofragment angular distributions do not show significant differences. The elimination of Br* fragment at 234.0 nm is mainly correlated with a parallel transition, giving rise to a large anisotropy parameter of 1.85, and thus can be considered as a single state excitation. The resulting recoil frame angles are optimized to 163.8{\deg} and 164.1{\deg} for {\alpha} and ḩi}, respectively, whereas {\phi}{\mu}d approaches close to 0o for the best fit. Since in the present case, the three vectors have an only slight spatial arrangement, the photofragment angular distributions of the two enantiomers do not show appreciable differences...
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All authors Masaaki Nakamura, Po-Yu Tsai, Shiun-Jr Yang, King-Chuen Lin, Toshio Kasai, Dock-Chil Che, Andrea Lombardi, Federico Palazzetti, Vincenzo Aquilanti

Geophysics · Cross-listed from stat.AP

Leveraging LLMs and Social Media to Understand User Perception of Smartphone-Based Earthquake Early Warnings

Hanjing Wang, S. Mostafa Mousavi, Patrick Robertson et al. (+10 more)

Android's Earthquake Alert (AEA) system provided timely early warnings to millions during the Mw 6.2 Marmara Ereglisi, Türkiye earthquake on April 23, 2025. This event, the largest in the region in 25 years, served as a critical real-world test for smartphone-based Earthquake Early Warning (EEW) systems. The AEA system successfully delivered alerts to users with high precision, offering over a minute of warning before the strongest shaking reached urban areas. This study leveraged Large Language Models (LLMs) to analyze more than 500 public social media posts from the X platform, extracting 42 distinct attributes related to user experience and behavior. Statistical analyses revealed significant relationships, notably a strong correlation between user trust and alert timeliness. Our results indicate a distinction between engineering and the user-centric definition of system accuracy. We found that timeliness is accuracy in the user's mind. Overall, this study provides actionable insights for optimizing alert design, public education campaigns, and future behavioral research to improve the effectiveness of such systems in seismically active regions.
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All authors Hanjing Wang, S. Mostafa Mousavi, Patrick Robertson, Richard M. Allen, Alexie Barski, Robert Bosch, Nivetha Thiruverahan, Youngmin Cho, Tajinder Gadh, Steve Malkos, Boone Spooner, Greg Wimpey, Marc Stogaitis

Biological Physics · Cross-listed from cond-mat.stat-mech

Internal stress drives ferromagnetic-like ordering in networks of proliferating bacteria

Nicola Pellicciotta, Luca Angelani and Roberto Di Leonardo

Proliferation is a defining feature of life. Through growth, division, and death, living systems consume energy and inject mass, breaking conservation laws and driving collective phenomena from biofilm formation to embryonic development. Yet, while active matter physics has advanced our understanding of self-propelled agents, quantitative frameworks for proliferating systems are still emerging, and most work focuses on simplified settings. Here, we study E.coli bacteria growing inside a network of single-file microchannels as a minimal model of structured environments. Competition for free volume drives the spontaneous emergence of coherent growth patterns that persist across generations but vanish when the channel links exceed the typical cell size at birth. Despite the strongly out-of-equilibrium character of the dynamics, the observed phenomenology can be quantitatively captured by an effective equilibrium description in which the flow state at each node is represented by a spin variable with ferromagnetic interactions. Simulations of growing elastic cells show that this coupling arises from internal stress accumulated at network nodes due to dynamical constraints. Our results reveal a surprising correspondence between proliferating active matter and equilibrium statistical mechanics, highlighting open fundamental questions and offering a first step toward describing growth phenomena in real-world complex environments.
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Plasma Physics

Optical modelling of shaped laser pulses in plasma

Igor A. Andriyash and Cedric Thaury

This work provides a brief review of the numerical methods for modelling the optical propagation of an ultrashort, intense laser pulse in plasmas and ionizable gases. These methods are implemented in an open-source simulation toolkit Axiprop, which is now actively used for design studies in the context of laser plasma acceleration of electrons (LPA). We present two examples of such studies: optical plasma waveguide generation, and phase-locked flying-focus LPA. These tools enable the identification of complex effects impacting both energy deposition during waveguide formation, and the pulse propagation dynamics that governs wakefield structure, ultimately determining the properties of the accelerated electron bunches. The developed tools and presented simulation designs are relevant to experiments on laser plasma interactions at modern high power laser facilities.
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Computational Physics

Revisiting the $r_s$ expansion of the uniform electron gas in $d$ dimensions: $\log r_s$ terms from coincident Mellin poles

Fumihiro Imoto

The high-density expansion of the correlation energy of the uniform electron gas contains $\log r_s$ terms, where $r_s$ is the Wigner–Seitz radius. Their form depends on the dimension $d$. Adapting the Mellin-transform analysis of Feynman integrals in relativistic field theory, we write the energy of the ring series and of diagrams linear in one screened interaction line in $d$ dimensions as Mellin convolutions of a radial kernel, fixed by the diagram, with a scaling function. The scaling function depends on the momentum transfer only through its ratio to a density scale. In the Mellin variable $s$, screening places poles at $s=N(d-1)$ with $N=1,2,\dots$, and the diagram places a pole at $s=d+1$ for the rings and at $s=2$ for a polarization insertion. Once the factors $\log(1/q)$, with $q$ the momentum transfer, cancel between the vertex and self-energy corrections, as the Ward identity requires, a $\log r_s$ term appears where two poles coincide. This rule reproduces the known $\log r_s$ terms in two and three dimensions. In two dimensions it gives the coefficient of the next $\log r_s$ term, $r_s^2\log r_s$, in closed form, $7/\pi+4\log2/\pi-160/(9\pi^2)-16G/\pi^2=-0.17546$~Ry with $G$ Catalan's constant. In three dimensions the screened second-order exchange diagram alone has an $r_s\log^2r_s$ term at high density and an $r_s^{-1/4}$ term at low density, and the Fock self-energy corrections cancel both.
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2603.23283 · 24 Mar · v4: substantially rewritten and extended, with a new title. Supersedes v1-v3, which treated only the screened second-order exchange (kite) diagram in three dimensions with a single-pole or static screened line. The spin-polarized kite is now in a companion paper (ChemRxiv, doi:10.26434/chemrxiv.15008489/v1). 96 pages including the Supporting Information, 6 figures

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Biological Physics

Synchronization-dissipation dynamics in the cardiorespiratory system

Joshua R. Border, Alain Nogaret, Andrew Lefevre et al. (+1 more)

Dissipative coupling is known to induce synchronization. Conversely it may be hypothesized that oscillators driven to synchronize may reduce power dissipation in their coupling. The latter scenario is realized in the human cardiorespiratory system where cardiac and respiratory rhythms are controlled by the central nervous system while interacting viscoelastically through the pulmonary vasculature. Here we examine the functional significance of this coupling which is observed in respiratory sinus arrhythmia (RSA). By modelling electrical and viscoelastic interactions within the cardiorespiratory system, we identify the conditions leading to synchronization. We demonstrate that, when present, synchronization reduces cardiac power losses by 10% in humans and up to 55% in other species. The predicted gain in cardiac output is compared to the gain observed in-vivo by pacing the heart with a device restoring RSA. It is therefore surmised that RSA may improve cardiac pumping efficiency by reducing dynamic stress and power dissipation in the pulmonary vasculature.
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All authors Joshua R. Border, Alain Nogaret, Andrew Lefevre, Vishal Jain