Peer Revenue Play credits. Real papers.

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Physics

physics Watch Physics

Friday 16 January

Physics and Society

An Epidemiological Modeling Take on Religion Dynamics

Bilge Taskin and Teddy Lazebnik

Religions are among the most consequential social institutions, shaping collective identities, moral norms, and political organization across societies and historical periods. Nevertheless, despite extensive scholarship describing conversion, competition, and secularization, there is still no widely adopted formal model that captures religious dynamics over time within a unified, mechanistic framework. In this study, we propose an epidemiologically grounded model of religious change in which religions spread and compete analogously to co-circulating strains. The model extends multi-strain compartmental dynamics by distinguishing passive believers, active missionaries, and religious elites, and by incorporating demographic turnover and mutation-like splitting that endogenously generates new denominations. Using computer simulations, we show that the same mechanism reproduces canonical qualitative regimes, including emergence from rarity, rapid expansion, long-run coexistence, and transient rise-and-fall movements. A reduced calibration variant fits historical affiliation trajectories with parsimonious regime shifts in effective recruitment and disaffiliation, yielding interpretable signatures of changing social conditions. Finally, sensitivity analyses map sharp regime boundaries in parameter space, indicating that modest shifts in recruitment efficacy or retention among active spreaders can qualitatively alter long-run religious landscapes. These results establish a general, interpretable framework for studying religion as a dynamical diffusion process and provide a tool for comparative inference and counterfactual analysis in sociological research.
Read the full abstract

Fluid Dynamics · Cross-listed from cond-mat.soft

Confinement-induced motion of ciliates

G. C. Antunes, C. Obst and H. Stark

The time dynamics of flagellar and ciliary beating is often neglected in theories of microswimmers, with the most common models prescribing a time-constant actuation of the surrounding fluid. By explicitly introducing a metachronal wave, coarse-grained to a sinusoidal surface slip velocity, we show that a spatial resonance between the metachronal wave and the corrugation of a confining cylindrical channel enables a ciliate to swim even when it cannot move forward in a bulk fluid. Using lubrication theory, we reduce the problem to the Adler equation that reveals an oscillatory and ballistic swimming regime. Interestingly, a ciliate can even reverse its swimming direction in a corrugated channel compared to the bulk fluid.
Read the full abstract

Optics

Wigner picture of partially coherent accelerating beams

Sergey A. Ponomarenko and Morteza Hajati

We advance a phase-space theory of partially coherent accelerating, non-diffracting beams employing the Wigner distribution function (WDF). We derive a general expression for the WDF of any accelerating, diffraction-free beam of arbitrary degree of spatial coherence and find an elegant closed-form expression for the WDF of such beam with a Gaussian energy spectrum of noise. We also show how partially coherent accelerating beams of finite power can be constructed within the Wigner picture.
Read the full abstract

Data Analysis and Statistics · Cross-listed from astro-ph.IM

Auditing Frozen-Encoder Anomaly Detection Across Mechanical Systems: Representation Provenance, Calibration, and Protocol Effects

Jose Sánchez Andreu

This version reports a reproducibility audit of the frozen-encoder experiments presented in version 1. The numerical discrimination results are reproducible from the preserved artifacts, but their original attribution to interferometric pretraining is not supported. The released checkpoint contains a nested model state that loads without missing parameters, whereas loading the outer checkpoint dictionary leaves almost the entire EfficientNet-B0 feature stack uninitialized. Preserved embeddings labelled as interferometric have norms of order $10^{-12}$, matching freshly initialized EfficientNet-B0 networks and differing by more than twelve orders of magnitude from the preserved ImageNet embeddings. A second, separately preserved near-zero embedding set produces almost the same IMS 4th-test anomaly scores ($r=0.987$) and record-level discrimination (AUC $0.9812$ versus $0.9818$). We therefore withdraw the causal claim that IMS performance demonstrates a morphological prior transferred from gravitational-wave instrumentation. We reanalyse the controlled IMS splits at matched observed false-positive rates and add multivariate classical signal baselines. The near-zero representations retain strong tail separation, particularly in the 2nd and 4th IMS runs, but this is now interpreted as an exploratory architecture-and-initialization effect coupled to Mahalanobis scoring. A separate PRONOSTIA audit shows that the original large warning times were induced by a lifetime-fraction baseline; under fixed-time evaluation, a ten-feature classical baseline outperforms the preserved encoder scores. These results illustrate how checkpoint provenance, finite-sample calibration, architecture, and target-domain baselines can create an appearance of cross-domain transfer. They also define the controls required before assigning physical meaning to frozen-representation anomaly scores.
Read the full abstract

Optics

Hysteresis in the complex nonlinear refractive index of a homogeneous and isotropic medium

Igor Kuzmenko, Y. B. Band, Yshai Avishai et al. (+1 more)

We calculate the permittivity, $\epsilon(\omega)$, for a medium with a quadratic electro-optic effect, modeling it as a Duffing oscillator. The nonlinear refractive index $n(\omega, E(\omega))$ and the nonlinear absorption coefficient $\alpha(\omega, E(\omega))$ exhibit hysteresis when the light intensity is varied [here $E(\omega)$ is the electric field strength at angular frequency $\omega$], and when the light frequency is varied. $n(\omega, E(\omega))$ can be negative when the resonances in the permittivity and permeability are close to one another.
Read the full abstract

All authors Igor Kuzmenko, Y. B. Band, Yshai Avishai, Marek Trippenbach

Optics

Resolving topological obstructions to vectorial structured field control

An Aloysius Wang, Yuxi Cai, Yifei Ma et al. (+2 more)

The use of structured matter, such as optical retarders, for vectorial control is a well-established and widely employed technique in modern optics, and has driven continued advances in the manipulation of complex, spatially varying vectorial fields. However, achieving arbitrary field conversion typically requires the use of cascaded elements, as intrinsic physical and fabrication constraints fundamentally limit individual devices to a restricted subset of transformations. This results in an overall continuous transformation potentially failing to be continuous at the level of the parameters of the cascade, leading to detrimental engineering consequences such as the introduction of complex, discontinuous aberrations that disrupt important topological properties of the underlying matter field. In this work, we establish a novel mathematical framework for analyzing the topological difficulties that emerge in the decomposition of an overall transformation into individual layers, and for determining the minimal depth required to overcome them. The strategy introduced provides a general pathway for optimizing designs for vectorial field control and matter field generation, with particular significance for the manipulation of topological phases in optical polarization fields, such as Stokes skyrmions, where continuity is of vital importance.
Read the full abstract

All authors An Aloysius Wang, Yuxi Cai, Yifei Ma, Patrick S Salter, Chao He

Optics

General in situ feedback control of cascaded liquid crystal spatial light modulators for structured field generation

An Aloysius Wang, Yuxi Cai, Zhenglin Li et al. (+4 more)

Cascaded liquid crystal spatial light modulators provide a versatile strategy for the generation of structured light and matter fields, with applications including optical communications, photonic computing, and topological field engineering. However, experimental imperfections, such as temperature-dependent liquid crystal response, variations between individual pixels, and alignment errors, present significant engineering challenges in generating high-quality fields. Moreover, changes in experimental conditions over time mean that calibrating each component once is insufficient for maintaining long-term, high-quality field generation. To address this, we present a general engineering approach based on a bespoke, physically informed, and manifold-constrained gradient-descent scheme that enables in situ feedback control, compensating for such errors in real time without the need to alter the experimental setup. We further demonstrate the correction efficacy of our proposed strategy through experiments in both spatially varying light and matter field generation, including scenarios in which complex vectorial aberrations are artificially introduced into the setup. Together, these demonstrations underscore the practicality of our method and its suitability for deployment in real-world experimental environments, paving the way for robust operation of cascaded architectures for structured field generation.
Read the full abstract

All authors An Aloysius Wang, Yuxi Cai, Zhenglin Li, Ruofu Liu, Yifei Ma, Patrick S Salter, Chao He

Atomic Physics · Cross-listed from hep-ph

Energy levels of multiscale bound states from QED energy-momentum trace

Michael I. Eides and Vladimir A. Yerokhin

Energy levels of QED bound states, which depend on a number of independent mass parameters, can be calculated as matrix elements of the QED energy-momentum tensor trace. As an example of such system we consider muonic hydrogen. The leading one-loop corrections to its energy levels depend on the electron and muon masses. These corrections are calculated as matrix elements of the energy-momentum tensor trace. Respective one-loop trace diagrams are different from the standard Lamb shift diagrams. We explain analytically and diagrammatically why two different sets of diagrams lead to the same results. Similar relationships should also hold beyond the one-loop approximation.
Read the full abstract

Computational Physics · Cross-listed from cond-mat.soft

NAVIS: A LAMMPS-Python framework for efficient computation of nanochannel velocity and thermal interfacial slip

Sleeba Varghese, Sobin Alosious, Jesper Schmidt Hansen et al. (+1 more)

We present NAVIS (NAnochannel Velocity and thermal Interfacial Slip), a LAMMPS-Python scripted toolkit for computing the Navier (hydrodynamic) friction coefficient and Kapitza (thermal) resistance at arbitrary solid-fluid interfaces. NAVIS is based on equilibrium molecular dynamics (EMD) methods for calculating the linear response friction and thermal resistance at the interface, as well as the corresponding velocity and temperature slips. The methodology is based on our previous studies (Hansen, et al., Phys. Rev. E 84, 016313 (2011); Varghese et al., J. Chem. Phys. 154, 184707 (2021); Alosious, et al., J. Chem. Phys. 151, 194502 (2019); Alosious, et al., Langmuir 37, 2355-2361 (2021)), and in this work we provide a pedagogical framework for the implementation of this toolkit on two systems: (i) a water-graphene system (for hydrodynamic slip) and (ii) a water-CNT system (for thermal slip). We provide detailed instructions for performing the EMD simulations using the LAMMPS package and processing the simulation outputs using Python modules to obtain the desired quantities of interest. We expect the toolkit to be useful for computational researchers studying interfacial friction and thermal transport, key factors for efficient and practical applications of nanofluidic systems.
Read the full abstract

All authors Sleeba Varghese, Sobin Alosious, Jesper Schmidt Hansen, Billy Dean Todd

Biological Physics · Cross-listed from q-bio.BM

Effects of 2.45 GHz radiofrequency upon Leuconostoc mesenteroides Glucose-6-phosphate dehydrogenase enzymatic activity

G. Miño-Galaz, V. Castro-Fernandez, J. Martínez-Oyanedel et al. (+3 more)

In this report we evaluate the effect in the enzyme activity of Glucose 6-phosphate Dehydrogenase from Leuconostoc mesenteroides by irradiation with 2.45 GHz radiofrequency at a power output of 0.1 W during a 91 h period. The results show that the RF irradiation preserves the activity of treated samples of this enzyme with respect to a non-treated sample that instead suffer an increased rate of activity loss. Our estimates indicate that the enzyme activation is due to a non-thermal effect. The results are consistent with reports about the effect of 2.45 GHz radiation upon other enzymatic systems.
Read the full abstract

All authors G. Miño-Galaz, V. Castro-Fernandez, J. Martínez-Oyanedel, R. Reeves, J. Staforelli-Vivanco, N. Martínez

Chemical Physics · Cross-listed from cond-mat.mtrl-sci

Chemical Origin of Exciton Self-trapping in Cs$_3$Cu$_2$X$_5$ Cesium Copper Halides

Zijin Wu, Shuxia Tao and Geert Brocks

Copper halides Cs3Cu2X5 (X=Cl, Br, I) are promising materials for optoelectronic applications due to their high photoluminescence efficiency, stability, and large Stokes shifts. In this work, we uncover the chemical bonding origin of the Stokes shift in these materials using density functional theory calculations. Upon excitation, one [Cu2X5]3- anion undergoes sizeable local distortions, driven by Cu-X and Cu-Cu bond formation. These structural changes coincide with the formation of a self-trapped exciton, where particularly the hole is strongly localized on one anion. Analysis of the electronic structure and bonding reveals reduced antibonding interactions and enhanced bonding character in the excited state, stabilizing the distorted geometry. Our results establish a direct link between orbital-specific hole localization and bond formation. It provides a fundamental understanding of the excitation mechanism in Cs3Cu2X5 and offers design principles to tune optical properties in 0D copper halides.
Read the full abstract

Fluid Dynamics

Differential Geometry of Deterministic Stokesian Dynamics

Sumedh R. Risbud

We present a differential geometric framework for the motion of a non-Brownian particle in the presence of fixed obstacles in a quiescent fluid, in the deterministic Stokesian regime. While one may think (owing to the Helmholtz Minimum Dissipation Theorem) that the hydrodynamic resistance tensor could be the natural candidate for a Riemannian metric shaping the particle trajectories, we demonstrate that the trajectories driven by constant external forces are not geodesics of this bare resistance metric. Instead, they experience a geometric drift due to the curvature induced by the presence of obstacles. By rigorously incorporating translational-rotational coupling through a modified effective resistance tensor $\tilde{\mathbf{R}} = \mathbf{R}_{\mathbf{FU}} - \mathbf{R}_{\mathbf{F\omega}}\mathbf{R}_{\mathbf{T\omega}}^{-1}\mathbf{R}_{\mathbf{F\omega}}^T$, which accounts for the hidden dissipation savings afforded by particle rotation, we introduce a unified geometric formalism. We prove that the physical particle trajectories are exact geodesics of a conformally scaled metric, $\tilde{g}_{ij} = \mathcal{D}(\mathbf{x})\tilde{R}_{ij}$, where $\mathcal{D}$ is the instantaneous power dissipation. This framework establishes that the affine parameter along the trajectory corresponds strictly to the cumulative energy dissipated. We apply this theory to the scattering of a spherical particle by a fixed spherical obstacle, showing that the exact analytical trajectory derived previously by the author is recovered as a geodesic of the dissipation-scaled manifold.
Read the full abstract

Instrumentation and Detectors

Nanofabricated torsion pendulums for tabletop gravity experiments

Jack Manley, Charles A. Condos, Zachary Fegley et al. (+5 more)

Measurement of mutual gravitation on laboratory scales is an outstanding challenge and a prerequisite to probing theories of quantum gravity. A leading technology in tabletop gravity experiments is the torsion balance, with limitations due to thermal decoherence. Recent demonstrations of lithographically defined suspensions in thin-film silicon nitride with macroscale test masses suggest a path forward, as torsion pendulums dominated by gravitational stiffness may achieve higher mechanical quality factors through dilution of material losses. Here we demonstrate a 250 micron by 5 mm by 1.8 micron torsion fiber supporting 87 grams and forming a Cavendish-style torsion pendulum with tungsten test masses that – to our knowledge – is the largest thin-film silicon-nitride-based oscillator to date. Torsion pendulums with thin-film, nanofabricated suspensions provide a test bed for near-term tabletop experiments probing classical and quantum gravitational interaction between oscillators.
Read the full abstract

All authors Jack Manley, Charles A. Condos, Zachary Fegley, Gayathrini Premawardhana, Thomas Bsaibes, Jacob M. Taylor, Dalziel J. Wilson, Jon R. Pratt

Accelerator Physics

Vacuum in Accelerators for Mechanical & Materials Engineering

Vincent Baglin

Vacuum systems are an intrinsic part of any accelerator around the world: all particles circulate under vacuum. This lecture gives rudiments on the fundamentals of vacuum science such as units, ideal gas law, partial pressure, mean free path, flow of molecules, conductance, pumping speed, and outgassing. An overview of standard vacuum instruments for pressure measurement and pumping is presented. Finally, the specificities of accelerator vacuum systems are introduced, discussing some design, construction, installation, and commissioning aspects, as well as fundamentals of beam-vacuum interactions with synchrotron radiation and electron cloud.
Read the full abstract

Fluid Dynamics

Analytical Solutions of the Minimal Nonlinear Equation for the Yaw Response of Tail Fins and Wind Vanes

Mohamed M. Hammam and David H. Wood

Analytical solutions for the yaw response of tail fins for small wind turbines, and wind vanes for wind direction measurement, are derived for any planform and any release angle $\gamma_0$. This extends current linear models limited to small $|\gamma_0|$ and low aspect ratio planforms. The equation studied here is the minimal form of the general second order equation for the yaw angle, $\gamma$, derived by Hammam and Wood (2023). The nonlinear damping is controlled by a small parameter that depends on the vortex flow coefficient, $K_v$, which is absent from all linear models. The minimal equation is analysed using perturbation techniques. A truncated series solution from the Krylov-Bogoliubov-Mitropolskii averaging method compares favourably with a numerical solution apart from some small deviations at large time. Another form of averaging due to Beecham and Titchener (1971) yields a compact solution in terms of the rate of amplitude decay, and the rate of change of phase angle. This allows the identification of an equivalent linear system with equivalent frequency and damping ratio. Two limiting analytic solutions for small and large $|\gamma_0|$ are obtained. The former is used to identify the model parameters from experimental data. Both approximate solutions showed that high $K_v$ is important for fast decay of yaw amplitude for tail fins at high $|\gamma_0|$. High aspect ratios for wind vanes would reduce the nonlinearity to minimize yaw error. Linear response that is independent of $K_v$ occurs whenever $\sin{(\pi \gamma_0)\approx \pi \gamma_0}$. Further, the low angle analytical solution allows an exact identification of the nonlinearity which could be used to extend the modelling of wind vanes to high $\gamma$.
Read the full abstract

Optics

Octave-spanning 10-GHz Er-doped solid-state optical frequency comb

Niccolò S. Barberio, Francesco Canella, Andrea Pertoldi et al. (+8 more)

Optical frequency combs provide a phase-coherent interface between optical and microwave domains, underpinning advances in precision metrology, spectroscopy, and time-frequency transfer. Most conventional comb architectures are limited to sub-gigahertz repetition rates, constraining integration and scalability. Here, we demonstrate a compact, 10-GHz Er-doped solid-state frequency comb operating near the 1550 nm telecommunications window. The system, assembled entirely from commercially available components, produces a coherent spectrum spanning from 1150 nm to 2350 nm with exceptionally low intensity and phase noise. Full frequency stabilization of both pulse repetition and carrier envelope offset frequencies is demonstrated with respect to an RF reference. Comprehensive characterization reveals performance exceeding that of previously reported solid-state combs in power-per-mode and noise suppression. These results establish a robust and accessible platform for multi-gigahertz-repetition-rate comb synthesis, bridging laboratory-grade performance with practical deployment in optical communication, precision timing, and astronomical instrumentation.
Read the full abstract

All authors Niccolò S. Barberio, Francesco Canella, Andrea Pertoldi, Benjamin Rudin, Oguzhan Kara, Florian Emaury, Antonio Caruso, Dario Giannotti, Francesco Leone, Paolo Laporta, Gianluca Galzerano

Optics

Terahertz emission and detection using Ge-on-Si photoconductive antennas

Dhanashree Chemate, Abhishek Singh, Utkarsh Pandey et al. (+5 more)

Germanium-on-Silicon (Ge-on-Si) is a promising, CMOS-compatible platform for integrated terahertz (THz) photonics, offering a low-cost alternative to III-V semiconductors. A primary challenge for Ge-based photoconductive antennas (PCAs), however, has been the long carrier lifetime of bulk Ge, preventing its use as a detector. Here, we demonstrate that amorphous Ge (a-Ge) films overcome this limitation, possessing inherent ultrashort carrier lifetimes ~ 1.11-1.38 ps. We leverage this property to demonstrate, for the first time to our knowledge, coherent THz pulse detection using undoped a-Ge-on-Si PCAs. We present a comparative study of devices fabricated on a-Ge films grown by plasma-enhanced chemical vapor deposition (PECVD) and DC magnetron sputtering. The PECVD-Ge device, with better homogeneity and a smoother morphology in the films, demonstrates superior performance for both THz emission and detection. As an emitter, the PECVD-Ge PCA achieves a 40 dB signal-to-noise ratio (SNR) with a bandwidth of ~ 3 THz. As a detector, it achieves a 32 dB SNR and a ~ 2 THz bandwidth, representing a ~2.5-fold increase in detected signal amplitude over the sputtered-Ge device. These results establish amorphous Ge-on-Si as a viable and scalable platform for both THz generation and detection, paving the way for fully integrated Si-based THz time-domain systems.
Read the full abstract

All authors Dhanashree Chemate, Abhishek Singh, Utkarsh Pandey, Ruturaj Puranik, Vivek Dwij, Priyanshu Gahlaut, Siddhartha P. Duttagupta, Shriganesh S. Prabhu

Biological Physics · Cross-listed from cond-mat.soft

Non-equilibrium geometric forces steer spiral waves on folded surfaces

Varun Venkatesh, Farzan Vafa, Martin Cramer Pedersen et al. (+1 more)

Spiral waves are ubiquitous signatures of non equilibrium dynamics, appearing across chemical, biological, and active systems. Yet, in many living systems these waves unfold on curved and folded surfaces whose geometry has rarely been treated as a dynamical factor. Here we show that surface curvature fundamentally shapes spiral wave behavior and can contribute to the organization of neural activity in the brain. Via analytical theory and simulations of the complex Ginzburg Landau equation (CGLE) on curved surfaces, we demonstrate that curvature enters through the Laplace Beltrami operator as a spatial modulation of effective diffusion. Gradients of this effective diffusion generate a geometric force on spiral defects, and the complex nature of the CGLE produces a complex mobility that leads to non central and non reciprocal responses. Applied to realistic cortical surfaces of the human brain, the model predicts that the pattern of cortical folding stabilizes and localizes spiral waves, while progressive smoothing of the surface erases these non equilibrium structures. This reveals that brain geometry is not a passive scaffold but an active physical constraint that shapes neural dynamics. More broadly, the same geometric mechanism provides a universal route by which curvature and topology control pattern formation across oscillatory, chemical, and active matter systems.
Read the full abstract

All authors Varun Venkatesh, Farzan Vafa, Martin Cramer Pedersen, Amin Doostmohammadi

Medical Physics

Building Digital Twins of Different Human Organs for Personalized Healthcare

Yilin Lyu, Zhen Li, Vu Tran et al. (+9 more)

Digital twins are virtual replicas of physical entities and are poised to transform personalized medicine through the real-time simulation and prediction of human physiology. Translating this paradigm from engineering to biomedicine requires overcoming profound challenges, including anatomical variability, multi-scale biological processes, and the integration of multi-physics phenomena. This survey systematically reviews methodologies for building digital twins of human organs, structured around a pipeline decoupled into anatomical twinning (capturing patient-specific geometry and structure) and functional twinning (simulating multi-scale physiology from cellular to organ-level function). We categorize approaches both by organ-specific properties and by technical paradigm, with particular emphasis on multi-scale and multi-physics integration. A key focus is the role of artificial intelligence (AI), especially physics-informed AI, in enhancing model fidelity, scalability, and personalization. Furthermore, we discuss the critical challenges of clinical validation and translational pathways. This study not only charts a roadmap for overcoming current bottlenecks in single-organ twins but also outlines the promising, albeit ambitious, future of interconnected multi-organ digital twins for whole-body precision healthcare.
Read the full abstract

All authors Yilin Lyu, Zhen Li, Vu Tran, Xuan Yang, Hao Li, Meng Wang, Ching-Yu Cheng, Mamatha Bhat, Viktor Jirsa, Roger Foo, Chwee Teck Lim, Lei Li

Accelerator Physics

Introduction to the Mechanical Design of Accelerators

Marc Timmins

Particle accelerators represent some of the most sophisticated engineering achievements of our time. Their construction requires a unique combination of physics insight and mechanical engineering expertise. The aim of this paper is to provide young mechanical engineers with an introduction to the principles, methods, and challenges associated with the mechanical design of accelerators. The lecture upon which this proceeding is based emphasized the translation of functional requirements into engineering specifications, the critical importance of robust and reliable design, and the need for precisely defined drawings supported by international standards such as ISO GPS and GD&T. Through illustrative examples and a practical case inspired by CERN's existing components, the paper underlines the necessity of anticipating lifecycle demands, ensuring manufacturability, and safeguarding operational reliability. Particular emphasis is placed on the contractual value of 2D drawings, the practical application of functional dimensioning, and tolerance chain analysis. By reviewing common pitfalls and exploring best practices, the paper seeks to orient engineers towards design choices that balance cost, reliability, and performance.
Read the full abstract

Applied Physics

In situ and operando laboratory X-ray absorption spectroscopy at high temperature and controlled gas atmosphere with a plug-flow fixed-bed cell

Sebastian Praetz, Emiliano Dal Molin, Delf Kober et al. (+10 more)

The capabilities of a plug-flow fixed-bed cell for operando studies of heterogeneous catalysts are demonstrated using laboratory-based X-ray absorption spectroscopy (XAS) with a von Hamos spectrometer. The cell operates at temperatures up to 1000 deg C and pressures up to 10 bar, equipped with three mass flow controllers and two infrared lamps for rapid heating under inert/reactive gas atmospheres. Proof-of-principle studies include in situ MnO oxidation in 5% Ni/MnO and operando Ni nanoparticle evolution in 20-NiO/COK-12 (20.2% NiO on SiO2) during CO2 methanation before/after activation. Within 5-15 min per spectrum, oxidation state changes are resolved while catalytic activity is simultaneously quantified by online GC. Extended datasets and methods are available in the ancillary file SI.pdf (Supplementary Information file). A shortened version of this work has been published as a Technical Note in Journal of Analytical Atomic Spectrometry (2026, 41, 1208-1211, DOI: 10.1039/D6JA00027D). This manuscript provides an extended version including additional datasets, analysis, and methodological details beyond the published article.
Read the full abstract

All authors Sebastian Praetz, Emiliano Dal Molin, Delf Kober, Marko Tesic, Christopher Schlesiger, Peter Kraus, Julian T. Müller, Jyothilakshmi Ravi Aswin, Daniel Grötzsch, Maged F. Bekheet, Albert Gili, Aleksander Gurlo, Birgit Kanngießer

Optics

Microscopic quantum description of surface plasmon polaritons: Revealing intrinsic ultrastrong light-matter coupling

Florian Maurer, Thomas F. Allard, Yanko Todorov et al. (+2 more)

We develop a microscopic quantum theory of surface plasmon polaritons valid for arbitrary metal-dielectric geometries. Our framework is based on the Power-Zienau-Woolley representation of quantum electrodynamics, which provides an optimal separation between electronic and photonic degrees of freedom and is therefore particularly well suited for constructing quantum descriptions of polaritonic excitations in strongly dispersive media. Within this formulation, the fundamental electronic oscillator is identified as the bulk plasmon mode, which is nonperturbatively coupled to the radiative continuum of free photon modes. This coupling induces a geometry-dependent renormalization of the bulk plasma frequency, giving rise to confined plasmonic resonances. As specific applications, we recover the localized surface plasmon modes of metallic nanoparticles, including radiative frequency shifts and decay, as well as the exact dispersion relation of propagating surface plasmon polaritons at planar interfaces. Our quantum treatment further reveals that light-matter interactions at metal-dielectric interfaces are inherently in the ultrastrong coupling regime. As a result, in the quasistatic limit, the system exhibits unconventional ground-state quantum fluctuations that can be controlled through the refractive index. These results open new intriguing perspectives in the field of quantum plasmonics.
Read the full abstract

All authors Florian Maurer, Thomas F. Allard, Yanko Todorov, Guillaume Weick, David Hagenmüller

Instrumentation and Detectors · Cross-listed from hep-ex

Light Dark Matter Search with 7.8 Tonne-Year of Ionization-Only Data in XENONnT

E. Aprile, J. Aalbers, K. Abe et al. (+174 more)

We report on a blinded search for dark matter (DM) using ionization-only (S2-only) signals in XENONnT with a total exposure of $7.83\mathrm{tonne}\times\mathrm{year}$ over 579 days in three science runs. Dedicated background suppression techniques and the first complete S2-only background model in XENONnT provide sensitivity to nuclear recoils of [0.5, 5.0] $\mathrm{keV_\mathrm{nr}}$ and electronic recoils of [0.04, 0.7] $\mathrm{keV_\mathrm{ee}}$. No significant excess over the expected background is observed, and we set 90% confidence level upper limits on spin-independent DM–nucleon and spin-dependent DM–neutron scattering for DM masses between 3 and 8 $\mathrm{GeV}/c^2$, as well as on DM–electron scattering, axion-like particles, and dark photons, improving on previous constraints. For spin-independent DM–nucleon scattering, we exclude cross sections above $6.0\times10^{-45} $cm$^2$ at a DM mass of 5 $\mathrm{GeV}/c^2$, pushing the XENONnT sensitivity closer to the region where coherent elastic neutrino-nucleus scattering ($\text{CE}\nu\text{NS}$) becomes an irreducible background.
Read the full abstract

All authors E. Aprile, J. Aalbers, K. Abe, M. Adrover, S. Ahmed Maouloud, L. Althueser, B. Andrieu, E. Angelino, D. Antón Martin, S. R. Armbruster, F. Arneodo, L. Baudis, M. Bazyk, V. Beligotti, L. Bellagamba, R. Biondi, A. Bismark, K. Boese, R. M. Braun, G. Bruni, G. Bruno, R. Budnik, C. Cai, C. Capelli, J. M. R. Cardoso, A. P. Cimental Chávez, A. P. Colijn, J. Conrad, J. J. Cuenca-García, V. D'Andrea, L. C. Daniel Garcia, M. P. Decowski, A. Deisting, C. Di Donato, P. Di Gangi, S. Diglio, K. Eitel, S. el Morabit, R. Elleboro, A. Elykov, A. D. Ferella, C. Ferrari, H. Fischer, T. Flehmke, M. Flierman, R. Frankel, D. Fuchs, W. Fulgione, C. Fuselli, F. Gao, R. Giacomobono, F. Girard, R. Glade-Beucke, L. Grandi, J. Grigat, H. Guan, M. Guida, P. Gyorgy, R. Hammann, C. Hils, L. Hoetzsch, N. F. Hood, M. Iacovacci, Y. Itow, J. Jakob, F. Joerg, Y. Kaminaga, M. Kara, S. Kazama, P. Kharbanda, M. Kobayashi, D. Koke, K. Kooshkjalali, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, A. Li, I. Li, S. Li, S. Liang, Z. Liang, Y.-T. Lin, S. Lindemann, M. Lindner, K. Liu, M. Liu, F. Lombardi, J. A. M. Lopes, G. M. Lucchetti, T. Luce, Y. Ma, C. Macolino, G. C. Madduri, J. Mahlstedt, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, S. Mastroianni, V. Mazza, A. Melchiorre, J. Merz, M. Messina, A. Michel, K. Miuchi, A. Molinario, S. Moriyama, M. Murra, J. Müller, K. Ni, C. T. Oba Ishikawa, U. Oberlack, S. Ouahada, B. Paetsch, Y. Pan, Q. Pellegrini, R. Peres, J. Pienaar, M. Pierre, G. Plante, T. R. Pollmann, F. Pompa, A. Prajapati, L. Principe, J. Qin, D. Ramírez García, A. Ravindran, A. Razeto, R. Singh, L. Sanchez, J. M. F. dos Santos, I. Sarnoff, G. Sartorelli, J. Schreiner, P. Schulte, H. Schulze Eißing, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, F. N. Semler, P. Shagin, S. Shi, H. Simgen, Z. Song, A. Stevens, C. Szyszka, A. Takeda, Y. Takeuchi, P.-L. Tan, D. Thers, G. Trinchero, C. D. Tunnell, K. Valerius, S. Vecchi, S. Vetter, G. Volta, B. von Krosigk, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, V. H. S. Wu, Y. Xing, D. Xu, Z. Xu, M. Yamashita, J. Yang, L. Yang, J. Ye, M. Yoshida, L. Yuan, G. Zavattini, Y. Zhao, M. Zhong, T. Zhu

Physics and Society

Decentralization can hinder frequency synchronization in power grids through multiple phase transitions

Jung-Ho Kim and Alex Arenas

Decarbonization is rapidly increasing the penetration of inverter-based renewables and other low-capacity generators, intensifying concerns about frequency synchronization in increasingly decentralized power grids. A common heuristic from Kuramoto onset theory and homogeneous parameter swing-equation models is that distributing generation across many smaller units reduces the effective heterogeneity of nodal injections (natural frequencies) and lowers the coupling required for synchronization. Here, using a second-order Kuramoto model, we investigate how decentralization affects frequency synchronization when inertia and damping scale with power generation and consumption. We find that decentralization does not always lower the critical frequency synchronization threshold. Instead, increasing decentralization can induce a non-monotonic dependence of the critical coupling strength and lead to a double phase transition in frequency synchronization. These behaviors remain robust under asymmetric inertia between consumers and generators. Even when empirical power-generation and power-consumption distributions are considered, a region in which the critical threshold remains nearly constant is observed as decentralization increases. Our results demonstrate that decentralization can give rise to complex collective dynamics and caution against assuming that decentralization alone ensures improved frequency synchronization.
Read the full abstract

Applied Physics

Compositional and morphological study of a Nuragic bronze figurine with neutron diffraction and neutron tomography

M. Cataldo, B. Billeci, S. Britto et al. (+6 more)

Nuragic figurines are rare and unique examples of the mastery achieved by Sardinian craftsmen in the early Iron Age. These bronze artefacts were most likely cast using the lost wax technique: the shapes were moulded with relative ease, and even complex figures could be represented. However, the manufacturing process was not always a single-step procedure: in some cases, the parts of the model were moulded separately and then assembled together. Therefore, the analytical study of Nuragic bronzes can help to understand the specific casting methods and to evaluate the techniques implemented by Sardinian craftsmen to produce such complex objects. In recent years, Time of Flight Neutron Diffraction (Tof-ND) and Neutron Imaging (NI) have proven to be among the most effective methods for non-invasive studies. Neutron diffraction and neutron imaging provide complementary quantitative and morphological information that can be the key to understanding the casting processes. In this work, the results of the analysis of a bronze figurine will be reported. The statuette represents a Nuragic warrior and was made available by the Soprintendenza Archeologia Belle Arti e Paesaggio per le province di Sassari e Nuoro (Sassari,Italy).
Read the full abstract

All authors M. Cataldo, B. Billeci, S. Britto, N. Canu, M. Clemenza, G. Marcucci, A. Scherillo, V. Sipala, P. Oliva

Atmospheric and Oceanic Physics

Solar and anthropogenic climate drivers: an updated regression model and refined forecast

Frank Stefani

In a recent paper attempts were made to quantify the respective solar and anthropogenic influences on the terrestrial climate, and to cautiously predict the global mean temperature over the next 130 years. In a double regression analysis, both the binary logarithm of carbon dioxide concentration and the geomagnetic aa-index were used as predictors of the sea surface temperature (SST) since the mid-19th century. The regression results turned out to be sensitive to end effects, leading to a broad range of the climate sensitivity between 0.6 K and 1.6 K per doubling of CO$_2$ when varying the final year. The aim of this paper is to narrow down this range. To this end, the correlations between the two predictors and the dependent variable (SST) are analysed in detail. It is demonstrated that the SST can be predicted until around 2000 almost perfectly using only the aa-index, whereas for later periods the role of CO$_2$ increases significantly. Hence, the weight of the aa-index is fixed to its robust outcome (around 0.04 K/nT) from the regressions up to 1990. The SST data, reduced by the aa-contribution thus specified, are then used in a single regression with CO$_2$ as the only remaining predictor. This results in a significant reduction in the range of CO$_2$ sensitivity, narrowing it to 1.1-1.4 K. Given the exceptionally high temperatures in recent years, these values are considered a kind of upper limit that could still be subject to downward corrections when future data are incorporated. Based on this estimate, the temperature forecast until 2100 is refined by using more precise predictions of the aa-index and the paths of atmospheric CO$_2$ content which are based on constant emission scenarios combined with a linear sink model. With the exception of the most “pessimistic” variant, the temperature is predicted to remain below the extraordinarily high value measured in 2024.
Read the full abstract

Plasma Physics

A new class of special functions arising in plasma linear susceptibility tensor calculations

Roberto Ricci

We investigate some fundamental properties of a peculiar class of special functions strictly related to Bessel, Anger and Weber functions, whose introduction was originally motivated by linear susceptibility tensor calculations in a hot, magnetised plasma. We show that these functions are solutions of an inhomogeneous Bessel ODE, with specified initial conditions and a distinct right-hand-side term fulfilling the Nielsen's requirement. Beside deriving recurrence relations and an alternative representation involving incomplete Anger-Weber functions, we show that these functions admit a simple series expansion in terms of Bessel functions of integer order, obtained by resorting to the Jacobi-Anger formula. In plasma applications this eventually leads to expressions involving infinite sums of products of Bessel functions, not particularly apt to numerical evaluation ought to their slow convergence rate when the particle's gyro-radius is larger than the wavelength. By exploiting the previously determined recurrence properties of the new class of functions we present a particularly simple derivation of the linear susceptibility tensor that enables to avoid this inconvenience.
Read the full abstract

Biological Physics

Ultrasensitive Real-Time Detection of SARS-CoV-2 Proteins with Arrays of Biofunctionalized Graphene Field-Effect Transistors

Hamid Reza Rasouli, David Kaiser, Ghazaleh Eshaghi et al. (+9 more)

With the growing interest in graphene field-effect transistors (GFETs) for biosensing applications, there is a strong demand for strategies enabling flexible and multiplexed biofunctionalization, as well as highly parallel, real-time electronic readout integrated with microfluidic control. Here we present a methodology that addresses these challenges by enabling real-time, parallel monitoring of multiple GFETs integrated on a single microfabricated chip within an automated electronic and microfluidic platform. We demonstrate the capabilities of this approach through ultrasensitive detection of the SARS-CoV-2 spike (S) and nucleocapsid (N) proteins. GFET chips are functionalized via van der Waals assembly using 1 nm-thick molecular two-dimensional (2D) materials - carbon nanomembranes - which enable multiplexed biofunctionalization. The chips are integrated into a custom-developed microelectronic and microfluidic system that allows parallel, real-time, and automated measurements of 15 GFETs. We present in situ biofunctionalization of the GFETs with antibodies, followed by highly specific detection of the S- and N-proteins with limits of detection down to 10 aM and a dynamic range spanning four orders of magnitude. Owing to its versatility, the presented methodology is readily adaptable for sensing a wide range of biological and chemical targets.
Read the full abstract

All authors Hamid Reza Rasouli, David Kaiser, Ghazaleh Eshaghi, Marco Reinhard, Alexander Rolapp, Dominik Gary, Tobias Fischer, Christof Neumann, Thomas Weimann, Katrin Frankenfeld, Michael Meister, Andrey Turchanin

Fluid Dynamics

Inertial Self-Caging: Dynamics of Macroscopic Swimmers at Moderate Reynolds Number Sustaining Chemical Wake Resonance

Alessandro Foradori and Paolo Bettotti

Self-propelled phoretic swimmers are generally studied in the laminar flow regime, where their low speed renders inertial effects negligible and trajectories highly predictable. This research tackles the challenge of propulsion in the inertial regime, at moderate Reynolds numbers (100 < Re < 200), where fluid dynamics becomes non-linear. By using a chemically driven macroscopic hydrogel this work demonstrates, through experiments and modeling, the existence of stable resonant states under confined geometry: as the swimmer circles, it interacts with its own lasting chemical wake. This chemical self-feedback creates a complex, stable motion characterized by both universal exponential speed decay with superimposed significant periodic speed oscillations. Furthermore, a critical threshold speed is identified, where the system abruptly transitions from the resonant oscillatory regime to a stochastic stop & go behavior. These findings provide a fundamental understanding of how chemical fields, hydrodynamic inertia, and confinement couple to determine the motion properties of high-speed active matter.
Read the full abstract

Applied Physics

Metagratings on Low-Cost Substrates for Efficient Anomalous Reflection: Addressing Dielectric Loss

Oz Diker and Ariel Epstein

We present a theoretical framework and practical methodology for designing high-efficiency metagratings (MGs), sparse periodic arrangements of subwavelength polarizable particles (meta-atoms), on low-cost dielectric substrates with non-negligible losses. The formulation incorporates these losses and exploits multiple degrees of freedom to optimize beam manipulation efficiency within a simple realistic printed-circuit-board (PCB) configuration. Importantly, the various loss mechanisms are analyzed using a judiciously devised equivalent circuit model, providing insights on their respective contributions. We validate our theory by designing, fabricating, and experimentally characterizing an efficient FR4-based anomalous reflection PCB MG, demonstrating good agreement between analytical predictions, full-wave simulations, and laboratory measurements. This work opens avenues for realizing efficient, low-profile, beam manipulation devices at reduced cost, offering practical solutions to mitigate loss limitations in diverse material sets across the electromagnetic spectrum.
Read the full abstract