Peer Revenue Returns subject to peer review

Papers

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

Physics Physics

physics Watch Physics

Wednesday 9 September

Optics

Resonant subspace approximation for photonic crystal slabs

Nikolay A. Gippius, Ilia M. Fradkin, Natalia S. Salakhova et al. (+1 more)

Resonant approximations are indispensable for the interpretation and efficient modeling of photonic crystal slabs, yet most of them describe an eigenmode as a pole in the complex energy plane at a fixed set of the remaining parameters. Tracking such poles and their hybridization across the Brillouin zone or upon variation of structural parameters is labor-intensive and severely limits the use of resonant approximations in band-structure calculations and structural optimization. Here we introduce a resonant subspace approximation that treats the photon energy and all other parameters on an equal footing. Considering a wide class of photonic crystal slabs that can be split into two non-resonant parts, we show that their resonances arise solely from the round-trip propagation of coupled Fourier harmonics between these parts, in direct analogy with Fabry–Pérot and waveguide modes. We generalize the scalar round-trip phase to round-trip and phase matrices, whose smooth dependence on all parameters allows us to project the problem onto a small resonant subspace defined at a single anchor point and to extrapolate it throughout a local region of parameter space of arbitrary dimensionality. As a result, rigorous computations at only a few points suffice to reconstruct the band structure, modal linewidths, complex hybridization, and optical spectra as functions of energy, wavevector, geometric dimensions, or permittivity within seconds. We demonstrate the accuracy and versatility of the approach on a strong hexagonal silicon grating, resolving intricate mode hybridization, symmetry-protected features, and subtle geometry-controlled effects that are hardly accessible to straightforward computations. The method is fast, accurate, and readily extensible, offering a practical route to the exploration, design, and optimization of resonant photonic crystal slabs.
Read the full abstract

All authors Nikolay A. Gippius, Ilia M. Fradkin, Natalia S. Salakhova, Sergey A. Dyakov

Computational Physics

Nonlinear flame describing function and mean shift kinematics of slit flames under combined axial-transverse forcing

Juhoon Son, Yong Jea Kim, Jungho Sohn et al. (+1 more)

This study investigates the nonlinear kinematics of a premixed slit flame using a two-dimensional $G$-equation level-set framework. Results show that combined forcing induces nonlinear saturation in the FDF, characterized by early gain flattening and premature phase drops, which intensify with the transverse forcing amplitude. Kinematic analysis reveals that this geometric nonlinearity manifests as a reduction in the time-averaged flame height, defined as the mean shift. In the quasi-steady limit, this mean shift is analytically quantified via a multivariate asymptotic expansion, where fourth-order terms successfully capture the saturation mechanism at elevated amplitudes. By introducing a scaling parameter to account for transverse dominance, the frequency-dependent decay of the mean shift in the compact limit collapses onto a single master curve, enabling the derivation of a unified theoretical model that integrates this asymptotic response with a second-order low-pass filter. Furthermore, because the mean shift reduces the physical extent of the flame, it alters the wrinkle propagation time. Correcting the Strouhal number using the measured mean shift collapses the dispersed nonlinear FDF curves onto the linear theory prediction. The analysis is further extended to disturbances convected at a finite speed, for which the linear transfer function is derived analytically and the correction with the measured mean shift continues to collapse the nonlinear FDF. These findings establish that the nonlinear FDF behavior under multidimensional forcing is fundamentally governed by the kinematic mean shift, providing a theoretical baseline for decoupling geometric nonlinearities from other thermo-diffusive or hydrodynamic instabilities in turbulent flames.
Read the full abstract

All authors Juhoon Son, Yong Jea Kim, Jungho Sohn, Dong-hyuk Shin

Optics · Cross-listed from cond-mat.mtrl-sci

Facile hBN-hBN Interfacial Overlap Engineering for Enhanced Quantum Emitter Formation

Nhat Minh Nguyen, Trung Vuong Doan, Md Shakhawath Hossain et al. (+12 more)

Quantum emitters in two-dimensional materials, particularly hBN, are promising platforms for quantum technologies. However, achieving high-density emitters at predetermined locations while preserving optical quality remains challenging. Here, we introduce a facile, cost-effective double-layer all-dry transfer approach to deterministically create overlap regions between hBN flakes. These pre-defined capped regions exhibit a significantly enhanced emitter density, with up to a 15-fold increase compared to uncapped areas. Importantly, this method does not compromise emitter quality: emitters within overlap regions demonstrate excellent optical performance, including high signal-to-background and signal-to-noise ratios, large Debye-Waller factors, high brightness, and strong spectral stability. Possible defect configurations are also discussed to contextualize the observed emission characteristics. This scalable strategy enables preferential formation of quantum emitters in targeted regions, achieving higher densities than simple treatments such as plasma irradiation while avoiding the complexity of advanced fabrication techniques. The approach provides a practical pathway for integrating high-quality quantum emitters into scalable quantum photonic platforms.
Read the full abstract

All authors Nhat Minh Nguyen, Trung Vuong Doan, Md Shakhawath Hossain, Akila Elangasinghe, Duc Anh Ngo, Ha Ngoc Duy Huynh, Thi Ngoc Anh Mai, Yongliang Chen, Kenji Watanabe, Takashi Taniguchi, Michael G. Ruppert, Chaohao Chen, Xiaoxue Xu, Toan Dinh, Toan Trong Tran

Plasma Physics · Cross-listed from astro-ph.SR

Connecting Dynamo Theory with DNS Data: A Computational Analysis of $\alpha$ and $\beta$ effects

Kiwan Park

We investigate the influence of current helicity on the turbulent magnetic diffusivity $\beta$ using three complementary derivations of the $\alpha$ and $\beta$ coefficients, based on the large-scale magnetic field $\overline{\mathbf{B}}$, the turbulent velocity $\mathbf{u}$, and the turbulent magnetic field $\mathbf{b}$. Applying these coefficients to raw DNS data, we reconstruct $\overline{\mathbf{B}}$ and compare the results with the original simulations. In the kinematic regime all models agree well with the DNS data. In the nonlinear regime, however, $\beta_{\mathrm{vv-vw}}$ alone produces unbounded growth of $\overline{\mathbf{B}}$. Including the contribution from turbulent magnetic fields ($\beta_{\mathrm{bb+jb}}$) suppresses this unphysical growth and restores agreement with the DNS results. We find that kinetic helicity drives $\beta$ more negative, while current helicity shifts it back toward zero. Weighted combinations of the coefficients further show that the $\beta$ effect dominates the evolution of $\overline{\mathbf{B}}$ throughout, whereas the $\alpha$ effect becomes important mainly for sustaining the field in the nonlinear regime. The corresponding IDL analysis scripts are provided to facilitate practical implementation of the theoretical models.
Read the full abstract

Applied Physics

Through-thickness coupling of diffusion and viscoelastic relaxation in the transient bending of bilayer microcantilevers

YingCheng Zhou, Kosuke Minami and Genki Yoshikawa

Static-mode microcantilever sensors detect chemical analytes through the bending of a bilayer beam whose polymer coating swells upon absorption. The transient bending is usually modeled as if the coating absorbed analyte uniformly, which is adequate for thin coatings but breaks down as the coating thickens and a moving diffusion front couples to depth-dependent viscoelastic relaxation. We resolve this coupling with a purpose-built finite-element solver requiring only one linear solve per time step, and show that the through-thickness structure controls the transient response in ways uniform-uptake models cannot capture. Verified against a published analytical solution, the solver reproduces the full transition from a pronounced curvature overshoot (up to nearly twice the steady-state value) when diffusion is fast relative to relaxation to a monotonic rise when it is slow. In the intermediate-thickness regime the analytical solution cannot reach, the thickness maximizing the steady-state signal and the thickness preserving the transient overshoot are governed by different physics, one geometric and one dynamic, so one coating cannot be optimized for both. The overshoot further survives realistic surface mass-transfer resistance, justifying the idealized surface boundary condition used throughout.
Read the full abstract

Applied Physics

Maximum signal-to-noise ratio enhancement by averaging under a limited measurement time

YingCheng Zhou, Kosuke Minami, Genki Yoshikawa et al. (+1 more)

Averaging through repetitive measurement is a ubiquitous strategy for improving signal-to-noise ratio (SNR) and is commonly assumed to yield a $\sqrt{N}$ enhancement with the number of repetitions $N$. This assumption, however, implicitly requires the signal amplitude to be independent of measurement duration. This condition does not generally hold in dynamical sensing systems with finite response time and a fixed measurement time. We derive a closed-form expression for the SNR enhancement factor by analytically accounting for the competition between statistical noise reduction and dynamical signal attenuation, and demonstrate the existence of a strict upper bound on the SNR enhancement. The enhancement factor is a non-monotonic function of $N$ with a well-defined maximum at an optimal repetition number, beyond which further averaging degrades the SNR. Moreover, below a threshold set by the ratio of measurement time to response time, averaging yields no enhancement at all. These two regimes delimit where the conventional $\sqrt{N}$ law breaks down. Experimental validation using nanomechanical gas sensing, with two receptor-analyte systems deliberately chosen to bracket this enhancement transition, confirms the theoretical predictions. Our results show that measurement time is a finite resource to be optimally partitioned between signal accumulation and averaging, and provide a quantitative guideline for selecting the repetition number in time-constrained sensing such as real-time and repetitive gas or odor detection.
Read the full abstract

All authors YingCheng Zhou, Kosuke Minami, Genki Yoshikawa, Gaku Imamura

History and Philosophy of Physics · Cross-listed from nucl-ex

Reinvestigation of the Yield of the Trinity Device

Eric B. Norman, Keenan J. Thomas and Pedro V. Guillaumon

Previous published analyses of trinitite to determine the yield of the Trinity nuclear explosion used various estimates of the fraction of fission products that became incorporated in trinitite. Furthermore, these studies utilized nuclear data that has subsequently been revised. Utilizing a planar germanium detector, we observed gamma rays produced by the decays of both 137Cs and 239Pu from four samples of trinitite. From the observed 137Cs/239Pu ratios of and a simple analysis method based on current nuclear data and weapons debris studies, we find an average yield of 9.1+-4.5 kilotons from our four samples. While this result is substantially lower than the established total yield of 21 kilotons, it is in reasonable agreement that attributable to fissions in the 239Pu core alone.
Read the full abstract

Instrumentation and Detectors · Cross-listed from hep-ex

Extended High-Mass Axion Search with an Auxetically Tuned Higher-Order-Mode Cavity

Jinsu Kim, Sungjae Bae, Junu Jeong et al. (+9 more)

Conventional high-mass axion haloscopes based on the TM$_{010}$ mode lose detection volume as the resonant frequency increases. We report an extended axion search using a dielectric-restored TM$_{020}$ cavity haloscope with symmetry-preserving auxetic tuning based on a single-degree-of-freedom mechanical architecture. Using a near-quantum-limited microwave receiver, we searched a frequency range of 4.98-5.07 GHz and exclude axion-photon couplings with sensitivity approaching the KSVZ benchmark. Together with two earlier searches, the present scans extend a multi-scan program based on this architecture, yielding nearly 300 MHz of contiguous high-mass axion coverage over 4.98-5.27 GHz, the first broad search reported with a single higher-order-mode haloscope. This work establishes higher-order-mode cavities as a practical, scalable route beyond the TM$_{010}$ volume penalty.
Read the full abstract

All authors Jinsu Kim, Sungjae Bae, Junu Jeong, Younggeun Kim, Jihn E. Kim, Arjan F. van Loo, Yasunobu Nakamura, Seonjeong Oh, Taehyeon Seong, Yannis K. Semertzidis, Sergey Uchaikin, SungWoo Youn

Atmospheric and Oceanic Physics

Boundary-layer scheme selection outweighs microphysics in WRF simulations of the August 2018 Kerala extreme rainfall event

Satyam Kumar, Akshay Sunil and Rashad PE

Because precipitation is regulated by intricate interactions between topography, cloud microphysics,cumulus convection, radiation, and boundary-layer processes, it is still difficult to accurately simulate orographically enhanced monsoon rainfall over the Western Ghats.

Applied Physics

A Predictive Design Framework for a Soft Robotic Ventricle using Contractile Actuators

Jeongmin Kim, Qiong Wang, Liuyang Cheng et al. (+4 more)

The natural cardiac cycle is divided into the systole and diastole phases which encompass four distinct stages: isovolumetric contraction and ejection during systole, followed by isovolumetric relaxation and filling during diastole. Cardiovascular modeling of this cycle ranges from high-fidelity multiphysics simulations to reduced-order lumped-parameter (Windkessel) representation of the heart-artery coupling. However, current models do not relate the mechanics of the actuator driving the ventricle pump to the hemodynamics. In this study, we develop and experimentally validate a predictive design framework for ventricle-like pumps using various types of soft contractile actuators. We build a circulatory loop which reproduces the entire loop including the isovolumetric phases-where pressure changes occur without volume shifts. The framework is based on a lumped-parameter model, hereafter referred to as the phase-dependent Actuator-driven Windkessel 3-element (AWK3) model, to bridge soft actuator mechanics to the cardiac pressure-volume (P-V) loop. Unlike traditional models that require either pressure or volume as a fixed input to estimate the other, our proposed model predicts both variables when informed by the isometric characteristics of the actuators. We validate the model using a ventricle-inspired pump driven by a linear contractile series-elastic actuator or twisted and coiled polymer actuators (TCPA). We relate the actuator isometric testing protocol to the phase-dependent AWK3 model, which replicates the Frank-Starling law, accurately describing cardiac behavior under varying conditions of preload, afterload, and inotropy (contractility). This approach provides a robust platform for the design and high-fidelity control of bio-inspired soft robotic circulatory systems.
Read the full abstract

All authors Jeongmin Kim, Qiong Wang, Liuyang Cheng, Samuel Tsai, Seong Hyeon Kim, Harma K. Turbendian, Sameh Tawfick

Applied Physics

Round-the-Clock Sub-Ambient Cooling via Dynamic Sky View Factor Steering

Qiuyu Chen, Minghao Dong, Zheng Zhang et al. (+3 more)

Passive daytime radiative cooling holds significant potential to address sustainability challenges such as the energy-water nexus. However, common static horizontal configurations cannot respond to dynamic changes of environmental conditions such as solar position and cloud coverage, thereby forfeiting the opportunity of optimizing the cooling performance in the 24-h day-night cycle. Here, inspired from the heliotropism of sunflowers, we develop a dynamic sky view factor steering (DSVFS) system. By dynamically steering the emitter to an optimal angle, this system not only relaxes the stringent dual requirement of ultra-high solar reflectivity and infrared emissivity of the radiative emitter, but also maximizes its cooling power round-the clock. Using this DSVFS system, we experimentally demonstrate sub-ambient cooling during a typical hot noon even with a near-blackbody emitter; with a selective emitter, we demonstrate an increase of cooling power by 135% as compared to its static counterpart. Case studies of multiple cities across the world indicate a maximum annual electricity saving of up to 200 kWh/m^2.
Read the full abstract

All authors Qiuyu Chen, Minghao Dong, Zheng Zhang, Xiaodonog Zhao, Peng Xiao, Zhen Chen

Plasma Physics

A polar-harmonic unified gas-kinetic scheme for magnetized ion dynamics from cyclotron kinetics to the Hall-Pedersen constitutive limit

Yixiao Wang, Zhigang Pu, Xing Ji et al. (+1 more)

Magnetized ion transport in weakly ionized plasmas ranges from gyroangle-dependent kinetics to Hall-Pedersen drift-diffusion as collisionality and magnetization vary. We develop a polar-harmonic unified gas-kinetic scheme (PH-UGKS) for the ion Vlasov-BGK equation in a uniform magnetic field. The scheme evolves the full ion distribution by coupling a conservative density update to exponential evolution of its nonequilibrium component. Exact collision-rotation integration in gyroangle Fourier space is combined with a time-averaged kinetic flux that incorporates spatial transport and electric acceleration, together with a compact Hall-Pedersen correction to the density flux. The scheme conserves ion number, and analysis establishes second-order temporal consistency and asymptotic preservation of the Hall-Pedersen density limit at fixed magnetization. Numerical tests reproduce ion Bernstein dispersion and Dory-Guest-Harris growth rates and resolve changes in the gyroharmonic spectrum as the collision-to-gyrofrequency ratio varies. The driven ion-flux response agrees with an independent characteristic-Volterra reference, including finite-frequency departures from the instantaneous Hall-Pedersen relation. In collisional tests, accurate responses are obtained with time steps far larger than both the collision time and the gyroperiod. Fixed-resolution density tests confirm convergence to the corresponding Hall-Pedersen discretization. The same kinetic formulation thus connects kinetic response and macroscopic transport without switching to a fluid solver or subcycling microscopic time scales.
Read the full abstract

All authors Yixiao Wang, Zhigang Pu, Xing Ji, Kun Xu

Instrumentation and Detectors

Spectral Discrimination of Deposited Gamma-Ray Energies in a Simulated CeBr$_3$ Scintillator

Andrey Elagin

We show that wavelength measurements of individual detected optical photons may provide additional information about gamma-ray energy deposited in a CeBr$_3$ crystal when the detected-photon-count distributions overlap for nearby gamma-ray energies. Monoenergetic 662 and 629 keV gammas are used in a Geant4 simulation of a $25\times25\times20~\mathrm{mm^3}$ CeBr$_3$ crystal. Assuming a light yield of $6.0\times10^4$ photons/MeV, a wavelength-independent photon-detection efficiency of 30%, and a wavelength resolution of $\sigma_{\lambda}=40$ nm, we find that the fraction of photons reconstructed above 385 nm gives an event-level separation of $\sim$ 2 standard deviations between the 662 and 629 keV event populations selected within the same $\sim$ 1%-wide detected-photon-count interval. No timing or reconstructed interaction-position information is used. The result demonstrates, within the present simulation model, that event-dependent optical spectra can retain energy information beyond an undifferentiated photon count.
Read the full abstract

Fluid Dynamics

Macroscale vortex impingement at a porous-fluid interface induces local heat-transfer enhancement

Thibaut K. Kemayo, Vishal Srikanth, Justin Courter et al. (+2 more)

Externally generated wakes can impinge on porous layers in several practical heat transfer applications. However, the transport of these macroscale vortices and their resulting influence on heat transfer in the porous layer remain unknown. In this paper, two-dimensional pore-resolved simulations are used to examine a square-bluff-body wake impinging on a porous layer composed of an in-line array of heated square obstacles at Re = 500-4000, Pr = 0.7 and 7.0, and porosities $\phi$ = 0.75, 0.85, and 0.95. The incident macroscale vortices break down starting immediately at the porous-fluid interface. Following macroscale turbulent thermal transport in this entrance region, fluctuations farther downstream are aligned with the pore geometry and are generated at the microscale level by pore-throat shear, separation, and repeated obstacle wakes. Direct impact locally improves heat transfer at the porous-fluid interface by increasing the local Nusselt number relative to a non-impingement region. The interfacial heat-transfer enhancement varies with porosity, Reynolds number, and Prandtl number, with a peak enhancement of 18.2% observed for $\phi$ = 0.85, Pr = 7.0, and Re = 1000. The wake-associated macroscale turbulent heat-flux contribution decays within a consistence entrance region extending approximately 3-4 unit cells into the porous layer across all investigated porosities, Reynolds numbers, and Prandtl numbers. For Re$\ge$1000, the persistent wake momentum deficit subsequently causes the heat-transfer contrast to become negative, resulting in lower heat transfer in the impingement region than in the non-impingement region.
Read the full abstract

All authors Thibaut K. Kemayo, Vishal Srikanth, Justin Courter, Rodrigo R. Caballero, Andrey V. Kuznetsov

Physics and Society

Energy pathway variety and the progress of the energy transition in European countries

Noam Abadi, Rossana Mastrandrea, Franco Ruzzenenti et al. (+1 more)

The integration of new energy forms into existing energy infrastructure has emerged as a critical challenge in the context of the pursuit of a sustainable energy transition. One of the main challenges is understanding how this integration takes place not only from the introduction, but also as energy follows existing paths or creates new ones through which it is transformed and used by different activities. Here we introduce techniques from network science to analyse this process for the case of 29 European countries between 1992 and 2021. We study how new energy forms increase or decrease the variety (heterogeneity) of paths through the system of each country by establishing new ones and replacing or phasing out existing ones. We find that the transition to systems based on renewable energy is characterised by an initial increase in the variety of paths while the heterogeneity of paths decreases at the end of the transition, when the proportion of non-renewables in the system tends to zero. We then demonstrate that greater heterogeneity (complexity) is associated with larger annual fluctuations in the proportion of non-renewable sources in the system, establishing a direct relationship between the progress of the transition and the complexity of the energy system in which it occurs. This contributes to the understanding of general properties of the dynamics of the energy transition and effects that accelerate or deter it.
Read the full abstract

All authors Noam Abadi, Rossana Mastrandrea, Franco Ruzzenenti, Andrea Diaz

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

Heteroepitaxial Growth of PbSe on InP Substrates via Lattice-Matched III-V Buffer Layers

Biridiana Rodriguez, Mark Martino, Brody Yeung et al. (+2 more)

Detector cost remains a barrier to the widespread adoption of mid-wave infrared (3-5 micron) technology. PbSe, an inexpensive narrow band gap IV-VI semiconductor that has been used since the early 1940s, delivers high performance for infrared detection despite the abundance of grain boundaries in polycrystalline films. Epitaxial growth, however, could provide superior crystalline quality and interfaces, but suitable substrates remain limited for PbSe. Recent PbSe heteroepitaxy has focused primarily on III-V, II-VI and group-IV substrates that each offer a comparatively narrow range of lattice-matched alloys for heterostructure engineering. Here we show that InP-based heteroepitaxy provides access to a broader materials platform while limiting the lattice mismatch with PbSe to approximately 4%. We grow 150-nm thick PbSe films by molecular beam epitaxy on 200-nm thick In0.53Ga0.47As and In0.52Al0.48As buffers on (001) InP substrates. Reflection high-energy electron diffraction and X-ray diffraction show (001)-oriented rock-salt PbSe with an out-of-plane lattice constant of 6.12 Angstrom on both buffers. Photoluminescence (PL) is observed from room-temperature down to 12 K and the peak wavelength red-shifts from 3.7 to 5.0 microns. Under identical measurement conditions, the room-temperature peak PL intensities from films on In0.53Ga0.47As and In0.52Al0.48As are approximately 1.9x and 1.3x that of a PbSe on GaAs substrate reference, respectively. These results establish an InP-compatible platform for integrating narrow band-gap PbSe with a broad range of ternary and quaternary III-V alloys, including, for example, structures in which In0.53Ga0.47As serves as both a short-wave infrared absorber and a template for PbSe growth.
Read the full abstract

All authors Biridiana Rodriguez, Mark Martino, Brody Yeung, Benjamin Sprenger, Leland Nordin

Physics Education

Mechanics Cognitive Diagnostic: Testing Fine-Grained Learning Objectives in Introductory Physics

Vy Le, Jayson M. Nissen, Jason W. Morphew et al. (+2 more)

Physics courses use research-based assessments (RBAs) such as the Force Concept Inventory (FCI), Force and Motion Conceptual Evaluation (FMCE), and Energy and Momentum Conceptual Survey (EMCS) to measure learning in introductory mechanics, but their fixed-length, pretest-posttest design makes them retrospective: posttest scores summarize completed instruction and arrive after a course ends. We are developing the Mechanics Cognitive Diagnostic (MCD), a cognitive diagnostic computerized adaptive test that reports students' mastery of fine-grained learning objectives (LOs) throughout instruction. Using evidence-centered design, we defined 14 LOs from introductory mechanics textbooks and AP Physics standards, mapped FCI, FMCE, and EMCS items onto them with a Q-matrix, and refined the mapping with the deterministic inputs, noisy "and" gate (DINA) model, using posttest responses from 24,394 students in 807 courses across 79 institutions through LASSO. The FCI and EMCS achieved good DINA model fit; the FMCE showed marginal fit. Classification accuracy for most LOs met or exceeded benchmarks for low-stakes formative assessment. RBA items, though not developed for LO-level diagnosis, support it reliably, giving the MCD a working 14-LO item bank built from RBAs that physics courses already use. As data accumulate, we can revise or retire weak LOs and items and add new items through online calibration without interrupting testing. We plan to expand the MCD to 35 LOs, two per week, to cover a typical introductory mechanics course.
Read the full abstract

All authors Vy Le, Jayson M. Nissen, Jason W. Morphew, Hua Hua Chang, Ben Van Dusen

Atomic Physics · Cross-listed from quant-ph

Thermal Quantum Sensing: Fisher Information and Work Beyond Gaussian Signals

Yash Chitgopekar, Nikolaos Koukoulekidis and Iman Marvian

Understanding how thermal fluctuations modify or suppress quantum-enhanced sensing is a central problem in quantum metrology. Closely related questions arise in quantum thermodynamics, particularly regarding the relation between the work induced by a signal and the information acquired by a sensor. Here, we establish general relations among the sensitivity of thermal quantum states, as quantified by different quantum Fisher information metrics, their temperature dependence, and the work induced by a unitary signal. We further show that, at high temperature, all monotone QFI metrics coincide to leading order with a universal quantity that can be expressed as the variance of a simple observable and itself defines a lesser-known QFI metric. This emergent uniqueness is reminiscent of the uniqueness of classical Fisher information in information geometry. In continuous-variable systems, the infinite-temperature limit is finite and generically non-zero for quadratic Gaussian signals, while it diverges for higher-degree signals. Remarkably, for any purely quadratic signal generator, the infinite-temperature QFI is at least twice the zero-temperature SLD QFI or, equivalently, at least eight times the ground-state variance of the generator. Consequently, the Cramér–Rao lower bound on the estimator variance is reduced by at least a factor of two. We illustrate these results using harmonic chains of bosonic modes relevant to trapped-ion platforms and quantum field-theoretic models.
Read the full abstract

Tuesday 8 September

Computational Physics

Representation-split Carleman lattice Boltzmann with near-unit step success probability on quantum computers

Hua-Dong Yao and Sauro Succi

The Carleman lattice Boltzmann method replaces the quadratic collision of the lattice Boltzmann equation by a linear map on a lifted state. Existing block encodings of this map succeed with probability $10^{-5}$ to $10^{-2}$ per step, so that the probability of a multi-step evolution decays exponentially with the number of steps. This study develops multi-relaxation-time Carleman lattice Boltzmann, a representation split in which the Carleman-lifted collision is performed in a moment basis on the amplitude-encoded state, while streaming remains a permutation in population space. The level-2 hierarchy closes under collision but not under streaming, which generates the work of pressure, advection and stress on the momentum flux. The state therefore remains the full pair array, and the moment representation is an orthogonal change of basis of the population one, with identical dynamics and truncation error. The operator to be block encoded changes with the basis, and with it the success probability of a quantum step. In the weighted Hermite basis with the amplitude encoding $f_i/\sqrt{w_i}$, the relaxation is a diagonal operator of norm one, and the level-2 collision stage becomes this diagonal plus a sparse coupling from products of conserved moments. A structured block encoding of this form raises the single-step success probability on the D2Q9 lattice from $10^{-2}$ for the best population encoding to 0.98. With the pair sector in relative coordinates and scaled, one step requires $O(\log^2 N)$ Toffoli gates and is verified by statevector simulation. The encoding and readout overhead of a $T$-step run is then polynomial in $T$ and $N$ rather than accumulating a factor $p^T$. For resolved flows, the remaining exponential loss in coherent multi-step Carleman lattice Boltzmann evolution is set by the non-equilibrium norm relaxed by dissipation rather than by the block encoding.
Read the full abstract

Data Analysis and Statistics

A State-Transition Information Space for Time-Series Dynamics: Theory and Application

Dragutin T Mihailović, Vijay P. Singh and Slavica Malinović-Milićević

Characterizing dynamical organization in time series requires distinguishing the diversity of accessible states from uncertainty in their temporal transitions. Here we introduce a state-transition information space based on two normalized entropy measures derived from ordinal patterns: K_q, quantifying ordinal-state diversity, and K_t, quantifying transition uncertainty. Their joint K_t-K_q representation provides a two-dimensional framework in which dynamical regimes and their temporal evolution can be examined. Theoretical properties establish the bounded relation 0 <= K_t <= K_q <= 1, while canonical time series identify distinct empirical domains ranging from ordered dynamics to near-maximal randomness. Sliding-window analysis further shows that systems can exhibit temporal trajectories through the K_t-K_q plane rather than remaining at a fixed dynamical state. Application to 1,879 monthly naturalized streamflow records from the U.S. rivers shows that river dynamics occupy a distinct intermediate region between ordered and highly disordered regimes. Moreover, river positions shift systematically toward higher K_t and K_q with increasing drainage area, revealing scale-dependent organization of streamflow dynamics. The framework therefore provides a compact means of comparing state diversity, transition uncertainty, and their temporal and spatial organization across time-series systems.
Read the full abstract

Atmospheric and Oceanic Physics

Scale analysis for the Madden$-$Julian oscillation

Hing Ong

This study performs a scale analysis for the dynamics of equatorial flow systems like the Madden$-$Julian oscillation (MJO). This analysis makes three assumptions about the geometry of the flow and focuses on the leading order terms of the mass continuity and momentum equation system. First, the flow is meridionally narrow. Second, the zonal structure is planetary wavenumber 1. Last, the flow is vertically shallow. When constrained by these geometric assumptions, the system shows a time scale much longer than a day depending on the meridional narrowness. Specifically, for equatorial Kelvin waves, the oscillation period ranges from 36 to 64 days given a ratio of the planetary radius to the meridional width scale from 6 to 8 (i.e., an e-folding latitude from 9.59$^\circ$ to 7.18$^\circ$ either side of the equator). Given the long, narrow, and shallow geometry, the dynamics can sustain Kelvin waves only at low frequencies. This result suggests that the intraseasonal time scale of the MJO arises from the Kelvin wave frequency limit due to the planetary wave geometry. This planetary intraseasonal scale relation is independent from thermodynamics, and an open question remains on what physical processes coordinate the thermodynamics in the same length or time scale.
Read the full abstract

Geophysics

Large-scale bioacoustic detection using semantic segmentation: a deep learning framework applied to fin whale calls in ocean-bottom seismometer recordings

Jocelyn Japnanto, Alex A. Saoulis, Miriam Romagosa et al. (+5 more)

Ocean-bottom seismometers (OBS), originally deployed for geophysical research, continuously record low-frequency sound for months to years across broad areas of ocean, offering a largely untapped resource for passive acoustic monitoring (PAM) of baleen whales. Realising this potential requires automated detection methods that operate reliably across the varied conditions in large sensor networks. We present a deep learning semantic segmentation framework that detects the 20-Hz notes of fin whales (Balaenoptera physalus) in OBS spectrograms, assigning each pixel a probability of belonging to a call and converting the resulting probability maps into time-frequency bounding boxes describing individual detections. We trained the model on hydrophone data from one OBS deployment in the Azores-Madeira-Canaries region and applied it without retraining to vertical-component seismometer data from a second, geographically distinct deployment, showing that a single trained model generalises across sensor types and recording environments. Applied to 378,912 h of recordings from 46 OBS sites, the detector identified 6.3 million calls, forming the largest fin whale call catalogue assembled to date, with high precision (~97%) across both deployments. The resulting catalogue resolves call timing and spectral structure accurately enough to support ecological analyses, revealing coherent seasonal shifts in three persistent inter-note interval (INI) groups across the singing season and basin-scale patterns in calling activity. By transforming existing geophysical infrastructure into a scalable sensing network, our approach substantially expands the spatial and temporal reach of PAM without new hardware investment, offering a transferable framework for tracking other low-frequency vocalising species and informing conservation planning, marine spatial management, and abundance estimation across large scales.
Read the full abstract

All authors Jocelyn Japnanto, Alex A. Saoulis, Miriam Romagosa, Rita Leitão, Gabrielle Arrieta, Mónica A. Silva, Matthew Graham, Ana M. G. Ferreira

Physics and Society

Assessment of Non-Institutional AI Tool Usage Among Clinicians

Sarah Pungitore and Jarrod Mosier

Generative artificial intelligence (AI) tools are increasingly accessible and have the potential to improve efficiency across clinical workflows. However, clinicians may also use non-institutional AI tools that are not provided, managed, or governed by their healthcare institutions, creating potential concerns related to privacy, security, accuracy, and clinician-AI interaction. Little is known about how clinicians currently use these tools for work-related tasks. We conducted a descriptive survey of clinicians recruited from the University of Arizona College of Medicine-Tucson and Banner University Medical Center-Tucson between May 20 and June 26, 2026. Participants reported their use of AI tool categories and the frequency with which they used AI for specific tasks across five workload categories: administrative work, clinical work, research, studying/continued education, and teaching. Forty-four respondents completed the survey. Forty-three respondents reported using AI for at least one work-related task during the preceding 6 months. Conversational AI and clinical decision support/diagnostic AI were the most used tool categories, each reported by 28 respondents. Administrative and clinical tasks demonstrated the most frequent use. AI was also used for higher-risk activities, including diagnostic assistance and clinical decision support. Non-institutional AI use was common among surveyed clinicians and extended across a broad range of work-related activities, including tasks with potential implications for clinical reasoning and patient care. Further research is needed to characterize how clinicians use these tools, how they evaluate AI-generated outputs, and how AI can be safely and effectively integrated into clinical workflows.
Read the full abstract

Space Physics · Cross-listed from astro-ph.SR

On modelling the 2017 galactic cosmic ray depression

O.P.M. Aslam, D. MacTaggart, M.S. Potgieter et al. (+2 more)

In the second half of 2017, as Solar Cycle 24 approached its minimum, a pronounced and rigidity-dependent depression in the galactic cosmic ray (GCR) proton flux was observed using AMS-02. This event was driven by a sequence of strong coronal mass ejections (CMEs). In this work, we model the modulation of GCR protons during this period using a steady-state Parker transport framework with parameters constrained by AMS-02 observations. Treating the event as a purely long-term modulation interval yields excellent agreement with the observed proton intensities, but implies an inferred rigidity dependence of particle mean free paths that is inconsistent with basic turbulence theory, corresponding to an effective inversion of the scattering regime. We argue that this behaviour arises from the ability of highly flexible transport parameterizations to reproduce integrated modulation signatures through correlated adjustments of diffusion coefficients during transient events. To address this inconsistency, we relax the commonly adopted assumption of a time-independent ratio of perpendicular to parallel diffusion coefficients and introduce a physically motivated reduction of this ratio during the CME-dominated interval. This modification preserves the quality of the spectral fits whilst restoring the expected rigidity ordering of mean free paths. Our results indicate that allowing the perpendicular-to-parallel diffusion ratio to vary in time provides an effective means of constraining transport solutions during the 2017 depression and may help to resolve similar inconsistencies reported in other GCR modulation studies.
Read the full abstract

All authors O.P.M. Aslam, D. MacTaggart, M.S. Potgieter, M.D. Ngobeni, I.I. Ramokgaba

General Physics

Bound states in the continuum of gravitational waves

Rodrigo Berté

Bound states in the continuum (BICs) are ubiquitous wave phenomena, but have not yet been demonstrated for gravitational waves (GWs). Here, in-plane periodic perturbations, exponentially localized at the plane $z = 0$, are shown to lead to distributional surface energy tensors at this plane and to be regular vacuum solutions ($T_{\mu \nu} = 0$) of the linearized Einstein field equations outside of it. These are achieved by explicitly calculating the Ricci tensor components and the Ricci scalar from the metric perturbation tensor. To fulfill each vacuum solution ($R_{{\sigma \nu}_{(+, \times)}} = 0$ and $R_{{}_{(+, \times)}} = 0$), different surface polariton-like dispersions are required. These bound perturbations decay exponentially to a flat metric ($h_{{BIC}_{(+,\times)}} \propto e^{- k_z |z|}$), and each localized metric has a correspondence to a different planar GW polarization ($+,\times$). The Lorenz gauge-fulfilling solutions exist at the $\Gamma$ point in momentum space, dwelling within the continuum of wavevectors of propagating GWs. The strains in the unit cell of the periodic perturbations have opposite parities relative to the corresponding planar GWs under a $C_2$ in-plane rotation, making them incompatible by symmetry with their propagating counterpart, indicating localization via symmetry protection.
Read the full abstract

Popular Physics

The Epistemic Risk of the 31st Spore: If Planets Aren't Fine Tuned, We're Doing Life Detection Wrong

Harrison B. Smith and Cole Mathis

Exploration of planetary bodies within our solar system will be essential for understanding the origin of life on Earth and the distribution of life in the universe. Planetary protection policy is concerned with balancing this desire for exploration against the risks of contaminating alien planets with Earth life, and contaminating Earth with alien life. However, at present, we have no fundamental scientific understanding of life's emergence or its nature beyond Earth. Given this nearly complete ignorance about the possibility of alien life, or Earth life's capacity to expand beyond our planet, it is difficult to reason about the real risks of space exploration. Here we contend that contemporary understandings of the risks of forward contamination are based on arguments which inconsistently apply our incomplete knowledge to the problem. We reason that a more assertive posture towards space exploration, focused on determining whether other planets in the solar system are inhabited, is warranted and explain why such a posture may not increase the epistemic risks of planetary contamination. Finally, we explore the consequences of our arguments for planetary protection protocols, and life detection efforts.
Read the full abstract

Atomic Physics

A metastable state in $\mathrm{Yb}^+$ with lifetime greater than 10 minutes

Hassan Farhat, William Liu and Wesley C. Campbell

We find through direct, time-domain measurement of trapped $\mathrm{Yb}^+$ ions that the excited ${}^3[11/2]_{9/2}^o$ state has a collision-free lifetime of 17.8(6) min, long enough for use in atomic clockwork or quantum information processing. We locate and benchmark a broad “repump” transition at $701\, \mathrm{nm}$ that readily transfers population back into the Doppler cooling cycle with the ground state, which may allow for quantum nondemolition measurement of sub-structure in the metastable manifold. Using a bi-stable Coulomb-crystal manometer, we find that the collisional quenching of this metastable ${}^3[11/2]_{9/2}^o$ manifold by background gas is more efficient than for ${}^2\mathrm{F}_{7/2}^o$, but nonetheless we observe an average lifetime exceeding 10 minutes at the base pressure of our apparatus.
Read the full abstract

Instrumentation and Detectors

Development and demonstration of the Korea ALICE Telescope using electron beams at KEK PF-AR

Jiyoung Kim, Meike Danisch, Sungwoon Choi et al. (+26 more)

The development of ultra-low-mass, high-precision vertex detectors is a key requirement for future collider experiments and motivates extensive research and development of novel silicon tracking technologies. In this work, we present the development and beam-test demonstration of the Korea ALICE Telescope (KATS), a silicon-tracking telescope designed to support R&D on next-generation cylindrical vertex detectors, such as the proposed ALICE ITS3 upgrade. The telescope consists of six ALPIDE Monolithic Active Pixel Sensors (MAPS) used as reference tracking planes, a bent ALPIDE sensor serving as the device under test, and a scintillating-fiber-based trigger system, all housed in a light-tight modular enclosure. This setup enables precise track reconstruction and detailed performance studies of both planar and curved silicon sensors. Beam tests were carried out using high-energy electron beams at the KEK Photon Factory Advanced Ring (PF-AR). The telescope system operated stably under realistic beam conditions, and its tracking performance was successfully validated. The bent ALPIDE sensor was operated at a bending radius of approximately 18 mm, consistent with ITS3's design goals, without any observable degradation in detection performance. The measured results confirm that the KATS provides a versatile and reliable platform for studies of curved MAPS technologies, alignment precision, and tracking performance. These results provide important experimental validation of key technologies for future low-mass cylindrical silicon vertex detectors and establish KATS as a valuable facility for ongoing and future detector R&D.
Read the full abstract

All authors Jiyoung Kim, Meike Danisch, Sungwoon Choi, Tatsuya Chujo, Taku Gunji, Yoonha Hong, Hangil Jang, Towa Katsuno, Ryotaro Kohara, MinJung Kweon, Sanghoon Lim, Inaba Motoi, Hikari Murakami, Hanseo Park, Jonghan Park, Shingo Sakai, Daito Shibata, Reita Wada, Kyungrim Woo, Yorito Yamaguchi, Seunghwan Yang, In-Kwon Yoo, Miljenko Suljic, Serhiy Senyukov, Giacomo Contin, Domenico Colella, Bong-Hwi Lim, Mihail-Bogdan Blidaru, Berkin Ulukutlu

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

The Role of Concentration in Determining NaCl Nucleation Mechanism: A Story of Pathways Coexistence

Porhouy Minh and Sapna Sarupria

Deciphering the microscopic details of crystal nucleation remains a key open problem in chemical physics. For aqueous sodium chloride (NaCl), the extent to which nucleation involves amorphous ion aggregation, and the supersaturation regime in which two-step-like behavior emerges, remains actively debated. In this work, we examine NaCl nucleation at 12, 13, and 14 mol/kg ($S = 3.2, 3.5, 3.8$) using unbiased path sampling with $\infty$RETIS. Through a combination of reaction coordinate analysis, joint and conditional probability distributions, diffusion tensor analysis, and conditional free energy landscapes, we identify nucleation pathways without a priori mechanistic assumptions. While all concentrations are governed by the same reaction coordinate, indicating that nucleus growth and structural ordering are central to crossing the barrier, the nature of reactive trajectories changes with supersaturation. At lower concentrations, nucleation mainly occurs via tightly coupled increases in cluster size and ordering, compatible with a one-step-like mechanism. As concentration increases, amorphous aggregation becomes increasingly decoupled from crystallization, and pathways involving substantial amorphous growth prior to crystallization become progressively more probable. Importantly, these pathways coexist within a single broad reaction channel rather than proceeding through distinct metastable intermediate states. Together, these results reconcile earlier, contradictory reports on NaCl nucleation mechanisms and support a view of nucleation as an ensemble of competing reactive pathways whose relative probabilities vary continuously with supersaturation. More broadly, our findings illustrate that substantial mechanistic diversity can emerge within a classical nucleation framework, without requiring distinct non-classical descriptions.
Read the full abstract

Plasma Physics

All field strengths are possible locally in Boozer coordinates

Taylor J. Klotz, Nathan Duignan, Joshua W. Burby et al. (+1 more)

The magnetic field strength is a central design object in the theory of magnetic confinement of plasma. Desirable confinement properties such as quasi-symmetry and omnigenity are characterized by special forms of the field strength when it is given in the particular coordinate system called “Boozer coordinates." We ask a basic realizability question: which functions of Boozer coordinates can arise as the magnitude of a magnetic field that is written in Boozer coordinates? Using exterior differential systems and the Cartan-Kähler theorem, we show that every positive analytic function is locally realizable. Thus there is no local analytic obstruction to prescribing the field strength in Boozer coordinates; though further restrictions might arise from global geometric or additional physical constraints.
Read the full abstract

All authors Taylor J. Klotz, Nathan Duignan, Joshua W. Burby, James D. Meiss