Optics
3D trapping of a meta-atom in an intensity minimum
Bin Lu, Adeel Afridi, Nadine Meyer et al. (+1 more)
High-refractive-index particles have recently attracted a growing interest in optical levitation experiments, offering the ability to further engineer optical forces through electromagnetic Mie resonances. Unlike standard silica particles, which are predominantly trapped in the dipole regime and exhibit trap frequencies mainly determined by material density, resonant meta-atoms formed by high-index particles enable qualitatively new trapping behaviors. In this work, we experimentally investigate the trapping of resonant silicon particles in an optical standing wave. A direct comparison of silicon and silica highlights the fundamental differences in their optical force scaling and trapping dynamics. Beyond conventional trapping at intensity-maxima, we demonstrate deterministic and stable three-dimensional trapping of silicon nanoparticles in optical intensity minima, a regime that remains inaccessible for silica particles. Drawing a mesoscopic analogy with blue-detuned atom trapping, our results establish meta-atoms as a versatile approach to further extend the optical manipulation tool box towards accessing novel trapping regimes e.g. in close proximity to a surface.
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All authors Bin Lu, Adeel Afridi, Nadine Meyer, Romain Quidant
Atmospheric and Oceanic Physics
Extremes on Rewind: Generating 1,000-Member Ensembles Initialized at a Final Condition
Jerry Lin, Mu-Ting Chien, Mansi Sakarvadia et al. (+1 more)
Scenario planning for rare, high-impact events often requires massive ensembles to stochastically sample relevant trajectories. Although autoregressive weather emulators can efficiently generate such ensembles, isolating trajectories of interest requires sifting through petabytes of data, a challenge that grows exponentially with lead time and rarity. In contrast, a non-autoregressive foundation model like
Climate in a Bottle
video (cBottle-
video) can directly sample trajectories terminating in extremes, avoiding large-ensemble search. We use cBottle-
video to generate 1000-member ensembles with start- and/or end-conditioning across three extreme events—the 2021 Pacific Northwest (PNW) heatwave, Superstorm Sandy, and Hurricane Ian. Antecedent 500 hPa geopotential height ($z_{500}$) spread at the free end of end-conditioned ensembles reaches 84–89% of the final-state spread of start-conditioned ensembles, revealing substantial diversity consistent with each extreme event. For the 2021 PNW heatwave, end-conditioned ensemble members begin uniformly warmer than reanalysis and stay warm, replacing the observed rapid intensification with persistent antecedent heat. For Superstorm Sandy, the leading modes of $z_{500}$ at the antecedent end of the end-conditioned ensemble explain 44% of the variance in track latitude, and roughly 10% of ensemble members begin as stronger hurricanes than Sandy. For Hurricane Ian, variation in the first landfall location among end-conditioned trajectories underscores the importance of accounting for intermediate hazard exposure in risk planning.
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All authors Jerry Lin, Mu-Ting Chien, Mansi Sakarvadia, Elizabeth A. Barnes
Instrumentation and Detectors
On-chip Bragg peak extraction from MHz frame rate X-ray detectors using a cellular automaton architecture
S. Fowler, S. Strempfer, D. Beniwal et al. (+13 more)
High-frame rate pixel detectors can produce data volumes that exceed available off-chip bandwidth, yet in many applications only a sparse subset of each frame carries relevant information. Spatially localized events, including diffraction peaks in crystallography, particle hits in tracking detectors, fluorescence spots in biological imaging, and other applications, all require that clusters of above-threshold pixels be identified and extracted from an otherwise featureless background. Conventionally this is performed in software
algorithms such as connected-component labeling on full frames, but at MHz frame rates the resulting throughput becomes prohibitive. We present a lightweight hardware architecture that performs peak localization and patch extraction directly in the sensor silicon, transmitting only small pixel patches rather than complete frames. FPGA-based testing on an AMD Alveo V80 validated the synthesizability and timing closure of the peak-finding module in real hardware. The design replaces global connected-component labeling with a cellular automaton that uses purely local, fixed-iteration neighborhood operations, eliminating the label storage and equivalence-resolution logic that make conventional approaches impractical on-chip. We validate the architecture on X-ray Bragg peak detection for far-field high-energy diffraction microscopy and show that every peak found by a software reference is recovered, with equivalent downstream reconstructions. The architecture sustains several-hundred-kHz frame rates in 130nm CMOS and exceeds 1MHz in 28nm.
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All authors S. Fowler, S. Strempfer, D. Beniwal, M. Hammer, H. Shi, S. Gnanasekaran, N. Contini, T. Guruswamy, Y. Chen, L. Rota, D. Doering, A. Dragone, T. Zhou, M. Cherukara, K. Yoshii, A. Miceli
Physics and Society
A Structured Framework for Calibrating Stochastic Car-Following Models: Data Adequacy, Parameter Sensitivity, and Objective Selection
Shirui Zhou, Junzhe Ding, Junfang Tian et al. (+3 more)
Calibrating a
stochastic car-following model is harder than its deterministic counterpart: the loss itself becomes a random variable, so a favorable random realization can be mistaken for a good parameter vector. This paper develops a structured framework for calibrating
stochastic car-following models – a completeness-controlled synthetic design, a corrected variance-based sensitivity analysis (VBSA), and the minimum-realization (MRMIN) calibration protocol – across two structurally different
stochastic mechanisms, QIDM and IDM2D. We test two claims from deterministic calibration – that a small number of parameters, and the trajectory itself above all, dominates the sensitivity ranking, and that spacing calibration keeps dominating speed calibration once dynamics are
stochastic – and ask whether a model's noise term can be calibrated on its own. In a balanced synthetic experiment, driving-regime completeness has a mean total-effect index on par with the model's most influential parameter and roughly two orders of magnitude above pair identity, extending rather than reversing the deterministic finding on trajectory-identity dominance. Under MRMIN, calibrating only the noise parameter against a population-wide deterministic fit more than doubles median spacing error across 1644 NGSIM trajectories, but fitting the deterministic parameters per trajectory first and calibrating noise on top recovers it. Spacing calibration remains more cross-dimensionally robust than speed calibration on average, but the deterministic guarantee that this dominance can never reverse is violated in 19-26% of trajectories for both mechanisms. A multi-objective screen in relative-error space then favors joint spacing-speed goodness-of-fit functions over single-dimension spacing calibration. Deterministic calibration guarantees should therefore be re-tested, not assumed, once a model is
stochastic.
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All authors Shirui Zhou, Junzhe Ding, Junfang Tian, Shiteng Zheng, Rui Jiang, Anci Shi
Atomic Physics · Cross-listed from quant-ph
Quantum-Enhanced Atomic Sensor via Spin Nonequilibrium Criticality
Ding Huang, Minwei Shi, Guzhi Bao et al. (+2 more)
The sensitivity of
quantum sensors is fundamentally constrained by the standard
quantum limit (SQL) arising from intrinsic
quantum fluctuations. While non-classical resources like squeezing or
entanglement can surpass this limit, their utility is often restricted by the extreme fragility of entangled states and the complexity of their preparation.
Quantum criticality offers a compelling alternative by harnessing divergent susceptibility to amplify signals without requiring fragile non-classical resources. However, the practical benefit of this approach has remained controversial due to the potential for the simultaneous amplification of
quantum noise. Here, we demonstrate a universal protocol for noiseless critical sensing by engineering a light-driven atomic ensemble near a dynamical critical point. Analogous to a Kapitza pendulum near its inverted orientation, the
spin system enters a non-
equilibrium regime where the signal susceptibility diverges while the
quantum noise periodically recedes to its coherent baseline. We exploit this “noise ebbing” to create a built-in noiseless amplifier, demonstrating a 3.3 dB metrological gain over the SQL in an atomic magnetometer. Our implementation exhibits intrinsic robustness against common experimental imperfections such as detection losses, establishing non-
equilibrium critical dynamics as a practical and versatile paradigm for surpassing the fundamental limits of
quantum sensing.
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All authors Ding Huang, Minwei Shi, Guzhi Bao, Keye Zhang, Weiping Zhang
Plasma Physics
High-power TCV scenario for conventional and alternative divertor studies
K. Lee, C. Theiler, M. Carpita et al. (+20 more)
Alternative divertor configurations (ADCs) must be evaluated under boundary
plasma conditions approaching reactor-level values to be considered a reliable, physics-based solution for tokamak power exhaust. Most ADC experiments performed to date were at relatively low exhaust power. This work presents a high-power scenario on the TCV tokamak enabling the study of a wide variety of divertor
magnetic shapes under an expanded SOL and power exhaust parameter space. The scenario is characterized by high power levels of electron cyclotron resonance heating ($2.5\,\text{MW}$ fully absorbed in a $\sim1\,\text{m}^{3}$
plasma) at high
plasma current (edge safety factor $q_{95}\approx 2.5$), and low upstream separatrix densities ($n_{e,\text{u}}\approx1\times10^{19}\,\text{m}^{-3}$, Greenwald fraction $f_{\text{G}}\approx 0.1$). Stationary parallel heat fluxes up to $100\,\text{MW m}^{-2}$ are measured at the divertor target, an order of magnitude above previous TCV power exhaust studies. The obtained SOL collisionality and Lengyel detachment scaling metric lie within range of values expected in future reactors (SPARC, ITER, ARC).
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All authors K. Lee, C. Theiler, M. Carpita, M. Zurita, P. Sintre, O. Février, F. Pastore, H. Reimerdes, K. Verhaegh, M. Winkel, D. Brida, B.Y.K. Brown, M.J.H. Cornelissen, R. Ducker, G. Durr-Legoupil-Nicoud, D. Hamm, R.I. Morgan, A. Perek, O. Sauter, E. Tonello, Y. Wang, the TCV Team, the EUROfusion Tokamak Exploitation Team
History and Philosophy of Physics
Stefan Bergman (1895-1977). Notes on His Bio- and Bibliography
Tilman Sauer
Stefan Bergman worked in the field of pure and applied mathematics and became known primarily for his work on complex analysis of several variables. He studied the theory of solutions to linear partial differential equations via integral operators and introduced the concept of the Bergmann kernel function. He also worked on problems in electrical engineering, the theory of elasticity, potential theory, and hydrodynamics, particularly supersonic flows. His academic career in Germany was cut short by the Nazi purge, leading to a peripatetic exile through the USSR and France before finally establishing a distinguished career in the United States, notably at Harvard and Stanford. The paper sketches his biography based on archival sources and complements a bibliography of his writings compiled by M.Skwarczy'nski in 1981 with a number of references primarily from his early career.
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Fluid Dynamics
Mach-disk formation and shock-structure transitions in underexpanded coflowing jets
Ganesh Dhungana, Srijan Satyal and Nek Sharan
The near-field shock structures of underexpanded sonic jets exiting into a subsonic coflow are investigated over a range of nozzle pressure ratio (NPR) and coflow-to-nozzle-exit velocity ratio ($U_c$), representative of a propulsive nozzle in subsonic flight. Time-averaged statistics from fully-resolved axisymmetric simulations and inviscid method-of-characteristics (MOC) analysis are used to understand how coflow alters the shock-
cell structures, in particular the Mach-disk formation. It is well established that increasing NPR transitions the centerline reflection from regular (characterized by oblique shocks) to Mach reflection (characterized by a near-normal Mach disk). We find that coflow has the opposite influence: a strong coflow shrinks the Mach disk until it vanishes, reverting Mach reflection to regular reflection, so the NPR for this transition increases with $U_c$. This effect has previously been attributed to a reduction in the jet-boundary inclination at the nozzle lip, which confines the lip Prandtl-Meyer fan to a smaller angle and weakens the embedded shock. We show instead that this inclination is determined by the non-uniform pressure the coflow imposes along the jet boundary, which is the primary driver of the shock-structure transitions in coflowing jets. The non-uniform pressure weakens the boundary-reflected compression waves and orients them at shallower angles, so the embedded shock reflects regularly or fails to form. A simulation-informed MOC analysis with this non-uniform pressure boundary condition reproduces the transition behavior with increasing coflow. Coflow also lengthens the first shock
cell linearly, which is accurately estimated by a simple correction to Prandtl classical shock-
cell length scaling.
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Optics
Remarkable Enhancement of High Harmonic Generation from Superhard Material under High Pressure
Zishao Wang, Tong Wu, Ziwen Wang et al. (+6 more)
High harmonic generation (HHG) in solids offers a pathway to develop compact extreme ultraviolet (EUV) sources crucial for attosecond science and advanced spectroscopy. Here, we demonstrate theoretically that high pressure dramatically enhances HHG in superhard hexagonal tungsten nitride (h-WN6). Compared with solid-state systems at ambient pressure, the reshaped electronic environment under high pressure leads to a unique band-gap widening in h-WN6, which raises the material's damage threshold, allowing the use of stronger
laser fields and enabling access to higher-energy bands. This pressure-induced band-gap widening offers a promising strategy to overcome the cutoff limitation of solid-state EUV light sources.
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All authors Zishao Wang, Tong Wu, Ziwen Wang, Shicheng Liu, Hui Li, Kun Zhao, Jian Sun, Chao Yu, Ruifeng Lu
Chemical Physics
Molecular Insights into Gas Nanofilms Confined Between Bulk Liquid Phases
Yafan Yang, Zufeng Zuo, Xingyu Zhao et al. (+2 more)
Nanometer-thick fluid films play a critical role in confined multiphase processes, yet the thermodynamics and stability of free gas nanofilms remain poorly understood compared with their
liquid counterparts. Here, molecular dynamics (MD) simulations are employed to systematically investigate gas nanofilms confined between bulk
liquid phases using Lennard-Jones argon as a model system. The results show that the surface tension decreases exponentially with decreasing film thickness, accompanied by an increasing magnitude of the negative disjoining pressure. Upon thinning, the planar gas film undergoes a distinct morphological transition from a stable planar state to a transient or persistent spherical bubble through the formation and growth of a
liquid bridge. The film surface area strongly affects its thermodynamic properties, with larger areas producing stronger thickness dependence and larger deviations from classical density functional theory (cDFT) predictions. The closer agreement between MD and cDFT at smaller surface areas suggests that the discrepancy primarily arises from thermal capillary-wave fluctuations, which are included in MD but omitted in mean-field cDFT. Moreover, at small film thicknesses, the magnitude of the disjoining pressure increases with decreasing temperature, consistent with the enhanced sensitivity of the confined gas phase to thickness variations and contrasting with the trend generally reported for
liquid nanofilms. These findings provide molecular insights into the thermodynamics and stability of gas nanofilms, with implications for confined multiphase transport and droplet coalescence.
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All authors Yafan Yang, Zufeng Zuo, Xingyu Zhao, Shuyu Sun, Denvid Lau
Fluid Dynamics
Orientation-dependent drag, lift, and torque correlations for regular Platonic polyhedral particles
Manuel A. Taborda and Berend van Wachem
In this work, particle-resolved direct numerical simulations are performed to investigate flow past the five Platonic solids, which represent a progression in particle sphericity with an increasing number of faces. The simulations cover particle Reynolds numbers in the range 0.1 <= Re_p <= 300 and multiple particle orientations relative to the incoming flow. Based on the numerical data, new correlations are developed for the drag, lift, and torque coefficients. The proposed drag correlation explicitly accounts for both Reynolds number and particle orientation, whereas the lift and torque coefficients are represented by orientation-dependent trigonometric and exponential basis functions whose coefficients vary with Reynolds number. The simulations are conducted using the immersed boundary method, and the resulting drag correlation accurately reproduces the numerical data. The lift and torque correlations capture the principal trends observed in the numerical simulations, including the strong dependence on particle orientation. The proposed correlations provide a computationally efficient framework for incorporating orientation-dependent hydrodynamic forces and torques into Euler–Lagrange and point-particle simulations, enabling a more realistic representation and predictions of non-spherical particle transport in multiphase flows.
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Fluid Dynamics
Hydrodynamic Brachistochrone: Conflicting Paths of Time and Energy Minima within Viscous Media
Ramin Gasimli, Lei Yi, Shrabin Bajracharya et al. (+2 more)
We experimentally and theoretically study the hydrodynamic analog of the classical brachistochrone problem: the time- and energy-minimizing paths for a spherical particle rolling down an incline within a viscous fluid. We show that in the presence of viscous dissipation, the paths of minima diverge from the classical cycloid, into curves of opposing
curvature for time and energy, and are characterized by an effective dimensionless parameter, $St_p$, representing the ratio of the particle's viscous response time scale to its gravitational time scale. Using a generalized variational framework, we show that the fastest path reduces to {nearly straight ramps}, however, beginning and terminating in localized cycloids of
curvature, $\kappa_c \sim St_p^{-2}$. Remarkably, the path of fastest descent on a given energy budget requires navigating a non-monotonic path ({\it“S-shaped”}) with an interior point of inflection. Our findings reveal a unification of temporal and energetic optimality for transport through dissipative media, and expand the celebrated brachistochrone solutions to the hydrodynamic regime.
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All authors Ramin Gasimli, Lei Yi, Shrabin Bajracharya, Anupam Pandey, Varghese Mathai
Medical Physics
Ultra-wideband MRE of the human liver and spleen for viscoelastic model identification in hepatic inflammation
Jakob Schattenfroh, Michael Fedders, Steffen P. Häseli et al. (+10 more)
Magnetic resonance elastography (MRE) is established for noninvasive assessment of liver fibrosis. Conventional abdominal MRE is typically limited to 40-60 Hz. Lower frequencies remain largely unexplored, particularly with regard to hepatic inflammation. We developed ultra-wideband MRE covering 5-80 Hz to investigate frequency-resolved viscoelastic dispersion of the liver and spleen and to identify biomechanical markers of hepatic inflammation. Following phantom validation, nine healthy volunteers and nine patients with inflammatory liver disease were examined at 12 frequencies. Spatiotemporal phase unwrapping and frequency-adaptive wavefield preprocessing enabled reconstruction of shear wave speed (SWS), penetration rate (PR), and loss angle ($\phi$). Six rheological models were evaluated. The largest inflammation-associated changes were observed at frequencies below 20 Hz: $\phi$ increased by 63% (p<0.001), PR decreased by 37% (p=0.003), and SWS increased by 8% (p=0.008), indicating predominantly dissipative, rather than stiffness-related, changes and a shift toward fluid-like behavior with minor stiffness changes in the lower frequency regime. The rheological springpot model with serial dashpot provided the best fit and revealed distinct dispersion functions for liver and spleen. In patients, springpot elastic modulus increased (101%, p=0.001), while viscosity and springpot power-law exponent decreased (52%, p=0.002 and 58%, p<0.001) suggesting a shift from soft-fluid to stiff-solid liver properties. Ultra-wideband MRE revealed that inflammatory liver disease is associated with property shifts toward stronger dissipation and fluid-like behavior at low frequencies while displaying solid-like behavior at higher frequencies. Ultra-low frequency MRE may provide a diagnostic window into inflammation-associated liver viscoelasticity without full rheological modeling.
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All authors Jakob Schattenfroh, Michael Fedders, Steffen P. Häseli, Tobias Puengel, Yanglei Wu, Tom Meyer, Hossein S. Aghamiry, Tim Ricken, Münevver Demir, Frank Tacke, Jing Guo, Rolf Reiter, Ingolf Sack
Optics
Invertible mapping between structured light and vector terahertz emission
Amirreza Sadeghpour and Daryoush Abdollahpour
Terahertz (THz) radiation provides a powerful platform for ultrafast spectroscopy, imaging, and communication, yet deterministic control over its spatial and polarization structure remains challenging. Here we establish a unified framework for generating and synthesizing vectorial THz beams through coherent control of ultrafast photocurrents in
semiconductors. By exploiting
quantum interference between one- and two-
photon excitation pathways driven by femtosecond vector beams, we demonstrate that the spatial phase and polarization structure of the optical fields can be directly mapped onto the magnitude and orientation of injected currents. This structured charge motion acts as a programmable THz
antenna, enabling tailored far-field emission. Beyond forward modeling of THz generation from cylindrical vector beams and full Poincaré beams, we introduce an inverse-design methodology that reconstructs the required current distribution–and corresponding excitation beam profiles–from a desired THz field pattern. This invertible mapping transforms coherent photocurrent control into a systematic design strategy for THz beam shaping. Our results bridge structured light and THz photonics, providing a route toward compact, all-optical, and reconfigurable THz sources with engineered amplitude, phase, and polarization profiles.
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Optics
Perturbation theory of mesoscale plasmonic waveguide with an analytical treatment of nonclassical electromagnetic boundary condition
Jiling Xue and Haitao Liu
The optical modes of mesoscale plasmonic waveguides (MPWs) are significantly affected by nonclassical
quantum effects, which can be comprehensively described by the nonclassical electromagnetic boundary condition (NEBC) formulated with the surface-response Feibelman d-parameters. In this paper, a perturbation theory for the nonclassical waveguide modes (NWMs) supported by MPWs under the NEBC is proposed. In this theory, by adopting the classical waveguide modes (CWMs) under the classical electromagnetic boundary condition (CEBC) as the basis functions and treating the NEBC as a first-order perturbation, a general expression of the propagation constant of the NWM with an analytical dependence on the NEBC is derived. This theory transparently reveals the underlying general relation between the nonclassical effects and the propagation properties of the NWMs, thereby providing an effective tool for the understanding and design of MPW devices, as well as for the experimental measurement of the d-parameters.
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Fluid Dynamics
Inter-turbine spacing and flow unsteadiness effects on wake-induced blade dynamics
Francisco J. G. de Oliveira, Adrian T. McGlade, Zahra Sharif Khodaei et al. (+1 more)
Wind turbines operating downstream of others in a farm are routinely exposed to waked inflow, with reduced mean velocity and elevated
turbulence driving power deficits and additional structural fatigue. The direct effect of wakes on blade-level structural loading remains under-explored experimentally, owing partly to the sparse spatial coverage of conventional point-based strain sensors. Here, we present a wind-tunnel study of wake-induced blade dynamics using two $1\,\mathrm{m}$-diameter turbine models, in which one blade of a downstream turbine ($WT_2$) is instrumented with distributed Rayleigh-backscattering fibre-optic strain sensors, providing spatially continuous strain measurement across the blade span. By changing the relative position of the upstream turbine ($WT_1$) to the downstream, waked turbine $WT_2$ across the streamwise and spanwise extent, we map power output, spanwise strain, and accumulated representative fatigue relevant loading across the wake profile. Full wake impingement suppresses blade loading through the associated velocity deficit, while partial wake overlap generates the strongest load intermittency and highest relative fatigue relevant loading, despite an intermediate power recovery. A combined performance-to-loading metric shows this partial-wake regime offers the least favourable trade-off between energy yield and structural loading. These results show that minimising partial-wake exposure, not only mean velocity deficits, should be a design consideration for wind-farm layout and turbine spacing.
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All authors Francisco J. G. de Oliveira, Adrian T. McGlade, Zahra Sharif Khodaei, Oliver R. H. Buxton
History and Philosophy of Physics
Hidden Variables in Quantum Mechanics: A Journey Into de Broglie-Bohm Pilot-Wave Theory
Andrea Oldofredi
This work provides an introduction to the most influential hidden-variable interpretation of the
quantum formalism, i.e., the de Broglie-Bohm pilot-wave theory. As the reader will see, the chapter offers a detailed discussion of the main formulations of the theory. Moreover, cogent topics such as the origin of the Born rule, the interpretation of probability, the nature of the wave function, the status of
spin, as well as extensions of the pilot-wave approach beyond non-relativistic
quantum mechanics will be examined. This essay, however, not only reviews existing relevant literature but also contributes new insights about (i) the existence of
spin in the context of pilot-wave theory, and (ii) whether the latter framework is formally and conceptually simpler than standard
quantum mechanics.
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Atomic Physics
$Ab$ $initio$ calculation of hyperfine-structure properties to extract nuclear magnetic octupole moments of $^{69}$Ga and $^{71}$Ga
Fei-Chen Li and Yong-Bo Tang
We calculate the hyperfine-structure properties of the low-lying states in $^{69}$Ga and $^{71}$Ga using the relativistic coupled-cluster method at the singles and doubles (RCCSD) level. The properties include the first-order hyperfine constants and the second-order corrections arising from off-diagonal hyperfine interactions. Based on our theoretical results, we reanalyze the previous hyperfine-splitting measurements of the $4p_{3/2}$ state in $^{69,71}$Ga [R. T. Daly and J. H. Holloway, Phys. Rev. 96, 539 (1954)], and refine the
nuclear magnetic octupole moments of these two isotopes. The refined values $\Omega(^{69}\mathrm{Ga})=0.123(9)\,\mu_N\times b $ and $\Omega(^{71}\mathrm{Ga})=0.165(15)\,\mu_N\times b $ are about 13% and 12% larger than the earlier results reported by Daly and Holloway. By providing the first independent ab initio determination, the present results offer a reliable set of reference values for the
magnetic octupole moments of $^{69,71}$Ga, which will benefit both future high-precision measurements and
nuclear-structure calculations.
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History and Philosophy of Physics
Could John Ellard Gore have pre-empted the Hertzsprung-Russell diagram?
Jeremy Shears
John Ellard Gore (1845-1910) was an Irish amateur astronomer, prolific science writer and civil engineer. He was an inaugural member of the British Astronomical Association when it was founded in 1890 and was invited to become the first Director of its Variable
Star Section. Through careful
reasoning, Gore reached remarkably modern conclusions about the nature of
stars, including their sizes, distances and luminosities. This paper explores whether he might have been able to produce an early form of what is now known as the Hertzsprung-Russell (H-R) diagram.
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Optics
Interference-engineered shortcut to perfect state transfer
Yichuan Zhang, Xuanyu Liu, Zemeng Lin et al. (+2 more)
Achieving fast, high-fidelity state transfer is fundamental to scalable integrated photonics and
quantum information processing. While adiabatic
evolution provides inherent robustness against control and fabrication imperfections, its requirement for slow driving leads to impractically long propagation distances in photonic
circuits. Existing acceleration strategies, such as shortcuts to adiabaticity (STA), can dramatically shorten
evolution times but generally rely on non-native auxiliary couplings or delicate
Hamiltonian engineering that are difficult to implement in practice. Here we introduce
evolution-pause synthesis (EPS), an interference engineered shortcut protocol that achieves fast, near-perfect state transfer strictly within the native system
Hamiltonian. It achieves this by treating transient excitations as coherent resources and canceling their accumulated amplitudes via strategically interleaved pauses. By decoupling relative dynamical phase accumulation from parameter variations, EPS steers open transition trajectories into a closed loop in complex amplitude space, enabling perfect state transfer without auxiliary fields or complex parameter detours. We demonstrate this mechanism in Landau-Zener dynamics and extend it to a multilevel STIRAP process, achieving an 11.8-fold acceleration over the adiabatic baseline. Further, we experimentally validate EPS on a silicon photonic platform, realizing high-fidelity state transfer in a $16\,{\mu}\mathrm{m}$ footprint, a nearly tenfold reduction in device length compared with a $150\,{\mu}\mathrm{m}$ adiabatic reference. EPS offers a general hardware-compatible framework for fast, practical coherent control across wave and
quantum platforms.
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All authors Yichuan Zhang, Xuanyu Liu, Zemeng Lin, Wange Song, Shuang Zhang
Physics and Society
Removing Population Size, World Cities Leave on Land a Footprint of Wealth
Victor Vignolles and Rémi Lemoy
Urban expansion builds on precious arable land, affecting ecosystems and health, despite worldwide measures to alleviate its impacts, in small and large cities. Nonetheless, the link between urban extent and population size is still unclear. Here we uncover a scaling law governing built-up land in 1800+ global urban areas. We observe that world cities have homothetic (or isometric) radial land use profiles, and that built-up footprint is proportional to total population. This spatial scaling law is important for the understanding and the definition of urban areas, to help build a science of cities and make them more sustainable. It implies that small and large cities have similar internal structures, and that built-up area per capita is constant across city sizes. The remaining variations are very strongly correlated to wealth measured by gross domestic product per capita, suggesting a pick between economic development and sustainabiliy.
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Geophysics
Scaling-law-informed neural point processes for earthquake sequence forecasting
Tianlu Xiong, Zaibo Zhao, Yunrui Li et al. (+3 more)
Earthquake sequence
forecasting requires models that can learn nonlinear history dependence while retaining robust statistical structure. We develop a scaling-law-informed neural marked point process, termed Fusion, that combines neural representations of catalog history with temporal features derived from the Epidemic-Type Aftershock Sequence model and magnitude information derived from the Gutenberg–Richter law. The model separates the magnitude cutoff applied to the input catalog from the fixed target-event threshold, allowing lower-magnitude earthquakes to inform forecasts without changing the target-event set. For the 2016–2017 Amatrice–Visso–Norcia sequence, Fusion achieves the highest target-event temporal likelihood when lower-magnitude events are retained, outperforming both ETAS and a purely neural point-process baseline. Event-wise and cumulative analyses show sustained timing gains through substantial portions of the Visso and Norcia sequences. Across five
benchmark catalogs, catalog-specific neural training with a fixed ETAS prior yields the highest temporal likelihood at the minimum evaluated magnitude cutoff. Magnitude likelihood shows no consistent predictive gain beyond the Gutenberg–Richter-based ETAS reference, indicating that the additional information captured by Fusion is primarily temporal. These results show that lower-magnitude catalog histories and empirical scaling-law information complement neural sequence learning for target-event timing.
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All authors Tianlu Xiong, Zaibo Zhao, Yunrui Li, Wenqi Liu, Yosef Ashkenazy, Yongwen Zhang
History and Philosophy of Physics
The Birth of Radar Meteor Astronomy at Jodrell Bank: The Collaboration between Bernard Lovell and Manning Prentice
Jeremy Shears
The discovery of radar echoes from meteor trains at Jodrell Bank in December 1945 heralded the beginning of a new era in meteor astronomy. This paper examines the early collaboration between Bernard Lovell, whose expertise in radar and physics transformed wartime technology into a new astronomical technique, and J. P. Manning Prentice, Director of the British Astronomical Association Meteor Section, whose knowledge of visual meteor observation proved essential to interpreting the discoveries. Drawing on previously unpublished correspondence from the Lovell Archive at the University of Manchester, the paper traces the development of their partnership, including the pioneering 1946 Perseid and Giacobinid observations, the contribution of BAA observers, and the establishment of radar meteor research at Jodrell Bank. It reveals how complementary professional and amateur expertise combined to create a new field of astronomy and a lasting scientific friendship.
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Atomic Physics
Electron Correlation Enables Phase-Coherent One-Attosecond Pulse Trains
Andrés Marchisio, Isobel McSweeney, Paraskevas Tzallas et al. (+2 more)
Attosecond synthesis is ultimately a phase problem: a broad spectrum produces an ultrashort waveform only if its harmonics remain phase-locked. We show theoretically that correlated two-electron high-harmonic generation in helium driven by a long, multicycle
laser pulse supports a train of soft-x-ray bursts with durations approaching 1 as. Using a two-electron strong-field approximation, we calculate the complex harmonic spectrum and reconstruct the temporal emission while retaining its full intrinsic spectral phase, rather than imposing a flat-phase approximation. Despite the trajectory-dependent phase accumulated by two continuum electrons, the correlation-extended plateau contains a broad phase-coherent region reaching the keV range. Its superposition produces reproducible bursts separated by one half-cycle of the driving field. These results identify electron correlation not only as a mechanism for extending the high-harmonic cutoff, but also as a route toward phase-coherent x-ray waveforms on the zeptosecond timescale.
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All authors Andrés Marchisio, Isobel McSweeney, Paraskevas Tzallas, Maciej Lewenstein, Marcelo F. Ciappina
Optics · Cross-listed from cond-mat.mtrl-sci
On the temperature dependence of the optical band gap in the material system of lithium niobate and lithium tantalate
Maximilian Henneke, Michael Ruesing, Nina A. Lange et al. (+13 more)
Lithium niobate and lithium tantalate see widespread use in optics and electronics, and are increasingly used for cryogenic applications. Despite their broad deployment, their optical band gap and its relation to the
crystal stoichiometry are not well characterised as a function of temperature. In this work, we study the optical absorption properties of congruent, stoichiometric, MgO-doped and Er-doped lithium niobate as well as congruent lithium tantalate across the temperature range between 7~K and 1000~K by means of optical transmission spectroscopy. Our results demonstrate that the difference of the optical band gap typically observed at room temperature between different stoichiometries is not primarily attributable to the intrinsic electronic structure, but rather to different electron-
phonon couplings and the average
phonon energies. Additionally, we exemplarily study the temperature shift of the 523 nm absorption line in Er-doped lithium niobate due to the increased interest in optically active dopants. To facilitate future analyses, we present the open-source software suite PhoQS-Treat (Tauc Regression Edge Analysis Tool), which enables automated Tauc regressions alongside additional analytical capabilities. This work advances the development of high-performance lithium niobate-based devices.
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All authors Maximilian Henneke, Michael Ruesing, Nina A. Lange, Timon Schapeler, Noah Spiegelberg, Ernst-Lukas Kuhlmann, Elke Beyreuther, Philipp Mues, Ludmila Eisner, Lukas M. Eng, Laura Padberg, Donat J. As, Klaus-Dieter Becker, Tim J. Bartley, Christine Silberhorn, Christof Eigner
Optics
Seeded SU(1,1) interferometry for Fourier-domain optical coherence tomography
Alejandra A. Padilla, Valentina Gacha, Daniel F. Urrego et al. (+1 more)
We demonstrate
Fourier-domain optical coherence
tomography (FD-OCT) based on a seeded SU(1,1) interferometer. Multilayer objects are probed with broadband light centered at 1550nm, while depth-resolved 3D images are reconstructed from
photon flux measurements centered at 810nm. We show that, in the low parametric-gain regime, seeding increases the
photon flux, enabling volumetric imaging with a spectrometer rather than single-
photon detectors. Our analysis further shows that, under the conditions considered, seeding provides a more effective route to sensitivity enhancement than increasing the parametric gain.
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All authors Alejandra A. Padilla, Valentina Gacha, Daniel F. Urrego, Juan P. Torres
Computational Physics · Cross-listed from hep-ex
FAST-HEP: Compiling Declarative Analysis Workflows for High-Energy Physics and Beyond
Luke Kreczko
High-energy physics analyses increasingly rely on complex software workflows whose scientific lifetime often exceeds that of the underlying software ecosystem. Maintaining reproducibility while accommodating evolving analysis software, data formats, and execution environments therefore remains a significant challenge. These challenges are not unique to high-energy physics and are shared by many data-intensive scientific analyses. We present FAST-HEP and its workflow engine, Flow, which combines a declarative workflow
language, compiler, and runtime. Flow separates the scientific description of a workflow from its implementation and execution, and compiles workflows into backend-independent execution plans through normalization, graph construction, dependency analysis, and execution planning. A common runtime then orchestrates the resulting plan using replaceable capabilities. This architecture enables static validation and modular replacement of analysis operations, execution backends, and storage technologies, while recording provenance throughout compilation and execution. Although developed for the requirements of high-energy physics analysis, Flow's workflow model and orchestration layer are domain-independent. By applying compiler techniques to scientific analysis workflows, FAST-HEP provides a foundation for workflows that are transparent, extensible, portable, and reproducible, allowing scientific analyses and their supporting software ecosystems to evolve independently.
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Atomic Physics · Cross-listed from hep-ex
Technical Proposal for the Atom Interferometer CERN Experiment (AICE) Facility
Gianluigi Arduini, Nadja Augst, Mark G. Bason et al. (+79 more)
We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inaccessible to other experiments, with a secondary goal of pioneering the exploration of gravitational waves (GWs) with frequencies in the range ${\sim}$0.03-3 Hz as a pathfinder for future longer-baseline detectors. The initial configuration employs ultracold $^{87}$Sr atoms in a single-
photon 698-nm interferometer with three shaft-based atom sources in a multi-source gradiometer geometry, supported by one surface reference source for
laser stabilisation and diagnostics, to target scalar ULDM. Operation with $^{88}$Sr will give sensitivity to
axion-like particles (ALPs), vector ULDM with $B-L$ couplings and violation of the principle of equivalence, while a $^{171}$Yb upgrade will improve the sensitivity to $B-L$ couplings and equivalence violations. Probing the Einstein equivalence principle (EP) and measuring $\alpha$ will proceed in parallel with the ULDM searches. A conceptual feasibility study and a detailed technical implementation study have established that PX46 is a uniquely mature and implementation-ready site, with no technical showstoppers. Completing site preparation works during LS3 would enable the subsequent installation and operation of AICE without impacting HL-LHC operations. The detector design builds on the VLBAI and MAGIS experiments and the AION-10 Technical Design Report, scaling the strontium gradiometer architecture to the $\sim$100 m baseline. AICE is endorsed by the TVLBAI Proto-Collaboration, comprising 57 institutions in 22 countries.
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All authors Gianluigi Arduini, Nadja Augst, Mark G. Bason, Charles Baynham, Andrea Bertoldi, Gianfranco Bertone, Diego Blas, Daniela Bortoletto, Sougato Bose, Roberto Ales Bozzi, Oliver Buchmueller, Tamara Alice Bud, Clare Burrage, Sergio Calatroni, John Carlton, Vassilis Charmandaris, Maria Luisa Chiofalo, Pierre Cladé, Jonathon Coleman, Fabio Corsanego, Albert De Roeck, Arnaud Devienne, Fabio Di Pumpo, John Ellis, Pierre Fayet, Chris Foot, Elina Fuchs, Naceur Gaaloul, Susan Gardner, Enno Giese, Eduardo Granados, Saïda Guellati-Khelifa, Michael Guinchard, Timo Hakulinen, Tiffany Harte, Richard Hobson, Michael Holynski, Angelo Infantino, Alex Kehagias, Eva Kilian-Rademacher, Wolfgang Korsch, Damien Lafarge, Samuel Lellouch, Lucas Lombriser, Elias Lopez Asamar, J. Luis Lopez-Gonzalez, Michele Maggiore, Charline Marcel, Anna Marchant, Christopher McCabe, Gaetano Mileti, Peter Millington, Jeremiah Mitchell, Noam Mouelle, Angel Navascues Cornago, François Pillon, Rosa Poggiani, Johann Rafelski, Ernst M. Rasel, Maike Reckermann, Albert Roura, Rui Samoes, Federico Sanchez Nieto, Jack Sander, Carlo Scarcia, Jesse Schelfhout, Wolfgang Schleich, Dennis Schlippert, Ulrich Schneider, Steven Schramm, Florian Schreck, Olga Sergijenko, Marcelle Soares-Santos, Guglielmo M. Tino, Jonathan N. Tinsley, Tristan Valenzuela, Daniel Valuch, Maurits van der Grinten, Klaasjan van Druten, Ville Vaskonen, Wolf von Klitzing, Michael Werner
Data Analysis and Statistics · Cross-listed from hep-ex
Exact time-correlated coincidence modeling with reset boundaries
Jinjing Li
Delayed-coincidence searches identify a rare
prompt-delayed signal, but their accidental background is not a simple product of marginal rates:
muon vetoes, event dead time, and delayed events created before the current window condition which event sequences can be recorded. We derive exact ordered coincidence rates, within a stated
stochastic model, for a recorded stream of uncorrelated
prompt-like singles and correlated
prompt-delayed sources subject to Poisson reset boundaries and event dead time. The calculation separates two tasks: a Markov history chain carries the delayed events still pending at reset boundaries across windows, and a current-window propagator evaluates the ordered within-window integrals in closed form with block-
matrix exponentials, the
matrix-analytic toolkit of applied probability. The construction extends to any prescribed finite multiplicity by increasing the block-chain depth. Here we report every ordered one-, two-, and three-fold rate formed from uncorrelated singles, correlated
prompts, and recorded delayed events, together with the genuine/accidental split of
prompt-delayed pairs, multiplicity efficiencies, and the aggregate rate for multiplicity four or more. For the default window-close convention, we derive a three-term a posteriori error bound for the finite pending-population truncation. An independent streaming toy Monte Carlo validates the ordered rates, two-fold time densities, matched dead-time conventions, and aggregate high multiplicity. Within the stated assumptions, the construction is exact on the retained finite state spaces and provides explicit, computable truncation-error bounds.
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Instrumentation and Detectors
Study of the intrinsic resolution of LaBr3(Ce,Sr) and NaI(Tl) crystals
Peiyi Feng, Xilei Sun, Zhenghua An et al. (+4 more)
The Gravitational wave burst high-energy Elec?tromagnetic Counterpart All-sky Monitor (GECAM) utilizes a large number of LaBr3 and NaI(Tl)
crystals as sensitive materials for its gamma-ray detectors. To address the fitting issues of the energy resolution curves in the ground calibration of the GECAM detectors, this work conducts a comprehensive testing and comparative study of the energy resolution of 1-inch LaBr3(Ce,Sr) and NaI(Tl)
crystals produced from the same batch. We employed a Hard X-ray Calibration Facility (HXCF), a PMT single-photoelectron calibration system, and Geant4 Monte Carlo simulation tools to quantify seven factors influencing energy resolution. The results indicate that the contributions of various components to energy resolution differ, with pho?toelectron statistical fluctuations and intrinsic resolution being predominant. For 100 keV X-rays, the total energy resolution of the LaBr3(Ce,Sr)
crystal is 3.71% \pm 0.03% (expressed as 1-{\sigma}), with a contribution from photoelectron statistical fluctuations of 2.69% \pm 0.00% and an intrinsic resolution of 2.45% \pm 0.05%. For 100 keV X-rays, the total energy resolution of the NaI(Tl)
crystal is 4.41% \pm 0.14% (expressed as 1-{\sigma}), with a contribution from photoelectron statistical fluctuations of 3.20% \pm 0.00% and an intrinsic resolution of 2.90% \pm 0.21%. We discussed the sources of intrinsic resolution, and the results indicate that the intrinsic resolution of the LaBr3(Ce,Sr)
crystal primarily arises from luminescence non-proportionality, while that of the NaI(Tl)
crystal mainly stems from fluctuations during energy transfer. This study emphasizes precise and specific experimental measurements and comparative research, demonstrating that both factors are important contributors to intrinsic resolution.
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All authors Peiyi Feng, Xilei Sun, Zhenghua An, Dali Zhang, Xinqiao Li, Shaolin Xiong, Hong Lu