Mesoscale and Nanoscale Physics
Electrothermal control of spin-reorientation transition in Co/Fe_3GaTe_2 heterostructures
Po-Wei Chen, Ming-Hsien Hsu, Cheng-Ying Hsiao et al. (+12 more)
Electrical control of
magnetic anisotropy in van der Waals (vdWs) magnets is a key step toward reconfigurable two-dimensional spintronics, yet how a conventional metallic ferromagnet competes with a van der Waals magnet across a direct interface has remained largely unexplored. Here we demonstrate reversible thermal and electrothermal control of a
spin-reorientation transition in Co/Fe_3GaTe_2 (FGaT)
heterostructures. As Joule heating weakens the FGaT anisotropy, the
heterostructure switches from an out-of-plane- to an in-plane-dominated state at a reorientation temperature of approximately 311 K, well below the Curie temperature, consistent with an exchange-mediated anisotropy competition between the Co overlayer and FGaT. An electrically driven device shows a closely matching loop
evolution within an 80-100 mW power window, reversibly over five measurement cycles, consistent with an electrothermal origin. In a Co-free FGaT device, Kerr microscopy traces the switching to a power-tunable domain nucleation barrier and demonstrates power-thresholded, field-assisted magnetization reversal at a threshold near 15 mW. These results demonstrate electrothermal anisotropy competition as a route to heat-assisted and device-level control of vdWs magnetism.
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All authors Po-Wei Chen, Ming-Hsien Hsu, Cheng-Ying Hsiao, Ming-Yang Ho, Masahiro Haze, Yan-Ru Chu, Yu-Cheng Shao, Po-Chun Chang, Chen-Yu Ou, Ruei Chen, Ko-Fan Chen, Chung-Ting Ke, Chao-Hung Du, Yukio Hasegawa, Wen-Chin Lin.
Optics
Conjugate phase-noise cancellation enables submicrometre dual-comb ranging with free-running megahertz-linewidth lasers
Yue You, Zaifan Wu, Yi Zou et al. (+9 more)
Frequency-domain dual-comb ranging combines rapid acquisition with interferometric sensitivity, but high-performance implementations often rely on mutually coherent or actively stabilised comb sources. Free-running sources can reduce this hardware burden, but their phase noise and drift of the optical frequency offset can blur
radio-frequency (RF) comb teeth and weaken probe-reference phase correlation. Previous phase-slope implementations have therefore relied on sufficiently resolved RF teeth, within-coherence-length probe-reference paths or explicit digital tracking of these fluctuations. Here we demonstrate a low-cost frequency-domain dual-comb ranging architecture that combines independent free-running distributed-feedback (DFB)
lasers with conjugate phase-noise cancellation (CPNC). By forming a self-conjugate signal before the phases of individual RF-comb teeth are extracted, CPNC cancels the common
laser phase factor and drifting optical-frequency-offset term while retaining the distance-dependent phase slope. Using electro-optic combs seeded by DFB
lasers with linewidths of 12 MHz and 9 MHz, we achieve an Allan deviation of $219~\mathrm{nm}$ at $246~\mu\mathrm{s}$ and reduce the single-frame distance standard deviation from $558~\mu\mathrm{m}$ to $9.31~\mu\mathrm{m}$ with CPNC. Across the tested megahertz-linewidth configurations, CPNC delivered minimum Allan deviations below $250~\mathrm{nm}$. These results show that CPNC enables submicrometre ranging in a low-cost frequency-domain dual-comb architecture with reduced source-stabilisation and phase-management complexity.
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All authors Yue You, Zaifan Wu, Yi Zou, Xiang Cai, Yixiao Zhu, Chenbo Zhang, Dan Lu, Siming Chen, Shujie Pan, Xian Zhou, Xiaopeng Xie, Fan Zhang
Fluid Dynamics
Statistical State Dynamics Eigenmodes and Equilibria support Couette Turbulence
Brian F. Farrell and Petros J. Ioannou
Wide-channel Couette (WCC)
turbulence consists primarily of quasi-steady roll-streak structures (RSS) maintained by a self-sustaining process (SSP), yet the Navier-Stokes equations in velocity variables admit no linear RSS instability or stable
equilibrium, leaving the WCC turbulent state's analytic basis obscure. We show that, in the statistical state dynamics (SSD) of a second-order closure of the Navier-Stokes equations, Couette
turbulence arises from a modal RSS instability and equilibrates as a stable fixed point at spanwise wavenumber 3. This fixed point comprises a streamwise-mean flow and a pair of counterpropagating neutral eigenmodes, regularized by roll advection rather than viscosity. This stable
equilibrium identifies both a canonical
turbulence solution and its self-sustaining process (SSP), and characterizes their analytic structure. WCC
turbulence arises as a spanwise tiling by this stable fixed-point RSS unit
cell. Predictions of this SSD theory are corroborated by comparison with direct numerical simulation.
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General Relativity and Quantum Cosmology
Optical and Thermodynamic Signatures of Lorentz Symmetry Breaking in Bumblebee AdS Black Holes
Behzad Eslam Panah, Abdullah Guvendi, Semra Gurtas Dogan et al. (+1 more)
We investigate the impact of spontaneous Lorentz
symmetry breaking on scalar wave propagation, null geodesics, and thermodynamic behavior of four-dimensional asymptotically AdS black holes in bumblebee
gravity. The static, spherically symmetric solutions are characterized by a dimensionless parameter $\ell > -1$ arising from the
vacuum expectation value of the bumblebee vector field, which globally rescales the radial geometry. Massless scalar fields are analyzed via the radial Klein–Gordon equation cast into a generalized Helmholtz form, yielding an effective frequency-dependent refractive index that identifies oscillatory and evanescent regions, classical turning points, and confinement induced by
curvature and Lorentz violation. In the high-frequency limit, wave propagation coincides with null geodesics, with $\ell$ controlling radial scaling and governing the
geometric-optics limit. The AdS boundary reflects waves, while the horizon acts as a one-way absorber. Thermodynamic analysis in non-extended and extended phase spaces confirms the first law and Smarr relation, with $\ell$ influencing heat capacity, free energy, and stability. \textcolor{black}{Modeling these black holes as heat engines, we construct explicit cycles and show that efficiency increases with $\ell$, leading to an upper bound imposed by $\eta \leq 1$. Our results provide a framework connecting Lorentz violation, wave propagation,
geometric optics, and AdS black hole thermodynamics in bumblebee
gravity.
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All authors Behzad Eslam Panah, Abdullah Guvendi, Semra Gurtas Dogan, Omar Mustafa
Mathematical Physics · Cross-listed from math.CA
Orthonormal Sobolev estimates with fractal measures
Neal Bez, Keith M. Rogers and Shunya Toyoshima
We prove a fractal version of Lieb's Hardy-Littlewood-Sobolev inequality for orthonormal functions. On the one hand, this can be viewed as a trace
theorem for orthonormal functions. On the other, it allows us to recover the Rozenblum-Tashchiyan bound for the number of negative
eigenvalues of $-\Delta-\mu$, where $\mu$ is a shell potential. We also recover Rozenblum's bound for the sum of negative
eigenvalues via a Lieb-Thirring kinetic inequality. Our proof is direct, avoiding both Schatten classes and variational arguments. We first reprove Adams' fractal Hardy-Littlewood-Sobolev inequality (for single functions) via
Fourier analysis. This yields the required endpoint estimate as well as a bound for the interaction energy of Frostman measures.
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High Energy Physics (Theory)
Heterotic moduli, the double extension and the alpha'^2 metric
Jock McOrist and Qianhe Yin
We compute the heterotic
moduli-space metric through $\alpha'^2$ for backgrounds admitting a smooth $\alpha'\to0$ limit. The Kaehler potential is unchanged when written in an appropriate field basis suggested by the ten-dimensional supersymmetry equations, while the metric receives $\alpha'^2$ corrections. We discuss this and clarify the roles of the extension bundle, F-terms, the D-terms and the string-derived
moduli space metric.
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Quantum Physics
The Fourier Wall: Why Public Tabular Datasets Refuse Quantum Advantage, and a Certified Recipe for Where It Lives
Javier Mancilla and Tomás Tagliani
Across public tabular
benchmarks,
quantum machine-learning (QML) models usually lose to carefully tuned classical baselines. We argue that this is a structural property of the
datasets rather than merely a limitation of current models. Because an angle-encoded
quantum neural network is a partial
Fourier series, a genuine advantage can arise only when the target spectrum is simultaneously off-grid, of interaction order at least three, high-frequency, supported by near-independent features, and dense beyond practical enumeration. We call the failure to satisfy these conditions the
Fourier wall. We operationalize the conditions as SPECTRA, a two-tier certificate: a simulator-free structural screen followed by a decisive comparison between a matched
quantum model and five tuned classical twins using paired-bootstrap confidence bounds. On industrial smart-meter data, SPECTRA correctly refuses the real peak-load target, for which gradient-boosted trees reach a held-out ROC-AUC of 0.999. On the same real energy phases with labels generated by an interacting
quantum process, the dynamics-matched
quantum model reaches 0.994 versus 0.699 for the best generic classical baseline, and collapses to chance when its interaction couplings are ablated. An exact classical simulator ties the
quantum model at small width but incurs measured exponential evaluation cost, with an estimated hardware crossover near 13-19 sites. These results provide a practical recipe for identifying, engineering, and deploying
quantum-advantage candidates in tabular data.
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Strongly Correlated Electrons
Thermal Order by Disorder in Resonating-Valence Bond States on the Checkerboard Lattice
Giorgi Gogaberishvili, Nika Kurdadze and Kirill Shtengel
We derive a local
spin-1/2
Hamiltonian with a resonating valence bond ground state on the checkerboard
lattice. The state is characterized by the exponential decay of singlet-singlet correlations, whereas dimer-dimer correlations decay with a power law in the corresponding
Quantum Dimer model. This observation leads to a novel mechanism for thermal Order by Disorder whereby thermal decoherence suppresses destructive
quantum interference between different contributions to the correlations in the ground state and results in a qualitatively different, quasi-long-range ordered mixed state.
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Medical Physics
Joint-decoupled iterative CBCT reconstruction with hybrid scatter estimation and voxel-adaptive beam hardening correction
Jianing Sun, Jean Michel Létang, Qixiang Sun et al. (+3 more)
Cone-beam computed
tomography (CBCT) is fundamentally challenged by scatter and beam hardening artifacts, which originate from X-ray scattering and the polychromatic nature of the X-ray spectrum, respectively. These two types of artifacts are intricately coupled in reconstructed images and manifest with similar streaking and cupping features, severely compromising high-precision CBCT imaging. This paper proposes a physics-driven iterative framework rooted in the polychromatic Polyquant attenuation model, which decouples these artifacts by establishing an optimization loop between scatter estimation and relative electron density (RED) reconstruction. We develop a hybrid strategy for scatter estimation, in which the first-order scattering component is analytically derived based on a polychromatic physical model to preserve high-frequency structural information, whereas the smoother multiple scattering component is efficiently estimated via an object-adaptive convolution module. Subsequently, for beam-hardening correction, we introduce a voxel-adaptive update mechanism that solves linearized, scatter-corrected polychromatic equations to derive optimal weights, enabling direct RED refinement without manual parameter tuning. The proposed method was validated through comprehensive studies on biomedical phantoms, utilizing both Monte Carlo simulations and physical experiments. Representative results demonstrate that the proposed method outperforms state-of-the-art techniques, with the mean relative error decreased from 11.96% to 1.27% for the anthropomorphic head phantom and from 12.55% to 5.46% for the physical Yin-Yang phantom.
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All authors Jianing Sun, Jean Michel Létang, Qixiang Sun, Guangyin Li, Ligen Shi, Xing Zhao
Optics
Experimental demonstration of Flying-Focus enhanced Thomson scattering
E. Gerstmayr, C. Mariani, R. Fitzgarrald et al. (+23 more)
We report the experimental demonstration of a spatiotemporally engineered "Flying-Focus"
laser pulse for enhanced x-ray generation in relativistic Thomson scattering. A combination of longitudinal chromatic aberration, angular dispersion, and group delay dispersion was applied to an ultrashort relativistically intense
laser pulse to control the motion of its focal point. Precise tuning of the group delay dispersion was used to match the velocity of the focus to the trajectory of a counterpropagating electron bunch, produced by a
laser wakefield accelerator. This prolonged the Thomson scattering interaction while reducing nonlinear effects, leading to an enhanced x-ray yield. The approach has the potential to increase the spectral density and brightness of the x-ray beam by orders of magnitude compared to equivalent focusing without spatiotemporal control. This experiment establishes a new technique for structured-light control at high intensity, demonstrating the realization of dynamic intensity structures that enhance light-matter interactions and for the generation of ultra-bright radiation sources.
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All authors E. Gerstmayr, C. Mariani, R. Fitzgarrald, M. VanDusen-Gross, C. Berger, Q. Chen, A. Di Piazza, M.S. Formanek, D.H. Froula, C.G.R. Geddes, A.J. Gonsalves, B. Greenwood, R. Jacob, A. Lu, A. McIlvenny, K. Nakamura, L. Obst-Huebl, J.P. Palastro, A. Picksley, K. Poder, D. Ramsey, H.G. Rinderknecht, G. Sarri, A.G.R Thomas, J. van Tilborg, M.J.V. Streeter
High Energy Physics (Theory) · Cross-listed from math.DG
The Aeppli Parameter for the Heterotic Moduli
Pei-Lin Wu
In this paper, we construct a family of solutions to the $3$-fold Hull-Strominger system using the Aeppli class, without introducing the auxiliary gauge connection on the tangent bundle. In particular, we deform the conformally balanced metric along an Aeppli class off-shell and then tune it by a hermitian $(1,1)$-form dependent on this Aeppli class on-shell to satisfy the anomaly cancellation condition. The existence of the family of solutions is then obtained by the implicit function
theorem. This refines the previous work by not introducing auxiliary gauge connection, thereby matching the expected dimension with the Bott-Chern parameter. This construction of the Aeppli parameter also extends to the $n$-fold Hull-Strominger system.
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Astrophysics of Galaxies
Chemical Evolution of Galaxies: Past, Present and Future
Francesca Matteucci
In this paper I will describe the basic principles of chemical
evolution of
galaxies, its main ingredients and uncertainties. By means of chemical
evolution we can perform the so-called
galactic archaeology, which consists in reconstructing the history of
star formation of
galaxies and in particular of the Milky Way, starting from the observed
stellar and gas abundances.
Galactic archaeology is a powerful tool to predict also the behaviour of
galaxies at high
redshift. In particular, we adopt the "time-delay model" which is a way of interpreting the [X/Fe] vs. [Fe/H] relations (X is the abundance of a specific chemical element) in terms of different timescales of the
stellar progenitors of the chemical elements relative to Fe, which is the indicator of "
metallicity". I will then describe how we can reconstruct the
star formation histories of
galaxies of different morphological type (spirals, ellipticals) starting from the available observations. Particular
attention will be paid to the study of the Milky Way which is the best studied
galaxy at the moment. I will start describing the first chemical
evolution models and then the most recent ones, the main difference between the old and new models being the observational data to compare with. Finally, I will foresee which could be the future improvements to chemical models and what constraints can we derive to better understand
galaxy evolution.
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Mathematical Physics
Metric tensors and two-forms in information geometry from the GNS construction
Marco Castrillón López, Florio M. Ciaglia, Laura González-Bravo et al. (+1 more)
We develop a GNS-based construction of
geometric tensors on smooth parametric statistical models over $C^*$-
algebras. Since the state space of a $C^*$-
algebra is generally not a smooth
manifold, the construction does not rely on pulling back tensors from an ambient state
manifold. Instead, the GNS
Hilbert spaces and their duals are organized into non-locally-trivial
Hilbert fibrations over the state space. For models satisfying a compatibility condition expressing derivatives of expectation values as continuous functionals on the realified GNS fibers, each tangent vector admits a canonical dual GNS representative. Pulling back the dual GNS Hermitian product along the corresponding canonical lift produces a Hermitian tensor $K$ on the complexified tangent bundle of the model, whose real and imaginary parts define, under suitable regularity assumptions, a smooth weak Riemannian metric tensor $G$ and a smooth two-form $\Omega$. In finite-dimensional parameter
manifolds the metric is, of course, strong. The construction recovers the Fisher–Rao metric in the commutative dominated case, the Fubini–Study geometry for pure states up to the normalization and sign convention imposed by the dual GNS pairing, and the SLD metric for faithful
quantum states. In finite-dimensional faithful models, the two-form $\Omega$ is proportional, up to convention, to the expected commutator of the SLD representatives, equivalently to the mean Uhlmann
curvature. We show through faithful
qubits and displaced thermal states that $\Omega$ need not be closed. For bundle-regular models, the associated fiberwise
symplectic form on the real dual GNS bundle admits connection-dependent closed extensions to the total space, while closedness of $\Omega$ on the parameter
manifold is controlled by the covariant exterior derivative of the canonical real dual GNS lift.
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All authors Marco Castrillón López, Florio M. Ciaglia, Laura González-Bravo, Alberto Ibort
Disordered Systems and Neural Networks
Quantum and classical entropic complexity of the thermal state: coherence, decoherence, and the ergodic-to-localized crossover in random-matrix and many-body models
Imre Varga and Onur Aktan
Does thermal averaging preserve signatures of eigenstate complexity? We study the entropic complexity C = S_1 - S_2 (Shannon minus second-order Renyi
entropy) across the ergodic-to-localized crossover of three disordered models: the Rosenzweig-Porter (RP) ensemble, the power-law banded random
matrix (PLBRM) ensemble, and the random-field Heisenberg chain. We compare a wavefunction-level quantity C_eig to the complexity of the thermal (Gibbs) state before and after pointer-basis dephasing, via the trace (C_tr) and diagonal (C_diag) complexities. The answer is mostly no: thermal averaging strongly suppresses, but does not eliminate, eigenstate-complexity signatures. C_eig develops a pronounced mid-phase maximum in RP and, at matching fractal dimension, in the structurally independent PLBRM model; a high-statistics scan resolves a weak (about 10%) but reproducible thermal shadow of this peak in the thermal diagonal complexity. This feature is confined to the two random-
matrix models; in the Heisenberg chain the eigenstate complexity instead peaks at the many-body localization transition. A second, genuinely thermal feature, an edge just inside the ergodic phase, has no eigenstate counterpart and, in PLBRM, recedes with system size. Both features are tracked by scale-invariant crossover indicators: the log-ratio of the trace and diagonal crossover temperatures, which vanishes upon localization, and the relative
entropy of coherence. Entropic complexity thus cleanly separates thermal-state and eigenstate physics: a sharp wavefunction-level feature, reproducible across unrelated random-
matrix constructions, leaves only a faint, structurally distinct imprint on thermal observables.
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High Energy Astrophysical Phenomena
A cosmic-ray loaded nascent outflow driven by a massive star cluster
Marianne Lemoine-Goumard, Lucia Härer, Lars Mohrmann et al. (+6 more)
Cosmic rays are widely held to drive
outflows from
star-forming
galaxies and profoundly influence
galaxy evolution. Direct evidence for
cosmic-ray carrying
outflows is however lacking. At the same time there is increasing awareness of the importance of massive
star clusters in the acceleration of
cosmic rays in
galaxies. Here we report on the discovery of a nascent
outflow driven by the massive
star cluster Westerlund 1. Giga-electronvolt gamma-ray emission coincident with a cavity visible in atomic hydrogen traces the emergence of a population of relativistic electrons out of the
Galactic Disc. The emission is offset from tera-electronvolt gamma-ray radiation surrounding the cluster, but connects to it smoothly spectrally and spatially. The implied energy density of co-accelerated
protons and
nuclei, assuming standard non-thermal electron/
proton injection efficiencies, is at least an order of magnitude higher than that in the general interstellar medium. These particles therefore have the potential to dynamically influence the
outflow. This discovery suggests that
cosmic-ray loaded
outflows may be a common feature of young massive
star clusters, with implications for the transport of
cosmic rays into the
halo of the
Galaxy.
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All authors Marianne Lemoine-Goumard, Lucia Härer, Lars Mohrmann, Romain Bernet, Jim Hinton, Giada Peron, Brian Reville, Luigi Tibaldo, Thibault Vieu
Instrumentation and Methods for Astrophysics
Radial velocity and atmospheric parameter calculations for the GaiaNIR spectrograph
Szabolcs Mészáros, David Hobbs, Anna Liptrott et al. (+8 more)
Context. The upcoming GaiaNIR mission is currently planning to add a near-infrared spectrograph to its payload in order to enhance its scientific return, particularly for mapping the
dust-obscured regions of the Milky Way. Aims. This study aims to identify the optimal wavelength region between 800 and 2300 nm for the proposed GaiaNIR spectrograph to maximize the precision of radial velocities and atmospheric parameters. Methods. To find its spectral range, we generated 10000 synthetic spectra from the BOSZ library across a wide range of
stellar parameters, with resolutions varying from 5000 to 20000. By cross-correlating these mock observations with ideal templates, we assessed the statistical scatter of velocity residuals to isolate six candidate windows for further atmospheric parameter testing. Results. Our analysis finds that the 1926 - 1968 nm window at R = 16100 - 20100 in the K-band is the preferred strategic choice, because it has the potential to reach radial velocity precision for the brightest FGKM
stars of about 160 - 260 m/s depending on resolution, while providing precision of the atmospheric parameters close to
Gaia's Radial Velocity Spectrometer. We also identified a second region between 1158 and 1202 nm (R = 9300 - 11600), that has slightly lower radial velocity precision, but at a wider temperature range than the K-band. Both regions make it possible to derive abundances of ten species at these resolutions: O, Na, Mg, Si, Ca, Ti, V, Cr, Mn, Ni in the K-band, and Mg, Si, K, Ca, Ti, V, Cr, Mn, Co, Ni between 1158 - 1202 nm. Conclusions. The K-band delivers sufficiently precise measurements for the mission's primary cool
star targets while taking advantage of significantly lower interstellar extinction, enabling the mapping of the
dust-obscured regions of the Milky Way.
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All authors Szabolcs Mészáros, David Hobbs, Anna Liptrott, David Katz, Ricardo Schiavon, Viktória Pap, Anthony G. A. Brown, George Seabroke, Joss Bland-Hawthorn, Ronny Blomme, Nicholas A. Walton
Optics
Triple-Resonance Spectroscopy Using a Cavity-Enhanced Frequency Comb Probe
Qinxue Nie, Vinicius Silva de Oliveira, Adrian Hjältén et al. (+3 more)
Accurate experimentally verified models of molecular hot-band transitions are essential for interpreting high-temperature spectra in environments ranging from exoplanetary atmospheres to combustion systems. However, line-resolved measurements of infrared hot-band transitions reaching highly excited vibrational states above 10000 cm$^{-1}$ are missing because these transitions are too weak to observe at room temperature and become spectrally congested at elevated temperatures. Here, we introduce a nonlinear spectroscopic approach that enables simultaneous measurement of individual infrared hot-band transitions between four vibrational bands up to 12000 cm$^{-1}$ over a broad spectral range with sub-Doppler resolution and sub-MHz frequency accuracy (10$^{-10}$ relative line position accuracy). The methods is based on an all-optical triple-resonance (AOTR) scheme that combines stepwise mid-infrared pumping using an optical-frequency-comb-stabilized, double-seeded continuous-wave optical parametric oscillator with broadband highly sensitive near-infrared probing using a cavity-enhanced optical frequency comb. As a proof of principle, we measure transitions between high polyads (P) of methane - groups of strongly interacting, near-degenerate vibrational energy states arising from couplings between the C-H stretching and bending modes. In a single probe spectrum, we simultaneously resolve sub-Doppler P4$\leftarrow$P0, P6$\leftarrow$P2 and P8$\leftarrow$P4 transitions, reaching the poorly understood polyad P8 near 12000 cm$^{-1}$ and providing the first set of 41 experimentally observed lines in the P8$\leftarrow$P4 spectral region.Comb-based AOTR spectroscopy opens a new route for broadband exploration of highly excited molecular states, delivering extensive high-accuracy spectroscopic data needed to refine molecular models and improve predictions of high-temperature spectra.
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All authors Qinxue Nie, Vinicius Silva de Oliveira, Adrian Hjältén, Isak Silander, Kevin K. Lehmann, Aleksandra Foltynowicz
Earth and Planetary Astrophysics
Accuracy Analysis of VLBI Universal Time Measurement Based on a GNSS Single-Station Regional Ionospheric Model
Xu-chong Duan, Dang Yao, Yuan-wei Wu et al. (+3 more)
Universal Time (UT1) is a key parameter characterizing Earth's rotation, and very long baseline interferometry (VLBI) is the mainstream technique for measuring UT1. To address the limitations in the timeliness and accuracy of existing global ionospheric models for single-frequency VLBI UT1 measurements, we construct a single-station regional ionospheric model using GNSS data from the VLBI stations on the Jilin-Kashi baseline. We apply this model to VLBI observations and compare its correction performance with that of a global predictive model and a global post-processed model. The results show that the line-of-sight ionospheric delays and baseline corrections calculated with the single-station regional model have precision close to that of the global post-processed model and are substantially better than those of the global predictive model. After correction with the single-station regional model, the derived UT1 values differ from the US Naval Observatory (USNO) reference values by a mean bias of -15.6 us and an RMS deviation of 82.3 us, both better than the results obtained with the other two model classes. A single-station regional ionospheric model constructed independently from GNSS data available at VLBI stations can effectively correct single-frequency VLBI observations and support quasi-real-time high-precision UT1 measurements. It therefore has important value for improving the timeliness of independent UT1 products.
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All authors Xu-chong Duan, Dang Yao, Yuan-wei Wu, Zhe Zhang, Jia Liu, Xu-hai Yang
Accelerator Physics
Alignment and Timing Jitter in Flying-Focus Inverse Compton Scattering
S.G. Rykovanov, I. Dubinkin, M.P. Malakhov et al. (+3 more)
Flying-focus
laser pulses can extend the effective interaction length in inverse Compton sources by controlling the trajectory of the focal intensity. Their practical advantage, however, depends on tolerance to shot-to-shot electron–
laser alignment and synchronization errors. We develop a semi-analytical model for the shot-averaged total
photon yield in head-on inverse Compton scattering of an axisymmetric Gaussian electron bunch with a flying-focus
laser pulse. The model includes finite electron-beam emittance,
laser diffraction, transverse
laser-centroid jitter, longitudinal focus-position jitter, and
laser arrival-time jitter at the nominal interaction point. The ensemble averaging over these independent Gaussian errors and the integration over the longitudinal electron and
laser coordinates are performed analytically, reducing the overlap problem to a single positive numerical quadrature. This formulation enables rapid evaluation of jitter-robust operating points and provides a compact tool for defining
alignment and synchronization tolerances in flying-focus inverse Compton sources.
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All authors S.G. Rykovanov, I. Dubinkin, M.P. Malakhov, A.M. Fedotov, A.S. Samsonov, I.Yu. Kostyukov
Mesoscale and Nanoscale Physics
Fermion parity of an Andreev molecule probed by nonlocal Josephson effect
S. Annabi, H. Riechert, K. Watanabe et al. (+5 more)
Fermion parity is a fundamental property of superconducting many-body states. Here, we show that the global
fermion parity of a delocalized superconducting state can be detected locally by exploiting the nonlocal Josephson effect. Using a carbon nanotube-based Andreev molecule formed by two coupled
quantum-dot Josephson junctions, we observe a pronounced nonlocal Josephson response and demonstrate the formation of delocalized Andreev molecular states extending across both junctions. We further show that changes in the molecular ground-state parity manifest as characteristic $\pi$-phase shifts in the nonlocal response. Supported by a minimal theoretical model, these results identify global
fermion parity as an experimentally accessible degree of freedom in hybrid superconducting
circuits that can be readily revealed through the nonlocal Josephson effect.
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All authors S. Annabi, H. Riechert, K. Watanabe, T. Taniguchi, J. Griesmar, E. Arrighi, L. Bretheau, J.-D. Pillet
Disordered Systems and Neural Networks
A Flickering Resonance Degeneracy on Entropy-Ruled Charge Transport in the Extended Hopping Sites for Biological Systems: Role of Static-to-Dynamic Disorder Transition
K. Navamani and M. Pavalamuthu
Charge transport (CT) in biological systems is of great interest due to its role in various functional activities like photobiology, bioenergetics, redox catalytic and other metabolic activities, etc. It has been observed by various studies that the presence of a dynamic disorder in biomolecules facilitates charge dynamics in the intermediate transport regime, i.e., far from hopping and towards a bank-like mechanism. Hitherto, the dynamic disorder (in a time scale, coupling between electronic and
nuclear dynamics) weightage on CT in molecules is not well-established for the measurement of molecular conductivity from small to long-range ordering. With this motivation, we propose the flickering resonance-coupled
entropy-ruled charge transport theory for transfer-rate and
diffusion-based mobility (D/{\mu}) calculations. The proposed analytical formalism incorporates the impact of dynamic disorder-correlated degeneracy (in a flickering-resonance manner) on the
entropy-ruled electron transfer rate and
diffusion-mobility, which are valid for localized hopping, delocalized band transport, and regimes in between. By this approach, it has been observed that the dynamics-driven electronic site matching probability enhances the degeneracy, which is quantified by the differential
entropy. The analysis clearly shows that for ultra-fast dynamical and degenerate cases, the
entropy-ruled mobility is transformed as band mobility, rather than the thermally activated hopping or
diffusion process.
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Statistical Mechanics
Scaling regimes of the Kuramoto-Sivashinsky equation from the functional renormalization group
Liubov Gosteva, Nicolás Wschebor and Léonie Canet
We revisit the renormalization group (RG) approach to the one-dimensional
stochastic Kuramoto-Sivashinsky (KS) equation and show that previous approaches based on perturbative Wilsonian RG with a sharp cutoff are not valid, even though they yield a qualitatively correct picture. The reason is that taking momentum derivatives while using the sharp cutoff is not well-defined in some cases and leads to intrinsic divergencies. This is a well-known problem of Wilsonian RG, which can be simply cured by using a smooth cutoff, and employing the functional renormalization group (FRG) framework. We establish the flow equations for the KS model within the FRG, and demonstrate that it flows to the Kardar-Parisi-Zhang (KPZ) fixed point at large scales. We then calculate the full two-point correlation function over a wide range of momenta and frequencies. We show that it exhibits three universal scaling regimes that we characterize: the KPZ regime (with dynamical exponent $z=3/2$), the Edwards-Wilkinson regime (with $z=2$) and the recently discovered inviscid regime (with $z=1$). The latter develops over an extended range of large wavenumbers and originates from the vanishing of the effective viscosity. Lastly, we investigate the large-scale behavior of the deterministic KS equation by studying the limit of vanishing noise and we determine the scales where the KPZ regime can emerge in the deterministic case.
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Optics
Electromagnetically induced transparency lasing in distributed resonant feedback system
Yaoyao Liang, Xinyue Wang, Hongyi Tian et al. (+3 more)
We demonstrate a loss-enabled mechanism that can realize single electromagnetically induced transparency (EIT) analogue in periodic waveguide-resonator structures. Unlike previously reported passband-based EIT analogues, which arise from compressed passbands in the intrinsic-loss-free limit, the proposed mechanism exploits resonator intrinsic loss to generate an isolated transparency mode within the original bandgap. The resulting EIT state remains immune to finite-size mode discretization, enabling robust single-frequency lasing through distributed resonant feedback while requiring a threshold modal gain lower than that of an equally long Fabry-Perot
laser. Our findings extend classical EIT analogues from passive spectral phenomena to active
laser operation.
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All authors Yaoyao Liang, Xinyue Wang, Hongyi Tian, Yulong Fan, Qi Qin, Feihu Wang
Other Condensed Matter
Reversible and irreversible dynamical topological transitions of magnetic Hopfions
S. Y. Lu, H. M. Dong, D. X. Yu et al. (+1 more)
Magnetic Hopfions are three-dimensional (3D) topological
solitons characterized by a nonzero
Hopf invariant and offer a promising platform for 3D spintronics. While their static stabilization has been widely studied, their nonlinear dynamics under alternating
magnetic (AM) fields remain largely unexplored. We show, using 3D micromagnetic simulations and analytical mode analysis, that an AM field drives two qualitatively distinct dynamical regimes of a confined
magnetic Hopfion. In the weak-field regime, resonant excitation of intrinsic Hopfion modes induces a nonlinear instability and an irreversible topological reconfiguration from a Hopfion to a toron. In contrast, in the strong-field regime, the system undergoes reversible field-locked topological switching at GHz frequencies, with the magnetization periodically alternating between a topologically trivial
ferromagnetic configuration and a Hopfion state. The switching pathway is selected by the driving frequency: a 2 GHz field drives a breathing pathway associated with the low-frequency collective response, whereas a 40 GHz field produces a nonresonant rotational pathway governed by strong Zeeman-torque-driven precession and field locking. These results identify field amplitude and frequency as independent control knobs and reveal that reversible Hopfion switching can arise either from nonlinear continuation of low-frequency collective motion or from nonresonant high-frequency field locking.
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All authors S. Y. Lu, H. M. Dong, D. X. Yu, K. Chang
Quantum Physics
Manipulating non-intrinsic outputs of a non-Hermitian coupled system by weak external driving
He Feng, Yi-Fan Xiang, Wei Li et al. (+1 more)
Measurement provides access to exploring and understanding nature and finds widespread applications. It is generally believed that the weak external driving used in measurement introduces negligible disturbance to the intrinsic output of the probed system. Here, we reveal that dissipation in a non-Hermitian
quantum coupled system induces interference between self-excitation and coupling-excitation spectral functions, giving rise to non-intrinsic outputs. These non-intrinsic outputs can be effectively manipulated by the ratio of weak external driving strengths applied to two channels, leading to significant phenomena: extreme suppression of dissipation by convergence effect of high-loss mode towards low-loss mode, and
giant shift of resonant frequency instead of original spectral Rabi splitting. Crucially, we discover the Pythagorean relation linking eigenlevel splitting, spectral Rabi splitting and average total decay rate, enabling precise measurement of the eigenlevel splitting and coupling strength. Numerical simulations confirm that the interference outputs also exist in classical coupled systems. Our work provides a profound insight into measurement and non-Hermitian physics.
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All authors He Feng, Yi-Fan Xiang, Wei Li, Xue-Hua Wang
Quantum Gases
Controlling charge and spin currents through nonreciprocal dissipative processes
Catalin-Mihai Halati and Jean-Sébastien Bernier
We investigate the generation and control of both charge and
spin currents via nonreciprocal dissipative mechanisms in a two-dimensional spinful fermionic atom
quantum system with broken inversion and time-reversal
symmetries. Within the Gorini-Kossakowski-Sudarshan-Lindblad master equation formalism and using an approach based on the time-dependent generalized Gibbs ensemble, we identify in the weak dissipative coupling regime the minimal set of nonreciprocal jump operators required to induce charge and
spin currents and to control both their direction and magnitude. We find that in the presence of finite tunneling, Rashba coupling and
magnetic field, the combine application of two jump operators nonreciprocally coupling each
spin species to a different spatial direction of motion is sufficient to generate both types of current. Furthermore, by tuning the degree of nonreciprocity of the jump operators we modify the dominant transport mechanism from
spin to charge. Finally, we checked that this nonreciprocal current generation mechanism is robust to the application of dephasing noise as even in the presence of this additional dissipative process the steady-state occupation distributions for the quasiparticle modes of the
Hamiltonian remains non-trivial, an essential requirement to obtain non-zero currents.
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Optics
Role of Spatial Coherence in Single-Shot Lensless Image Reconstruction
Ganesh M. Balasubramaniam, Xiao-Liu Chu and Matthew R. Foreman
Lensless imaging is a technique that recovers object information computationally from diffraction patterns recorded without imaging optics, making its performance strongly dependent on the forward model used during image reconstruction. A common source of reconstruction error is the assumption of fully coherent propagation, even when the illumination exhibits partial spatial coherence in practice. Here, the role of spatial coherence is examined for assorted object classes using a coherence-aware forward model based on generalised van Cittert-Zernike Schell propagation. Simulated measurements are generated over a controlled range of effective source spatial coherence lengths and reconstructed using either a partially coherent forward model or a conventional coherent propagation model. Our results show that decreasing spatial coherence progressively degrades reconstructions under the coherent assumption, whereas incorporating partial coherence can preserve object structure and improve image quality, particularly for dense high-spatial-frequency features. Reconstructions from experimental measurements further confirm the practical need to use coherence-aware inversion under partially spatially coherent illumination. These findings establish spatial coherence as a defining component of the inverse problem in lensless imaging and provide a route to optimization of partially coherent lensless imaging systems.
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Atomic Physics
Three-dimensional three-photon Stark spectroscopy of a single Rb Rydberg atom in an ultrahigh-vacuum glass cell with eight electrodes
S. A. Spirin, E. A. Yakshina, A. K. Sologub et al. (+9 more)
Quantum computing and
quantum simulation with ultracold neutral atoms require Rydberg excitation of individual atoms in atomic arrays. Rydberg states are extremely sensitive to external electric fields, therefore precise three-dimensional control of the electric field is essential. We performed a spectroscopic study of three-
photon Rydberg excitation of a single Rb atom in an optical dipole trap in the presence of an external DC electric field. The field was generated by eight electrodes deposited on the inner surfaces of an ultrahigh-
vacuum glass
cell. The used three-
photon scheme of
laser excitation of Rydberg nP states allows the Stark shift and the splitting of the resonances to be observed simultaneously, which simplifies calibration of the electric field. In addition, in the commonly used two-
photon Rydberg excitation schemes, the light shifts can complicate accurate determination of the DC Stark shift, particularly when the external electric field is scanned across different spatial directions, and different Stark components are excited. These shifts are absent in the three-
photon excitation scheme used in our experiment. We demonstrated the ability to independently tune the electric field along all three spatial directions and to compensate for stray electric fields. The measured three-
photon spectra exhibit Stark shifts and splittings of the three-
photon resonance that are in good agreement with theoretical calculations. These results are also of interest for Rydberg electrometry.
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All authors S. A. Spirin, E. A. Yakshina, A. K. Sologub, G. Suliman, A. M. Minnigaliev, V. V. Gromyko, P.I. Betleni, D. B. Tretyakov, V. M. Entin, N. N. Bezuglov, I. I. Beterov, I. I. Ryabtsev
Strongly Correlated Electrons
Machine-learning test of the single-ion model for $dd$ excitations in cuprates
Maryia Zinouyeva, Leonardo Martinelli, Riccardo Arpaia et al. (+12 more)
We investigate $dd$ excitations in Resonant Inelastic X-ray Scattering spectra of YBa$_2$Cu$_3$O$_6$ and La$_2$CuO$_4$ using the local single-ion model. The data are analyzed by conventional global fitting and by a convolutional neural network trained within the same theoretical framework. For YBa$_2$Cu$_3$O$_6$, the excited state energies obtained with the two methods coincide, leading to the $xy$, $3z^2-r^2$, $xz/yz$ sequence for increasing energy. This result validates the use of machine learning tools for the analysis of RIXS spectra dominated by $dd$ excitations. By contrast, for La$_2$CuO$_4$, the two methods do not converge to a single solution, revealing the limitations of the single-ion model in describing $dd$ excitations in cuprates and pointing to the role of additional contributions beyond a purely local picture in shaping high-energy excitations.
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All authors Maryia Zinouyeva, Leonardo Martinelli, Riccardo Arpaia, Nicholas B. Brookes, Daniele Di Castro, Kurt Kummer, Floriana Lombardi, Giacomo Merzoni, Francesco Rosa, Alessandro Tarasio, Enrico Tassi, Flora Yakhou-Harris, Ezio Puppin, Marco Moretti Sala, Giacomo Ghiringhelli
General Relativity and Quantum Cosmology
The weight of light: colliding pulses of radiation in General Relativity
Jorge Expósito Patiño, Vitor Cardoso and Hannes R. Rüter
We study the gravitational interaction of very strong pulses of electromagnetic radiation, up to and beyond gravitational collapse. We demonstrate the existence of very compact states close to the threshold of collapse, both for a single pulse, and a head-on collision of such pulses, and we measure their compactness to be above the maximum value proposed by the hoop
conjecture. For a single pulse above the threshold of collapse, a fast black hole is produced. Depending on the amount of tuning, head-on collisions can form two horizonless states, two small black holes or one big black hole. Our results show that the gravitational interaction of massless fields can lead to nontrivial final or intermediate states, while giving rise to extremely high luminosity and compactness.
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