Chemical Physics
Explainable Molecular Structure Inference from GC–MS with Diffusion Models and LLM Reranking
Changlin Liu, Tianyu Yi, Chengchun Liu et al. (+2 more)
GC–EI–MS is an important technique for analyzing volatile and semivolatile compounds in complex samples. However, conventional methods rely heavily on reference spectral library matching, limiting their ability to identify compounds absent from these libraries and to infer complete molecular structures directly from fragmentation information. Here, we present DiffGCMS, a spectrum-conditioned discrete graph
diffusion model for de novo structure elucidation from GC–EI–MS, and further develop a framework that integrates DiffGCMS with second-stage
reasoning by a large
language model (LLM). In the first stage, DiffGCMS generates candidate molecular structures from input spectra; in the second stage, the LLM uses mass spectral information to validate, repair, and rerank the candidates and provides interpretable analysis of fragment-ion peaks. This framework can generate plausible molecular structures for compounds absent from reference spectral libraries and provide traceable evidence supporting its decisions. On a test set comprising 13,696 spectra from NIST 20, the generative model achieved Acc@1 and Acc@10 of 6.01% and 15.76%, respectively. On the test subset containing molecules with no more than 10 heavy atoms, LLM-assisted molecular graph repair and reranking increased Acc@1 from 21.28% to 21.95%, Acc@10 from 46.91% to 47.99%, and candidate validity from 91.04% to 100%. These results demonstrate that spectrum-aware postprocessing can correct errors produced by the generative model while providing auditable and traceable explanations for the final ranking.
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All authors Changlin Liu, Tianyu Yi, Chengchun Liu, Boxuan Zhao, Fanyang Mo
Quantum Physics
Analytical controls for dispersive multi-qubit interactions in mediator-coupled quantum registers
Bora Baran, Tommaso Calarco, James O'Sullivan et al. (+2 more)
Fast control of long-lived
quantum registers often relies on an auxiliary degree of freedom, a mediator, but real mediator excitation can introduce decoherence, leakage, or loss when the mediator is not the coherence-optimized component. We introduce dispersive interaction via analytical linear inversion (DIAL), an analytical control construction for excitation-suppressed interaction engineering in mediator-coupled
quantum registers. In the dispersive regime, we show that off-resonant driving of an effective two-level mediator transition yields a diagonal
Hamiltonian whose Pauli-\(Z\) interaction rates depend linearly on the drive intensities through a transfer
matrix determined by the register-resolved transition spectrum. This establishes a direct linear map from experimentally accessible controls to induced multi-
qubit interactions, enabling control design without iterative propagation of the full driven dynamics. We turn this structure into the target-aware DIAL
algorithm, which selects favorable off-resonant tones and determines their drive intensities for a prescribed target interaction. We
benchmark the resulting controls across 100 register realizations for each register size \(n=2,3,4,5\), targeting the highest-order interaction \(Z_1\cdots Z_n\) with an interaction phase of magnitude \(\pi/4\), which generates an \(n\)-
qubit GHZ state up to local equivalence. Propagation under the full driven mediator-register dynamics yields typical gate fidelities above \(0.997\), while the maximum transient mediator excitation remains near \(1\%\) on average, far below what is typically possible with resonant Rabi drives. The manuscript is accompanied by an open-source Python package implementing the target-aware DIAL
algorithm and the associated numerical validation workflow.
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All authors Bora Baran, Tommaso Calarco, James O'Sullivan, Matthias M. Müller, Felix Motzoi
Mathematical Physics
The monatomic limit of polyatomic gases as concentration of the internal-energy measure
Tommaso Ruggeri
In Rational Extended Thermodynamics, the monatomic limit of polyatomic gases is often singular. For the internal-state density $\phi(I)=I^a$, with $a=(D-5)/2$, we prove that the normalized
equilibrium distribution of the molecular internal energy $I$ concentrates at $I=0$ as $D\to3$, providing a rigorous justification of the Dirac prescription and its first-order correction. In classical ET14, the internal-mode energy differs from
equilibrium by $-3\Pi/2$; positivity yields $-p<\Pi<(D-3)p/3$, while the exact
entropy develops a boundary corner at $\Pi=0$. Negative dynamic pressures remain admissible, but fixed negative values do not approach the monatomic state with the prescribed total energy. This explains the need for compatible initial data. In the relativistic case, the internal energy is conditionally gamma distributed at fixed momentum; the constitutive integrals follow directly, and we derive an exact energy identity and the first correction to the Synge energy.
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Optics
Metasurface-on-Lithium-Niobate Architecture for Spin-decoupled Second Harmonic Wavefront Shaping
Yiwen Liu, Chao Meng, Sergey I. Bozhevolnyi et al. (+1 more)
Nonlinear metasurfaces (NMSs) enable simultaneous generation and manipulation of harmonic light with ultrathin nanophotonic platforms. However, conventional NMSs typically adopt a monolithic single-layer configuration in which frequency conversion, polarization selection and wavefront engineering are intertwined to simultaneously occur within the same nonlinear meta-atoms, making these functionalities intrinsically interdependent and imposing constraints on material choice, structural
symmetry, and the available
geometric parameter space. Here, we propose and experimentally demonstrate a metasurface-on-lithium-niobate architecture that physically separates harmonic light generation and wavefront manipulation. In this platform, a z-cut thin-film LN layer serves as a
spin-selective second-harmonic source through its intrinsic bulk second-order nonlinearity, while an overlaid dielectric metasurface subsequently and independently molds wavefronts of generated harmonic fields. The two-step process, by virtue of harmonic generation being decoupled from wavefront shaping, removes
symmetry constraints associated with conventional nonlinear meta-atoms and enables the direct transfer of well-established linear metasurface design strategies to harmonic wavefront engineering. As proof-of-concept demonstrations, we realize
spin-decoupled second-harmonic beam steering and
spin-multiplexed holography, achieving high-contrast routing of harmonic signals with orthogonal
spin states into distinct diffraction channels and high-fidelity reconstruction of independent
holographic images. By redirecting the harmonic wavefront control from the meta-atom engineering to the modular system-level design, our approach establishes a versatile route toward integrated nonlinear meta-optics and provides a scalable platform for advanced optical functionalities.
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All authors Yiwen Liu, Chao Meng, Sergey I. Bozhevolnyi, Fei Ding
Geophysics
Spatially Organized Hillslope Weakening Localizes Retrogressive Thaw Slumps across the Tibetan Plateau
Yuting Yang, Gang Mei, Nengxiong Xu et al. (+2 more)
Long-term permafrost warming on the Tibetan Plateau is continuously and broadly reshaping cold-region landscapes, and has produced numerous localized and clustered retrogressive thaw slumps (RTSs). However, the question why RTSs are highly localized and clustered under the widespread permafrost warming remains incompletely understood. To understand and explain the RTS localization and clustering, we propose the Hillslope Weakening Field (HWF), which represents the spatial distribution of relative hillslope weakening states jointly formed by multiple environmental conditions, including thermal conditions, moisture and soil properties, topographic setting, permafrost and ground-ice conditions, and land-surface cover. We examined the correspondence between the HWF and RTS spatial selectivity across seven study regions on the Tibetan Plateau. Positive HWF-RTS correspondence was observed in six of the seven regions, with consistently strong relationships in five. In these five regions, RTSs preferentially occurred on more strongly weakened hillslopes, with occurrence rates 3.35-5.09 times the regional background rate within the 10% most strongly weakened slope units. Moreover, high-weakening hillslopes were not spatially isolated but correlated and connected across the landscape. RTS-bearing slope units and their surrounding hillslopes showed higher weakening levels than RTS-unrecorded slope units and their surroundings, and the weakening contrast declined with distance. These results suggest that RTSs preferentially occur on more strongly weakened hillslopes and cluster where high-weakening states are spatially continuous and connected. Our findings show how spatial differences in hillslope weakening states can help explain why geomorphic responses to widespread permafrost warming are highly heterogeneous across permafrost landscapes.
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All authors Yuting Yang, Gang Mei, Nengxiong Xu, Yongshuang Zhang, Jianbing Peng
High Energy Astrophysical Phenomena
The 2015-2017 Large EVPA Rotation in OJ 287: Dominant Propagating Component in a Helical Magnetic Field with Time-Dependent Viewing Geometry
Wanchaloem Khwammai, Minchul Kam, Motoki Kino et al. (+11 more)
We present high-cadence, multi-frequency monitoring of the blazar OJ 287 using KVN (22–129 GHz), ALMA (91.5–343.5 GHz), and Metsähovi (37 GHz), covering 2012–2023, together with published optical polarimetry. Within this decade-long
dataset, an exceptionally large and smooth EVPA rotation is observed only during 2015–2017. The millimeter-band EVPA rotates by more than $\sim$300 deg over $\sim$1.5 yr, with a comparably large and more rapidly evolving rotation observed at optical wavelengths, while remaining comparatively stable at other epochs. The rotation coincides with a sequence of strong
radio flares from 37 to 343 GHz whose peak amplitudes increase toward 2017 March, when the rotation ends. Modeling the ALMA 91.5 GHz light curve yields variability Doppler factors of $\delta_{\rm var} \sim 8$–$11$ during the EVPA-rotation interval, with no systematic increase across the
flare sequence. The absence of a monotonic change in $\delta_{\rm var}$ indicates that progressively enhanced relativistic beaming is unlikely to be the primary driver of the rising
flare envelope. The confinement of the large EVPA rotation to this interval, together with the nearly constant $\delta_{\rm var}$, indicates that the 2015–2017 event occurred when a single newly ejected disturbance temporarily dominated the polarized emission while propagating through structured inner-jet regions threaded by a helical
magnetic field under modest jet-direction changes. Large EVPA rotations therefore arise intermittently as the jet orientation evolves, and are realized only when emission dominance and viewing geometry align favorably.
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All authors Wanchaloem Khwammai, Minchul Kam, Motoki Kino, Sascha Trippe, Hiroshi Nagai, Seiji Kameno, Ilje Cho, Ioannis Myserlis, Jeffrey A. Hodgson, Do-Young Byun, Sang-Sung Lee, Taehyun Jung, Anne Lahteenmaki, Merja Tornikoski
Astrophysics of Galaxies
No Convincing Evidence for Tidal Binary Clusters in the Galaxy
Juan Casado and Zahra Al
Context. The existence of
tidal binary clusters (TBCs) in the Milky Way has been repeatedly suggested using
Gaia DR3 astrometry and recent catalogs of binary clusters and groups. However, the dynamical feasibility of forming truly bound binary clusters through
tidal capture remains uncertain. Aims. We perform a systematic reassessment of twenty
star clusters, currently claimed as members of TBCs from the catalog of binary and grouped clusters of Liu et al. (2025) to ascertain their classification. Methods. For each candidate pair, we use
Gaia DR3 astrometry and photometry to perform a simultaneous and self-consistent opti mization of age, distance modulus, reddening, and
metallicity. Results. Our analysis shows that all studied TBCs fail in the required physical condition that ages are compatible with independent formation. After applying strict evolutionary criteria, these systems are more naturally explained as co-eval members of
primordial cluster pairs or groups rather than products of
tidal capture. Conclusions. We conclude that genuine
tidal binary clusters, if present in the Milky Way, must be extremely rare. This work un derscores the importance of robust age determinations and physically motivated selection criteria in future searches for dynamically assembled cluster pairs.
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Quantum Physics
Direct estimation of $g^{(2)}(0)$ from click statistics of a multiplexed detector
Jaromír Fiurášek
We present and theoretically analyze a method for direct estimation of the second-order correlation function $g^{(2)}(0)$ from the click statistics of a multiplexed detector composed of M binary on-off detection channels. The method uses linear
estimators of the first and second moments of the
photon-number operator and can provide accurate results even for optical fields with substantial mean
photon numbers. For a fixed number of channels, the detection range can be extended by introducing additional losses before the detector. We demonstrate the performance of the method for coherent, thermal, amplitude-squeezed, and
photon-added coherent states. We also derive a nonclassicality criterion based on the estimated correlation function and show how the method can be adapted to unbalanced detectors. Our work establishes direct estimation of $g^{(2)}(0)$ as a simple and versatile method for quantitatively characterizing
quantum light using multiplexed click detectors.
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Lattice Field Theory
Critical coupling and $\Delta\langle\phi^2\rangle$ in three-dimensional $\phi^4$ theory
Stephan Durr and Tolga S. H. Kiel
We consider the $\phi^4$ theory with $\phi(x)\in\mathbb{R}$ in three Euclidean dimensions. For a variety of self-couplings $\hat{\lambda}$, the critical (bare) parameter $\hat{\mu}_{0\mathrm{c}}^2(\hat{\lambda})$ is determined where the
lattice-regulated system changes from the symmetric phase to the broken phase. Next, we send the box volume to infinity and switch to a universal scheme; this yields $\hat{\mu}_\mathrm{c}^2(\hat{\lambda})$ for each simulated $\hat{\lambda}$. Finally, a continuum extrapolation gives $f_\mathrm{c}=\lim_{\hat{\lambda}\to0} \hat{\lambda}^2/\hat{\mu}_\mathrm{c}^2(\hat{\lambda})$, and we find $f_\mathrm{c} = 18.808(64)_{\mathrm{stat}}(45)_{\mathrm{sys}} = 18.808(78)_{\mathrm{tot}}$. In addition, $\Delta\langle\phi^2\rangle_\mathrm{c}/\lambda = -0.00303(12)_{\mathrm{stat}}(12)_{\mathrm{sys}} = -0.00303(17)_{\mathrm{tot}}$ is determined in the combined continuum and infinite-volume limit.
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Quantum Physics
Spatiotemporal quantum advantages for rare-event sampling
Akshat Gupta, Jianjun Chen, Chengran Yang et al. (+4 more)
In a world fraught with uncertainty, it behooves us to consider the most disastrous possible outcomes, in order that we can best mitigate against them. Often these are extreme risk events – of high consequence, but low probability. Yet, the rarity of such events limits our ability to study them; there is a paucity of past occurrences to draw upon, and sampling such rare events from models is typically costly in time. Here, we introduce an approach for rare-event sampling based on
quantum stochastic models. This integrates the
memory advantages of
quantum stochastic modelling – and its associated efficient means of preparing
quantum sample states – with the `speed-ups' of
quantum amplitude amplification, to yield simultaneous reductions in spatial and temporal computational complexity compared to classical Monte Carlo-based approaches.
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All authors Akshat Gupta, Jianjun Chen, Chengran Yang, Mile Gu, Caterina Doglioni, Jayne Thompson, Thomas J. Elliott
High Energy Physics (Experiment)
Entanglement-sensitive observables in $e^+e^- \to \tau^+\tau^-$ at STCF: a detector-level feasibility study
Chentao Bao, Xi Tao, Hai Chen et al. (+3 more)
Quantum entanglement in $\tau^+\tau^-$ production provides a direct probe of non-classical
spin correlations in a relativistic
quantum system, with the $\tau$ decay products serving as
spin analyzers. We investigate the detector-level feasibility of such measurements in $e^+e^-\to\tau^+\tau^-$ at the Super Tau-Charm Facility (STCF) at $\sqrt{s}=7$ GeV, using the $\rho\rho$ and $\pi\rho$ decay channels. Signal and dominant background processes are simulated with the full STCF detector and reconstruction framework. Dedicated reconstruction and event-selection procedures yield overall signal efficiencies of approximately $4.5\%$ and $4.8\%$, with corresponding purities of about $87.6\%$ and $93.2\%$ for the $\rho\rho$ and $\pi\rho$ channels, respectively. From the reconstructed decay kinematics, the $\tau^+\tau^-$
spin-density
matrix is inferred and the concurrence $C[\rho]$ together with the Bell-sensitive quantity $m_{12}[C]$ are evaluated in a selected fiducial region. For the
benchmark requirement $|\cos\theta|<0.2$ and an integrated luminosity of $1~\mathrm{ab}^{-1}$, the projected relative precision on $C[\rho]$ is about $2.2\%$ in both channels, while that on $m_{12}[C]$ is approximately $1.4\%$ for $\rho\rho$ and $1.5\%$ for $\pi\rho$, including statistical and detector-resolution uncertainties. The reconstructed $m_{12}[C]$ shows a larger separation from its reference threshold in the $\rho\rho$ channel, making this
topology particularly sensitive to Bell-type
spin correlations. These results demonstrate the detector-level feasibility of probing
quantum entanglement and non-classical
spin correlations in hadronic $\tau$ decays at STCF.
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All authors Chentao Bao, Xi Tao, Hai Chen, Lailin Xu, Xiaorong Zhou, Mingyi Liu
Nuclear Theory
Energy-Resolved Spin and Parity Distributions of Fission Fragments
Petar Marević, Nicolas Schunck, Antonio Bjelčić et al. (+1 more)
Fission fragments are born rotating rapidly, but the
evolution of this
spin with excitation energy and its impact on fission observables remain largely unknown. Combining state-of-the-art microscopic and statistical reaction theory, we simulate the full fission process - from the initial state, through scission, to fragment decay - and report the first microscopic, energy-resolved
spin and parity distributions of the fragments produced in $^{239}$Pu(n,f). From thermal energy to $E_n = 10$ MeV, the
spin of individual fragments evolves non-monotonically, tracking their deformation. The parity content, strongly non-statistical at thermal energy, remains correlated with
spin throughout this range. For the first time, we quantify the impact of microscopic
spin-parity distributions on
prompt photon multiplicities, demonstrating the predictive potential of parameter-free microscopic inputs.
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All authors Petar Marević, Nicolas Schunck, Antonio Bjelčić, Guillaume Scamps
Optics
Nonreciprocal Coupling Induced Non-Hermitian Entanglement in Optomechanical Systems
W. Y. Hu, H. Yi, H. N. Liu et al. (+4 more)
Quantum entanglement, one of the most intrinsic properties of
quantum mechanics, corresponds to a key resource for
quantum information. Exceptional points (EPs) are special phase transition points in non-Hermitian systems. Nonreciprocity achieves one-way motion by breaking reciprocal
symmetries. However, the connections among
quantum entanglement, EPs, and nonreciprocity remain unexplored in non-Hermitian systems. In this paper, we investigate the manipulation of optomechanical
entanglement by non-Hermitian coupling between two counter-propagating optical modes based on a whispering-gallery-mode (WGM) resonator coupled with two Rayleigh scatterers. EPs can periodically appear by controlling the relative angle between two nanoparticles. Moreover, the spinning resonator can induce opposite frequency shifts in two counter-propagating optical modes. The logarithmic negativity of
entanglement reaches the maximum at EPs, leading to significant enhancement of optomechanical
entanglement. In contrast, the
entanglement is suppressed at non-EPs but can be recovered by the Sagnac-Fizeau shift. Specially, by driving the resonator at EPs while spinning it at the optimal rotation speed, we achieve switching between classical and
quantum nonreciprocity.
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All authors W. Y. Hu, H. Yi, H. N. Liu, S. Y. Ge, Cheng Shang, Yan-Hui Zhou, H. Z. Shen
Superconductivity
Binary kagome superconducting candidates hosting topological electronic states
Xin-Wei Yi, Jing-Yang You and Gang Su
Topological superconductivity has attracted broad interest because of its connection to Majorana
fermions and
quantum computation. Kagome materials provide a natural setting in which interesting electronic structures, topological surface states, and superconductivity may occur in nearby energy windows. Here we carry out a systematic first-principles search for binary kagome superconducting candidates with topological electronic states across several structural families $A_mB_n$ ($m$:$n$=3:1; 3:2; 1:1). The screening combines formation-energy and
phonon-stability filtering,
magnetic-ground-state searches, electron-
phonon-coupling calculations, and topological electronic-structure analysis. We identify 286 nonmagnetic dynamically stable candidates for electron-
phonon-coupling analysis, among which 84 have estimated transition temperatures above 3 K and seven exceed the $\sim 9$ K reference scale of existing ambient-pressure kagome
superconductors. In addition, several systems are predicted to host abundant topological surface states near the
Fermi level. NbBi is identified as a $\mathbb{Z}_2$ topological metal with clear Dirac-cone topological surface states and a kagome-derived flat band near $E_F$. Ti$_3$Si, with the largest estimated $T_\text{c}=15.2$ K in this
dataset, shows nodal-line-derived drumhead surface states and selected nodes that survive
spin-orbit coupling near $E_F$. Combining superconductivity with nontrivial topological electronic structures, the binary kagome compounds predicted here represent compact and chemically tunable candidate platforms for topological superconductivity and for exploring kagome-related
quantum phenomena.
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Data Analysis and Statistics · Cross-listed from cs.LG
Temporal Geometry of Deep Networks: Hyperbolic Representations of Training Dynamics for Intrinsic Explainability
Ambarish Moharil
Intrinsic explainability remains a challenging problem, particularly in contexts where multilayer perceptrons (MLPs) require dynamic re-training within an optimization environment. This paper investigates how MLPs and their training dynamics can be represented and studied in non-Euclidean spaces; our representation features the Poincaré model of
hyperbolic geometry. We aim to capture the
geometric evolution of their weighted
topology and self-organization over time. Instead of restricting the analysis to single checkpoints—as per established measure-based explainability methods—we construct temporal parameter graphs, i.e., snapshots over time $T$ steps of the optimization/training process for MLPs. This reflects the view that neural networks encode information not only in their weights but also in the trajectory traced during training. Drawing on the idea that many complex networks admit
embeddings in hidden metric spaces where distances correspond to connection likelihood, we present a
geometric and temporal graph-based metalearning framework for obtaining dynamic
hyperbolic representations of the underlying neural parameter graphs. Our model embeds temporal parameter graphs in the Poincaré model ball, and learns from them while maintaining equivariance to within-snapshot
neuron permutations and invariance to permutations of past snapshots. In doing so, the approach preserves functional equivalence over time and recovers the latent evolving geometry of the network. Experiments on regression and classification tasks with trained MLPs show strong meta-network performance, accompanied by
hyperbolic temporal representations. This reveals how the network structure emerges over time under specific training environments, thus providing insights into the network's self-organization.
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Materials Science
Ab initio design of enhanced and sign-reversible spin Hall and spin Nernst conductivity in skutterudite materials
Saikat Debnath, Babu Baijnath Prasad and Shishir Kumar Pandey
The search for novel materials capable of robust
spin-current generation remains an active area of research. Here, we investigate the intrinsic
spin Hall and
spin Nernst effects in Co- and Rh-based skutterudites and explore their enhancement through heavy-metal substitution and site-selective doping. Using first-principles calculations and Wannier-based tight-binding models, we analyze the
spin Berry
curvature and
spin-transport responses of pristine MX$_3$, where M = Co, Rh and X = As, Sb, as well as chemically modified systems. Despite sizable momentum-resolved
spin Berry
curvature, the pristine compounds exhibit relatively small net
spin Hall responses due to substantial cancellation across the Brillouin zone. Isoelectronic Ir and Bi substitution at 8$c$ Wycoff M site produces little enhancement near the E$_F$, whereas non-isoelectronic Pt substitution yields a relatively better response. Most interestingly, the incorporation of Pt at the interstitial $2a$ Wycoff site of RhAs$_3$ nearly doubles the
spin Hall conductivity to $\sim400~(\hbar/e)(\Omega,\mathrm{cm})^{-1}$ near the E$_F$ when compared to Pt substitution at 8$c$ position. At 300 K, the same interstitially filled system exhibits a
spin Nernst conductivity of $\sim1.46~(\hbar/e),\mathrm{A,m^{-1}K^{-1}}$ at the E$_F$, nearly an order of magnitude larger than that of $M$-site Pt substitution. The enhanced responses arise from Pt $5d$ states, strong
spin-orbit coupling, and avoided crossings that generate pronounced
spin-Berry-
curvature hot spots. These results demonstrate that site-selective chemical engineering can effectively overcome momentum-space cancellation resulting in enhanced
spin Hall and
spin Nernst responses in skutterudites. Our results provide a possible route towards robust
spin-current generation in this class of materials.
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Quantum Physics
Two-qutrit Werner state is always local
Paweł Caban and Muhammad Mohsin
In our paper, we show that a two-qutrit Werner state admits a local hidden-variable model for all values of the parameter in a scenario involving two projective measurements per site, with three outcomes per measurement. To this end, we derive a simple sufficient condition under which a two-qutrit state satisfies the Collins-Gisin-Linden-Massar-Popescu inequality for arbitrary choices of Alice's and Bob's observables, and show that the Werner state always satisfies this condition. Next, we use the fact that any two-qutrit state satisfying the Collins-Gisin-Linden-Massar-Popescu inequality for arbitrary choices of Alice's and Bob's observables admits a local hidden variable model.
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High Energy Astrophysical Phenomena
Comparing the size evolution of GRB 221009A with afterglow models
S. Giarratana, O. S. Salafia, B. Marcote et al. (+10 more)
We present very long baseline interferometry (VLBI) observations of GRB221009A obtained with the global-VLBI network at 5 GHz between 231 and 750 days after the burst. The quality of our observations allowed us to measure the sub-milliarcsecond full-width at half maximum of the source surface brightness distribution with a one-sigma equivalent error of 13% and 30% at 231 and 391 days post-burst, respectively. By fitting the temporal
evolution of these new size measurements alongside those previously published in the literature at 5 and 8 GHz with a single power law $\propto t^a$, we find a slope of $a = 0.52^{+0.14}_{-0.12}$. Using the public code VegasAfterglow, we model the 5 GHz size
evolution considering the afterglow emission of the forward shock produced by a jet decelerating in either a homogeneous interstellar medium (ISM) or into a surrounding medium with a wind-like density profile. The model constrains the collimation-corrected Sedov ratio, that is, the ratio of the jet kinetic energy $E_\mathrm{jet}$ to the density of the surrounding medium ($n$ in the ISM scenario, or $A_\star$ in the wind scenario), in the range $\log[(E_\mathrm{jet}/n)\,\mathrm{erg}^{-1}\,\mathrm{cm}^{-3}] = 54.2^{+0.4}_{-0.5}$ for the ISM scenario and $\log[(E_\mathrm{jet}/A_\star)\,\mathrm{erg}^{-1}] = 51.7^{+0.4}_{-0.2}$ for the wind scenario. Among the works in the literature that fit the light curves and spectra of GRB221009A based on the standard afterglow model, and which can be reproduced with VegasAfterglow, none has best-fitting parameters that are compatible with these constraints within $2\sigma$. Moreover, we show that their predicted size
evolution is not compatible with the observed one. Our results highlight the importance of size measurements of GRB afterglows as an independent probe of their dynamics, structure, and emission mechanisms.
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All authors S. Giarratana, O. S. Salafia, B. Marcote, Z. Paragi, M. Giroletti, G. Ghirlanda, L. Nava, A. van der Horst, J. K. Leung, L. Rhodes, P. G. Edwards, M. Pérez-Torres, J. Yang
Atomic Physics
Interaction-induced period shift of the Kohn oscillation in a parity-time-symmetric harmonic trap
Gaoqing Meng and Mingshu Zhao
The center of mass of a Bose–Einstein condensate in a harmonic trap oscillates at the trap frequency independently of the interactions. Without interactions a parity-time-symmetric gain-loss gradient leaves this frequency unchanged, and a cloud of the ground-state width is translated rigidly while the atom number is periodically modulated. With interactions the protection is lost, because the gain and the loss change the number of atoms; the modulated atom number drives the width of the cloud, and the width acts back on the center of mass. At small gain the period grows quadratically with the gain strength, with a coefficient that in the Thomas–
Fermi regime is set by the size of the cloud alone. The family of periodic orbits continued from the Kohn oscillation can be followed up to a critical gain, where it comes into resonance with highly excited states of the trap, and over the computed families this critical gain decreases with the amplitude of the oscillation and with the size of the cloud. A five-variable moment model reproduces the period and the width of the cloud along the orbits nearly up to the critical gain.
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Quantum Physics
Einstein–Langevin source correlations in closed non-relativistic systems
Peng Xu and Li-E Qiang
Stochastic semiclassical
gravity represents stress–energy fluctuations through the Einstein–Langevin noise kernel. We examine its Newtonian projection for specified closed, particle-number-conserving non-relativistic sources and distinguish the source covariance from a reduced matter channel. The connected one-particle covariance is state dependent and differs from the universal potential-noise law postulated in the Diósi–Penrose model. To relate the source spectrum to dephasing, we define a separate static probe subject to a prescribed Gaussian noise law. For a finite-variance source operator in an isolated non-degenerate eigenstate, the full connected spectral measure has a gap around zero. The probe dephasing exponent is then bounded and its long-time slope vanishes. Stationary doublets can instead carry static or low-frequency spectral lines, while a specified freely spreading Gaussian source gives a finite limiting exponent. Continuum results depend on preparation, normalisation, infrared regularisation and the order of limits. We also compare coherent and incoherent many-body preparations and establish no-signalling for fixed classical-noise channels. These results identify the spatial, temporal and dynamical assumptions needed to relate source fluctuations to a matter-decoherence model. They do not exclude Markovian limits in other number-conserving non-relativistic preparations.
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Superconductivity
Sideband fingerprint of the Leggett mode in terahertz two-dimensional coherent spectroscopy of multiband superconductors
Silvia Neri, Ryo Shimano, Dirk Manske et al. (+1 more)
Collective modes of the superconducting condensate encode fundamental information on the pairing interaction, yet their direct detection remains experimentally challenging. In multiband
superconductors, the Leggett mode, i.e., a coherent oscillation of the relative phase between two condensates, is Raman-active and couples to light only nonlinearly in ordinary situations. Here we show theoretically that terahertz two-dimensional coherent spectroscopy (2DCS) provides a direct fingerprint of the Leggett mode (with frequency $\omega_L$) through sideband emission at the detection frequency $\omega_t = \omega_L\pm\Omega$ ($\Omega$ is the central frequency of the incident pulses) in the nonlinear 2D spectrum. The key insight is that the finite duration of the THz pulses is the physical mechanism that makes the mode accessible: the broad spectral content of a finite pulse provides the nonlinear frequency combinations needed to resonantly excite the mode at {\omega}L without any prior knowledge of its value or tuning of external parameters. We demonstrate robustness of this signature against temperature and quasiparticle relaxation, and show that sweeping $\Omega$ allows unambiguous identification of the Leggett mode.
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All authors Silvia Neri, Ryo Shimano, Dirk Manske, Naoto Tsuji
Materials Science
Optimizing the magnetic hyperthermia efficiency from the structural dependence of dipolar interactions in magnetic nanoparticles assemblies
Abdelhamid Morjane, François Vernay and Vincent Russier
Magnetic hyperthermia, based on the conversion of the
magnetic energy of
magnetic nanoparticles (MNP) under an alternating external field into heat, presents a great interest, especially because of important applications such as promising advances in cancer treatment. The underlying frequency-dependent response of the MNP assembly under the excitation field depends on the first hand on the individual properties of the MNP such as their size, shape and magnetocrystalline anisotropy and on the other hand on collective properties generated by interactions between MNP. Due to the long-range dipolar component of the latter, the first consequence is the so-called demagnetizing effects, making the response dependent on the external sample shape. This is the reason for studying the properties of MNP in assemblies of anisotropic external shapes such as films, chains, or elongated aggregates. In the present work, using a recently developed Time Quantified Monte Carlo (TQMC) framework for dynamic simulations, we focus more precisely on the importance of the local structure in such anisotropic aggregates to the dipolar interactions contribution of the response to the external field. Here the local structure is understood as both the location of the nanoparticles and the distribution of their easy axes. We show that the latter must be determined in a self-consistent way starting with the
equilibrium structure of a ferrofluid modeled as the dipolar hard sphere fluid.
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High Energy Astrophysical Phenomena
XMM-Newton Resolves Parsec-scale X-ray Jets in the PeVatron Microquasar V4641 Sgr
Naomi Tsuji, Caterina Tresoldi, Kaya Mori et al. (+34 more)
The microquasar V4641 Sagittarii (V4641 Sgr) has recently been established as one of the most powerful
Galactic PeV
cosmic-ray accelerators (PeVatrons) through the detection of degree-scale gamma-ray emission to 0.8 PeV. Using XMM-Newton, we performed an X-ray survey of its gamma-ray-emitting regions during the quiescent phase. We discovered extended X-ray emission to the north and south of V4641 Sgr, aligned with the
radio-jet axis, revealing X-ray jet structures extending over several tens of parsecs for the first time. The northern and southern
knot-like features, dubbed n1 and s1, are located approximately 20 pc from the central binary and spatially coincident with the gamma-ray emission. The X-ray emission from each
knot, characterized by a
photon index of $\Gamma_X = 1.9 \pm 0.1_{\rm stat} \pm 0.5_{\rm syst}$ and an energy flux of $\sim$(2–4)$\times10^{-13}$~erg~cm$^{-2}$~s$^{-1}$ in the 2–10 keV band, is likely non-thermal in origin, indicating synchrotron radiation from accelerated electrons. The morphological coincidence between the X-ray and gamma-ray emission favors a leptonic scenario for the gamma rays, although the X-ray emission is more compact than the gamma-ray-emitting region and the hadronic scenario cannot be excluded. Through X-ray to gamma-ray modeling, we obtain a weak
magnetic field strength of 3–5~$\mu$G. We propose that the newly detected X-ray
knots represent particle-acceleration sites, such as jet termination or (re-)collimation regions powered by V4641 Sgr, or downstream structures analogous to the
knots of the outer jets in SS~433/W50. This discovery suggests that extended X-ray emission along jets would be a key signature, yet previously overlooked, in PeVatron microquasars.
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All authors Naomi Tsuji, Caterina Tresoldi, Kaya Mori, Hiromasa Suzuki, Matthew Lundy, Dmitry Khangulyan, Samar Safi-Harb, Laura Olivera-Nieto, Felix Aharonian, Shotaro Abe, Zhen Cao, Sabrina Casanova, Maria Chernyakova, Yi-Heng Chi, Stephane Corbel, E. de la Fuente, Hua Feng, Tatsuki Fujiwara, Noa Grollimund, Dezhi Huang, Yoshiyuki Inoue, Ryohei Kanazashi, Shigeo S. Kimura, Marianne Lemoine-Goumard, Jonathan Mackey, Alessio Marino, Samaresh Mondal, Kai Morita, Maxime Parra, Gabriele Ponti, Brian Reville, Megumi Shidatsu, Shunya Takekawa, Michelle Tsirou, Xiaojie Wang, Heshou Zhang, Ping Zhou
High Energy Physics (Theory)
Ultraviolet dissipation and defect OPE in bottom-up holographic interfaces
Mianqi Wang
We study the radial ultraviolet dissipation quantity $c_{UV}$ defined in arXiv:2601.16888v3 and defect OPE data in bottom-up
holographic interfaces. We relate $c_{UV}$ along with the defect primary spectrum and BOPE coefficients in the large defect dimension limit to the optical length $\rho$ in the
holographic bulk. In addition, we prove a new
holographic bound for conformal interfaces relating
entanglement entropy, energy transmission and UV dissipation: \[ c_{LR}\geq \frac{2c_{\mathrm{eff}}}{2+\pi(c/c_{\mathrm{UV}}-1)}. \] This compliments the upper bound of $c_{LR}$ by $c_\text{eff}$ proved in arXiv:2404.01515.
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High Energy Astrophysical Phenomena
Candidate X-ray Counterparts of Ultra-High-Energy Emission of the Galactic Microquasar V4641 Sgr Revealed by Einstein Probe
Yi-Heng Chi, Shao-Qiang Xi, Ping Zhou et al. (+20 more)
Microquasars have emerged as promising PeVatron candidates capable of accelerating particles to PeV energies, with recent observations revealing ultra-high-energy (UHE) $\gamma$-ray emission from extended structures associated with these systems. Multi-wavelength studies of such extended structures are crucial for understanding the acceleration, transport, and radiation processes of UHE
cosmic rays (CRs), yet observational evidence remains limited. Here, we report the discovery of diffuse X-ray structures spatially coincident with the TeV $\gamma$-ray emission regions to the north and south of the microquasar V4641 Sgr, using the Follow-up X-ray
Telescope (FXT) onboard the Einstein Probe. We identify X-ray structures located $\sim20$-$40$ pc from V4641 Sgr, extending over several arcminutes. These structures exhibit X-ray fluxes of $\sim1$-$3\times10^{-13}$ erg s$^{-1}$ cm$^{-2}$ and
photon indices of $\Gamma\sim2$-3 in 0.5-8 keV per individual
knot. Under the one-zone leptonic interpretation, the weak X-ray emission implies a
magnetic field of order $1-2 \mu$G. Stronger fields remain possible if only part of the TeV-PeV emission is produced by inverse Compton scattering, with the remaining emission arising from hadronic interactions. The EP-FXT observations support the presence of relativistic electrons on tens-of-parsec scales, while the origin of the UHE $\gamma$-ray emission remains open.
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All authors Yi-Heng Chi, Shao-Qiang Xi, Ping Zhou, Hua Feng, Ruo-Yu Liu, Songzhan Chen, Naomi Tsuji, Caterina Tresoldi, Gabriele Ponti, Zhen Cao, Yong Chen, Shumei Jia, Chi-Chuan Jin, Chengkui Li, Yuan Liu, Matthew Lundy, Kaya Mori, Haiwu Pan, Lian Tao, Junfeng Wang, Weimin Yuan, Juan Zhang, Haisheng Zhao
Plasma Physics
Numerical and diagnostic extensions to the gyrokinetic $\delta f$ code stella
Sven Stroteich, Georgia Acton, Michael Barnes et al. (+2 more)
Understanding
turbulence in magnetised
plasmas requires robust numerical tools capable of capturing complex free-energy transfer processes across scales. We demonstrate the utility of free energy as a diagnostic for both physical
turbulence characteristics and numerical stability in gyrokinetic simulations with the stella code. Applied to the W7-X high-mirror configuration, free-energy diagnostics reveal characteristic power-law behaviour in the turbulent cascade, act as sensitive indicators of numerical instabilities undetected by conventional diagnostics, and expose localised structures in real space not apparent in the electrostatic potential alone. To support these analyses, we present a systematic comparison of explicit time-integration schemes, showing that the optimal choice depends critically on the regime: SSP22 achieves the lowest computational cost in linear ITG simulations, while SSP33 is most efficient in the nonlinear saturated state, with nonlinear simulations requiring two to three orders of magnitude more computational cost than linear cases. These results establish free-energy diagnostics as a valuable tool for interpreting
plasma turbulence and provide practical guidance for scheme selection in stella simulations.
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All authors Sven Stroteich, Georgia Acton, Michael Barnes, Pavlos Xanthopoulos, Ralf Schneider
Solar and Stellar Astrophysics
T. Merle, P. F. L. Maxted, O. L. Creevey et al. (+23 more)
The ESA PLATO mission aims to detect and characterise Earth-size
exoplanets orbiting bright, late-type
stars using high-precision photometry and asteroseismology. Precise
stellar parameters of host
stars are essential for
exoplanet characterisation and model benchmarking. This work defines the PLATO
benchmark stars (PBS) catalogue, a comprehensive sample of well-characterised
stars designed to support all mission phases. We compiled data from eclipsing and spectroscopic binaries, interferometry, asteroseismology, and large spectroscopic and photometric surveys. Fundamental and atmospheric
stellar properties (mass, radius, luminosity, age, effective temperature, surface
gravity, density, and limb darkening) were assigned quality levels (B1, B2, B3) reflecting their degree of model dependence. Homogenized ancillary parameters (including
Gaia DR3 bias-corrected parallaxes,
metallicities, bolometric fluxes, extinction, rotation periods, and X-ray fluxes for M
dwarfs) are also provided. The PBS catalogue contains 1090 FGKM main-sequence and subgiant
stars, divided into three quality tiers based on model-independent (B1) parameters: gold (15
stars with B1 mass, radius, and luminosity), silver (195 with B1 mass and radius), and bronze (416 with at least one B1 property). The remaining
stars feature well-characterised model-dependent (B2) or empirical (B3) properties. About 40% of the sample lies within the PLATO fields of view (285 in LOPN1 and 143 in LOPS2). The PBS sample represents the largest catalogue of
benchmark stars assembled to date, providing a key resource for validating automated pipelines, testing evolutionary models, and cross-survey calibration. The catalogue is available online at https://astro.ulb.ac.be/pbs and will be updated regularly.
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All authors T. Merle, P. F. L. Maxted, O. L. Creevey, U. Heiter, D. B. Palakkatharappi, K. G. Hełminiak, C. C. Aguilera Gómez, M. Bazot, S. Cassisi, N. Ebrahimkutty, R. E. Giribaldi, P. Jofré, F. Kiefer, M. N. Lund, N. Miller, T. Morel, D. Mourard, N. Nardetto, J.-D. do Nascimento, Jr., T. Olander, G. N. Pawar, A. Rebassa-Mansergas, R. Raddi, B. Rojas-Ayala, J. Southworth
Quantum Physics
Resource Theory of Aquaternionicity: Every Pure State Is a Replicable Resource for Exact Simulation of Arbitrary Quantum Operations
Hayato Arai and Yasuaki Nakayama
An alchemical resource theory admits a nonfree state that can be exactly replicated by free operations and whose finitely many copies enable exact simulation of arbitrary
quantum instruments. The only known nontrivial examples, imaginarity and parity asymmetry, exhaust the
qubit case (arXiv:2609.12988) and exhibit an all-or-nothing property: any nonmaximal resource exactly simulates only free
unitaries. We introduce aquaternionicity for even-dimensional qudits $d\ge4$, based on a quaternionic structure represented by an antiunitary $\Theta$ with $\Theta^2=-I$. It is extremal in two senses: every pure state is alchemical, and alchemicality is maximally abundant under mixing. Within this framework, for any nontrivial $d$-dimensional resource theory and pure alchemical state $g$, the admissible pure-mixing set satisfies $\dim\mathcal M_g\le 2d-4,$ which aquaternionicity saturates for every pure state. Conversely, these two extremal properties characterize the quaternionic structure. Because every pure state is alchemical, the initial resource can be chosen to match the known noise structure. Moreover, when the noisy resource states remain within a common isotropic subspace, the same free processor works exactly for all of them while returning the resource unchanged. This enables recalibration-free exact simulation, including universal
quantum computation, and is realized for standard dephasing and dissipative noise, where aquaternionicity substantially outperforms imaginarity and parity asymmetry.
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Quantum Physics
Root-sparsity scaling for Hamiltonian simulation, differential equations and linear-system solvers
Dominic W. Berry, Abhishek Rawat, Sophia Simon et al. (+1 more)
We give
quantum algorithms for
Hamiltonian simulation, linear differential equations, and linear systems with square-root dependence on sparsity. For an $s$-sparse Hermitian
matrix with row and column Euclidean norms bounded by $\eta$,
evolution for time $t$ to error $\epsilon$ uses $\mathcal{O}(\sqrt{s}\tau+\sqrt{s\tau\log(1/\epsilon)}+\log(1/\epsilon))$ queries, where $\tau=\eta|t|$. The same bound holds for time-dependent
Hamiltonians with coherent time-indexed sparse access and certified time discretisation. Our construction combines an exact entrywise representation with Cayley transducers. A joint lower bound nearly matches the time, sparsity, and precision dependence, ruling out a uniformly additive bound in $\sqrt{s}\tau$ and $\log(1/\epsilon)$. For dissipative linear differential equations we obtain $\mathcal{O}(\bar g[\sqrt{s}(\tau+\sqrt{\tau})+1]\log(C\bar g/\epsilon))$ queries, where $\tau$ is the
evolution time multiplied by a norm bound, $\bar g$ bounds the ratio of combined input and source norms to the final-solution norm, and $C$ is an absolute constant. We sharpen this bound by separating
Hamiltonian and dissipative components, and treat general constant generators. Lower bounds capture joint parameter dependence for time-dependent equations and precision hardness for constant positive semidefinite dissipation. For linear systems, a Cayley walk and Chebyshev filter give $\mathcal{O}(\kappa\sqrt{s}\log(1/\epsilon))$ queries when $\|A\|\le1$ and $\|A^{-1}\|\le\kappa$, and we give an alternative proof of a matching joint lower bound. We also give gate-efficient implementations of time-independent
Hamiltonian simulation and the dissipative ODE solver, including Lipschitz time dependence, retaining the query bounds with polylogarithmic overhead in inverse precision given efficient entry decoding, arithmetic, and required source preparations.
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All authors Dominic W. Berry, Abhishek Rawat, Sophia Simon, Guang Hao Low
Optics
A Theory of Nested Cascading in Directed Logic
Ihar Babushkin, Oliver Melchert, Ayhan Demircan et al. (+1 more)
In directed logic (DL), electronically controlled optical elements serve as photonic gates. Such electro-optical elements are of mixed nature: they have two inputs–electronic and optical–but only one, optical, output. This makes cascading such gates without repeated conversion between optical and electronic representations cumbersome. This problem can be largely overcome using the nested cascading scheme proposed by Shamir and Hardy [Opt. Express, 17, 150 (2007)]. Although promising as a solution to the cascading problem, the Shamir-Hardy scheme has so far been proved or implemented only for a few simplest cases. Here, we develop a general rigorous theory of nested cascading, valid for an arbitrary number of gates. We propose a variant of the
algorithm which easily extendable to large number of gates, and rigorously prove its validity. Furthermore, we analyze how nested cascading scales with the size of the corresponding Boolean formula. We show that good (linear) scalability is guaranteed in many important cases, while the average scaling with respect to the corresponding Boolean formulas is only moderately
polynomial, with an exponent of approximately 3/2. Yet, the worst-case scaling remains exponential with respect to more general Boolean
circuits allowing sharing and reuse of intermediate results.
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All authors Ihar Babushkin, Oliver Melchert, Ayhan Demircan, Uwe Morgner