Mesoscale and Nanoscale Physics
Inertial Dynamics of a Skymeron
Mona Bhukta, Duc Minh Tran, Kilian Leutner et al. (+19 more)
Topological
spin textures in antiferromagnets inherit the compensated
magnetic order of the host material, resulting for skyrmions in the suppression of the skyrmion
Hall effect and enabling ultrafast dynamics that make them attractive for low-power spintronic devices. In intrinsic antiferromagnets, the two sublattices are identical, but synthetic antiferromagnets offer additional control mechanisms by enabling independent tuning of the properties of two
ferromagnetic layers. Analogous to a ferrimagnet, the total
magnetic moment can be adjusted by compensating the two-layer moments. Here, we demonstrate that tuning the effective
magnetic anisotropy difference between the two layers drives a
spin-flop transition where one layer reorients and thus stabilizes an orthogonal configuration with one layer oriented along the out-of-plane direction and the other in-plane. In this transition, an
antiferromagnetic skyrmion undergoes a homotopic reconfiguration into a complex
spin texture comprising a skyrmion coupled to an in-plane bimeron. Element-specific X-ray microscopy resolves this texture layer by layer: one hosts an out-of-plane skyrmion coupled to an in-plane bimeron in the other. We refer to this previously unexplored three-dimensional
spin texture as a skymeron. By using time-resolved pump-probe X-ray microscopy, we discover unique polarity ,dependent dynamics during current pulses: a short post-pulse inertia-like continuation of the motion, and a slower return towards the pinned initial state. Micromagnetic simulations reveal that the inertia-like propagation originates from the finite-time relaxation of reorientation of the skymeron. Our results establish layer-selective anisotropy engineering as a route to uncharted composite
spin textures with internal dynamical degrees of freedom, not possible in conventional antiferromagnets with identical sublattices.
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All authors Mona Bhukta, Duc Minh Tran, Kilian Leutner, Takaaki Dohi, Nikolai S. Kiselev, Filipp N. Rybakov, Olle Eriksson, Fabian Kammerbauer, Sebastian Wintz, Markus Weigand, Hendrik Ohldag, Maria-Andromachi Syskaki, Robin Tietgen, Edoardo Mangini, Sabrina Kerber, Thibaud Denneulin, Joseph Vimal Vas, Rafal E. Dunin-Borkowski, Bastian Pfau, Oleg A. Tretiakov, Robert Frömter, Mathias Kläui
Exactly Solvable and Integrable Systems · Cross-listed from math.RA
Rational linear forms of linearizable ordinary differential equations
Dmitry Lyakhov
Every scalar ordinary differential equation of order at least three with rational right-hand side that is locally linearizable by a point transformation admits a linear form with rational coefficients over the same coefficient field. We prove this by restricting the derived
symmetry algebra to a coordinate line and recovering a scalar differential operator from rational
symmetry-jet data. The construction uses differential elimination and linear
algebra; it does not require the
symmetry generators or a linearizing transformation to be solved for. A single integer parameter suffices to choose the line.
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Strongly Correlated Electrons
Robustness of the Verwey transition against remanent strain-induced defects in magnetite
M. A. Gala, K. J. Grzywa, K. Komędera et al. (+16 more)
The Verwey transition in magnetite is a
benchmark electronically driven phase transition that is highly sensitive to
lattice imperfections and external perturbations. Doping, deviations from oxygen stoichiometry, and irradiation-induced point defects are known to lower the Verwey transition temperature, $T_{\rm V}$. By contrast, the role of remanent strain fields and extended defect structures generated by uniaxial stress has remained largely unexplored. Here we combine dark-field x-ray microscopy (DFXM) and ac
magnetic susceptibility to determine how strain-induced defects affect the Verwey transition in stoichiometric single-crystalline magnetite after uniaxial compression and unloading. The DFXM measurements were performed on two samples compressed along the same $[011]$ direction: loading to $200~\mathrm{MPa}$ generated stable line-like defects and remanent strain fields, whereas loading beyond the fracture threshold produced denser defect networks and mechanical fracture. To test the effect of a different loading geometry, we also measured the ac susceptibility of a sample fractured by compression along $[001]$. Real-space DFXM imaging,
lattice-orientation mapping, and residual strain mapping show substantial remanent structural disorder after compression. Nevertheless, neither the transition temperature $T_{\rm V}$ nor the sharpness of the transition changes measurably in any of the compressed or fractured samples. This behavior contrasts with the strong suppression of $T_{\rm V}$ by point-like disorder. Our results show that extended line-like defects and remanent strain fields produced by plastic deformation do not measurably perturb the macroscopic electronic ordering responsible for the Verwey transition, thereby distinguishing the effects of point defects from those of extended slip-related defects in magnetite.
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All authors M. A. Gala, K. J. Grzywa, K. Komędera, R. Zalecki, A. Baczmański, Z. Kąkol, A. Pacanowska, C. M. N. Kumar, R. Rodriguez Lamas, C. Detlefs, C. Yildirim, C. Marin, J. Debray, G. Beutier, L. Ortega, A. Kozłowski, N. Barišić, J. E. Lorenzo, W. Tabiś
Quantum Physics
Achieving Identical Stored Energy in Cascaded Collisional Quantum Battery Charging: Analytical Result
Longyan Gong, Jing Zhang and Yongtao Li
Charging uniformity across distinct trials is an essential requirement for reliable
quantum batteries. Nevertheless, intrinsic
quantum stochasticity poses a fundamental challenge to this goal. This work investigates a two-
qubit quantum battery within the framework of cascaded collision models. We propose an adaptive measurement on the charger after each collision, yielding two conditional battery states of equal expected stored energy. For chargers prepared in the excited state, we analytically prove that complete suppression of trajectory-dependent stored-energy fluctuations is attainable; for chargers prepared in general superposition states, our theory reveals that full suppression is fundamentally prohibited owing to battery-phase-dependent recursive dynamics. Numerical simulations are in excellent quantitative agreement with theoretical predictions. These findings provide a feasible pathway toward high-uniformity
quantum-battery charging.
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Medical Physics
Quiet, rapid 3D multiparametric mapping using magnetization-prepared zero echo time MRI
Alireza Samadifardheris, Shishuai Wang, Ana Beatriz Solana et al. (+10 more)
Purpose: To introduce and evaluate MuPa-ZTE, a quiet, rapid 3D framework combining native and magnetization-prepared zero echo time (ZTE) acquisitions for multiparametric mapping. Methods: MuPa-ZTE combines steady-state native ZTE with transient-state magnetization-prepared ZTE. Two implementations were evaluated: T2T1-ZTE for apparent
proton density, T1, and T2 mapping, and T1-ZTE for apparent
proton density and T1 mapping. Both were assessed in an ISMRM/NIST system phantom and two healthy volunteers; T2T1-ZTE was also demonstrated in a patient with
brain metastases. The 10-minute phantom and 4.5-minute in vivo acquisitions were retrospectively truncated to 3, 2, and 1 minute and reconstructed with and without deep learning-based denoising. Evaluations included phantom agreement, precision, short-term repeatability, apparent SNR, edge sharpness, and consistency with full-duration in vivo maps. Results: T1 estimates remained close to nominal phantom values across implementations, durations, and reconstructions. T2 accuracy was maintained down to 2 minutes over the
brain-relevant range, with limited sensitivity to longer T2 values. Denoising generally reduced variability and improved short-term repeatability. In vivo, 1.1-mm isotropic whole-
brain maps were obtained in 4.5 minutes; denoising increased apparent SNR while preserving edge sharpness and yielded promising image quality after retrospective truncation to 2 minutes. Conclusion: MuPa-ZTE enables quiet, isotropic 3D multiparametric mapping within 4.5 minutes, supporting robust T1 mapping and T2 mapping over a
brain-relevant range, with promising acceleration toward 2 minutes using deep learning-based denoising.
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All authors Alireza Samadifardheris, Shishuai Wang, Ana Beatriz Solana, Jose de Arcos, Noemi Sgambelluri, Emil Langensee Ljungberg, Sagar Mandava, Mika Vogel, Steven C. R. Williams, Stefan Klein, Juan Antonio Hernandez-Tamames, Dirk H. J. Poot, Florian Wiesinger
Quantum Physics
Preservability of Measurement Incompatibility: Purification, Activation, and a No-Go Theorem
Chao-Hsien Wu, Franco Nori and Huan-Yu Ku
Measurement incompatibility is a fundamental
quantum resource that enables advantages in many
quantum information tasks, including cryptography and communication. However, unavoidable interactions between a system and its environment can degrade or even completely destroy measurement incompatibility; such a process is referred to as a measurement-incompatibility-annihilating channel. Recently, the capability of noisy
quantum dynamics to preserve measurement incompatibility has been characterized within the resource theory of measurement incompatibility preservability. This motivates studying how to purify the preservation of measurement incompatibility and how to activate it from a measurement-incompatibility-annihilating channel. To this end, we first introduce our figures of merit as robustness-based resource monotones within this resource theory. We demonstrate that while pre-filtering operations can strengthen measurement incompatibility preservability, they cannot activate it from an incompatibility-annihilating channel, establishing a no-go
theorem. Furthermore, we explicitly demonstrate that an incompatibility-annihilating channel can be stochastically activated via post-filtering operations. Our results provide a practical framework for exploiting measurement incompatibility in
quantum information processing.
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Disordered Systems and Neural Networks · Cross-listed from cs.LG
EP-Flow: Disordered Crystal Structure Prediction without Site-Level Annotations
Qiuliang Liu, Liming Wu, Qi Li et al. (+5 more)
Generative models have made rapid progress in ordered
crystal structure prediction, yet many functional materials are intrinsically disordered, with substitutional mixing, vacancies, or interstitial species controlling their properties. Existing
crystal generators either assume deterministic site occupations or require site-level disorder annotations, which are often unavailable when the chemical formula is the primary input. We formulate disordered
crystal structure prediction through an Occupancy Distribution
Matrix (ODM), a continuous site-by-species representation that unifies ordered
crystals, solid solutions, vacancy disorder, and interstitial occupancy. A valid ODM must satisfy coupled site-wise occupancy, mass-conservation, and non-negativity constraints, placing each sample on a formula-dependent transportation polytope. We propose Entropic Polytope Flow (EP-Flow), a marginal-constrained flow matching framework that canonicalizes heterogeneous polytopes into a shared double-centered space, learns a marginal-preserving flow, and recovers feasible occupancies through a Sinkhorn inverse map. By jointly generating occupancies, fractional coordinates, and
lattice parameters, EP-Flow achieves state-of-the-art performance on formula-conditioned disordered CSP
benchmarks derived from COD and MPDS, substantially outperforming adapted ordered-
crystal generators. Analyses further show that EP-Flow recovers sparse and chemically meaningful local disorder patterns rather than merely matching global composition statistics.
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All authors Qiuliang Liu, Liming Wu, Qi Li, Zhonglong Peng, Chang Chen, Xiaolong Chen, Wenbing Huang, Shifeng Jin
Applied Physics
Determination of van der Waals thin film thickness via characteristic X-ray photon yield
Guoshun Luo, Shichao Zhao, Xinyu Liu et al. (+7 more)
Characteristic X ray generation is essential for producing X ray sources and for investigating light matter interactions. Here, we demonstrate that characteristic X ray generation can also be employed to determine the thickness of van der Waals thin films in a non destructive manner. Specifically, we establish a sixth order
polynomial model that relates film thickness to the characteristic X ray yield. The model can both predict the X ray yield of graphite films at arbitrary thicknesses and infer the film thickness from a corresponding characteristic X ray yield. We validate the model by comparing its predicted X ray yields for graphite films with those obtained from Monte Carlo simulations. Additionally, we experimentally validated the reliability and feasibility of the proposed method for extracting graphite film thickness via X ray
photon yield characterization. Our results provide a non destructive approach for determining the thickness of van der Waals thin films.
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All authors Guoshun Luo, Shichao Zhao, Xinyu Liu, Suguo Chen, Yue Wang, Ping Zhang, Zhigang Lu, Shaomeng Wang, Sunchao Huang, Yubin Gong
High Energy Physics (Experiment)
Search for charged-lepton-flavour violating $e\mu tq$ interactions at $\sqrt{s}=13$ TeV with the ATLAS detector
ATLAS Collaboration
A search for charged-
lepton-flavour violation (cLFV) in top-
quark production and decay is presented. The data analysed correspond to 140 fb$^{-1}$ of
proton-
proton collisions recorded at a centre-of-mass energy of $\sqrt{s}= 13$ TeV by the ATLAS detector at the Large
Hadron Collider. The possible cLFV contribution is studied via two mechanisms. The first is via the production of a leptonically-decaying single-top
quark in association with a pair of oppositely-charged different-flavour
leptons. The second is the production of top-
quark pairs, where one top
quark decays into a pair of oppositely-charged different-flavour
leptons and a $u$- or $c$-
quark, while the other decays into a leptonically-decaying $W$
boson and a $b$-
quark, according to the Standard Model. The signal processes contain three charged
leptons, taken to be electrons or
muons. No significant deviation from the Standard Model prediction is observed, and these results are interpreted within an Effective Field Theory framework. Upper limits are placed at 95% confidence level on six Wilson coefficients, ranging from $|C^{\mathrm{tensor}}_{e\mu tu}|/\Lambda^2 < 0.018$ TeV$^{-2}$ to $|C^{\mathrm{scalar}}_{e\mu tc}|/\Lambda^2 < 0.32$ TeV$^{-2}$ for the tensor $u$-
quark and scalar $c$-
quark couplings, respectively. These Wilson coefficient limits are translated into 95% confidence level upper limits on cLFV top-
quark decay branching ratios, ranging from $B(t \to e\mu u) < 6 \cdot 10^{-9}$ to $B(t \to e\mu c) < 2.7 \cdot 10^{-7}$ for the scalar $u$-
quark and tensor $c$-
quark couplings, respectively.
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High Energy Physics (Theory)
Gravity and generalised geometry from a Lie 2-algebroid perspective
Athanasios Chatzistavrakidis, Chris Hull, Larisa Jonke et al. (+2 more)
We revisit the problem of defining natural torsion and
curvature tensors for generalised connections and of using them to reconstruct the effective action for the massless modes of the closed string from generalised geometry. The starting point is the description of a Courant algebroid as a differential graded (dg)
symplectic manifold. A systematic procedure for split dg
manifolds singles out a generalised Lie bracket as part of a larger Lie 2-algebroid structure, with the right properties to unambiguously define torsion and Riemann
curvature tensors together with their corresponding Bianchi identities. This framework eliminates the structural circularity and ambiguity problems of previous approaches in the literature. We show that a unique generalised metric compatible generalised connection with fixed (con)torsion exists for any choice of ordinary connection that splits the dg
manifold, while at the same time all Lie 2-algebroids obtained in this way are equivalent up to $L_{\infty}$ quasi-isomorphisms. For a given Lie 2-algebroid we demonstrate that the unique compatible generalised connection reproduces the effective closed string action from a
geometric action based on the new generalised
Ricci tensor upon making a canonical choice of torsion.
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All authors Athanasios Chatzistavrakidis, Chris Hull, Larisa Jonke, Sylvain Lavau, Peter Schupp
Materials Science
Pressure induced structural transitions, coordination crossover, and optoelectronic response in divalent metavanadate CaV$_2$O$_6$
Bhagyashri Giri, Asish Kumar Mishra, Bidisha Mukherjee et al. (+3 more)
High-pressure synchrotron X-ray diffraction, Raman spectroscopy, photoluminescence (PL), and UV-Vis absorption measurements were carried out on the divalent metavanadate CaV$_2$O$_6$ up to 31 GPa at room temperature. Ambient CaV$_2$O$_6$ crystallizes in a centrosymmetric pseudo-brannerite monoclinic structure ($C2/m$), where vanadium atoms reside in fivefold-coordinated VO$_5$ trigonal bipyramids. Under hydrostatic compression, the system undergoes a structural phase transition starting at $\sim$1 GPa to a lower-
symmetry, non-centrosymmetric monoclinic phase ($C2$), which becomes the single stable phase above 5.2 GPa. This transition involves an increase in vanadium coordination from VO$_5$ bipyramids to edge-sharing distorted VO$_6$ octahedra. High-pressure Raman scattering corroborates the structural phase boundaries, exhibiting mode softening ($\gamma_3 = -0.42$, $\gamma_9 = -0.46$) within the mixed-phase regime (1.0 - 4.4 GPa) and sharp anomalies in mode frequencies and linewidths across 5.2 GPa. The optical measurements show complete PL quenching near 1 GPa due to non-radiative recombination pathways introduced by local polyhedral distortions, alongside a non-monotonic
evolution of the indirect optical band gap. Above 20 GPa, an anomaly in polyhedral distortion and internal strain drives an isosymmetric structural modification within the $C2$ phase, marked by an alteration in bulk compressibility and stabilization of the optical gap. Comparative high-pressure band-gap measurements on the sister compound MgV$_2$O$_6$ validate the explicit coupling between cation coordination changes and optoelectronic response in divalent metavanadates.
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All authors Bhagyashri Giri, Asish Kumar Mishra, Bidisha Mukherjee, Debabrata Samanta, Nico Giordano, Goutam Dev Mukherjee
Nuclear Theory
Hadronization into Nuclei: Does Size Matter?
Anton Andronic, Peter Braun-Munzinger, Hjalmar Brunßen et al. (+1 more)
We investigate an extension of the statistical hadronization model (SHM) that takes (hyper)
nucleus sizes into account. The spatial extent of
nuclear wave functions relative to the fireball volume is used to calculate a size correction, which describes the suppression with respect to a point-like treatment of the (hyper)
nucleus at hadronization. For several species of light
nuclei (d, ${}^{3}\mathrm{H}$, ${}^{3}\mathrm{He}$) and for the hypernucleus ${}^{3}_{\Lambda}\mathrm{H}$, the predicted effects of the size correction on SHM yields are compared to yield measurements in pp, p-Pb, and Pb-Pb collisions in the ALICE experiment. The experimental data suggest that this size correction, based on applying final-state wave functions at chemical freeze-out, does not give a consistent description of (hyper)
nucleus production in
nuclear and hadronic collisions. By contrast, the SHM without a
nuclear-size correction provides a substantially better description of the data. This result lends further support to the interpretation that such
nuclear states are formed from initially compact (multi-
quark) configurations which after hadronization expand to their final-state wave functions.
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All authors Anton Andronic, Peter Braun-Munzinger, Hjalmar Brunßen, Johanna Stachel
Soft Condensed Matter
Ideal gas of active particles in a box
Siran Li, Ralf Eichhorn and Lennart Dabelow
Extending a fundamental concept of thermodynamics to the nonequilibrium realm of active matter, we derive an ideal gas law for a suspension of noninteracting active particles confined to a finite rectangular box. The law is exact for run-and-tumble particles (RTPs) in one dimension and established by a systematic analytical expansion of the steady-state probability density for active Ornstein-Uhlenbeck particles in any dimension. It also agrees well with numerical results for active Brownian particles and RTPs in higher dimensions and recovers previously known relations for the limit of large system sizes. Together, these results demonstrate the applicability of the ideal active gas law to the three most widely studied theoretical models of colloidal active matter. As an application, we analyze thermodynamic processes involving active matter on a macroscopic level, without recourse to microscopic particle trajectories or self-propulsion fluctuations.
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Soft Condensed Matter
Inclined surfaces bias bacterial swarming expansion and edge organization
Pengxi Gu, Zixiang Lin, Hui Ren et al. (+5 more)
Bacterial swarming is the collective expansion of dense populations of motile
cells across hydrated soft surfaces, yet
gravity is usually treated as a fixed background condition in standard horizontal assays. We used surface inclination to examine how agar-surface orientation relative to
gravity affects the expansion of Enterobacter sp. SM3 swarms. Colony expansion depended non-monotonically on inclination, with the strongest spreading at intermediate inclinations and weaker expansion under shallow or near-inverted conditions. Paired up-facing acute and down-facing obtuse configurations with the same tilt magnitude showed different expansion responses, suggesting that swarm expansion depended on both tilt magnitude and which side of the agar surface faced upward relative to
gravity. Inclination also produced downhill-biased colony morphologies. PIV analysis showed generally lower mean activity under inclination than in the flat references, with a non-monotonic angular response and inward increases in speed and spatial velocity-correlation length. The downhill tip showed slower motion, shorter spatial correlations and smaller
vortex cores than the upper region. To interpret the macroscopic trends, we extended a two-phase thin-film model by introducing an effective
gravity coupling projected normal and tangential to the agar surface. Simulations suggest that the surface-tangential component mainly drives lateral redistribution, whereas the surface-normal component modifies film pressure and thereby pressure-dependent water replenishment, helping distinguish up-facing from down-facing configurations.
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All authors Pengxi Gu, Zixiang Lin, Hui Ren, Jin Zhu, Anqi Li, Omar Said, Weijie Chen, Zijie Qu
Quantum Physics
Linear-Time Encodable Quantum Codes near the CSS GV Bound
Rachel Yun Zhang
We construct
quantum CSS codes with rate-distance tradeoff approaching the CSS GV bound, which can be encoded by a
quantum circuit of logarithmic depth and a linear number of gates. Our construction is heavily inspired by a work of Brehm and Resch and can be viewed as a
quantum analogue of classical repeat multiple accumulate codes. The encoder has a particularly simple structure, consisting of a single constant depth outer
quantum circuit followed by several classical accumulation and inverse-accumulation layers.
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Optics
A Mid-Infrared Absorber Inspired by the Wing-Scale Photonic Structure of Troides magellanus
Amandine Marchand, Kevin Delmote, Olivier Deparis et al. (+1 more)
Growing environmental and energy-related challenges have intensified the search for technologies capable of improving energy recovery and resource efficiency. Bioinspired photonic structures offer promising opportunities for the development of efficient infrared absorbers by exploiting optical mechanisms found in natural systems. In this work, we present a bioinspired approach for the design and optimization of a broadband mid-infrared absorber based on the highly absorbing wing scales of the Troides magellanus Magellan birdwing butterfly. The characteristic geometry of the biological structure is rescaled and adapted to shift its optical response from the visible to the infrared spectral range. Numerical simulations are used to investigate the influence of the main geometrical parameters on the spectral absorptance and to identify an optimized configuration. The optimized structure achieves an absorption enhancement of 391% compared with a flat steel reference. The improved optical response is attributed to the optimized high-aspect-ratio geometry, which enhances multiple scattering and light trapping, thereby increasing the effective light-matter interaction area. These results demonstrate the potential of bioinspired
geometric scaling as an effective strategy for engineering efficient infrared absorbers and tailoring their spectral response for thermal radiation management and infrared photonic applications.
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All authors Amandine Marchand, Kevin Delmote, Olivier Deparis, Sébastien R. Mouchet
Instrumentation and Detectors
State of the Art in Direct Dark Matter Detectors: Technologies, Performance, and Future Directions
Muad Ghaith and Khaled Obaideen
Identifying the particle nature of dark matter remains one of the most significant challenges in modern physics. Direct detection experiments aim to observe rare scattering events between dark matter particles and terrestrial targets, a task that demands extreme background suppression and sensitivity to minute energy depositions. This review critically assesses the current experimental landscape, organizing detector technologies by the fundamental physical trade-offs that define their scientific reach. We contrast the multi-tonne scalability of noble-
liquid Time Projection Chambers (TPCs), which currently define the sensitivity frontier for high-mass Weakly Interacting Massive Particles (WIMPs), with the precision of cryogenic
semiconductors and Charge-Coupled Device (CCD)- based sensors, which dominate the search for low-mass and sub-GeV candidates. Special emphasis is placed on the role of advanced reconstruction pipelines and machine learning (ML) as integral components of detector performance. Finally, we discuss the strategic roadmap for the next decade as experiments approach the
neutrino fog, where coherent elastic
neutrino-
nucleus scattering (CE{\nu}NS) produces an increasingly significant and ultimately irreducible background that can mimic DM-induced
nuclear recoils. We argue that future progress will rely not on a single technology but on a complementary global program combining increased target mass, ultra-low energy thresholds, improved background discrimination, and distinct observables - such as directionality and temporal signatures - to maintain robust discovery capability in the presence of
neutrino-induced backgrounds.
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General Relativity and Quantum Cosmology
Charged Hawking Mass on CMC Collars with Charged Matter
Sehong Park
We study strictly stable minimal horizons in three-dimensional time-symmetric charged initial data sets with cosmological constant, allowing charged matter. Along the constant-mean-
curvature foliation issuing from the horizon through leaves with positive Jacobi operator, we prove exact first-variation identities for the charged Hawking mass. When the charge density has one sign compatible with the horizon charge, Hawking masses are nondecreasing, and equality between the two boundary values of the fixed-charge mass forces the entire collar to be isometric to an annulus in a source-free constant-
curvature Reissner–Nordström–(anti-)de Sitter model. From this we recover the local
rigidity results under a local maximality condition. At the minimal endpoint the defect entering these identities computes the fixed-charge Hawking-mass Hessian along the normalized lapse, and its vanishing characterizes the model horizon data.
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General Relativity and Quantum Cosmology
Reconstruction of $f(Q)$ Gravity from Geodesic Congruence Dynamics: Raychaudhuri Equation
Tuhina Ghorui, Prabir Rudra and Farook Rahaman
In this study, we use the Raychaudhuri equation as the essential geometrical tool to reconstruct the functional form of $f(Q)$
gravity within the context of symmetric teleparallel
gravity. The expansion scalar and the congruence dynamics recorded in the Raychaudhuri equation are used to relate the non-metricity scalar $Q$ with the kinematical
evolution of the Universe in order to establish the reconstruction method. We obtain explicit forms of $f(Q)$ that can explain the observed accelerated expansion of the Universe without the need for an additional dark energy component by taking into account appropriate cosmological assumptions. Moreover, the reconstructed model can also be extended to the infinite past to model the early universe for certain scenarios. In an FLRW spacetime we have considered a constant deceleration parameter and a constant jerk parameter to facilitate our reconstruction analysis. We further discuss the, general relativity limit, Friedmann consistency and background physical viability of the reconstructed models. The analysis indicates that Raychaudhuri equation, interpreted as an equation governing the focusing/defocusing of cosmological geodesic congruences, can be used as the central equation in an inverse reconstruction of $f(Q)$
gravity.
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Quantum Physics · Cross-listed from cs.LG
Context-Aware Error Mitigation Orchestration for Hybrid Quantum Reinforcement Learning on NISQ Systems
Bisma Majid, Shabir Ahmed Sofi and Mir Mohammad Yousuf
Quantum Reinforcement Learning (QRL) integrates reinforcement learning with parameterized
quantum circuits and is a promising approach to combinatorial optimization. On Noisy Intermediate-Scale
Quantum (NISQ) devices, however, decoherence, gate imperfections, and measurement errors reduce policy quality and make learning less reliable. Existing error mitigation techniques are generally applied as fixed corrections that do not adapt to changing noise conditions or to the evolving state of training. This work presents Adaptive Policy-Guided Error Mitigation (APGEM) as a context-aware orchestration layer of the hybrid
quantum-classical training loop that dynamically selects the most suitable mitigation strategy during QRL training. APGEM evaluates Zero-Noise Extrapolation (ZNE), Probabilistic Error Cancellation (PEC), Clifford Data Regression (CDR), and Readout Error Mitigation (REM) using policy-level indicators, including
quantum-state fidelity, policy
entropy, cumulative reward, and approximation ratio, and integrates the selected strategy directly into the reinforcement learning loop. The framework is evaluated on the Capacitated Vehicle Routing Problem (CVRP), a representative NP-hard problem in urban logistics, under a range of NISQ noise models and noise levels. APGEM consistently outperforms conventional static mitigation methods, reaches approximately 94% of the utility of an oracle strategy, maintains higher
quantum-state fidelity as noise increases, and produces more stable learning behaviour throughout training. Ablation studies show that the framework learns context-aware mitigation policies that adapt to different noise environments and
circuit execution conditions. These findings demonstrate that integrating adaptive error mitigation into the learning process substantially improves the robustness and reliability of QRL on NISQ hardware.
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Applied Physics
Correlation Imaging via Hybrid Entanglement between Microwave Photons and Surface Acoustic Wave Phonons
Yu-Yuan Chen, Ling-An Wu and Yu-xi Liu
Establishing effective spatial correlations between distinct
quantum fields is essential for multi-physics
quantum sensing.~We here propose a correlation imaging approach based on the hybrid
entanglement between microwave
photons and microwave surface acoustic wave
phonons generated via a superconducting
quantum circuit.~At matched microwave frequencies, the five order-of-magnitude wavelength disparity between
photons and
phonons leads to a unique
quantum entanglement resource, which allows the optimal field for probing an object to be distinct from that used for readout.~This resource enables two imaging modalities with
giant spatial scaling: a $10^{-8}-10^{-6}$-fold demagnification of macroscopic object profiles onto microscopic phononic chips, and conversely, a $10^{4}-10^{6}$-fold magnification of microscopic object profiles into macroscopic photonic readout devices. By interfacing free-space long-wavelength microwaves with on-chip short-wavelength surface acoustic waves, our correlation imaging approach provides a general framework for cross-scale
quantum sensing.
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Solar and Stellar Astrophysics
Towards solar many-line inversions
Johannes Hölken
The Sun's atmosphere is significantly influenced by events that often measure only tens of kilometres in the horizontal direction. They happen in both quiet and active regions and are determined by magneto-hydro-dynamic processes. Their origins often lie in the lowest layers of the
solar atmosphere. To improve the understanding of chromospheric and coronal heating, the
solar dynamo and its activity cycle, or to improve the prediction of space weather events we must therefore enhance our understanding of such small-scale events. In this work I first describe the process of calibrating spectropolarimetric observations with very high spatial resolution and put together the building blocks for the mathematical proof the MOMFBD image reconstruction
algorithm. In the second part I describe the FISS-SP prototype which is designed to fully exploit the resolution power of a 1.6m
telescope. This instrument is built to provide suitable data for image reconstruction of spectropolarimetric data. The resulting data can resolve small-scale features down to the diffraction limit. The simultaneous interpretation of a few lines is still the norm for spatially highly resolved
solar spectra. Theoretical works have shown that the simultaneous interpretation of multiple
solar lines can greatly improve the robustness against noise. Using observations from FISS-SP I advance the theoretical idea into a practical technique. With this I can retrieve a coherent model of the local
solar atmosphere, resolving structures down to a horizontal size of about 49~km. Finally, I use those new techniques to interpret an observation of a
solar pore. In this last part I describe and analyse small-scale structures, which could not be spectropolarimetrically resolved before. Typical pore-boundary features - namely, dark striations with bright grains moving into the pore - are identified as convective features.
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Statistical Mechanics
Work fluctuation speed limit in boundary conformal field theories
Shihao Xia, Ahsan Nazir and Harry J. D. Miller
We explore the fundamental limits on finite-time driving in
quantum critical systems described by boundary conformal field theory. We show that
stochastic work fluctuations arising from external driving are a resource for speedy control, and derive an exact, saturable fluctuation-based speed limit in weakly driven boundary conformal field theories at finite temperature. The bound and saturating protocol can be expressed entirely in terms of the universal scaling dimension, and the result interpolates between the Kibble–Zurek regime,where temporal correlations are strongly nonlocal, and an adiabatic regime where linear driving becomes optimal. For small scaling dimension, the enhanced temporal correlations produce pronounced departures from linear protocols and a larger optimization advantage. These results establish a universal work precision–time tradeoff for boundary-critical control, applicable to
quantum impurity, fractional
quantum Hall, and superconducting-
circuit platforms.
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Solar and Stellar Astrophysics
Structure of Convective-Reactive Zone in a Supernova Progenitor
M. Mocak, C. Meakin, F. Rizzuti et al. (+5 more)
Convective-reactive events are phases of
stellar evolution where turbulent mixing and
nuclear burning directly compete, since their timescales become similar within convection zones. During these events the convection zone structure is shaped by a complex and dynamic interaction of convective transport and
nuclear burning of individual chemical elements, with
plasma streams connecting the entrainment regions with the burning layers. Here we analyse a 3D hydrodynamic simulation of an oxygen–neon shell merger in a massive pre-
supernova star. We study the emergent structure using the Reynolds-Averaged Navier-Stokes (RANS) mean-field composition transport equation. We find that the merged convective zone develops a complex,
turbulence-driven mixing structure of multiple nested convective-reactive shells, all contained within the single convection zone. Key controlling factors include not only the mean stratification and mixing, but also emergent collective behaviour of involved
nuclear reactions for every chemical isotope. Almost all layers show a quasi-steady balance between burning and mixing. We categorise the various layers, and discuss/contrast with 1D
stellar evolution code treatments, highlighting some implications.
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All authors M. Mocak, C. Meakin, F. Rizzuti, S. W. Campbell, V. Varma, R. Hirschi, C. Georgy, W.D. Arnett
Quantum Physics
Experimental quantification of quantum coherence for a set of quantum states
Tianle Zheng, Liangsheng Li, Wenting Zhou et al. (+1 more)
We present a direct experimental verification of
quantum coherence for a set of
quantum states in a basis-independent manner. We find that the theory of
quantum coherence for a set of
quantum states matches our experimental results perfectly and can be applied to protocols like BB84 and
quantum secure direct communication. Using a Sagnac interferometer, we experimentally quantify the
quantum coherence for two sets of experimental states. Moreover, we introduce a novel application of set coherence, illustrating that the states employed in the BB84 protocol exhibit maximal set coherence. Our results pave the way for wider applications of
quantum coherence for a set of
quantum states, including
quantum key distribution protocols and probabilistic
quantum cloning.
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All authors Tianle Zheng, Liangsheng Li, Wenting Zhou, Chengjie Zhang
Solar and Stellar Astrophysics
Probing Accretion and Outflow in V1180 Cas through High-Resolution Optical Spectroscopy
Tarak Chand, Saurabh Sharma, Koshvendra Singh et al. (+9 more)
We present an analysis of a high-resolution optical spectrum of V1180 Cas obtained with HIRES at the W. M. Keck Observatory during a bright photometric state of the source. The spectrum is dominated by strong emission lines, including H$\alpha$, the Ca II infrared triplet, He I, and O I, along with numerous Fe I and Fe II transitions and several forbidden lines such as [O I] and [S II], indicating ongoing
accretion and mass-loss activity. A weak Li I $\lambda$6708 absorption feature confirms the youth of the source. Using the Li I absorption and selected Fe I emission lines, we report for the first time a radial velocity of $-16 \pm 3$ km s$^{-1}$ for V1180 Cas. The H$\alpha$ and H$\beta$ profiles exhibit asymmetric structures with blueshifted absorption components, suggesting outflowing material along the line of sight. The He I $\lambda$5876 line displays a narrow component likely associated with post-shock
accretion regions and a broad, slightly blueshifted component probably arising from magnetospheric flows and/or inner disk winds. The [O I] $\lambda$6300 profile is decomposed into low- and high-velocity components, tracing a slow disk wind and a fast jet. Using the forbidden [O I] line, we estimate for the first time a disk inclination angle of $\approx50^\circ$. The derived mass
accretion and jet mass-loss rates imply $\dot{M}_{jet}/\dot{M}_{acc} \sim 0.01$–$0.03$, at the lower end of, but consistent with, the range observed for Class II YSOs. Forbidden-line diagnostics indicate densities $\sim10^{3}$ and $10^{6}$ cm$^{-3}$ with temperatures of $\sim10^{4}$ K, supporting a multi-component
outflow scenario. Overall, the results support a picture in which V1180 Cas is an actively accreting, moderately inclined system hosting a multi-component
outflow.
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All authors Tarak Chand, Saurabh Sharma, Koshvendra Singh, Joe P. Ninan, Arpan Ghosh, Devendra K. Ojha, Jyotirmoy Dey, Manojit Chakraborty, Kartik Gokhe, Aayushi Verma, Mamta, Ajay Kumar Singh
Mesoscale and Nanoscale Physics
Composite fermions in ideal Chern bands
Songyang Pu, Liangtao Peng and Shaffique Adam
The composite-
fermion framework maps the strongly correlated fractional
quantum Hall state onto a weakly interacting integer
quantum Hall state in a reduced effective
magnetic field. We ask how this framework is modified for fractional Chern
insulators, where the role of a uniform
magnetic field is replaced by the nonuniform Berry
curvature of a Chern band. Specifically, we construct composite-
fermion wave functions for Jain states and their quasiparticles and quasiholes in Aharonov-Casher bands, a widely used model for ideal Chern bands. We find that these states overlap closely with exact eigenstates over a broad range of field modulation. Using these wave functions, we demonstrate that the emergent composite-
fermion band structure goes beyond the conventional picture of effective Landau levels, correctly capturing the quasiparticle dispersion. Remarkably, we find that an isolated quasiparticle band carries a total Berry flux that is different from a Landau level. These results establish a composite-
fermion description for mobile fractional Chern
insulator anyons and provide a framework to understand their stability.
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High Energy Astrophysical Phenomena
25 Years of Mrk 421 with XMM-Newton: Unveiling Structured Jets and Energy-Dependent Escape
Tek P. Adhikari, Gopal Bhatta, Sangeetha Kizhakkekalam et al. (+4 more)
We present a long-term X-ray spectral and timing analysis of the TeV blazar Mrk~421 based on nearly a quarter century of archival XMM-Newton/pn observations obtained between 2000 and 2025. Our sample comprises 76 epochs obtained with the pn instrument in both IMAGING and TIMING modes, allowing us to trace the source's variability and spectral
evolution. Mrk~421 exhibits flux variations by approximately an order of magnitude, with prominent flaring periods interspersed with low-activity states. A clear harder-when-brighter trend is observed, accompanied by scatter in the hardness ratio (HR), suggesting flux alone does not uniquely determine the spectral state. Fractional variability in the hard band ($2-10$ keV) correlates tightly with that in the soft band ($0.3-2$ keV), with a steeper slope indicating pronounced variability at higher energies. The flux distribution is non-Gaussian and lognormal-like, dominated by moderate flux levels with a tail of bright
flares. Spectral analysis shows that power-law model is not sufficient; 59 epochs are best described by a broken power-law (BPL) and 17 by a log-parabola (LP). This fluctuation between BPL and LP models suggests the emission region transitions between a distinct acceleration shockfront and downstream
stochastic turbulence. The spectral break energy of BPL remains predominantly clustered around $2$ keV across all flux states, while the average spectral steepening above the break is mild ($\Delta \Gamma \approx 0.19$), inconsistent with standard one-zone cooling models. Our results support structured jet scenarios or energy-dependent electron escape, providing key constraints on the long-term behavior of relativistic jets in high-synchrotron-peaked blazars.
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All authors Tek P. Adhikari, Gopal Bhatta, Sangeetha Kizhakkekalam, Navaneeth P K, Alex Markowitz, Zhicheng He, Santanu Mondal
Optics
Vector solitons in nonlinear lattices with competing SPM and XPM terms
Liangwei Zeng, Boris A. Malomed, Dumitru Mihalache et al. (+1 more)
We demonstrate that two-component photonic nonlinear
lattices with opposite signs of the out-of-phase spatially modulated SPM and XPM coefficients can support two types of optical vector
solitons (VSs), the fundamental and mixed ones. The fundamental VSs are composed of two Gaussian-like components, while the mixed ones combine Gaussian-like and dipole components. The structures and stability of both types of the VSs are investigated. The VSs are stable, except for narrow intervals at small values of the propagation constant.
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All authors Liangwei Zeng, Boris A. Malomed, Dumitru Mihalache, Xing Zhu
Astrophysics of Galaxies
Chemical complexity in feedback from supernova remnants: first detection of PO+ in IC443 and W44
G. Cosentino, F. Priestley, S. Scibelli et al. (+1 more)
Supernova remnant (SNR) may shape the physical and chemical properties of
star formation. By releasing refractory elements into the gas phase, they inject material of pre-biotic relevance into molecular clouds. Such elements may be inherited by planetary systems and become relevant for the emergence of life. We investigate the presence of P-bearing species in molecular clouds impacted by SNR-shocks. P is a crucial biological element, but its presence and reservoir in molecular clouds remain elusive. We present high-sensitivity 3 mm observations obtained with the IRAM 30m, toward the interaction sites between the SNRs W44 and IC443 and their associated molecular clouds. Focusing on PO+(2-1) and PN(2-1), we derive molecular column densities and abundances in local thermodynamic
equilibrium. We investigate the correlation between P-bearing species and the shock tracer Silicon Monoxide (SiO). We detect, for the first time, PO+ toward SNRs, with abundances X(PO+)~8e-12-5e-11, but no significant PN emission. PO+ toward both SNRs is associated with strong SiO emission, showing similar linewidths but velocity offsets, suggesting that PO+ preferentially traces the most compressed and more strongly ionised layers of the shock. By comparing the derived abundances with those reported in literature, we suggest that the PO+ abundance mainly depends on a combination of shock strength and shocked medium density. Our results indicate that P-chemistry in SNR shocks is shifted toward an ion-dominated regime, likely driven by enhanced
cosmic-ray ionisation rates. In this scenario, neutral species such as PN are efficiently destroyed, while ion-molecule reactions favour the production of PO+. This suggests that SNR shocks may play a role in processing P-bearing material and shaping gas-phase P chemistry in molecular clouds, with potential implications for the chemical inventory of
star-forming environments.
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All authors G. Cosentino, F. Priestley, S. Scibelli, F. Fontani