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2602.14906 2026-02-18 hep-ph hep-ex

Probing Quark Electric Dipole Moment with Topological Anomalies

Chao-Qiang Geng, Xiang-Nan Jin, Chia-Wei Liu, Bin Wu

Comments 4 pages, 3 figures; references added; minor corrections

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CP-odd observables originating from the strange-quark electric dipole moment ($d_s$) are identified in $γ^\ast\to K^+K^-π^0$ and evaluated in the chiral limit. A nonzero T-odd asymmetry $A_T$ requires anomalous couplings descending from a five-dimensional Chern-Simons construction. Modeling the running of $F_A$ and $F_V$ with vector-meson dominance, we estimate sensitivities to $d_s$ at the level of $\mathcal{O}(10^{-16})\,e\cdot\mathrm{cm}$ in $e^+e^-$ data at CMD-3 and $\mathcal{O}(10^{-18})\,e\cdot\mathrm{cm}$ using existing $J/ψ$ samples at BESIII. Future experiments at the Super Tau-Charm Facility and Belle~II can further improve the reach by an order of magnitude.

2602.14667 2026-02-18 physics.flu-dyn physics.comp-ph

Recursive regularised lattice Boltzmann method for magnetohydrodynamics

Alessandro De Rosis

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We present and test a recursive regularised lattice Boltzmann method for incompressible magnetohydrodynamic (MHD) flows. The approach is based on a double-distribution formulation, in which the magnetic field is evolved using a standard BGK lattice Boltzmann scheme, while the fluid solver is enhanced through a Hermite-based recursive regularisation of the non-equilibrium moments. The method exploits a fourth-order Hermite expansion of the equilibrium distribution on the D2Q9 lattice, allowing higher-order isotropy to be retained while selectively filtering spurious non-hydrodynamic contributions. The regularisation procedure reconstructs the non-equilibrium distribution from physically consistent Hermite coefficients, avoiding explicit evaluation of velocity gradients. The resulting scheme preserves the correct incompressible MHD limit, improves numerical stability at low viscosities, and reduces lattice-dependent artefacts. The proposed formulation provides a robust and versatile framework for MHD simulations and offers a systematic route for extending regularised lattice Boltzmann methods to coupled multiphysics systems.

2602.14392 2026-02-18 math.NA cs.NA

Flux-Balanced Patankar-type Schemes for the Compressible Euler Equations

Thomas Izgin, Andreas Meister, Chi-Wang Shu, Davide Torlo

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Positivity preservation of key physical quantities in the context of fluid flows, such as density and internal energy, is an essential property of a numerical scheme as otherwise the solution lacks physical relevance and has a not well-defined equation of state. One time integration technique that is capable of preserving the positivity of quantities for every time step size is the Patankar-trick and its variants. However, in the context of the Euler equations of gas dynamics, we wonder whether the Patankar-trick should be applied to the density and total energy equations or only to one of them. In this work, we discuss one drawback of the schemes when blindly applied to every positive conserved variable and additionally point out how to overcome the issue by balancing the involved numerical fluxes correctly. To illustrate our findings, we investigate modified Patankar--Runge--Kutta (MPRK) schemes in the context of the compressible Euler equations with and without stiff source terms. We discover that it is beneficial to only apply the Patankar-trick in the density equation and to balance the remaining numerical fluxes consistently rather than applying the trick also to the energy equation. This leads also to the preservation of contact discontinuities. We perform numerical experiments to demonstrate that the accuracy of the methods is maintained while the performance of our approach is superior to the traditional application of MPRK schemes.

2602.13753 2026-02-18 math.AP

Entire solutions to a strongly competitive nonlinear Schrödinger system

Pierpaolo Esposito, Pablo Figueroa, Angela Pistoia, Giusi Vaira

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We build infinitely-many non-radial positive solutions to the Schrödinger system \begin{equation*} \left\{\begin{aligned} &-Δu_1+u_1=u_1^{{\mathfrak p} }-Λu_1^{a_1} u_2^{a_2}\ \hbox{in}\ \mathbb R^N\\ &-Δu_2+u_2=u_2^{{\mathfrak p} }-Λu_1^{b_1}u_2^{b_2} \ \hbox{in}\ \mathbb R^N\\ \end{aligned}\right. \end{equation*} with sub-critical $\mathfrak p$-growth as $Λ\to +\infty$. The profile of each component is the sum of several copies of the positive solution to $-ΔU+U=U^{{\mathfrak p} }$ in $\mathbb R^N$, centered at suitable {\em peaks} whose mutual distances diverge as $Λ$ increases. More precisely, given two concentric regular polygons with $k$ sides and very large radii, the peaks of the first component are arranged along the edges of the {\em outer} polygon, alternated with those of the second component, and along the $k$ rays joining the vertices of the two polygons. To the best of our knowledge, this provides the first example of non-radial positive solutions for strongly competitive Schrödinger systems in the whole space.

2602.13500 2026-02-18 physics.flu-dyn

The Unsteady Taylor--Vortex Dynamo is Fast

Liam O'Connor, Daniel Lecoanet, Geoffrey M. Vasil, Kyle C. Augustson, Florentin Daniel, Evan H. Anders, Keaton J. Burns, Jeffrey S. Oishi, Benjamin P. Brown

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Astrophysical and geophysical fluids commonly generate organized magnetic fields, despite having enormous magnetic Reynolds numbers $\rm{Rm}$ and abundant small-scale turbulence. Flow-induced dynamo action produces these fields, with the ``kinematic dynamo problem'' devoted to determining the rate at which a flow exponentially amplifies weak magnetic fields. However, previous studies on high-Rm kinematic dynamos have generated flows via imposed volumetric forcing or oscillatory boundary conditions. In this letter, we investigate a system with three important attributes: realistic flow conditions, fast dynamo action (operational for $\rm{Rm}\to\infty$), and a subharmonic spatio-temporal structure. We show that unsteady Taylor--vortex flow, a regime observed in laboratory experiments, gives rise to fast dynamos with time and length scales twice those of the flow at high $\rm{Rm}$. By numerically integrating a Floquet system driven by periodic oscillations of Taylor vortices, we solve the kinematic dynamo problem up to $\rm{Rm} = 3.2 \cdot 10^6$, calculating the dynamo's growth rate as a function of Rm and streamwise wavenumber. We find the onset of instability and compute Finite-Time Lyapunov Exponents, which identify the regions of Lagrangian chaos required for fast dynamo action. To our knowledge, unsteady Taylor--vortex flow produces the most physically motivated fast dynamo to date.

2602.13380 2026-02-18 stat.ME

Robust Design in the Presence of Aleatoric and Epistemic Uncertainty

Luis G. Crespo

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This paper proposes strategies for designing a system whose computational model is subject to aleatory and epistemic uncertainty. Aleatory variables, which are caused by randomness in physical parameters, are draws from a possibly unknown distribution; whereas epistemic variables, which are caused by ignorance in the value of fixed parameters, are free to take any value in a bounded set. Chance-constrained formulations enforcing the system requirements at a finite number of realizations of the uncertain parameters are proposed. These formulations trade off a lower objective value against a reduced robustness by eliminating an optimally chosen subset of such realizations. Risk-aware designs are obtained by accounting for the severity of the requirement violations resulting from this elimination process. Furthermore, we propose a computationally efficient design approach in which the training dataset is sequentially updated according to the results of high-fidelity reliability analyses of suboptimal designs. Robustness is evaluated by using Monte Carlo analysis and Robust Scenario Theory, with the latter approach accounting for the infinitely many values that the epistemic variables can take.

2602.13146 2026-02-18 quant-ph

Mean-Force Hamiltonians from Influence Functionals

Gerard McCaul

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The Hamiltonian of mean force (HMF) provides the standard starting point for strong-coupling thermodynamics, yet explicit operator forms are known only in restricted settings. We present a quenched density framework that uses the Hubbard-Stratonovich transformation to rewrite the reduced equilibrium state as an average over local propagators in imaginary time. This approach rigorously separates the statistical definition of the environment from the algebraic structure of the system response. We apply this framework to the minimal case of a harmonic environment with a coupling commuting with the system Hamiltonian. In this scenario the correction to the HMF has an exact, closed-form expression. We validate this result against finite-bath trace-out calculations and stochastic imaginary-time sampling in a five-level projector-coupled model.

2602.12694 2026-02-18 cs.CE

Discovering the mechanics of ultra-low density elastomeric foams in elite-level racing shoes

Jeremy A. McCulloch, Scott L. Delp, Ellen Kuhl

Comments 19 pages, 8 figures

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Ultra-low-density elastomeric foams enable lightweight systems that combine high compliance with efficient energy return. In high-performance racing shoes, these foams are critical for low weight, high cushioning, and efficient energy return; yet, their constitutive behavior remains difficult to model and poorly understood. Here we integrate mechanical testing and machine learning to discover the mechanics of two ultra-low density elastomeric polymeric foams used in elite-level racing shoes. Across uniaxial tension, confined and unconfined compression, and simple shear, both foams exhibit pronounced tension-compression asymmetry, negligible lateral strains consistent with an effective Poisson's ratio close to zero, and low hysteresis indicative of an efficient energy return. Both foams provide a similar compressive stiffness (268kPa vs. 299kPa), while one foam exhibits nearly double the shear stiffness (219kPa vs. 117kPa), implying a substantially greater lateral stability at a comparable vertical energy return (83% vs. 89%). By integrating these data into constitutive neural networks, paired with sparse regression, we discover compact, interpretable single-invariant models, supplemented by mixed-invariant or principal-stretch based terms, that capture the unique signature of the foams with R2 values close to one. From a human performance perspective, these models enable finite-element and gait-level simulations of high-performance racing shoes to quantify running economy, performance enhancements, and injury risks on an individual athlete level. More broadly, this work establishes a scalable and interpretable approach for constitutive modeling of highly compressible, ultra-light elastomeric foams with applications to wearable technologies, soft robotics, and energy-efficient mobility systems.

2602.12412 2026-02-18 math.QA math-ph math.AT math.GT math.MP

Chern-Simons factorization algebras and knot polynomials

Kevin Costello, John Francis, Owen Gwilliam

Comments 75 pages; preliminary version, comments welcome

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This work identifies the Reshetikhin-Turaev invariant of links in terms of a trace map on factorization homology. In particular, to recover the knot invariants associated to Chern-Simons theories, we construct a filtered $\mathcal{E}_3$-algebra $\mathcal{A}^λ$ by BV quantization of Chern-Simons theory for a semi-simple Lie algebra ${\frak g}$ with invariant pairing~$λ$, and we prove that a finite-dimensional representation $V$ of the Drinfeld-Jimbo quantum group $U_\hbar{\frak g}$ defines a perfect $\mathcal{A}^λ$ module~$\mathcal{V}$. For any framed link $K$ in $\mathbb{R}^3$, we then prove that there is an equality \[\int_{K\subset\mathbb{R}^3}{\rm tr}(V) = Z_V(K\subset\mathbb{R}^3) \] between the factorization homology trace for $V$ and the Reshetikhin-Turaev link invariant determined by~$V$.

2602.12319 2026-02-18 physics.atom-ph

Measurements of diffusion coefficients for rubidium--inert gas mixtures using coherent scattering from optically pumped population gratings

Alexander Pouliot, Eduardo Chomen Ramos, Gehrig Carlse, Thomas Vacheresse, Jaskaran Randhawa, Louis Marmet, A. Kumarakrishnan, Jacek Kłos, Eite Tiesinga

Comments 20 pages, 12 figures

Journal ref Physical Review A 111, 033108 (12 March, 2025)

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We present comprehensive determinations of the diffusion coefficients $D$ at $T=24\,\degree$C for trace amounts of naturally abundant Rb atoms in inert, naturally abundant He, Ne, N$_2$, Ar, Kr, and Xe buffer gases using a single measurement technique. We establish a spatially periodic population grating in the Rb sample using two laser beams that intersect at a small angle $θ$ of a few milliradians. The atomic population grating decays exponentially in time due to diffusive motion induced by momentum-changing elastic collisions between Rb and buffer gas atoms or molecules, and is monitored by observing the scattered field from a read-out beam. We distinguish the contribution of diffusion from other collisional processes by measuring the characteristic $θ^2$ dependence of the decay rate. We also measure the systematic dependence of the decay rate on the buffer gas pressure over a range of $7\,000$ Pa to $90\,000$ Pa. In this manner, we obtain diffusion coefficients at standard atmospheric pressure of $101\,325$ Pa and at a temperature of 24.0(5)~$^\circ$C. We obtain weighted averages of $0.33(5)$ cm$^2$/s, $0.214(14)$ cm$^2$/s, $0.132(7)$ cm$^2$/s, $0.123(9)$ cm$^2$/s, $0.093(9)$ cm$^2$/s, and $0.073(4)$ cm$^2$/s for Rb in He, Ne, N$_2$, Ar, Kr, and Xe, respectively. We compare this data with diffusion coefficients obtained using quantum, classical, and semi-classical theoretical methods based on the most accurate interatomic interaction potentials from the literature. Our computed diffusion coefficients based on the quantum theory agree with the experimental determinations when systematic effects are taken into account. Our measurements and modeling are relevant to the optimization of magnetometers, imaging using spin-polarized noble gases, tests of collision models based on interatomic potentials, and the development of pressure sensors.

2602.12019 2026-02-18 astro-ph.CO

Is cosmic birefringence due to dark energy or dark matter? Simulation-based inference

Florie Carralot, Patricia Diego-Palazuelos, Adriaan J. Duivenvoorden, Eiichiro Komatsu, Nicoletta Krachmalnicoff, Carlo Baccigalupi

Comments 26 pages, 11 figures. Updated references and modified labels of figure 4

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Simulation-based inference (SBI) is a powerful inference technique for cases where the exact functional form of the likelihood is not known. A prime example is the likelihood of cross-correlation power spectra of the cosmic microwave background (CMB) fields at low multipoles, $\ell\lesssim 10$. In this paper, we investigate a parity-violating cross-correlation between $E$- and $B$- mode polarization fields using SBI. The $EB$ correlation at low $\ell$ is essential to distinguish between possible axion dark energy and dark matter interpretations of `cosmic birefringence', a rotation of the plane of linear polarization of the CMB, recently reported from WMAP, Planck, and Atacama Cosmology Telescope data. We use neural likelihood estimation to infer the likelihood of the $EB$ correlation at low $\ell$ and show that it is highly non-Gaussian. We then employ neural posterior estimation to constrain the scalar field mass ($m_ϕ$), the cosmic birefringence amplitude ($gϕ_\mathrm{in}/2$), and the instrumental miscalibration angle ($α$), from simulated datasets. We find that the posterior on $m_ϕ$ shows two regimes, with a transition marked by $10^{-32}$ eV, highlighting a strong sensitivity to the scale dependence of cosmic birefringence. To quantify this behavior, we compute the probability $p(m_ϕ < 10^{-32}$ eV) for various fiducial values of $m_ϕ$. We find that $α$ and the contribution of lensed $B$ modes ultimately limit our ability to exclude the dark energy scenario fully.

2602.11809 2026-02-18 astro-ph.HE

Impact of crust-core connection procedures on the tidal deformability of neutron stars

Junbo Pang, Hong Shen, Jinniu Hu

Comments 14 pages, 10 figures, 3 tables, has been accepted by Physical Review C

Journal ref Phys. Rev. C 113, 025806 (2026)

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We study the impact of crust-core connection procedures on various neutron-star properties, especially on the tidal deformability. We consider three types of connection procedures to treat the discontinuity in a nonunified equation of state around the crust-core transition: (1) the direct connection procedure, (2) the crossover connection procedure, and (3) the segmented method. Our results indicate that the mass-radius relations of neutron stars are almost unaffected by the details of the connection procedure. However, the tidal deformabilities of neutron stars are sensitive to the crust-core connection procedures. The tidal deformability is closely related to gravitational-wave measurements. For a canonical 1.4$M_\odot$ neutron star, uncertainties in the tidal deformability $Λ_{1.4}$ from different connection procedures can exceed 20\%. We find that the direct connection procedure yields significantly larger uncertainties in the tidal deformability, while the segmented method and crossover connection procedure provide relatively stable results.

2602.11573 2026-02-18 cs.DB

Fast Tuning the Index Construction Parameters of Proximity Graphs in Vector Databases

Wenyang Zhou, Jiadong Xie, Yingfan Liu, Zhihao Yin, Jeffrey Xu Yu, Hui Li, Zhangqian Mu, Xiaotian Qiao, Jiangtao Cui

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k-approximate nearest neighbor search (k-ANNS) in high-dimensional vector spaces is a fundamental problem across many fields. With the advent of vector databases and retrieval-augmented generation, k-ANNS has garnered increasing attention. Among existing methods, proximity graphs (PG) based approaches are the state-of-the-art (SOTA) methods. However, the construction parameters of PGs significantly impact their search performance. Before constructing a PG for a given dataset, it is essential to tune these parameters, which first recommends a set of promising parameters and then estimates the quality of each parameter by building the corresponding PG and then testing its k-ANNS performance. Given that the construction complexity of PGs is superlinear, building and evaluating graph indexes accounts for the primary cost of parameter tuning. Unfortunately, there is currently no method considered and optimized this process.In this paper, we introduce FastPGT, an efficient framework for tuning the PG construction parameters. FastPGT accelerates parameter estimation by building multiple PGs simultaneously, thereby reducing repeated computations. Moreover, we modify the SOTA tuning model to recommend multiple parameters at once, which can be efficiently estimated using our method of building multiple PGs simultaneously. Through extensive experiments on real-world datasets, we demonstrate that FastPGT achieves up to 2.37x speedup over the SOTA method VDTuner, without compromising tuning quality.

2602.11013 2026-02-18 physics.chem-ph

Initial Guesses for Multicomponent Mean-Field Methods: Assessment and New Developments

Denis G. Artiukhin

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The convergence of self-consistent field equations in mean-field nuclear-electronic orbital methods strongly depends on the choice of initial guesses for quantum nuclei. Although several such guesses have been proposed in the literature, a systematic comparison of their performance as well as attempts of constructing novel approximations based on model tasks of quantum mechanics were not reported to date. In this work, we address both issues by introducing novel nuclear initial guesses derived from the analytical solutions of the three-dimensional quantum harmonic oscillator and benchmarking them against existing approaches. We demonstrate that the isotropic variant of our guess outperforms existing approximations in nuclear-electronic orbital density functional theory calculations employing a simultaneous self-consistent field convergence protocol. Although our guess requires the computation of partial Hessians, we demonstrate that these can be evaluated with low-cost methods without affecting the accuracy of resulting protonic density matrices. Our results demonstrate that the proposed guess is robust and efficient and could provide a route to improved convergence in mean-field nuclear-electronic orbital computations.

2602.10694 2026-02-18 math.OA math-ph math.FA math.MP math.SP

Noncommutative $L_p$-differentiability and trace formulae

Arup Chattopadhyay, Clément Coine, Saikat Giri, Chandan Pradhan

Comments We have corrected several typographical errors; for example, the $τ$-measurability of $a$ and $b$ was previously omitted in some places. In addition, we have relaxed the assumptions on the perturbation when proving the continuity of the $n$-th derivative of $f(a+tb)$ and when establishing the trace formula

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Let $\mathcal{M}$ be a semifinite von Neumann algebra equipped with a normal faithful semifinite trace $τ$, and let $L_p(\mathcal{M})$ denote the associated noncommutative $L_p$-space for $1<p<\infty$. Let $n\in\mathbb{N}$ and let $a, b$ be $τ$-measurable self-adjoint operators such that $b\in L_p(\mathcal{M})\cap L_{np}(\mathcal{M})$. For a function $f\in C^n(\mathbb{R})$ whose derivatives $f^{(k)}$ are bounded for $1\le k\le n$, we prove that the map $ϕ:t\in\mathbb{R}\mapsto f(a+tb)-f(a)$ is $n$-times differentiable in the $\|\cdot\|_{L_p}$-norm. This strengthens the corresponding result of de Pagter and Sukochev for $p\neq 2$ and extends it to higher-order derivatives. In addition, if $f^{(n)}\in C_0(\mathbb{R})$ or $b\in \mathcal{M}$, then $ϕ^{(n)}$ is continuous on $\mathbb{R}$. Consequently, we extend the Potapov--Skripka--Sukochev higher-order trace formula from bounded $L_n$-perturbations to not necessarily bounded perturbations in $L_n(\mathcal{M})\cap L_{n^{2}}(\mathcal{M})$. Moreover, we show that this trace formula holds for a broader class of admissible functions than the classes previously considered in the literature.

2602.09715 2026-02-18 physics.soc-ph cond-mat.dis-nn cond-mat.stat-mech math-ph math.MP nlin.AO

Topology and higher-order global synchronization on directed and hollow simplicial and cell complexes

Runyue Wang, Timoteo Carletti, Ginestra Bianconi

Comments 24 pages, 10 figures

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Higher-order networks encode the many-body interactions of complex systems ranging from the brain to biological transportation networks. Simplicial and cell complexes are ideal higher-order network representations for investigating higher-order topological dynamics where dynamical variables are not only associated with nodes, but also with edges, triangles, and higher-order simplices and cells. Global Topological Synchronization (GTS) refers to the dynamical state in which identical oscillators associated with higher-dimensional simplices and cells oscillate in unison. On standard unweighted and undirected complexes this dynamical state can be achieved only under strict topological and combinatorial conditions on the underlying discrete support. In this work we consider generalized higher-order network representations including directed and hollow complexes. Based on an in depth investigation of their topology defined by their associated algebraic topology operators and Betti numbers, we determine under which conditions GTS can be observed. We show that directed complexes always admit a global topological synchronization state independently of their topology and structure. However, we demonstrate that for directed complexes this dynamical state cannot be asymptotically stable. While hollow complexes require more stringent topological conditions to sustain global topological synchronization, these topologies can favor both the existence and the stability of global topological synchronization with respect to undirected and unweighted complexes.

2602.07893 2026-02-18 cs.SE

Is Your Private Information Logged? An Empirical Study on Android App Logs

Zhiyuan Chen, Soham Sanjay Deo, Poorna Chander Reddy Puttaparthi, Vanessa Nava-Camal, Yiming Tang, Xueling Zhang, Weiyi Shang

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With the rapid growth of mobile apps, users' concerns about their privacy have become increasingly prominent. Android app logs serve as crucial computer resources, aiding developers in debugging and monitoring the status of Android apps, while also containing a wealth of software system information. Previous studies have acknowledged privacy leaks in software logs and Android apps as significant issues without providing a comprehensive view of the privacy leaks in Android app logs. In this study, we build a comprehensive dataset of Android app logs and conduct an empirical study to analyze the status and severity of privacy leaks in Android app logs. Our study comprises three aspects: (1) Understanding real-world developers' concerns regarding privacy issues related to software logs; (2) Studying privacy leaks in the Android app logs; (3) Investigating the characteristics of privacy-leaking Android app logs and analyzing the reasons behind them. Our study reveals five different categories of concerns from real-world developers regarding privacy issues related to software logs and the prevalence of privacy leaks in Android app logs, with the majority stemming from developers' unawareness of such leaks. Additionally, our study provides developers with suggestions to safeguard their privacy from being logged.

2602.07204 2026-02-18 math.DG math.DS math.GT

Entropy-Minimizing Diffeomorphisms on a $G_2$-Manifold

Ollie Thakar

Comments 13 pages

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In this paper, we construct infinitely many diffeomorphisms of a Joyce manifold $M$ which achieve Yomdin's homological lower bound for topological entropy, imitating a recent construction of Farb-Looijenga for K3 surfaces. Moreover, following a recent paper by Crowley-Goette-Hertl, we show these diffeomorphisms act freely on a connected component of the Teichmüller space of $G_2$ structures on $M$, and hence that the homotopy moduli space of $G_2$ structures on $M$ has infinite fundamental group. We also discuss a putative analogy between dynamics on a $G_2$ manifold and that of an algebraic surface, and prove a theorem about its limitations.

2602.07110 2026-02-18 quant-ph cond-mat.str-el hep-ph hep-th math.QA

Beyond Wigner: Non-Invertible Symmetries Preserve Probabilities

Thomas Bartsch, Yuhan Gai, Sakura Schafer-Nameki

Comments 4 pages + Supplementary Material, v2: references added

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In recent years, the traditional notion of symmetry in quantum theory was expanded to so-called generalised or categorical symmetries, which, unlike ordinary group symmetries, may be non-invertible. This appears to be at odds with Wigner's theorem, which requires quantum symmetries to be implemented by (anti)unitary -- and hence invertible -- operators in order to preserve probabilities. We resolve this puzzle for (higher) fusion category symmetries $\mathcal{C}$ by proposing that, instead of acting by unitary operators on a fixed Hilbert space, symmetry defects in $\mathcal{C}$ act as isometries between distinct Hilbert spaces constructed from twisted sectors. As a result, we find that non-invertible symmetries naturally act as trace-preserving quantum channels. Crucially, our construction relies on the symmetry category $\mathcal{C}$ being unitary. We illustrate our proposal through several examples that include Tambara-Yamagami, Fibonacci, and Yang-Lee as well as higher categorical symmetries.

2602.03650 2026-02-18 astro-ph.SR

The Tarantula massive binary monitoring VII. The nature of the eccentric O+BH binary candidate VFTS 812

K. Deshmukh, H. Sana, O. Verhamme, R. Willcox, P. Marchant, T. Shenar, F. Backs, S. Janssens, B. Ludwig, L. Mahy, J. O. Sundqvist, J. I. Villaseñor

Comments 8 pages, 6 figures. Accepted in A&A

Journal ref A&A 706, L17 (2026)

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Massive O-type stars ($M\gtrsim15\,M_\odot$) with an X-ray quiet black hole (BH) companion represent a crucial stage in massive binary evolution leading to binary BH mergers. The population of such binaries remains elusive, with $\lesssim5$ candidate or confirmed systems. The Tarantula nebula harbors thousands of massive stars, 2-3 % of which are expected to have BH companions. It is therefore an ideal place to hunt for such systems. Here we analyse 30 epochs of VLT/FLAMES IFU high-resolution observations of the H$δ$ region, as well as archival FLAMES spectroscopy, of VFTS 812, a 17-day single-lined spectroscopic binary with an O4V primary and a minimum secondary mass of $5.1\,M_\odot$. Following careful removal of the nebular contamination, spectral disentangling on the new data did not reveal any signature of the hidden companion. We derive $T_\mathrm{eff}=49^{+3}_{-4}$ kK, $\log L/L_\odot=5.7\pm0.1$ and $v_\mathrm{rot,max}{\rm \,sin\,}i=110^{+25}_{-35}$ km/s for the O4V component, yielding a (single star) evolutionary mass of $53^{+6}_{-5}$ $M_\odot$ and an age in the range of 0-1.6 Myr. Using injection tests of various luminous artificial companions in our data, we exhaustively rule out the presence of any luminous signature from a main sequence star more massive than $6\,M_\odot$. We discuss the possible nature of the companion, suggesting that the rejuvenated O star + BH companion is the most suitable scenario to consistently explain the location, (rejuvenated) young age, eccentricity and lack of companion signature. While this establishes VFTS 812 as a strong candidate O+BH system, follow-up observations are deemed necessary for robust confirmation and to search for accretion signatures on the O4V star.

2602.02652 2026-02-18 astro-ph.GA

WLM: Dynamics of an isolated Dwarf Irregular Galaxy Under Ram Pressure in the Local Group

Neel Kolhe, Francois Hammer, Yanbin Yang, Brenda Namumba, Laurent Chemin, Philippe Amram, Roger Ianjamasimanana, Claude Carignan

Comments 15 pages, 17 Figures, accepted in Astronomy and Astrophysics, 18th January 2026

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WLM is an archetypal dwarf irregular galaxy that has not experienced interactions with major Local Group galaxies within the past 8 Gyr. It has recently been shown that WLM is losing its gas due to ram pressure forces exerted by the surrounding intergalactic medium (IGM). In this work, we explore how ram pressure may also affect the WLM gas kinematics, and we show that its dynamics is especially perturbed at its outskirts, explaining the asymmetric rotation between the approaching and receding sides. Moreover, we have been able to decompose WLM in two main components, a compact one with a solid-body rotation that resembles a bar-like structure, and a more extended one with a characteristic double-horn profile suggesting an edge-on disk. The former is relatively unaffected by ram pressure while the latter has its dynamics considerably affected by ram pressure. This study shows that mass estimates of a dwarf galaxy like WLM should account for a full modeling of its dynamical components, especially accounting for its asymmetric rotation curve.

2602.02042 2026-02-18 math.AG

Singularities in any Characteristic

Gert-Martin Greuel

Comments 41 pages. In Memoriam Wolfgang Ebeling. Titel changed. Accepted for publication in the Journal of Singularities, Special volume in honor of Wolfgang Ebeling

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We give an overview of the fundamental definitions and results concerning hypersurface singularities, defined by convergent power series over an arbitrary real valued field. This approach combines, on the one hand, the classical case of analytic power series over the complex numbers with formal power series over arbitrary fields, but on the other hand, it goes significantly beyond that. Besides general definitions and basic results, we report on the classification of contact simple and right simple singularities in positive characteristic. Some of the results are new in this general setting, for which we provide complete proofs.

2602.01987 2026-02-18 math.OA

Unitary normalizers in finite-dimensional inclusions

Keshab Chandra Bakshi, Silambarasan C

Comments Minor changes, typos corrected, 33 pages

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We study regular inclusions of finite-dimensional von Neumann algebras from a matrix-theoretic perspective. To this end, we introduce a new combinatorial invariant of an inclusion, called the normalizer matrix, which encodes the structure of the normalizer purely at the level of the inclusion matrix. Using this invariant, we obtain a complete characterization of regular inclusions of finite-dimensional von Neumann algebras. As consequences, we show that every regular inclusion decomposes into finite direct sums and tensor products of basic building blocks, and that regular inclusions are necessarily of depth two. We further investigate the existence of unitary orthonormal bases in the sense of Pimsner-Popa and prove that, under a natural spectral condition, regularity is equivalent to the existence of a unitary orthonormal basis contained in the normalizer. These results provide a unified description of regularity, unitary bases, and depth through the normalizer matrix formalism.

2601.23029 2026-02-18 math.OA math.KT

The uniqueness theorem for Kasparov theory

Gábor Szabó

Comments v2 33 pages; rewritten intro, extra corollaries, improved notation and minor corrections

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Answering a question of Carrión et al in their recent landmark paper on C*-algebra classification, we prove a general uniqueness theorem for $KK$-theory. Given arbitrary separable C*-algebras $A$ and $B$ and a Cuntz pair consisting of two absorbing representations $φ,ψ: A\to\mathcal{M}(B\otimes\mathcal{K})$, the induced element of $KK(A,B)$ vanishes if and only if $φ$ and $ψ$ are strongly asymptotically unitarily equivalent. This improves upon the Lin-Dadarlat-Eilers stable uniqueness theorem. The conclusion is deduced by first showing the $K_1$-injectivity of an auxiliary C*-algebra associated to the C*-pair $(A,B)$, which is sometimes called the Paschke dual algebra in the literature. Most of the article is concerned with the treatment of an umbrella theorem, which yields such a uniqueness theorem for other variants of $KK$-theory. This encompasses nuclear $KK$-theory, ideal-related $KK$-theory, equivariant $KK$-theory, or any combinations thereof.

2601.22772 2026-02-18 cs.CR

Rust and Go directed fuzzing with LibAFL-DiFuzz

Timofey Mezhuev, Darya Parygina, Daniil Kuts

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英文摘要

In modern SSDLC, program analysis and automated testing are essential for minimizing vulnerabilities before software release, with fuzzing being a fast and widely used dynamic testing method. However, traditional coverage-guided fuzzing may be less effective in specific tasks like verifying static analysis reports or reproducing crashes, while directed fuzzing, focusing on targeted program locations using proximity metrics, proves to be more effective. Some of the earliest directed fuzzers are, for example, AFLGo and BEACON, which use different proximity metric approaches. Although most automated testing tools focus on C/C++ code, the growing popularity of Rust and Go causes the need for precise and efficient testing solutions for these languages. This work expands the applicability of directed fuzzing beyond traditional analysis of C/C++ software. We present a novel approach to directed greybox fuzzing tailored specifically for Rust and Go applications. We introduce advanced preprocessing techniques, rustc compiler customizations, and elaborate graph construction and instrumentation methods to enable effective targeting of specific program locations. Our implemented fuzzing tools, based on LibAFL-DiFuzz backend, demonstrate competitive advantages compared to popular existing fuzzers like afl$.$rs, cargo-fuzz, and go-fuzz. According to TTE (Time to Exposure) experiments, Rust-LibAFL-DiFuzz outperforms other tools by the best TTE result. Some stability issues can be explained by different mutation approaches. Go-LibAFL-DiFuzz outperforms its opponent by the best and, in the majority of cases, by average result, having two cases with orders of magnitude difference. These results prove better efficiency and accuracy of our approach.

2601.18277 2026-02-18 cond-mat.mes-hall cond-mat.mtrl-sci

Voltage-controlled topological spin textures in the monolayer limit

Yangliu Wu, Bo Peng, Zhaozhuo Zeng, Chendi Yang, Haipeng Lu, Peiheng Zhou, Jianliang Xie, Difei Liang, Linbo Zhang, Peng Yan, Haizhong Guo, Renchao Che, Longjiang Deng

Comments 4 figures

Journal ref Nature Communications 2026

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英文摘要

The physics of phase transitions in low-dimensional systems has long been a subject of significant research interest. Long-range magnetic order in the strict two-dimensional limit, whose discovery circumvented the Mermin-Wagner theorem, has rapidly emerged as a research focus. However, the demonstration of a non-trivial topological spin textures in two-dimensional limit has remained elusive. Here, we demonstrate the out-of-plane electric field breaks inversion symmetry while simultaneously modulating the electronic band structure, enabling electrically tunable spin-orbit interaction for creation and manipulation of topological spin textures in monolayer CrI3. The realization of ideal two-dimensional topological spin textures may offer not only an experimental testbed for probing the Berezinskii-Kosterlitz-Thouless mechanism, but also potential insights into unresolved quantum phenomena including superconductivity and superfluidity. Moreover, voltage-controlled spin-orbit interaction offers a novel pathway to engineer two-dimensional spin textures with tailored symmetries and topologies, while opening avenues for skyrmion-based next-generation information technologies.

2601.16789 2026-02-18 astro-ph.HE astro-ph.SR

[HP99] 159 -- Properties of the first Supersoft X-ray Source with a Helium star donor

Hélène Szegedi, Philip A. Charles, David A. H. Buckley, Pieter J. Meintjes, Przemek Mróz, Andrzej Udalski

Comments 8 pages, 8 figures, Accepted for publication in MNRAS

Journal ref Mon Not R Astron Soc (2026)

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英文摘要

[HP99] 159 is remarkable as the first supersoft X-ray source (SSS) identified with an evolved helium star donor. With a likely orbital period of 1.164 d or 2.327 d, the origin of the SSS component is controversial, with the two current models being either steady He-burning on the white dwarf surface, or that it is a helium nova in the decaying phase. To help resolve this issue we present extensive new long-term spectroscopy (with SALT) and photometry (at SAAO and with OGLE) of [HP99] 159 which (a) supports 2.327 d as the orbital period, and (b) finds only a small He II radial velocity modulation. The latter is surprising as it implies a very low inclination system, whereas our light curve modelling suggests $i{\sim}50^\circ$, and hence that the He II must be produced in outflowing material further above, or beyond, the disc. We find that the decaying nova model cannot fit our OGLE light curve and the observed SSS flux level. [HP99] 159 has been essentially constant as an SSS over several decades, implying a sustained high level of mass-transfer from its He star donor, making it the only confirmed single-degenerate scenario SN Ia progenitor. We have updated the known SSS binary parameters and find a clear $\sim$1.5 mag difference in their $M_{\rm V}$ when compared to the $M_{\rm V} - Σ$ properties of LMXBs, likely due to the larger irradiated areas and more luminous donors.

2601.16716 2026-02-18 cond-mat.stat-mech

What is nonequilibrium?

Christian Maes

Comments About 100 pages of introduction to nonequilibrium stuff. Updates available via https://fys.kuleuven.be/english/staff/christ/onderwijs-teaching-material

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英文摘要

Lecture notes on elements of nonequilibrium statistical mechanics: (1) a characterization of the nonequilibrium condition, largely by contrast to equilibrium; (2) a retelling of some of the great performances of the more distant past, including the perspectives of Boltzmann and Onsager; and (3) more recent methods and concepts, from local detailed balance and the identification of entropy fluxes to dynamical fluctuation theory, and the importance of dynamical activity.

2601.15999 2026-02-18 eess.SP

A Covariance Matching Approach to Graph Topology Identification

Yongsheng Han, Raj Thilak Rajan, Geert Leus

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英文摘要

Graph topology identification (GTI) is a central challenge in networked systems, where the underlying structure is often hidden, yet nodal data are available. Conventional solutions to address these challenges rely on probabilistic models or complex optimization formulations, commonly suffering from non-convexity or requiring restrictive assumptions on acyclicity or positivity. In this paper, we propose a novel covariance matching (CovMatch) framework that directly aligns the empirical covariance of the observed data with the theoretical covariance implied by an underlying graph. We show that as long as the data-generating process permits an explicit covariance expression, CovMatch offers a unified route to topology inference. We showcase our methodology on linear structural equation models (SEMs), showing that CovMatch naturally handles both undirected and general sparse directed graphs - whether acyclic or positively weighted - without explicit knowledge of these structural constraints. Through appropriate reparameterizations, CovMatch simplifies the graph learning problem to either a conic mixed integer program for undirected graphs or an orthogonal matrix optimization for directed graphs. Numerical results confirm that, even for relatively large graphs, our approach efficiently recovers the true topology and outperforms standard baselines in accuracy. These findings highlight CovMatch as a powerful alternative to log-determinant or Bayesian methods for GTI, paving the way for broader research on learning complex network topologies with minimal assumptions.

2601.14296 2026-02-18 cs.MA

From Agent Simulation to Social Simulator: A Comprehensive Review (Part 2)

Xiao Xue, Deyu Zhou, Ming Zhang, Xiangning Yu, Fei-Yue Wang

Comments This paper is Part II of a planned multi-part review series on "From Agent Simulation to Social Simulator". It is a self-contained article and can be read independently of Part I. Although the authors have previously published related work, this submission is not a revision or updated version of any earlier paper

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英文摘要

The study of system complexity primarily has two objectives: to explore underlying patterns and to develop theoretical explanations. Pattern exploration seeks to clarify the mechanisms behind the emergence of system complexity, while theoretical explanations aim to identify the fundamental causes of this complexity. Laws are generally defined as mappings between variables, whereas theories offer causal explanations of system behavior. Agent Based Modeling(ABM) is an important approach for studying complex systems, but it tends to emphasize simulation over experimentation. As a result, ABM often struggles to deeply uncover the governing operational principles. Unlike conventional scenario analysis that relies on human reasoning, computational experiments emphasize counterfactual experiments-that is, creating parallel worlds that simulate alternative "evolutionary paths" of real-world events. By systematically adjusting input variables and observing the resulting changes in output variables, computational experiments provide a robust tool for causal inference, thereby addressing the limitations of traditional ABM. Together, these methods offer causal insights into the dynamic evolution of systems. This part can help readers gain a preliminary understanding of the entire computational experiment method, laying the foundation for the subsequent study.