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2505.21054 2026-04-17 cond-mat.str-el hep-ph

Polaron formation as the vertex function problem: From Dyck's paths to self-energy Feynman diagrams

Tomislav Miškić, Juraj Krsnik, Stefano Ragni, Andrey S. Mishchenko, Osor S. Barišić

Comments 25 pages, 4 figures, 2 tables

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We present an iterative method for generating the complete set of self-energy Feynman diagrams at arbitrary order for the single-polaron problem with arbitrary linear coupling to the lattice. The approach combines a combinatorial representation of noncrossing diagrams, based on Dyck paths associated with Stieltjes-Rogers polynomials, with the constraints of the Ward-Takahashi identity to systematically incorporate vertex corrections. This construction yields a one-to-one correspondence between terms in the expansion based on Stieltjes-Rogers polynomials and diagrammatic contributions, and provides, through a sequence of simple steps, a closed, algorithmic framework for generating all diagrams of a given order, together with their relative weights. The method enables efficient, unbiased evaluation of diagrammatic series and improves the convergence of diagrammatic Monte Carlo by eliminating the need for stochastic weighting between different topologies. We further outline how the construction can be generalized to finite-density electron systems.

2505.20954 2026-04-17 cond-mat.dis-nn cond-mat.stat-mech

Finding the right path: statistical mechanics of connected solutions in constraint satisfaction problems

Damien Barbier

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We define and study a statistical mechanics ensemble that characterizes connected solutions in constraint satisfaction problems (CSPs). Built around a well-known local entropy bias, it allows us to better identify hardness transitions in problems where the energy landscape is dominated by isolated solutions. We apply this new device to the symmetric binary perceptron model (SBP), and study how its manifold of connected solutions behaves. We choose this particular problem because, while its typical solutions are isolated, it can be solved using local algorithms for a certain range of constraint density $α$ and threshold $κ$. With this new ensemble, we unveil the presence of a cluster composed of delocalized connected solutions. In particular, we demonstrate its stability until a critical threshold $κ^{\rm no-mem}_{\rm loc.\, stab.}$ (dependent on $α$). This transition appears as paths of solutions shatter, a phenomenon that more conventional statistical mechanics approaches fail to grasp. Finally, we compared our predictions to simulations. For this, we used a modified Monte-Carlo algorithm, designed specifically to target these delocalized solutions. We obtained, as predicted, that the algorithm finds solutions until $κ\approxκ^{\rm no-mem}_{\rm loc.\, stab.}$.

2505.07427 2026-04-17 stat.AP cs.CE

Value of Information-based assessment of strain-based thickness loss monitoring in ship hull structures

Nicholas E. Silionis, Konstantinos N. Anyfantis

Comments 39 pages, 18 figures, Preprint submitted to journal

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Recent advances in Structural Health Monitoring (SHM) have attracted industry interest, yet real-world applications, such as in ship structures remain scarce. Despite SHM's potential to optimise maintenance, its adoption in ships is limited due to the lack of clearly quantifiable benefits for hull maintenance. This study employs a Bayesian pre-posterior decision analysis to quantify the value of information (VoI) from SHM systems monitoring corrosion-induced thickness loss (CITL) in ship hulls, in a first-of-its-kind analysis for ship structures. We define decision-making consequence cost functions based on exceedance probabilities relative to a target CITL threshold, which can be set by the decision-maker. This introduces a practical aspect to our framework, that enables implicitly modelling the decision-maker's risk perception. We apply this framework to a large-scale, high-fidelity numerical model of a commercial vessel and examine the relative benefits of different CITL monitoring strategies, including strain-based SHM and traditional on-site inspections.

2505.05220 2026-04-17 math.GR math.MG math.RT

A fixed point theorem for the action of linear higher rank algebraic groups over local fields on symmetric spaces of infinite dimension and finite rank

Federico Viola

Comments V2: we have generalized the result for SL_n(F) from the first version to all almost simple linear higher rank algebraic groups over F, with the assumption that F has characteristic zero and its residue field has at least three elements. 29 pages

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Let F be a non-archimedean local field of characteristic zero whose residue field has at least three elements. Let G be an almost simple linear algebraic group over F, with rank_F(G) >= 2. Let X be a simply connected symmetric space of infinite dimension and finite rank, with non-positive curvature operator. We prove that every continuous action by isometries of G on X has a fixed point. If the group G contains SL_3(F), the result holds without any assumption on the non-archimedean local field F. The result extends to cocompact lattices in G if the cardinality of the residue field of F is large enough, with a bound that depends on rank_F(G).

2505.05109 2026-04-17 physics.comp-ph physics.bio-ph

Structure determination from single-molecule X-ray scattering images using stochastic gradient ascent

Steffen Schultze, D. Russell Luke, Helmut Grubmüller

Comments 24 pages, 6 figures

Journal ref J. Chem. Theory Comput. 2025, 21, 16, 8227-8234

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Scattering experiments using ultrashort X-ray free electron laser (XFEL) pulses have opened a new path for structure determination of a wide variety of specimens, including nano-crystals and entire viruses, approaching atomistic spatial and femtoseconds time resolution. However, random and unknown sample orientations as well as low signal to noise ratios have so far prevented a successful application to smaller specimens like single biomolecules. We here present resolution-annealed stochastic gradient ascent (RASTA), a new approach for direct atomistic electron density determination, which utilizes our recently developed rigorous Bayesian treatment of single-particle X-ray scattering. We demonstrate electron density determination at 2Å resolution of various small proteins from synthetic scattering images with as low as 15 photons per image.

2505.00563 2026-04-17 gr-qc astro-ph.CO hep-ph

Dark matter and modified gravity: Einstein clusters from a non-minimally coupled vector field

Pedro G. S. Fernandes, Vitor Cardoso

Comments 5 pages: V2: expanded discussion and new title

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We show that a vector field non-minimally coupled to gravity reproduces exactly the dynamics of an Einstein cluster -- a large ensemble of non-interacting particles moving on circular geodesics under their collective gravitational field. Since Einstein clusters are known to be able to account for flat galactic rotation curves, our results suggest that such rotation curves may arise as a manifestation of modified gravity.

2504.15692 2026-04-17 math-ph cond-mat.mtrl-sci math.MP

A new representation formula for the logarithmic corotational derivative -- a case study in application of commutator based functional calculus

Michal Bathory, Miroslav Bulíček, Josef Málek, Vít Průša

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The logarithmic corotational derivative is a key concept in rate-type constitutive relations in continuum mechanics. The derivative is defined in terms of the logarithmic spin tensor, which is a skew-symmetric tensor/matrix given by a relatively complex formula. Using a newly developed commutator based functional calculus, we derive a new representation formula for the logarithmic spin tensor. In addition to the result on the logarithmic corotational derivative we also use the newly developed functional calculus to answer some problems regarding the matrix logarithm and the monotonicity of stress-strain relations. These results document that the commutator based functional calculus is of general use in tensor/matrix analysis, and that the calculus allows one to seamlessly work with tensor/matrix valued functions and their derivatives.

2504.10166 2026-04-17 cs.MM

Fact-Checking with Contextual Narratives: Leveraging Retrieval-Augmented LLMs for Social Media Analysis

Arka Ujjal Dey, Muhammad Junaid Awan, Georgia Channing, Christian Schroeder de Witt, John Collomosse

Comments This work has been submitted to the IEEE for possible publication

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We propose CRAVE (Cluster-based Retrieval Augmented Verification with Explanation); a novel framework that integrates retrieval-augmented Large Language Models (LLMs) with clustering techniques to address fact-checking challenges on social media. CRAVE automatically retrieves multimodal evidence from diverse, often contradictory, sources. Evidence is clustered into coherent narratives, and evaluated via an LLM-based judge to deliver fact-checking verdicts explained by evidence summaries. By synthesizing evidence from both text and image modalities and incorporating agent-based refinement, CRAVE ensures consistency and diversity in evidence representation. Comprehensive experiments demonstrate CRAVE's efficacy in retrieval precision, clustering quality, and judgment accuracy, showcasing its potential as a robust decision-support tool for fact-checkers.

2504.08978 2026-04-17 quant-ph hep-th

Non-Abelian Extensions of the Dirac Oscillator: A Theoretical Approach

Abdelmalek Boumali, Sarra Garrah

Comments accepted for publication in Modern Physics Letters A (MPLA)

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We formulate the Dirac oscillator covariantly in the presence of external non-Abelian gauge fields. More precisely, the matter field is written as $Ψ_{αA}(x)$, where $α$ denotes the Dirac index and $A$ the isospin index, so that the Hamiltonian acts on the tensor-product space $\mathbb{C}^{4}\otimes\mathbb{C}^{2}$ in the fundamental representation. Starting from the gauge-covariant Dirac equation, we then implement the oscillator interaction through the standard non-minimal substitution and promote the construction to an $\mathrm{SU}(2)$ background. In this way, we derive the associated non-Abelian field-strength tensor and isolate the commutator contribution, which has no Abelian analogue. Consequently, the generalized Pauli interaction $σ^{μν}\mathcal{F}_{μν}$ produces matrix-valued spin--isospin couplings. At the same time, the Abelian sector reduces to the conventional Moshinsky--Szczepaniak Dirac oscillator, whose exactly solvable spectrum provides a natural benchmark for the extended theory.

2504.06739 2026-04-17 cond-mat.str-el

Selective Kondo screening and strange metallicity by sliding Dirac semimetals

Hanting Zhong, Shuxiang Yang, Chao Cao, Xiao-Yong Feng, Jianhui Dai

Comments 21 pages, 18 figures (including 5 appendices)

Journal ref Phys. Rev. B 113, 075111 (2026)

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Kondo screening of local moments in normal metals typically leads to hybridized conduction and valence bands separated by a Kondo gap, resulting in an insulating state at half-band filling. We show a dramatic change of this scenario in a Dirac-semimetal-based correlated system -- a bilayer honeycomb lattice heterostructure where a local moment lattice is stacked on a Dirac semimetal breaking the inversion symmetry. This system is modeled by an extended Anderson honeycomb lattice involving the real-space dependence of major interlayer hybridization parameters on the relative sliding distance along the armchair direction. First, we unveil multiple Kondo scales and successive Kondo breakdown transitions in this correlated heterostructure under sliding. Second, we demonstrate the existence of a genuine selective Kondo screening phase which is stabilized near the A-B stack pattern and is accessible by applying interlayer voltage. Third, we find a nearly flat hybridized band located concomitantly within the Kondo gap, resulting in an unprecedented metallic state at half-band filling. This unconventional heavy fermion state is characterized by violation of Luttinger theorem and appearance of a Van Hove singularity at the Fermi energy. The general sliding-driven band structure landscape and the implications of our results for the broad context of multiorbital Kondo physics are briefly discussed.

2504.03865 2026-04-17 cs.CG

Towards an Optimal Bound for the Interleaving Distance on Mapper Graphs

Erin Wolf Chambers, Ishika Ghosh, Elizabeth Munch, Sarah Percival, Bei Wang

Comments Reformulated the problem into both a binary problem and a loss computation problem

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Mapper graphs are widely used tools in topological data analysis and visualization. They can be understood as discrete approximations of Reeb graphs, providing insight into the shape and connectivity of complex data. Given a high-dimensional point cloud together with a real-valued function defined on it, a mapper graph summarizes the induced topological structure: each node represents a local neighborhood, and edges connect nodes whose corresponding neighborhoods overlap. Our focus is the interleaving distance for mapper graphs, arising as a discretized analogue of the interleaving distance for Reeb graphs-a quantity known to be NP-hard to compute. This distance measures how similar two mapper graphs are by quantifying how much they must be ``stretched'' to be made comparable. Recent work introduced a loss function that gives an upper bound on this distance. The loss evaluates how far a given collection of maps, called an assignment, is from being a true interleaving. Importantly, it is computationally tractable, offering a practical way to bound the distance, however the quality of the bound is dependent on the choice of assignment. In this paper, we develop the first framework for bounding the interleaving distance on mapper graphs. We present the bound in two ways: first, by formulating an integer linear program (ILP) that determines whether an $n$-interleaving exists for a given $n$; and second, by constructing an ILP that identifies an assignment with minimal loss for that $n$. We also evaluate the method on small examples where the interleaving distance is known, and on benchmark and simulated datasets, demonstrating the utility of the approach for classification tasks based on mapper graphs.

2504.01885 2026-04-17 cond-mat.quant-gas cond-mat.str-el quant-ph

Observing Spatial Charge and Spin Correlations in a Strongly-Interacting Fermi Gas

Cyprien Daix, Maxime Dixmerias, Yuan-Yao He, Joris Verstraten, Tim de Jongh, Bruno Peaudecerf, Shiwei Zhang, Tarik Yefsah

Comments 13 pages, 11 figures

Journal ref Phys. Rev. Lett. 136, 153402 (2026)

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In this work, we explore two-dimensional attractive Fermi gases at the microscopic level by probing spatial charge and spin correlations in situ. Using atom-resolved continuum quantum gas microscopy, we directly observe fermion pairing and study the evolution of two- and three-point correlation functions as inter-spin attraction is increased. The precision of our measurement allows us to reveal nonlocal anticorrelations in the pair correlation function, fundamentally forbidden by the mean-field result based on Bardeen-Cooper-Schrieffer (BCS) theory but whose existence we confirm in exact auxiliary-field quantum Monte Carlo calculations. We demonstrate that the BCS prediction is critically deficient not only in the superfluid crossover regime but also deep in the weakly attractive side. Guided by our measurements, we find a remarkable relation between two- and three-point correlations that establishes the dominant role of pair-correlations. Finally, leveraging local single-pair losses, we independently characterize the short-range behavior of pair correlations, via the measurement of Tan's Contact, and find excellent agreement with numerical predictions. Our measurements provide an unprecedented microscopic view into two-dimensional Fermi gases and constitute a paradigm shift for future studies of strongly-correlated fermionic matter in the continuum.

2503.24221 2026-04-17 math.NT math.AG math.RT

The Categories of Lubin-Tate and Drinfeld Bundles

James Taylor

Comments v2: journal version

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For a finite extension $F$ of $\mathbb{Q}_p$ and $n \geq 1$, we show that the category of Lubin-Tate bundles on the $(n-1)$-dimensional Drinfeld symmetric space is equivalent to the category of finite-dimensional smooth representations of the group of units of the division algebra of invariant $1/n$ over $F$.

2503.19774 2026-04-17 quant-ph gr-qc

Collapse-based models for gravity do not violate the entanglement-based witness of non-classicality

Tianfeng Feng, Vlatko Vedral, Chiara Marletto

Comments 5 pages, 1 figure

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It is known that an entanglement-based witness of non-classicality can be applied to testing quantum effects in gravity. Specifically, if a system can create entanglement between two quantum probes by local means only, then it must be non-classical. Recently, claims have been made that collapse-based models of classical gravity, i.e. Diósi-Penrose model, can predict gravitationally induced entanglement between quantum objects, resulting in gravitationally induced entanglement is insufficient to conclude that gravity is fundamentally quantum, contrary to the witness statement. Here we vindicate the witness. We analyze the underlying physics of collapse-based models for gravity and show that these models have nonlocal features, violating the principle of locality.

2503.14502 2026-04-17 physics.chem-ph cond-mat.str-el quant-ph

Precise Quantum Chemistry calculations with few Slater Determinants

Clemens Giuliani, Jannes Nys, Rocco Martinazzo, Giuseppe Carleo, Riccardo Rossi

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Slater determinants have underpinned quantum chemistry for nearly a century, yet their full potential has remained challenging to exploit. In this work, we show that a variational wavefunction composed of a few hundred optimized non-orthogonal determinants can achieve energy accuracies comparable to the state of the art. This is obtained by introducing an optimization method that leverages the quadratic dependence of the variational energy on the orbitals of each determinant, enabling an exact iterative optimization, and uses an efficient tensor-contraction algorithm to evaluate the effective Hamiltonian with a computational cost that scales as the fourth power of the number of basis functions. We benchmark the accuracy of the proposed method with exact full-configuration interaction results where available, and we achieve lower variational energies than coupled cluster (CCSD(T)) for several molecules in the double-zeta basis.

2502.04690 2026-04-17 cond-mat.str-el

Multichannel active-space embedding of atomic multiplets in plane-wave DFT/PAW for core-level spectroscopies

Alessandro Mirone, Mauro Rovezzi, Christoph Sahle, Alessandro Longo

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We introduce an active-space embedding framework for core-level spectroscopies that connects localized atomic multiplets to continuum resonances within a plane-wave DFT/PAW description. The approach is complementary to widely used core-level Bethe--Salpeter implementations based on a two-particle (core-exciton) picture with typically static screening: here a correlated multiplet manifold of the absorber (including the core hole and open-shell configurations) is coherently coupled to a plane-wave photoelectron, enabling a unified treatment of localized multiplet structure and continuum lineshapes. Spectra are computed in a general time-domain formulation equivalent to Fermi's golden rule: a transition operator tailored to the specific spectroscopy technique is applied to the correlated ground state to generate an excited wavepacket, and the corresponding wavepacket autocorrelation function is evaluated without explicit real-time propagation, using Lanczos tridiagonalization or the kernel polynomial method; the spectral intensity follows from its Fourier representation. We validate the method at the Ce \(N_{4,5}\) edges, reproducing in quantitative agreement with experiment both high-\(Q\) multiplet features and the low-\(Q\) giant dipole resonance continuum, including a characteristic low-energy shoulder relevant for robust Ce valence assignments. The implementation is available open-source within the Quantum ESPRESSO XSPECTRA package (xspectruplet mode), together with reproducible inputs and scripts.

2501.17927 2026-04-17 hep-th cond-mat.str-el math-ph math.AT math.MP quant-ph

Engineering of Anyons on M5-Probes via Flux Quantization

Hisham Sati, Urs Schreiber

Comments 48 pages with many figures, extended lecture notes based on parts of the course "Introduction to Hypothesis H" held at 45th Srni Winter School GEOMETRY AND PHYSICS in Jan 2025; v2: added §6 "Digest for Algebraic Topologists" as presented at ICMS25; v3: published version with small corrections in the very last proof

Journal ref SciPost Phys. Lect. Notes 107 (2025)

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These extended lecture notes survey a novel derivation of anyonic topological order (as seen in fractional quantum Hall systems) on single magnetized M5-branes probing Seifert orbi-singularities ("geometric engineering" of anyons), which we motivate from fundamental open problems in the field of quantum computing. The rigorous construction is non-Lagrangian and non-perturbative, based on previously neglected global completion of the M5-brane's tensor field by flux-quantization consistent with its non-linear self-duality and its twisting by the bulk C-field. This exists only in little-studied non-abelian generalized cohomology theories, notably in a twisted equivariant (and "twistorial") form of unstable Cohomotopy ("Hypothesis H"). As a result, topological quantum observables form Pontrjagin homology algebras of mapping spaces from the orbi-fixed worldvolume into a classifying 2-sphere. Remarkably, results from algebraic topology imply from this the quantum observables and modular functor of abelian Chern-Simons theory, as well as braid group actions on defect anyons of the kind envisioned as hardware for topologically protected quantum gates.

2501.10998 2026-04-17 cond-mat.supr-con

Pseudo-spin-polarized topological superconductivity in kagome RbV$_3$Sb$_5$

Xilin Feng, Zi-Ting Sun, Ben-Chuan Lin, K. T. Law

Comments 12 pages,5 figures

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Kagome superconductors AV$_3$Sb$_5$ (A=K, Rb, Cs) have sparked considerable interest due to the presence of several intertwined symmetry-breaking phases within a single material. Interestingly, in a recent experiment, magnetic hysteresis was observed in the superconducting state through magnetoresistance measurements in RbV$_{3}$Sb$_{5}$ [Nature Comm \textbf{17}, 1310 (2026)], providing strong evidence of a spontaneous time-reversal symmetry breaking superconducting state. The magnetic hysteresis, combined with crystalline symmetry, imposes strong constraints on the possible pairing symmetries of the superconducting state. In this work, we propose that RbV$_3$Sb$_5$ is a nodal topological superconductor with pseudo-spin-polarized Cooper pairs. The pseudo-spin-polarized superconducting domains resemble the properties of ferromagnetic domains and induce hysteresis. Moreover, the nodal topological superconducting state possesses Majorana flat band modes at the sample boundary, which can be detected by tunneling experiments.

2501.08217 2026-04-17 hep-lat hep-ph

Topological susceptibility and excess kurtosis in SU(3) Yang-Mills theory

Stephan Durr, Gianluca Fuwa

Comments 21 pages, 12 tables, 10 figures. v2: some runs (in particular central ensemble L/a=18,beta=6.1912,7_stout) prolonged, now correcting for (tiny) finite-volume effects, text improved, primary data available at github.com/GianlucaFuwa/topology_data_25

Journal ref Phys.Rev.D 113 (2026), 054508

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We present a high-precision study of the topological susceptibility in $SU(3)$ pure gauge theory in four space-time dimensions. The result is based on ensembles at seven lattice spacings and in seven physical volumes to facilitate a controlled continuum and infinite-volume extrapolation. We use a gluonic topological charge measurement, with gradient flow smoothing in the operator. Two complementary smoothing strategies are used (one keeps the flow time fixed in lattice units, one in physical units). Our data support the idea that both strategies yield a universal continuum limit; we find $χ_\mathrm{top}^{1/4}r_0=0.4775(14)(11)$ or $χ_\mathrm{top}^{1/4}=198.1(0.7)(2.7)\,\mathrm{MeV}$. Our appendix data suggest that the excess kurtosis $\langle q^4 \rangle / \langle q^2 \rangle^2-3$ decreases $\propto L^{-2}$ for large box sizes $L$.

2412.21050 2026-04-17 math.DG math.AP

Parabolic gap theorems for the Yang-Mills energy

Anuk Dayaprema, Alex Waldron

Comments 51 pages

Journal ref Math Phys Anal Geom 29, 12 (2026)

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We prove parabolic versions of several known gap theorems in classical Yang-Mills theory. On an $\mathrm{SU}(r)$-bundle of charge $κ$ over the 4-sphere, we show that the space of all connections with Yang-Mills energy less than $4 π^2 \left( |κ| + 2 \right)$ deformation-retracts under Yang-Mills flow onto the space of instantons, allowing us to simplify the proof of Taubes's path-connectedness theorem. On a compact quaternion-Kähler manifold with positive scalar curvature, we prove that the space of pseudo-holomorphic connections whose $\mathfrak{sp}(1)$ curvature component has small Morrey norm deformation-retracts under Yang-Mills flow onto the space of instantons. On a nontrivial bundle over a compact manifold of general dimension, we prove that the infimum of the scale-invariant Morrey norm of curvature is positive.

2412.16062 2026-04-17 quant-ph cond-mat.stat-mech

Multipartite entanglement structure of monitored quantum circuits

Arnau Lira-Solanilla, Xhek Turkeshi, Silvia Pappalardi

Comments This work contains 5 pages and 4 figures

Journal ref Phys. Rev. Lett. 135, 080401 (2025)

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Monitored quantum circuits have attracted significant interest as an example of synthetic quantum matter, intrinsically defined by their quantum information content. Here, we propose a multipartite entanglement perspective on monitored phases through the lens of quantum Fisher information. Our findings reveal that unstructured monitored random circuits fail to exhibit divergent multipartite entanglement even at criticality, highlighting their departure from standard quantum critical behavior. However, we demonstrate that genuinely multipartite entangled phases can be realized through two-site measurements, provided a protection mechanism is in place. This work positions multipartite entanglement as a valuable perspective for the study of interacting monitored circuits and broader frameworks of noisy quantum dynamics.

2412.06319 2026-04-17 math.OC

Uniformly Optimal and Parameter-free First-order Methods for Convex and Function-constrained Optimization

Qi Deng, Guanghui Lan, Zhenwei Lin

Comments Accepted to INFORMS Journal on Computing

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This paper presents new first-order methods for achieving optimal oracle complexities in convex optimization with convex functional constraints. Oracle complexities are measured by the number of function and gradient evaluations. To achieve this, we enable first-order methods to utilize computational oracles for solving diagonal quadratic programs in subproblems. For problems where the optimal value $f^*$ is known, such as those in overparameterized models and feasibility problems, we propose an accelerated first-order method that incorporates a modified Polyak step size and Nesterov's momentum. Notably, our method does not require knowledge of smoothness levels, Hölder continuity parameter of the gradient, or additional line search, yet achieves the optimal oracle complexity bound of $\mathcal{O}(\varepsilon^{-2/(1+3ρ)})$ under Hölder smoothness conditions. When $f^*$ is unknown, we reformulate the problem as finding the root of the optimal value function and develop inexact fixed-point iteration and secant method to compute $f^*$. These root-finding subproblems are solved inexactly using first-order methods to a specified relative accuracy. We employ the accelerated prox-level (APL) method, which is proven to be uniformly optimal for convex optimization with simple constraints. Our analysis demonstrates that APL-based level-set methods also achieve the optimal oracle complexity of $\mathcal{O}(\varepsilon^{-2/(1+3ρ)})$ for convex function-constrained optimization, without requiring knowledge of any problem-specific structures. Through experiments on various tasks, we demonstrate the advantages of our methods over existing approaches in function-constrained optimization.

2411.17815 2026-04-17 cond-mat.supr-con cond-mat.mtrl-sci cond-mat.str-el

Obstructed Cooper pairs in flat band systems - weakly-coherent superfluids and exact spin liquids

Tamaghna Hazra, Nishchhal Verma, Jörg Schmalian

Comments Qualitative new insights including compact localized eigenstates and extensive degeneracies in the many-body spectrum, connecting the physics of obstructed pairs with recent literature on `many-body caged spin glass' and `interference-caged quantum many-body scars'. Correction to the regime of validity for the exact mapping of the strong-pairing Hamiltonian to a solvable quantum dimer model

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Superconductivity in a partially filled flat band presents a vexing conceptual hurdle because the absence of a Fermi surface precludes a weak-coupling regime where one can extend insights from the Bardeen-Cooper-Schrieffer picture of a Fermi surface instability. We approach the strongly correlated problem of flat band superconductivity from the strong coupling limit of local attractive interactions on line-graph lattices, whose non-interacting bandstructures host exactly flat bands. In this limit, the pair kinetic energy which sets the superfluid stiffness is expected to scale inversely with the pair binding interaction. Here we demonstrate a striking counterexample. We show that when doped charges propagate on the line-graph of a lattice with strong pairing interaction, they bind into obstructed Cooper pairs whose motion is frustrated by destructive interference. As a result, the leading-order pair kinetic energy vanishes identically in the strong-coupling expansion, producing a flat bosonic band of compact localized pair states, zero superfluid stiffness at leading order, and an extensively degenerate many-body ground state manifold. At quarter filling, the frustrated pair dynamics maps onto a quantum dimer model with a $d$-wave resonating-valence-bond spin liquid ground state, which becomes exact at the analytically solvable Rokhsar-Kivelson point. The pairing Hamiltonian in this limit thus has a topologically ordered ground state with long-range entanglement and deconfined holon excitations. Interestingly, we find exact compact localized eigenstates and extensive degeneracies in the many-body eigenstates of this emergent dimer model. Our results establish a disorder-free mechanism for interaction-driven localization, in which strong pairing collapses the kinetic energy of Cooper pairs.

2410.23657 2026-04-17 cs.SE

Secret Leak Detection in Software Issue Reports using LLMs: A Comprehensive Evaluation

Sadif Ahmed, Md Nafiu Rahman, Zahin Wahab, Gias Uddin, Rifat Shahriyar

Comments Accepted at the International Conference on Mining Software Repositories (MSR) 2026

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In the digital era, accidental exposure of sensitive information such as API keys, tokens, and credentials is a growing security threat. While most prior work focuses on detecting secrets in source code, leakage in software issue reports remains largely unexplored. This study fills that gap through a large-scale analysis and a practical detection pipeline for exposed secrets in GitHub issues. Our pipeline combines regular expression-based extraction with large language model (LLM)-based contextual classification to detect real secrets and reduce false positives. We build a benchmark of 54,148 instances from public GitHub issues, including 5,881 manually verified true secrets. Using this dataset, we evaluate entropy-based baselines and keyword heuristics used by prior secret detection tools, classical machine learning, deep learning, and LLM-based methods. Regex and entropy based approaches achieve high recall but poor precision, while smaller models such as RoBERTa and CodeBERT greatly improve performance (F1 = 92.70%). Proprietary models like GPT-4o perform moderately in few-shot settings (F1 = 80.13%), and fine-tuned open-source larger LLMs such as Qwen and LLaMA reach up to 94.49% F1. Finally, we also validate our approach on 178 real-world GitHub repositories, achieving an F1-score of 81.6% which demonstrates our approach's strong ability to generalize to in-the-wild scenarios.

2410.11126 2026-04-17 physics.optics eess.IV physics.med-ph

Label-free subcellular 3D imaging of oocytes and embryos via reflection matrix microscopy

Elsa Giraudat, Victor Barolle, Flavien Bureau, Nicolas Guigui, Paul Balondrade, Christine Ho, Vincent Brochard, Olivier Dubois, Amélie Bonnet-Garnier, Alexandre Aubry

Comments 32 pages, 11 figures, 1 table

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Non-invasive morphological assessment is the cornerstone of oocyte and embryo selection in assisted reproductive technology, yet clinical practice remains limited by two-dimensional, qualitative microscopy. While three-dimensional (3D) fluorescence imaging provides cellular insights, its inherent phototoxicity precludes routine clinical use. Conversely, existing label-free modalities fail to resolve subcellular structures in thick specimens due to two distinct physical barriers: large-scale refractive index heterogeneities, such as the cumulus cells surrounding oocytes, that induce severe aberrations; and short-scale fluctuations, primarily from cytoplasmic lipids, that generate a multiple scattering ``fog''. Here, we report an ultra-fast Reflection Matrix Imaging (RMI) platform designed to overcome these depth and resolution limits. By capturing the back-scattered electromagnetic field for a set of plane-wave illuminations at multiple wavelengths, we record a multi-spectral reflection matrix. From this matrix, we leverage digital adaptive focusing algorithms to computationally compensate for sample-induced aberrations while realigning forward multiple scattering trajectories with the single-scattering contribution. This approach enables label-free 3D visualization of oocytes and blastocysts with an unprecedented subcellular resolution of 300 nm throughout the entire specimen volume. We demonstrate the reliable identification of germinal vesicles and nuclear status in stages previously inaccessible to conventional optics, including imaging through dense cumulus cells. Our method provides a powerful, non-invasive tool for objective grading across all pre-implantation stages, potentially transforming decision-making in clinical IVF.

2408.15853 2026-04-17 cs.SE

An Empirical Study of API Misuses of Data-Centric Libraries

Akalanka Galappaththi, Sarah Nadi, Christoph Treude

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Developers rely on third-party library Application Programming Interfaces (APIs) when developing software. However, libraries typically come with assumptions and API usage constraints, whose violation results in API misuse. API misuses may result in crashes or incorrect behavior. Even though API misuse is a well-studied area, a recent study of API misuse of deep learning libraries showed that the nature of these misuses and their symptoms are different from misuses of traditional libraries, and as a result highlighted potential shortcomings of current misuse detection tools. We speculate that these observations may not be limited to deep learning API misuses but may stem from the data-centric nature of these APIs. Data-centric libraries often deal with diverse data structures, intricate processing workflows, and a multitude of parameters, which can make them inherently more challenging to use correctly. Therefore, understanding the potential misuses of these libraries is important to avoid unexpected application behavior. To this end, this paper contributes an empirical study of API misuses of five data-centric libraries that cover areas such as data processing, numerical computation, machine learning, and visualization. We identify misuses of these libraries by analyzing data from both Stack Overflow and GitHub. Our results show that many of the characteristics of API misuses observed for deep learning libraries extend to misuses of the data-centric library APIs we study. We also find that developers tend to misuse APIs from data-centric libraries, regardless of whether the API directive appears in the documentation. Overall, our work exposes the challenges of API misuse in data-centric libraries, rather than only focusing on deep learning libraries. Our collected misuses and their characterization lay groundwork for future research to help reduce misuses of these libraries.

2408.09294 2026-04-17 econ.TH

How to Make an Action Attractive

Marilyn Pease, Mark Whitmeyer

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英文摘要

A policymaker often wants to steer a decision-maker toward one of two actions, but lacks reliable knowledge of how the decision-maker perceives uncertainty or evaluates risk. We formalize a notion of robust paternalism: a modification a' of a desired action a is robustly more attractive than a relative to b if, for every belief over states and every increasing concave utility function, whenever the decision-maker prefers a to b, she also prefers a' to b. We characterize all such modifications directly in terms of state-dependent payoffs and discuss applications to political competition, bilateral trade, insurance, and information acquisition.

2408.02299 2026-04-17 math.CO cs.DM cs.GT cs.LO math.LO

Various Properties of Various Ultrafilters, Various Graph Width Parameters, and Various Connectivity Systems (with Survey)

Takaaki Fujita

Comments 131 pages and Supplemental Figure(https://www.researchgate.net/publication/383432866_Supplemental_Figure_Comparing_Graph_Width_Parameter_Graph_Parameter_Hierarchy)

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英文摘要

This book studies ultrafilters on connectivity systems, that is, on pairs \((X,f)\) where \(X\) is a finite set and \(f:2^{X}\to \mathbb{N}\) is a symmetric submodular function. Ultrafilters, which play a fundamental role in topology and set theory, are considered here in this broader setting, with particular emphasis on their connections to graph width parameters and to the structural analysis of graph complexity. We develop several results on ultrafilters on connectivity systems and examine related notions such as prefilters, ultra-prefilters, and filter subbases. We also discuss additional width-, length-, and depth-type parameters that naturally arise in this framework, thereby broadening the perspective from which graph structure may be studied. In addition, the book compares a wide range of graph width parameters and related concepts, with the aim of providing a unified viewpoint and a useful point of departure for further research in graph theory and computational complexity. More broadly, the book highlights connections with several neighboring areas of mathematics, including set theory, lattice theory, and matroid theory. It also contains survey-style material intended to clarify the current landscape of graph width theory and to stimulate further developments in the subject.

2407.10851 2026-04-17 physics.atm-clus

Electronic State Chromatography of Lutetium Cations

Biswajit Jana, EunKang Kim, Aayush Arya, Elisa Romero Romero, Elisabeth Rickert, Harry Ramanantoanina, Sebastian Raeder, Michael Block, Mustapha Laatiaoui

Comments 9 pages, 10 figures

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英文摘要

Relativistic effects strongly influence the electronic structures of the heaviest elements, thereby shaping their chemical and physical properties. Studying ion mobility within a noble gas environment reveals how the ion-neutral interactions depend on the ion's electronic configurations, thus providing an avenue for exploring these effects. An ion mobility spectrometer with a cryogenic drift tube was developed to precisely measure the low-field reduced mobility of heavy lanthanide and actinide cations. The apparatus was characterized by optimizing the bunching operation of ions with a miniature RF coulomb buncher and evaluating the chromatography performance of the drift tube operated with helium buffer gas at a temperature of 298K. Systematic ion mobility measurements of lutetium cations (Lu$^{+}$) drifting in helium gas were carried out as a case study. The electronic state chromatography of Lu$^{+}$ has been demonstrated. The low-field reduced ion mobility for the ground and lowest meta-stable state of Lu$^{+}$ have been examined. In addition, the variation of both states' reduced mobility and the quenching of meta-stable population has been investigated under different reduced electric fields ($E/n_0$), the ratio of an electric field to neutral gas number density.

2407.05790 2026-04-17 stat.CO stat.ML

Kinetic Interacting Particle Langevin Monte Carlo

Paul Felix Valsecchi Oliva, O. Deniz Akyildiz

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英文摘要

This paper introduces and analyses interacting underdamped Langevin algorithms, termed Kinetic Interacting Particle Langevin Monte Carlo (KIPLMC) methods, for statistical inference in latent variable models. We propose a diffusion process that evolves jointly in the space of parameters and latent variables and show that the stationary distribution of this diffusion concentrates around the maximum marginal likelihood estimate of the parameters. We then provide two explicit discretisations of this diffusion as practical algorithms to estimate parameters of statistical models. For each algorithm, we obtain nonasymptotic rates of convergence in Wasserstein-2 distance for the case where the joint log-likelihood is strongly concave with respect to latent variables and parameters. We achieve accelerated convergence rates clearly demonstrating improvement in dimension dependence. To demonstrate the utility of the introduced methodology, we provide numerical experiments that illustrate the effectiveness of the proposed diffusion for statistical inference. Our setting covers a broad number of applications, including unsupervised learning, statistical inference, and inverse problems.