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Mathematics

arXiv preprints from January 1, 2026 through July 21, 2026 — 08:20:27 EST

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Posted in math.AP · 2026-01-06 · Mohamed Wakrim

The W-Operator: A Volterra Fractional Time Operator with Sharp Bernstein Threshold and Regularized Memory

We introduce a new two-parameter fractional time operator with Volterra structure, denoted by ${}^{W}D_{t}^{α,β}$, defined through the Laplace symbol \[ Φ_{α,β}(s) = \frac{s^α}{\bigl(1+(1-α)s^{α-1}\bigr)^β}, \qquad 0<α<1, \ β\ge0. \] The operator preserves the Caputo-type high-frequency behavior while allowing a controlled...

💬 0 commentsarXiv:2601.02876v2PDF
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Posted in math.AP · 2026-01-06 · Takanobu Hara

Global Hölder Solvability of parabolic equations on domains with capacity density conditions

We investigate the Cauchy-Dirichlet problem for linear parabolic equations in divergence form. Under mild assumptions on the source term and the domain, we prove the existence of globally Hölder continuous solutions. Notably, our results accommodate data exhibiting singularities nearly as critical as the inverse square of the distance...

💬 0 commentsarXiv:2601.02863v1PDF
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Posted in math.AP · 2026-01-06 · Grigori Rozenblum, Nikolay Shirokov

Higher order H{ö}lder approximation by solutions of second order elliptic equations

For a given second order elliptic operation $\mathcal{L}$ in a domain $Ω\subset{\mathbb{R}}^\mathbf{N}$, $\mathbf{N}\ $, and a compact set $\mathbf{K}\subsetΩ$, order $\mathbf{N}$-$2$-Ahlfors-David regular, we define the space $\mathcal{H}^{\mathbf{r}+ω}_{\mathcal{L}}(\mathbf{K})$ of continuous functions $f(x),\, x\in\mathbf{K}$,...

💬 0 commentsarXiv:2601.02859v1PDF
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Posted in math.OC · 2026-01-06 · Felix Laurent, Feiran Zhao, Jaap Eising, Florian Dörfler

Adaptive Control of Unknown Linear Switched Systems via Policy Gradient Methods

We consider the policy gradient adaptive control (PGAC) framework, which adaptively updates a control policy in real time, by performing data-based gradient descent steps on the linear quadratic regulator cost. This method has empirically shown to react to changing circumstances, such as model parameters, efficiently. To formalize...

💬 0 commentsarXiv:2601.03016v1PDF
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Posted in math.OC · 2026-01-06 · Higor V. M. Ferreira, Camila A. Tavares, Nelson H. T. Lemes, José P. C. dos Santos

An overview of the fractional-order gradient descent method and its applications

Recent studies have shown that fractional calculus is an effective alternative mathematical tool in various scientific fields. However, some investigations indicate that results established in differential and integral calculus do not necessarily hold true in fractional calculus. In this work we will compare various methods presented...

💬 0 commentsarXiv:2601.03318v2PDF
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Posted in math.NA · 2026-01-06 · Angelo Iollo, Jon Labatut, Pierre Mounoud, Tommaso Taddei

Mathematical aspects of registration methods in bounded domains

Registration methods in bounded domains have received significant attention in the model reduction literature, as a valuable tool for nonlinear approximation. The aim of this work is to provide a concise yet complete overview of relevant results for registration methods in $n$-dimensional domains, from the perspective of parametric...

💬 0 commentsarXiv:2601.03010v1PDF
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Posted in math.OC · 2026-01-06 · Lianghai Xiao, Yitian Qian, Shaohua Pan

A Relaxation Method for Nonsmooth Nonlinear Optimization with Binary Constraints

We study binary optimization problems of the form \( \min_{x\in\{-1,1\}^n} f(Ax-b) \) with possibly nonsmooth loss \(f\). Following the lifted rank-one semidefinite programming (SDP) approach\cite{qian2023matrix}, we develop a majorization-minimization algorithm by using the difference-of-convexity (DC) reformuation for the rank-one...

💬 0 commentsarXiv:2601.03008v1PDF
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Posted in math.PR · 2026-01-06 · Renxing Li, Xue Zhang

G-BSDEs with time-varying monotonicity condition

In this paper, we study backward stochastic differential equations driven by G-Brownian motion where the generator has time-varying monotonicity with respect to y and Lipsitz property with respect to z. Through the Yosida approximation, we have proved the existence and uniqueness of the solutions to these equations.

💬 0 commentsarXiv:2601.03006v2PDF
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Posted in math.GR · 2026-01-06 · Zhouxiang Huang, Dekui Peng, Gao Zhang

Remarks on $d$-independent topological groups

A non-trivial topological group is called \emph{$d$-independent} if for every subgroup of cardinality less than the continuum there exists a countable dense subgroup intersecting it trivially. This notion was introduced by Márquez and Tkachenko and has been intensively studied in the metrizable setting. In particular, they proved that...

💬 0 commentsarXiv:2601.03000v1PDF
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Posted in math.CO · 2026-01-06 · Colin Geniet, Fatemeh Ghasemi, Mamadou Moustapha Kanté

Transducing Linear Decompositions of Tournaments

Bojańczyk, Pilipczuk, and Grohe [LICS '18] proved that for graphs of bounded linear clique-width, clique-decompositions of bounded width can be produced by a CMSO transduction. We show that in the case of tournaments, a first-order transduction suffices. This implies that the logics CMSO and existential MSO are equivalent over bounded...

💬 0 commentsarXiv:2601.02999v2PDF
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Posted in math.PR · 2026-01-06 · Wei Qian

Coupling Brownian loop soups and random walk loop soups at all polynomial scales

Lawler and Trujillo Ferreras constructed a well-known coupling between the Brownian loop soups on $\mathbb{R}^2$ and the (discrete-time) random walk loop soups on $\mathbb{Z}^2$ (one rescales the random walk loops by $1/N$, their time parametrizations by $1/(2N^2)$, and lets $N\to \infty$), which led to numerous applications. It...

💬 0 commentsarXiv:2601.02992v3PDF
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Posted in math.NA · 2026-01-06 · Jiyu Liu, Zhixuan Li, Jiatu Yan, Zhiqi Li, Qinghai Zhang

A Fourth-Order Cut-cell Multigrid Method for Solving Elliptic Equations on Arbitrary Domains

To numerically solve a generic elliptic equation on two-dimensional domains with rectangular Cartesian grids, we propose a cut-cell geometric multigrid method that features (1) general algorithmic steps that apply to two-dimensional constant-coefficient elliptic equations with both divergence and non-divergence forms and all types of...

💬 0 commentsarXiv:2601.02975v3PDF
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Posted in math.AG · 2026-01-06 · Livia Campo, Kento Fujita, Taro Sano, Luca Tasin

K-stability of Fano weighted hypersurfaces via plt flags and convex geometry

We develop a framework to study the K-stability of weighted Fano hypersurfaces based on a combination of birational and convex-geometric techniques. As an application, we prove that all quasi-smooth weighted Fano hypersurfaces of index 1 with at most two weights greater than 1 are K-stable. We also construct several examples of...

💬 0 commentsarXiv:2601.02974v1PDF
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Posted in math.GR · 2026-01-06 · Muhammad Shah, S. Shpectorov

Enumerating AG-monoids algebraically

An AG-monoid is an AG-groupoid (a groupoid satisfying the identity called left invertive law $(xy)z=(zy)x$) and having a left identiy. In this paper we enumerate AG-monoids algebraically and then implement them in GAP to compute them computationally.

💬 0 commentsarXiv:2601.03312v1PDF
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Posted in math.CO · 2026-01-06 · Darij Grinberg, Ekaterina A. Vassilieva

The left-to-right minima basis of the group algebra of the symmetric group (updated version)

We introduce a new basis of the group algebra of the symmetric group, built using the left-to-right minima sets of permutations. We show that on this basis, the descent algebra acts by triangular operators, thus making it an analogue of a cellular basis. The proof involves Dynkin elements (nested commutators) of the free algebra and...

💬 0 commentsarXiv:2601.02952v2PDF
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Posted in math.OC · 2026-01-06 · Arjan van der Schaft

Hopfield neural networks as port-Hamiltonian and gradient systems

The structure of continuous Hopfield networks is revisited from a system-theoretic point of view. After adopting a novel electrical network interpretation involving nonlinear capacitors, it is shown that Hopfield networks admit a port-Hamiltonian formulation provided an extra passivity condition is satisfied. Subsequently it is shown...

💬 0 commentsarXiv:2601.02951v1PDF
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Posted in math.PR · 2026-01-06 · Alexander Iksanov, Zakhar Kabluchko, Vitali Wachtel

First passage times for decoupled random walks

Motivated by a connection to the infinite Ginibre point process, decoupled random walks were introduced in a recent article Alsmeyer, Iksanov and Kabluchko (2025). The decoupled random walk is a sequence of independent random variables, in which the $n$th variable has the same distribution as the position at time $n$ of a standard...

💬 0 commentsarXiv:2601.03109v1PDF
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Posted in math.AP · 2026-01-06 · Côme Tabary

On the monotonicity of the entropy production in the Landau-Maxwell equation

We study the homogeneous Landau equation with Maxwell molecules and prove that the entropy production is non-increasing provided the directional temperatures are well-distributed and the solution admits a moment of order $\ell$, for some $\ell$ arbitrarily close to $2$. It implies that for an initial condition with finite moment of...

💬 0 commentsarXiv:2601.03107v3PDF
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Posted in math.AT · 2026-01-06 · Dan Petersen, Victor Roca i Lucio, Sinan Yalin

Point-set models for homotopy coherent coalgebras

We show a first rectification result for homotopy chain coalgebras over a field. On the one hand, we consider the $\infty$-category obtained by localizing differential graded coalgebras over an operad with respect to quasi-isomorphisms; on the other, we give a general definition of an $\infty$-category of coalgebras over an enriched...

💬 0 commentsarXiv:2601.03101v2PDF
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Posted in math.DG · 2026-01-06 · Iury Domingos, Irene. I. Onnis

Spherical Ricci tori with rotational symmetry

In this article, we study $c$-spherical Ricci metrics, that is, Riemannian metrics whose Gaussian curvature $K$ satisfies \begin{equation*} (K - c)ΔK - |\nabla K|^2 - 4K(K - c)^2 = 0, \end{equation*} for some $c>0$. We explicitly construct a two-parameter family of such metrics with rotational symmetry and show that infinitely many...

💬 0 commentsarXiv:2601.03096v1PDF