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Suppose that W is a finite, unitary reflection group acting on the complex vector space V. Let A = A(W) be the associated hyperplane arrangement of W. Terao has shown that each such reflection arrangement A is free. There is the stronger…

Group Theory · Mathematics 2013-03-04 Torsten Hoge , Gerhard Roehrle

In this paper we study the local cohomology modules of Du Bois singularities. Let $(R,m)$ be a local ring, we prove that if $R_{red}$ is Du Bois, then $H_m^i(R)\to H_m^i(R_{red})$ is surjective for every $i$. We find many applications of…

Algebraic Geometry · Mathematics 2019-02-20 Linquan Ma , Karl Schwede , Kazuma Shimomoto

In this article, we pursue two main objectives. The first is to show that the fundamental results of Green-Lazarsfeld (1987, 1991) on generic vanishing theorems, and works of Budur-Wang (2015, 2020) on cohomology jumping loci, can be…

Algebraic Geometry · Mathematics 2025-11-11 Junyan Cao , Ya Deng , Christopher D. Hacon , Mihai Paun

We derive a local index theorem in Quillen's form for families of Cauchy-Riemann operators on orbifold Riemann surfaces (or Riemann orbisurfaces) that are quotients of the hyperbolic plane by the action of cofinite finitely generated…

Algebraic Geometry · Mathematics 2024-04-19 Leon A. Takhtajan , Peter Zograf

Let $G$ be a compact connected Lie group. We show that the category $\mathbf{Loc}_{\infty}(BG)$ of $\infty$-local systems on the classifying space of $G$, can be described infinitesimally as the category…

Algebraic Topology · Mathematics 2021-05-04 Camilo Arias Abad , Santiago Pineda Montoya , Alexander Quintero Velez

In the first paper of the Graph Minors series [JCTB '83], Robertson and Seymour proved the Forest Minor theorem: the $H$-minor-free graphs have bounded pathwidth if and only if $H$ is a forest. In recent years, considerable effort has been…

Combinatorics · Mathematics 2025-12-02 Édouard Bonnet , Benjamin Duhamel , Robert Hickingbotham

The seminal work of Waldhausen, Farrell and Jones, Igusa, and Weiss and Williams shows that the homotopy groups in low degrees of the space of homeomorphisms of a closed Riemannian manifold of negative sectional curvature can be expressed…

Algebraic Topology · Mathematics 2019-08-12 Lars Hesselholt

Suppose $G$ is a simple algebraic group defined over an algebraically closed field of good characteristic $p$. In 2018 Korhonen showed that if $H$ is a connected reductive subgroup of $G$ which contains a distinguished unipotent element $u$…

Group Theory · Mathematics 2024-10-22 Michael Bate , Sören Böhm , Benjamin Martin , Gerhard Roehrle

We give new information about the relationship between the low-dimensional homology of a group and its derived series. This yields information about how the low-dimensional homology of a topological space constrains its fundamental group.…

Geometric Topology · Mathematics 2014-11-11 Tim D. Cochran , Shelly Harvey

We obtain a system of relations between linear Hodge integrals. As an application, we show that its first non-trivial relation implies the Witten's Conjecture/Kontsevich Theorem.

Algebraic Geometry · Mathematics 2007-05-23 Yon-Seo Kim , Kefeng Liu

This is an introduction to the notion of local subgroupoid introduced by the author and R. Brown. It can also serve as an introduction to an application of sheaf theory, and so could be useful to beginners in that theory. The main results…

Category Theory · Mathematics 2009-09-25 Ilhan Icen

Given a torsion theory (Y,X) in an abelian category C, the reflector I from C to the torsion-free subcategory X induces a reflective factorisation system (E, M) on C. It was shown by A. Carboni, G.M. Kelly, G. Janelidze and R. Par\'e that…

Category Theory · Mathematics 2014-01-08 Tomas Everaert , Marino Gran

We prove G\"ortz's combinatorial conjecture \cite{Go01} on dual shellability of admissible sets in Iwahori-Weyl groups, proving that the augmented admissible set $\widehat{\mathrm{Adm}}(\mu)$ is dual shellable for any dominant coweight…

Algebraic Geometry · Mathematics 2025-09-16 Xuhua He , Qingchao Yu

One of the better-known independence results in general mathematics is Shelah's solution to Whitehead's problem of whether $\mathrm{Ext}^1(A,\mathbb{Z})=0$ implies that an abelian group $A$ is free. The point of departure for the present…

Logic · Mathematics 2025-12-16 Jeffrey Bergfalk , Chris Lambie-Hanson , Jan Šaroch

An N-parameter Brownian sheet in R^d maps a non-random compact set F in R^N_+ to the random compact set B(F) in \R^d. We prove two results on the image-set B(F): (1) It has positive d-dimensional Lebesgue measure if and only if F has…

Probability · Mathematics 2007-05-23 Davar Khoshnevisan , Yimin Xiao

We begin by introducing schemes of binoids, invertible $\mathcal{O}_M$-sets and cohomology of sheaves of abelian groups defined on schemes of binoids. We define the so-called punctured combinatorial \v{C}ech-Picard complex, whose first…

Commutative Algebra · Mathematics 2016-11-09 Davide Alberelli

In this article I describe my recent geometric localization argument dealing with actions of NONcompact groups which provides a geometric bridge between two entirely different character formulas for reductive Lie groups and answers the…

Representation Theory · Mathematics 2007-05-23 Matvei Libine

We construct a localic groupoid $\mathbb{G}_{KH}$ such that for any locale $X$ the category of compact Hausdorff locales in the topos of sheaves over $X$ is equivalent to a category whose objects are principal $\mathbb{G}_{KH}$-bundles over…

Category Theory · Mathematics 2023-10-13 Simon Henry , Christopher Townsend

Let $X$ be a locally compact Abelian group, $\alpha_{j}, \beta_j$ be topological automorphisms of $X$. Let $\xi_1, \xi_2$ be independent random variables with values in $X$ and distributions $\mu_j$ with non-vanishing characteristic…

Group Theory · Mathematics 2018-05-25 Gennadiy Feldman , Margaryta Myronyuk

In this paper, we study the Cohen-Macaulayness of non-affine normal semigroups in $\mathbb{Z}^n$. We do this by establishing the following four statements each of independent interest: 1) a Lazard type result on $I$-supported elements of…

Commutative Algebra · Mathematics 2013-02-26 Mohsen Asgharzadeh , Mehdi Dorreh