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The goal of this paper is to show that fundamental concepts in higher-order Fourier analysis can be nauturally extended to the non-commutative setting. We generalize Gowers norms to arbitrary compact non-commutative groups. On the…

Group Theory · Mathematics 2024-07-11 Balazs Szegedy

In a series of papers the authors associated to an $L^2$-acyclic group $\Gamma$ an invariant $\mathcal{P}(\Gamma)$ that is a formal difference of polytopes in the vector space $H_1(\Gamma;\Bbb{R})$. This invariant is in particular defined…

Geometric Topology · Mathematics 2016-11-08 Stefan Friedl , Wolfgang Lück , Stephan Tillmann

We propose a new method to compute the $C_{2^n}$-equivariant homotopy groups of the Eilenberg-Mac Lane spectrum $H\underline{\mathbb{Z}}$ as a $RO(C_{2^n})$-graded Green functor using the generalized Tate squares. As an example, we…

Algebraic Topology · Mathematics 2023-02-06 Guoqi Yan

A locally compact group $G$ is a cocompact envelope of a group $\Gamma$ if $G$ contains a copy of $\Gamma$ as a discrete and cocompact subgroup. We study the problem that takes two finitely generated groups $\Gamma,\Lambda$ having a common…

Group Theory · Mathematics 2025-10-29 Adrien Le Boudec

We study the Equivariant Cartan Homotopy Formula for the $DG$-algebra obtained by a finite group action.

K-Theory and Homology · Mathematics 2020-06-02 Safdar Quddus

We describe generators of universal Lefschetz groups consisting of self-maps of equivariant 1-spheres. This allows to formulate a normalization axiom which, together with the usual axioms, determines an equivariant Lefschetz number…

Algebraic Topology · Mathematics 2013-01-31 Philipp Wruck

We describe the groups that have the same holomorph as a finite perfect group. Our results are complete for centerless groups. When the center is non-trivial, some questions remain open. The peculiarities of the general case are illustrated…

Group Theory · Mathematics 2019-01-09 A. Caranti , F. Dalla Volta

We use representation theory to construct spaces of matrices of constant rank. These spaces are parametrized by the natural representation of the general linear group or the symplectic group. We present variants of this idea, with more…

Algebraic Geometry · Mathematics 2022-12-09 J. M. Landsberg , L. Manivel

We show that the bicategory of (representable) orbifolds and good maps is equivalent to the bicategory of orbifold translation groupoids and generalized equivariant maps. We use this result to define an orbifold version of Bredon…

Algebraic Topology · Mathematics 2010-03-10 Dorette Pronk , Laura Scull

We give a new proof of the universal property of $KK^G$-theory with respect to stability, homotopy invariance and split-exactness for $G$ a locally compact group, or a locally compact (not necessarily Hausdorff) groupoid, or a countable…

K-Theory and Homology · Mathematics 2019-12-09 Bernhard Burgstaller

This paper develops a basic theory of H-groups. We introduce a special quotient of H-groups and extend some algebraic constructions of topological groups to the category of H-groups and H-maps. We use these constructions to prove some…

Algebraic Topology · Mathematics 2010-09-28 Ali Pakdaman , Hamid Torabi , Behrooz Mashayekhy

For a group $G$ and a subset $X$ of $G$, the commuting graph of $X$, denoted by $\Gamma(G,X)$ is the graph whose vertex set is $X$ and any two vertices $u$ and $v$ in $X$ are adjacent if and only if they commute in $G$. In this article,…

Combinatorics · Mathematics 2018-06-12 Vipul Kakkar , Gopal Singh Rawat

Given a general finite group $G$, there are various finite categories whose cohomology theories are of great interests. Recently Balmer and Grodal gave some new characterizations of the groups of endotrivial modules, via \v{C}ech cohomology…

Group Theory · Mathematics 2023-09-01 Fei Xu , Chenyou Zheng

Let $M$ be a closed, oriented, simply connected 6-manifold. After localization away from 2, we give a homotopy decomposition of $\Sigma M$ in terms of spheres, Moore spaces and other recognizable spaces. As applications we calculate…

Algebraic Topology · Mathematics 2022-03-15 Tyrone Cutler , Tseleung So

Let w: Map(X,Y;f) -> Y denote a general evaluation fibration. Working in the setting of rational homotopy theory via differential graded Lie algebras, we identify the long exact sequence induced on rational homotopy groups by w in terms of…

Algebraic Topology · Mathematics 2007-05-23 Gregory Lupton , Samuel Bruce Smith

This paper provides an introduction to equivariant cohomology and homology using the approach of Goresky, Kottwitz, and MacPherson. When a group G acts suitably on a variety X, the equivariant cohomology of X can be computed using the…

Algebraic Geometry · Mathematics 2007-05-23 Julianna S. Tymoczko

Given a CW-complex A we define an `A-shaped' homology theory which behaves nicely towards A-homotopy groups allowing the generalization of many classical results. We also develop a relative version of the Federer spectral sequence for…

Algebraic Topology · Mathematics 2014-05-12 Miguel Ottina

We give a detailed description of the structure of the actor 2-crossed module related to the automorphisms of a crossed module of groupoids. This generalises work of Brown and Gilbert for the case of crossed modules of groups, and part of…

Category Theory · Mathematics 2007-05-23 R. Brown , I. Icen

This is a survey about finite group actions on CW-complexes and related topics, primarily based on our joint work. The main applications are to finite $G$-CW-complexes which are homotopy equivalent to spheres. We have tried to give a fairly…

Algebraic Topology · Mathematics 2026-05-05 Ian Hambleton , Ergun Yalcin

We introduce the concept of homotopy equivalence for Hopf Galois extensions and make a systematic study of it. As an application we determine all H-Galois extensions up to homotopy equivalence in the case when H is a Drinfeld-Jimbo quantum…

Quantum Algebra · Mathematics 2010-03-25 Christian Kassel , Hans-Juergen Schneider