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We compute Euler characteristics of p-subgroup categories of finite groups

Category Theory · Mathematics 2015-04-22 Martin Wedel Jacobsen , Jesper M. Moller

The Euler characteristic of a finite category is defined and shown to be compatible with Euler characteristics of other types of object, including orbifolds. A formula for the cardinality of the colimit of a diagram of sets is proved,…

Category Theory · Mathematics 2010-02-04 Tom Leinster

We develop an approach to the character theory of certain classes of finite and profinite groups based on the construction of a Lie algebra associated to such a group, but without making use of the notion of a polarization which is central…

Representation Theory · Mathematics 2007-05-23 Mitya Boyarchenko , Maria Sabitova

We introduce notions of finiteness obstruction, Euler characteristic, L^2-Euler characteristic, and M\"obius inversion for wide classes of categories. The finiteness obstruction of a category Gamma of type (FP) is a class in the projective…

Algebraic Topology · Mathematics 2010-09-22 Thomas M. Fiore , Wolfgang Lück , Roman Sauer

We explore some of the special features with respect to Bredon cohomology of groups having all its finite subgroups either nilpotent or p-groups or cyclic p-groups. We get some results on dimensions and also a formula for the equivariant…

Group Theory · Mathematics 2013-03-13 Conchita Martínez-Pérez

We discuss the universal orbifold Euler characteristic and generalized orbifold Euler characteristics corresponding to finitely generated groups $A$ (the $A$-Euler characteristics). We show that the collection of all $A$-Euler…

Algebraic Geometry · Mathematics 2024-05-15 Sabir M. Gusein-Zade , Ignacio Luengo , Alejandro Melle-Hernández , Antonio Viruel

We introduce the universal Euler characteristic of orbit space definable groupoids, a class of groupoids containing cocompact proper Lie groupoids as well as translation groupoids associated to proper definable group actions. We show that…

Differential Geometry · Mathematics 2025-07-22 Carla Farsi , Emily Proctor , Christopher Seaton

Clifford theory relates the representation theory of finite groups to those of a fixed normal subgroup by means of induction and restriction, which is an adjoint pair of functors. We generalize this result to the situation of a…

Representation Theory · Mathematics 2023-01-27 Alexander Zimmermann

The Poincare duality of classical cohomology and the extension of this duality to quantum cohomology endows these rings with the structure of a Frobenius algebra. Any such algebra possesses a canonical ``characteristic element;'' in the…

q-alg · Mathematics 2007-05-23 Lowell Abrams

Let $\mathsf{F}_r$ be a free group of rank $r$, $\mathbb{F}_q$ a finite field of order q, and let $\mathrm{SL}_n(\mathbb{F}_q)$ act on $\mathrm{Hom}(\mathsf{F}_r, \mathrm{SL}_n(\mathbb{F}_q))$ by conjugation. We describe a general algorithm…

Algebraic Geometry · Mathematics 2014-07-02 Samuel Cavazos , Sean Lawton

This paper provides the theory of integration with respect to Euler characteristics of finite categories. As an application, we use sensors to enumerate the targets lying on a poset. This is a discrete analogue to Baryshnikov and Ghrist's…

Combinatorics · Mathematics 2015-08-18 Kohei Tanaka

In this paper, we introduce a new function related to the sum of element orders of finite groups. It is used to give some criteria for a finite group to be cyclic, abelian, nilpotent, supersolvable and solvable, respectively.

Group Theory · Mathematics 2019-04-09 Marius Tărnăuceanu

In a previous article, we introduced notions of finiteness obstruction, Euler characteristic, and L^2-Euler characteristic for wide classes of categories. In this sequel, we prove the compatibility of those notions with homotopy colimits of…

Algebraic Topology · Mathematics 2011-03-28 Thomas M. Fiore , Wolfgang Lück , Roman Sauer

For a finitely presented discrete group $\Gamma$, we introduce two generalizations of the orbifold Euler characteristic and $\Gamma$-orbifold Euler characteristic to a class of proper topological groupoids large enough to include all…

Algebraic Topology · Mathematics 2022-10-19 Carla Farsi , Christopher Seaton

A notion of degeneration of elements in groups is introduced. It is used to parametrize the orbits in a finite abelian group under its full automorphism group by a finite distributive lattice. A pictorial description of this lattice leads…

Group Theory · Mathematics 2011-03-02 Kunal Dutta , Amritanshu Prasad

Let $G$ be a finitely generated abelian-by-finite group and $k$ a field of characteristic $p\ge 0$. The Euler class $[k_G]$ of $G$ over $k$ is the class of the trivial $kG$-module in the Grothendieck group $G_0(kG)$. We show that $[k_G]$…

Rings and Algebras · Mathematics 2007-05-23 Martin Lorenz

In this paper we give a combinatorial formula to calculate the Euler characteristic of an analogue of a Deligne-Lusztig variety if we replace Frobenius morphism with conjugation by an element for $GL_n$. The main theorem states that it only…

Representation Theory · Mathematics 2016-06-14 Dongkwan Kim

There are (at least) two different approaches to define equivariant analogue of the Euler charateristic for a space with a finite group action. The first one defines it as an element of the Burnside ring of the group. The second approach…

Algebraic Geometry · Mathematics 2016-05-11 S. M. Gusein-Zade , I. Luengo , A. Melle-Hernández

We consider the question whether a Sylow like theorem is valid in the normalized units of integral group rings of finite groups. After a short survey on the known results we show that this is the case for integral group rings of Frobenius…

Rings and Algebras · Mathematics 2016-06-01 Wolfgang Kimmerle , Leo Margolis

The Euler characteristic was defined for finite strict n-categories by Leinster using the theory of enriched categories. This was an extension of some of his earlier work, which defined Euler characteristic for finite categories. Building…

Category Theory · Mathematics 2015-07-24 Alex Gonzalez , Gabe Necoechea , Andrew Stratmann
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