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We show that in an ultraproduct of finite fields, the mod-$n$ nonstandard size of definable sets varies definably in families. Moreover, if $K$ is any pseudofinite field, then one can assign "nonstandard sizes mod $n$" to definable sets in…

Logic · Mathematics 2019-12-17 Will Johnson

For a group $G$ of not prime power order, Oliver showed that the obstruction for a finite CW-complex $F$ to be the fixed point set of a contractible finite $G$-CW-complex is the Euler characteristic $\chi(F)$. He also has the similar…

Algebraic Topology · Mathematics 2025-04-02 Sylvain Cappell , Shmuel Weinberger , Min Yan

There are two abelian groups which can naturally be associated to an additive category A: the split Grothendieck group of A and the triangulated Grothendieck group of the homotopy category of (bounded) complexes in A. We prove that these…

Category Theory · Mathematics 2011-09-12 David E. V. Rose

We define a "circle Euler characteristic" of a circle action on a compact manifold or finite complex X. It lies in the first Hochschild homology group of ZG where G is the fundamental group of X. It is analogous in many ways to the ordinary…

K-Theory and Homology · Mathematics 2007-05-23 Ross Geoghegan , Andrew Nicas

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

Generating functions for the number of commuting m-tuples in the symmetric groups are obtained. We define a natural sequence of ``orbifold Euler characteristics'' for a finite group G acting on a manifold X. Our definition generalizes the…

Combinatorics · Mathematics 2007-05-23 Jim Bryan , Jason Fulman

In this article, we study Euler characteristic techniques in topological data analysis. Pointwise computing the Euler characteristic of a family of simplicial complexes built from data gives rise to the so-called Euler characteristic…

Machine Learning · Computer Science 2024-07-25 Olympio Hacquard , Vadim Lebovici

We lift the Euler characteristic of a nearly perfect complex to a relative algebraic K-group by passing to its l-adic Euler characteristics.

K-Theory and Homology · Mathematics 2007-05-23 David Burns , Bernhard Köck , Victor Snaith

We compute the weighted Euler characteristic, equivariant with respect to the action of the symplectic group of degree six over the field of two elements, of the moduli space of principally polarized abelian threefolds together with a level…

Algebraic Geometry · Mathematics 2018-04-26 Jonas Bergström , Olof Bergvall

Let $F$ be a probability distribution on $\mathbb{R}^d$ which admits a bounded density. We investigate the Euler characteristic of the \v{C}ech complex on $n$ points sampled from $F$ i.i.d. as $n\to\infty$ in the thermodynamic limit regime.…

Probability · Mathematics 2024-09-27 Tobias Fleckenstein , Niklas Hellmer

We extend Auslander and Buchsbaum's Euler characteristic from the category of finitely generated modules of finite projective dimension to the category of modules of finite G-dimension using Avramov and Martsinkovsky's notion of relative…

Commutative Algebra · Mathematics 2007-12-18 Sean Sather-Wagstaff , Diana White

Let G be a finite group of order n and V an irreducible representation over the complex numbers of dimension d. For some nonnegative number e, we have n=d(d+e). If e is small, then the character of V has unusually large degree. We fix e and…

Group Theory · Mathematics 2008-08-28 Noah Snyder

We classify the finite groups $G$ which satisfies the condition that every complex irreducible character,whose degree's square doesn't divide the index of its kernel in $G$, lies in the same Galois conjugacy class.

Group Theory · Mathematics 2022-08-17 Yu Zeng , Dongfang Yang

A closed form formula (generating function) for the Euler characteristic of the configuration space of $\scriptstyle n$ particles in a simplicial complex is given.

General Topology · Mathematics 2010-03-15 S. R. Gal

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

We present a combinatorial analogue of the nerve theorem for covers of small categories, using the Grothendieck construction. We apply our result to prove the inclusion-exclusion principle for the Euler characteristic of a finite category.

Category Theory · Mathematics 2015-08-18 Kohei Tanaka

We define Euler characteristics on classes of residually finite and virtually torsion free groups and we show that they satisfy certain formulas in the case of amalgamated free products and HNN extensions over finite subgroups. These…

Group Theory · Mathematics 2016-07-19 Konstantinos Tsouvalas

We prove that the minimal Euler characteristic of a closed symplectic four-manifold with given fundamental group is often much larger than the minimal Euler characteristic of almost complex closed four-manifolds with the same fundamental…

Geometric Topology · Mathematics 2007-05-23 D. Kotschick

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 compute Euler characteristics of p-subgroup categories of finite groups

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