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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

We give explicit computations of the $\Gamma$-Euler characteristic of several families of orbit space definable translation groupoids. These include the translation groupoids associated to finite-dimensional linear representations of the…

Algebraic Topology · Mathematics 2025-08-27 Carla Farsi , Hannah Mobley , Christopher Seaton

We introduce the $\Gamma$-Euler-Satake characteristics of a general orbifold $Q$ presented by an orbifold groupoid $\mathcal{G}$, generalizing to orbifolds that are not necessarily global quotients the generalized orbifold Euler…

Differential Geometry · Mathematics 2014-10-01 Carla Farsi , Christopher Seaton

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

Let G be a finite group and let M be a G-manifold. We introduce the concept of generalized orbifold invariants of M/G associated to an arbitrary group Gamma, an arbitrary Gamma-set, and an arbitrary covering space of a connected manifold…

Group Theory · Mathematics 2014-10-01 Hirotaka Tamanoi

The notion of the orbifold Euler characteristic came from physics at the end of 80's. There were defined higher order versions of the orbifold Euler characteristic and generalized ("motivic") versions of them. In a previous paper the…

Algebraic Geometry · Mathematics 2019-06-06 S. M. Gusein-Zade , I. Luengo , A. Melle-Hernández

We determine the extent to which the collection of $\Gamma$-Euler-Satake characteristics classify closed 2-orbifolds. In particular, we show that the closed, connected, effective, orientable 2-orbifolds are classified by the collection of…

Differential Geometry · Mathematics 2011-04-12 Whitney DuVal , John Schulte , Christopher Seaton , Bradford Taylor

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

Let G be a countable discrete group and let M be a smooth proper cocompact G-manifold without boundary. The Euler operator defines via Kasparov theory an element, called the equivariant Euler class, in the equivariant K-homology of M. The…

K-Theory and Homology · Mathematics 2014-11-11 Wolfgang Lueck , Jonathan Rosenberg

We generalize the notions of the orbifold Euler characteristic and of the higher order orbifold Euler characteristics to spaces with actions of a compact Lie group. This is made using the integration with respect to the Euler characteristic…

Algebraic Topology · Mathematics 2014-05-07 S. M. Gusein-Zade , I. Luengo , A. Melle-Hernández

The Euler characteristic is the only additive topological invariant for spaces of certain sort, in particular, for manifolds with some finiteness properties. A generalization of the notion of a manifold is the notion of a V-manifold. Here…

Geometric Topology · Mathematics 2018-04-27 S. M. Gusein-Zade , I. Luengo , A. Melle-Hernández

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 a general method for computing the homological Euler characteristic of finite index subgroups G of GL_m(O_K) where O_K is the ring of integers in a number field K. With this method we find, that for large, explicitly computed…

Group Theory · Mathematics 2007-05-23 Ivan E. Horozov

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 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 discrete group $\Gamma$ satisfying some finiteness conditions we give a Bredon projective resolution of the trivial module in terms of projective covers of the chain complex associated to certain posets of subgroups. We use this to…

Group Theory · Mathematics 2012-02-27 Conchita Martínez-Pérez

We introduce the notion of generalized orbifold Euler characteristic associated to an arbitrary group, and study its properties. We then calculate generating functions of higher order (p-primary) orbifold Euler characteristic of symmetric…

Algebraic Topology · Mathematics 2014-10-01 Hirotaka Tamanoi

We geometrically construct a homology theory that generalizes the Euler characteristic mod 2 to objects in the unoriented cobordism ring N_*(X) of a topological space X. This homology theory Eh_* has coefficients Z/2 in every nonnegative…

Algebraic Topology · Mathematics 2007-05-23 Julia Weber

Let $M$ be a compact Riemannian manifold, $\pi:\widetilde{M}\rightarrow M$ be the universal covering and $\omega$ be a smooth $2$-form on $M$ with $\pi^*\omega$ cohomologous to zero. Suppose the fundamental group $\pi_1(M)$ satisfies…

Differential Geometry · Mathematics 2018-03-01 Bing-Long Chen , Xiaokui Yang

It is well known that given a finitely generated torsion module $M$ over the Iwasawa algebra $\mathbb Z_p[[\Gamma]]$, where $\Gamma \cong \mathbb Z_p$, there exists a continuous $p$-adic character $\rho$ of $\Gamma$ such that, for the twist…

Number Theory · Mathematics 2017-10-12 Somnath Jha , Sudhanshu Shekhar
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