Cup and cap products for cohomology and homology groups of ample groupoids

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Hauptverfasser: Matui, Hiroki, Mori, Takehiko
Format: Preprint
Veröffentlicht: 2024
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author Matui, Hiroki
Mori, Takehiko
author_facet Matui, Hiroki
Mori, Takehiko
contents This paper explores the cup and cap products within the cohomology and homology groups of ample groupoids, focusing on their applications and fundamental properties. Ample groupoids, which are étale groupoids with a totally disconnected unit space, play a crucial role in the study of topological dynamical systems and operator algebras. We introduce the cup product, which defines a bilinear map on cohomology classes, providing a graded ring structure, and the cap product, which defines a bilinear map relating homology and cohomology. The paper aims to make these concepts accessible to a broader mathematical audience, offering clear definitions and detailed explanations. We also demonstrate an application of the cap product in the analysis of automorphisms of groupoid $C^*$-algebras. Specifically, we show how it helps determine the asymptotic innerness of automorphisms. Our results include the first explicit computations of cup products in the cohomology of tiling spaces, which may pave the way for new research in this area.
format Preprint
id arxiv_https___arxiv_org_abs_2411_14906
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Cup and cap products for cohomology and homology groups of ample groupoids
Matui, Hiroki
Mori, Takehiko
Operator Algebras
Dynamical Systems
37B05 (Primary) 46L55, 37B52 (Secondary)
This paper explores the cup and cap products within the cohomology and homology groups of ample groupoids, focusing on their applications and fundamental properties. Ample groupoids, which are étale groupoids with a totally disconnected unit space, play a crucial role in the study of topological dynamical systems and operator algebras. We introduce the cup product, which defines a bilinear map on cohomology classes, providing a graded ring structure, and the cap product, which defines a bilinear map relating homology and cohomology. The paper aims to make these concepts accessible to a broader mathematical audience, offering clear definitions and detailed explanations. We also demonstrate an application of the cap product in the analysis of automorphisms of groupoid $C^*$-algebras. Specifically, we show how it helps determine the asymptotic innerness of automorphisms. Our results include the first explicit computations of cup products in the cohomology of tiling spaces, which may pave the way for new research in this area.
title Cup and cap products for cohomology and homology groups of ample groupoids
topic Operator Algebras
Dynamical Systems
37B05 (Primary) 46L55, 37B52 (Secondary)
url https://arxiv.org/abs/2411.14906