Cohomology Theories of Partial Groups

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1. Verfasser: Pfammatter, Sandro
Format: Preprint
Veröffentlicht: 2025
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author Pfammatter, Sandro
author_facet Pfammatter, Sandro
contents We initiate a systematic study of cohomology theories for partial groups, algebraic structures introduced by Chermak that generalize groups by allowing only partially defined products. Inspired by classical group cohomology, we develop two parallel approaches - an algebraic theory based on Chermak's framework and a simplicial-set-based theory using local coefficient systems - and show that they coincide. As an application, we illustrate how the extension theory of partial groups, as developed by Broto and Gonzalez, can be interpreted and computed using our cohomology theory, including explicit examples such as extensions of free partial groups, and compare these results with classical group extensions.
format Preprint
id arxiv_https___arxiv_org_abs_2512_05618
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Cohomology Theories of Partial Groups
Pfammatter, Sandro
Algebraic Topology
Group Theory
55R15 (Primary) 55R35, 55N25, 55U10, 20N99, 18N50 (Secondary)
We initiate a systematic study of cohomology theories for partial groups, algebraic structures introduced by Chermak that generalize groups by allowing only partially defined products. Inspired by classical group cohomology, we develop two parallel approaches - an algebraic theory based on Chermak's framework and a simplicial-set-based theory using local coefficient systems - and show that they coincide. As an application, we illustrate how the extension theory of partial groups, as developed by Broto and Gonzalez, can be interpreted and computed using our cohomology theory, including explicit examples such as extensions of free partial groups, and compare these results with classical group extensions.
title Cohomology Theories of Partial Groups
topic Algebraic Topology
Group Theory
55R15 (Primary) 55R35, 55N25, 55U10, 20N99, 18N50 (Secondary)
url https://arxiv.org/abs/2512.05618