English

On the homology of partial group representations

Algebraic Topology 2025-10-16 v2 Group Theory K-Theory and Homology

Abstract

We study how the partial group (co)homology of a group GG with coefficient in a partial representation MM can be described using the usual group (co)homology. To address this, we introduce the concept of the \textit{universal globalization} Λ(M)\Lambda(M) of a partial group representation MM of GG. Our main result shows that the partial group homology Hpar(G,M)H^{\text{par}}_{\bullet}(G, M) is naturally isomorphic to the classical group homology H(G,Λ(M))H_{\bullet}(G, \Lambda(M)). We extend this result to the cohomological framework, obtaining a spectral sequence involving the classical group cohomology that converges to the partial group cohomology. Notably, when GG is countable, the spectral sequence collapses, resulting in a natural isomorphism Hpar(G,M)H(G,HomKparG(Λ(KparG),M))H^{\bullet}_{\text{par}}(G, M) \cong H^{\bullet}(G, \operatorname{Hom}_{K_{\text{par}} G}(\Lambda(K_{par}G), M)), where KparGK_{par}G stands for the partial group algebra of GG.

Keywords

Cite

@article{arxiv.2404.14650,
  title  = {On the homology of partial group representations},
  author = {Emmanuel Jerez},
  journal= {arXiv preprint arXiv:2404.14650},
  year   = {2025}
}

Comments

This version is a more compact version of the previous one, focusing primarily on partial representations of groups and omitting sections on the homology of partial actions. This change aims to make the structure of the paper more concise and centered on addressing the main problem. The title has been updated accordingly. Minor typographical errors were also corrected