English

The category of partial group actions: quotients, (co)limits and groupoids

Group Theory 2024-04-24 v4

Abstract

We consider the category of partial actions, where the group and the set upon which the group acts can vary. Within this framework, we develop a theory of quotient partial actions and prove that this category is both (co)complete and encompasses the category of groupoids as a full subcategory. In particular, we establish the existence of a pair of adjoint functors, denoted as Φ:GrpdPA\Phi : \textbf{Grpd} \to \textbf{PA} and Ψ:PAGrpd\Psi : \textbf{PA} \to \textbf{Grpd}, with the property that ΨΦ1Grpd\Psi \Phi \cong 1_{\textbf{Grpd} }. Next, for a given groupoid Γ\Gamma, we provide a characterization of all partial actions that allow the recovery of the groupoid Γ\Gamma through Ψ\Psi. This characterization is expressed in terms of certain normal subgroups of a universal group constructed from Γ.\Gamma.

Keywords

Cite

@article{arxiv.2311.06223,
  title  = {The category of partial group actions: quotients, (co)limits and groupoids},
  author = {Emmanuel Jerez},
  journal= {arXiv preprint arXiv:2311.06223},
  year   = {2024}
}

Comments

The previous version was an incorrect file that was uploaded. I have corrected some typographical errors and improved the proof of Proposition 2.18