English

Toposes over which essential implies locally connected

Category Theory 2022-04-07 v1

Abstract

We introduce the notion of an EILC topos: a topos E\mathcal{E} such that every essential geometric morphism with codomain E\mathcal{E} is locally connected. We then show that the topos of sheaves on a topological space XX is EILC if XX is Hausdorff (or more generally, if XX is Jacobson). Further examples of Grothendieck toposes that are EILC are Boolean \'etendues and classifying toposes of compact groups. Next, we introduce the weaker notion of CILC topos: a topos E\mathcal{E} such that any geometric morphism f:FEf : \mathcal{F} \to \mathcal{E} is locally connected, as soon as ff^* is cartesian closed. We give some examples of topological spaces XX and small categories C\mathcal{C} such that Sh(X)\mathbf{Sh}(X) resp. PSh(C)\mathbf{PSh}(\mathcal{C}) are CILC. Finally, we show that any Boolean elementary topos is CILC.

Keywords

Cite

@article{arxiv.2204.02749,
  title  = {Toposes over which essential implies locally connected},
  author = {Jens Hemelaer},
  journal= {arXiv preprint arXiv:2204.02749},
  year   = {2022}
}

Comments

17 pages

R2 v1 2026-06-24T10:39:42.343Z