Topoi with enough points

Les topos avec assez de points

Morgan Rogers (1) , Ivan Di Liberti (2)

1 LIPN - Laboratoire d'Informatique de Paris-Nord
2 Department of Philosophy, Linguistics and Theory of Science

We extend Deligne's original argument showing that locally coherent topoi have enough points, clarified using collage diagrams. We show that our refinement of Deligne's technique can be adapted to recover every existing result of this kind, including the most recent results about $\kappa$-coherent $\kappa$-topoi. Our presentation allows us to relax the cardinality assumptions typically imposed on the sites involved. We show that a larger class of locally finitely presentable toposes have enough points and that a closed subtopos of a topos with enough points has enough points.

Mots clés: topos theory; categorical logic; completeness theorem; spatial locale

Domaines: Catégories et ensembles [math.CT]; Logique [math.LO]

Morgan Rogers, Ivan Di Liberti. Topoi with enough points. 2024. ⟨hal-04523900⟩