A formal characterization of discrete condensed objects

Abstract

Condensed mathematics, developed by Clausen and Scholze over the last few years, proposes a generalization of topology with better categorical properties. It replaces the concept of a topological space by that of a condensed set, which can be defined as a sheaf on a certain site of compact Hausdorff spaces. Since condensed sets are supposed to be a generalization of topological spaces, one would like to be able to study the notion of discreteness. There are various ways to define what it means for a condensed set to be discrete. In this paper we describe them, and prove that they are equivalent. The results have been fully formalized in the Lean proof assistant.