Fra\"iss\'e Theory for Cuntz semigroups

Abstract

We introduce a Fra\"iss\'e theory for abstract Cuntz semigroups akin to the theory of Fra\"iss\'e categories developed by Kubi\'s. In particular, we show that any (Cuntz) Fra\"iss\'e category has a unique Fra\"iss\'e limit which is both universal and homogeneous. We also give several examples of such categories and compute their Fra\"iss\'e limits. During our investigations, we develop a general theory of Cauchy sequences and intertwinings in the category Cu.