Approaching the UCT problem via crossed products of the Razak–Jacelon algebra

Abstract

We show that the UCT problem for separable, nuclear C*-algebras relies only on whether the UCT holds for crossed products of certain finite cyclic group actions on the Razak–Jacelon algebra. This observation is analogous to and in fact recovers a characterization of the UCT problem in terms of finite group actions on the Cuntz algebra ${\mathcal{O}}_2$ established in previous work by the authors. Although based on a similar approach, the new conceptual ingredients in the finite context are the recent advances in the classification of stably projectionless C*-algebras, as well as a known characterization of the UCT problem in terms of certain tracially AF C*-algebras due to Dadarlat.