Let be a discrete group acting on a unital -algebra by -automorphisms. We characterize (in terms of the dynamics) when the inclusion has a unique conditional expectation, and when it has a unique pseudoexpectation in the sense of Pitts; we do likewise for the inclusion . As an application, we re-prove (and potentially extend) some known -simplicity results for .
"Unique expectations for discrete crossed products." Ann. Funct. Anal. 10 (1) 60 - 71, February 2019. https://doi.org/10.1215/20088752-2018-0008