Crossed products by spectrally free actions

摘要

We define spectral freeness for actions of discrete groups on C*-algebras. We relate spectral freeness to other freeness conditions; an example result is that for an action a of a finite group G, spectral freeness is equivalent to strong pointwise outerness, and also to the condition that (Gamma) over tilde(alpha(g)) not equal {1} for every g is an element of G {1}.