On pathological properties of fixed point algebras in Kirchberg algebras

Abstract: We investigate how the fixed point algebra of a C*-dynamical system can differ from the underlying C*-algebra. For any exact group $\Gamma$ and any infinite group $\Lambda$, we construct an outer action of $\Lambda$ on the Cuntz algebra $\mathcal{O}2$ whose fixed point algebra is almost equal to the reduced group C*-algebra ${\rm C}^\ast{\rm r}(\Gamma)$. Moreover, we show that every infinite group admits outer actions on all Kirchberg algebras whose fixed point algebras fail the completely bounded approximation property.