Extension problems for representations of crossed-product C*-algebras
  We consider the following problem. Suppose $\alpha$ is an action of a locally compact group $G$ on a $C^*$-algebra $A$, $H$ is a closed subgroup of $G$, and $(\pi,U)$ is a covariant representation of $(A,H,\alpha)$. For which closed subgroups $K$ containing $H$ is there a covariant representation $(\pi,V)$ of $(A,K,\alpha)$ such that $V|_H=U$?   We answer this problem by providing a criterion involving the induced representation of $(A,G,\alpha)$. We then consider the dual problem for coactions of locally compact groups. 
Astrid an Huef, S. Kaliszewski, Iain Raeburn and Dana P. Williams