Dynamics of iwip automorphisms of free products

Abstract

Let $G$ be a free product and $\mathrm{Out}(G)$ the outer automorphism group of $G$. In this article using the theory of laminations we give a criterion for a subgroup $H$ of $\mathrm{Out}(G)$ to contain a nonabelian free subgroup. We also study the centraliser of an iwip element of $\mathrm{Out}(G)$ and the stabiliser of its associated lamination.