Generics in invariant subsets of some highly homogeneous permutation groups

Abstract

Let $G$ be a closed highly homogeneous subgroup of $S_{\infty}$ not involving circular orderings. We show that the closure of a conjugacy class from $G$ contains a conjugacy class which is comeagre in it. Furthermore, we show that the family of finite partial maps extendable to elements of this conjugacy class has the cofinal amalgamation property. Similar statements are proved for automorphisms of typical ultrahomogeneous partial orderings.