On compact uniformly recurrent subgroups

Abstract

Let a group $\hat{I}“$ act on a paracompact, locally compact, Hausdorff space $M$ by homeomorphisms and let $2^M$ denote the set of closed subsets of $M$. We endow $2^M$ with the Chabauty topology, which is compact and admits a natural $\hat{I}“$-action by homeomorphisms. We show that for every minimal $\hat{I}“$-invariant closed subset $\mathcal{Y}$ of $2^M$ consisting of compact sets, the union $\bigcup \mathcal{Y}\subset M$ has compact closure. As an application, we deduce that every compact uniformly recurrent subgroup of a locally compact group is contained in a compact normal subgroup. This generalizes a result of UÅ¡akov on compact subgroups whose normalizer is compact.

Todor Tsankov added as author, statements generalized, proofs shortened. 10 pages