On compact uniformly recurrent subgroups

Abstract Let a group Γ 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 Γ-action by homeomorphisms. We show that for every minimal Γ-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 Ušakov on compact subgroups whose normalizer is compact.

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Publication Details

Journal
Proceedings of the Edinburgh Mathematical Society
Published
2025-10-14
DOI
https://doi.org/10.1017/s0013091525100783
Primary Topic
Advanced Topology and Set Theory
Type
article
Field-Weighted Citation Impact
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article

On compact uniformly recurrent subgroups

Waltraud Lederle, Gil Goffer, Todor Tsankov, Pierre‐Emmanuel Caprace
Proceedings of the Edinburgh Mathematical Society
Advanced Topology and Set Theory
article

On compact uniformly recurrent subgroups

Waltraud Lederle, Gil Goffer, Todor Tsankov, Pierre‐Emmanuel Caprace
article en

Abstract

Abstract Let a group Γ 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 Γ-action by homeomorphisms. We show that for every minimal Γ-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 Ušakov on compact subgroups whose normalizer is compact.

Proceedings of the Edinburgh Mathematical Society
Université Claude Bernard Lyon 1 (FR), Laboratoire de Mathématiques d'Orsay (FR), University of California San Diego (US), Institut Camille Jordan (FR), Technische Universität Dresden (DE)
Openalex Percentile: Top 65%
Advanced Topology and Set Theory
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