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arXiv · 2605.03993

Invariant random compacts

Bryna Kra·Scott Schmieding
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Abstract

For a compact metric space $X$ with a group $G$ acting on it continuously, an invariant random compact is a Borel probability measure on the space of nonempty compact subsets of $X$ that is invariant under the action of $G$. The action is IC-rigid if, with respect to every invariant random compact, every compact set is almost surely either finite or $X$. We give sufficient conditions for an action to be IC-rigid, and show there are natural examples of such actions. We further consider a notion of weak IC-rigidity, and prove that the Chacon system is weakly IC-rigid but not IC-rigid. As an application, we prove results concerning multiplicative largeness of dilations of sets on the circle.

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Bryna Kra, Scott Schmieding. 2026-05-27. Invariant random compacts. https://arxiv.org/abs/2605.03993

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