The multivariate mean equicontinuity characterization of finite topomorphic extensions

Let (X,φ)(X,\varphi) be a minimal topological dynamical system, and let (Y,ψ)(Y,\psi) be its maximal equicontinuous factor (MEF). For mNm\in\mathbb{N}, say that (X,φ)(X,\varphi) is mean mm-equicontinuous if, for every ε>0\varepsilon>0, there exists δ>0\delta>0 such that sufficiently close mm-tuples have Besicovitch mm-distance less than ε\varepsilon. Say that (X,φ)(X,\varphi) is an mm:1 topomorphic extension of its MEF if mm is the least integer for which there is a measurable choice of at most mm points in almost every fibre of the factor map to (Y,ψ)(Y,\psi), with full measure for every φ\varphi-invariant measure. The multivariate mean equicontinuity conjecture. (X,φ)(X,\varphi) is mean (m+1)(m+1)-equicontinuous but not mean mm-equicontinuous if and only if it is an mm:1 topomorphic extension of its MEF. The known implication is that every minimal mm:1 topomorphic extension is mean (m+1)(m+1)-equicontinuous. For m=1m=1, the corresponding equivalence is known, whereas the converse in the multivariate case is stated as a conjecture and is not pursued in the paper.

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Primary source

Jonas Breitenbücher, Lino Haupt and Tobias Jäger, “Multivariate mean equicontinuity for finite-to-one topomorphic extensions”, arXiv:2409.08707 (2024).

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