Multivariate Frequent Stability and Diam-Mean Equicontinuity

Abstract: In this paper, we introduce and investigate multivariate versions of frequent stability and diam-mean equicontinuity. Given a natural number $m > 1$, we call those notions "frequent $m$-stability" and "diam-mean $m$-equicontinuity". We use these dynamical rigidity properties to characterise systems whose factor map to the maximal equicontinuous factor (MEF) is finite-to-one for a residual set, called "almost finite-to-one extensions", or a set of full measure, called "almost surely finite-to-one extensions". In the case of a $\sigma$-compact, locally compact, abelian acting group it is shown that frequently $(m+1)$-stable systems are equivalently characterised as almost $m$-to-one extensions of their MEF. Similarly, it is shown that a system is diam-mean $(m+1)$-equicontinuous if and only if it is an almost surely $m$-to-one extension of its MEF.