Veech's theorem of higher order

TL;DR

This paper extends Veech's theorem to higher order for minimal systems with abelian groups, characterizing the regionally proximal relation of order d through sequences and limit conditions.

Contribution

It provides a higher order generalization of Veech's theorem, linking regionally proximal relations to sequences in abelian groups and limit behaviors.

Findings

Characterization of $ extbf{RP}^{[d]}$ via sequences in $G^d$

Establishment of limit conditions for higher order proximality

Extension of Veech's theorem to abelian group actions

Abstract

For an abelian group $G$, $\vec{g}=(g_1,\ldots,g_d)\in G^d$ and $\epsilon=(\epsilon(1),\ldots,\epsilon(d))\in \{0,1\}^d$, let $\vec{g}\cdot \epsilon=\prod_{i=1}^{d}g_i^{\epsilon(i)}$. In this paper, it is shown that for a minimal system $(X,G)$ with $G$ being abelian, $(x,y)\in \mathbf{RP}^{[d]}$ if and only if there exists a sequence $\{\vec{g}_n\}_{n\in \mathbb{N}}\subseteq G^d$ and points $z_{\epsilon}\in X,\epsilon\in \{0,1\}^d$ with $z_{\vec{0}}=y$ such that for every $\epsilon\in \{0,1\}^d\backslash\{ \vec{0}\}$, \[ \lim_{n\to\infty}(\vec{g}_n\cdot\epsilon)x= z_\epsilon\quad \mathrm{and} \quad \lim_{n\to\infty}(\vec{g}_n\cdot\epsilon)^{-1}z_{\vec{1}}=z_{\vec{1}-\epsilon}, \] where $\mathbf{RP}^{[d]}$ is the regionally proximal relation of order $d$.