Topological Sequence Entropy of co-Induced Systems

TL;DR

This paper investigates the topological sequence entropy of co-induced systems from subgroup actions, establishing conditions under which entropy properties are preserved or infinite, with implications for understanding complex dynamical behaviors.

Contribution

It provides a detailed calculation of the maximal pattern entropy for co-induced systems, linking subgroup index to entropy nullity and demonstrating cases with infinite entropy.

Findings

H action nullity iff co-induced G action is null for finite index subgroups

Finite index subgroups with non-trivial H actions can have equal pattern entropy to co-induced G actions

Infinite index subgroups lead to infinite maximal pattern entropy in co-induced systems

Abstract

Let $G$ be a discrete, countably infinite group and $H$ a subgroup of $G$. If $H$ acts continuously on a compact metric space $X$, then we can induce a continuous action of $G$ on $\prod_{H\backslash G}X$ where $H\backslash G$ is the collection of right-cosets of $H$ in $G$. This process is known as the co-induction. In this article, we will calculate the maximal pattern entropy of the co-induction. If $[G:H] < +\infty$ we will show that the $H$ action is null if and only if the co-induced action of $G$ is null. Also, we will discuss an example where $H$ is a proper subgroup of $G$ with finite index where the maximal pattern entropy of the $H$ action is equal to the co-induced action of $G$. If $[G:H] = +\infty$ we will show that the maximal pattern entropy of the co-induction is always $+\infty$ given the $H$-system is not trivial.