Special cases on the relative rank of G-equivariant functions over an infinite G-set

TL;DR

This paper investigates the relative rank of the monoid of G-equivariant functions over an infinite G-set, providing specific cases where this rank is finite and calculating its value.

Contribution

It identifies particular scenarios with infinite G-sets where the relative rank of G-equivariant functions is finite and explicitly computes it.

Findings

Identifies cases with finite relative rank on infinite G-sets

Calculates the exact relative rank in these cases

Extends understanding of G-equivariant function monoids to infinite sets

Abstract

Given the action of a group $G$ on a set $ X $ , the set of $ G $ -equivariant functions, those that commute with the action, i.e., $ f(g \cdot x) = g \cdot f(x) $ for all $ x \in X $ , $ g \in G $ , forms a monoid under function composition. It is known that when a finite group $ G $ acts on a finite set $ X $ , a finite number of elements in this monoid are sufficient to generate it along with its group of units. The minimum number of elements required to generate the monoid is called the relative rank. This paper presents two particular cases where $ G $ is a finite group, $ X $ is an infinite set, and the relative rank of the monoid of $ G $ -equivariant functions is finite; moreover, we compute it.