On the Bieri-Neumann-Strebel-Renz $\Sigma$-invariants of the Bestvina-Brady groups

TL;DR

This paper investigates the $ ext{Sigma}$-invariants of Bieri-Stallings and Bestvina-Brady groups, providing new criteria and complete descriptions of these invariants for specific classes of groups, including wreath products.

Contribution

It establishes a new criterion linking the $ ext{Sigma}$-invariants of subgroups and overgroups, and applies this to fully describe the invariants of certain complex groups.

Findings

Criteria for $ ext{Sigma}$-invariants of groups of type $FP_n$ and $F_n$.

Complete description of $ ext{Sigma}$-invariants for Bieri-Stallings groups $G_m$.

Extension of the criterion to wreath products.

Abstract

We study the Bieri-Neumann-Strebel-Renz invariants and we prove the following criterion: for groups $H$ and $K$ of type $FP_n$ such that $[H,H] \subseteq K \subseteq H$ and a character $\chi : K \to \mathbb{R}$ with $\chi([H,H]) = 0$ we have $[\chi] \in \Sigma^n(K, \mathbb{Z})$ if and only if $[\mu] \in \Sigma^n(H, \mathbb{Z})$ for every character $\mu : H \to \mathbb{R}$ that extends $\chi$. The same holds for the homotopical invariants $\Sigma^n(-)$ when $K$ and $H$ are groups of type $F_n$. We use these criteria to complete the description of the $\Sigma$-invariants of the Bieri-Stallings groups $G_m$ and more generally to describe the $\Sigma$-invariants of the Bestvina-Brady groups. We also show that the "only if" direction of such criterion holds if we assume only that $K$ is a subnormal subgroup of $H$, where both groups are of type $FP_n$. We apply this last result to wreath products.