Universal localizations, Atiyah conjectures and graphs of groups

TL;DR

This paper proves that groups formed from graphs of groups with finite edge groups and vertex groups satisfying the strong Atiyah conjecture also satisfy it, and explores the algebraic structure of associated rings and localizations.

Contribution

It establishes the closure of the strong Atiyah conjecture under graph of groups constructions and describes the universal localization of related group rings.

Findings

Strong Atiyah conjecture holds for groups from certain graphs of groups.

The $ ext{ extasterisk}- ext{regular}$ closure is a universal localization of the graph of rings.

Results on $K_0$ and $K_1$ groups of the associated rings.

Abstract

Let $G$ be a countable group that is the fundamental group of a graph of groups with finite edge groups and vertex groups that satisfy the strong Atiyah conjecture over $K \subseteq \mathbb{C}$ a field closed under complex conjugation. Assume that the orders of finite subgroups of $G$ are bounded above. We show that $G$ satisfies the strong Atiyah conjecture over $K$. In particular, this implies that the strong Atiyah conjecture is closed under free products. Moreover, we prove that the $\ast$-regular closure of $K[G]$ in $\mathcal{U}(G)$, $\mathcal{R}_{\small K[G]}$, is a universal localization of the graph of rings associated to the graph of groups, where the rings are the corresponding $\ast$-regular closures. As a result, we obtain that the algebraic and center-valued Atiyah conjecture over $K$ are also closed under the graph of groups construction provided that the edge groups are finite. We also infer some consequences on the structure of the $K_0$ and $K_1$-groups of $\mathcal{R}_{\small K[G]}$. The techniques developed allow us to prove that $K[G]$ fulfills the strong, algebraic and center-valued Atiyah conjectures and that $\mathcal{R}_{\small K[G]}$ is the universal localization of $K[G]$ over the set of all matrices that become invertible in $\mathcal{U}(G)$ if $G$ lies in a certain class of groups $\mathcal{T}_{\small \mathcal{VLI}}$, which contains in particular virtually-{locally indicable} groups that are the fundamental group of a graph of virtually free groups.