# Envelopes of certain solvable groups

### Tullia Dymarz

University of Wisconsin, Madison, USA

## Abstract

A discrete subgroup $\Gamma$ of a locally compact group $H$ is called a *uniform lattice* if the quotient $H/\Gamma$ is compact. Such an $H$ is called an *envelope* of $\Gamma$. In this paper we study the problem of classifying envelopes of various solvable groups including the solvable Baumslag-Solitar groups, lamplighter groups and certain abelian-by-cyclic groups. Our techniques are geometric and quasi-isometric in nature. In particular we show that for every $\Gamma$ we consider there is a finite family of preferred *model spaces*$X$ such that, up to compact groups, $H$ is a cocompact subgroup of $Isom(X)$. We also answer problem 10.4 in \cite{FM3} for a large class of abelian-by-cyclic groups.

## Cite this article

Tullia Dymarz, Envelopes of certain solvable groups. Comment. Math. Helv. 90 (2015), no. 1, pp. 195–224

DOI 10.4171/CMH/351