Property (T) in $k$-gonal random groups

Abstract

The $k$-gonal models of random groups are defined as the quotients of free groups on $n$ generators by cyclically reduced words of length $k$. As $k$ tends to infinity, this model approaches the Gromov density model. In this paper we show that for any fixed $d_0\in (0,1)$, if positive $k$-gonal random groups satisfy Property (T) with overwhelming probability for densities $d>d_0$, then so do $nk$-gonal random groups, for any $n\in \mathbb{N}$. In particular, this shows that for densities above 1/3, groups in $3k$-gonal models satisfy Property (T) with probability 1 as $n$ approaches infinity.

7 pages, 1 figure V2: updated references, minor revisions