Random groups at density $d<3/14$ act non-trivially on a CAT(0) cube complex

Abstract

For random groups in the Gromov density model at $d<3/14$, we construct walls in the Cayley complex $X$ which give rise to a non-trivial action by isometries on a CAT(0) cube complex. This extends results of Ollivier-Wise and Mackay-Przytycki at densities $d<1/5$ and $d<5/24$, respectively. We are able to overcome one of the main combinatorial challenges remaining from the work of Mackay-Przytycki, and we give a construction that plausibly works at any density $d<1/4$.

30 pages, 17 figures Several revisions to exposition made based on reviewer comments. Replaced Definition 4.6 with Definition 4.6 and Construction 4.7. Accepted version, to appear in Transactions of the AMS