Cocompact Lattices in Locally Pro-$p$-complete Rank 2 Kac-Moody Groups

TL;DR

This paper explores cocompact lattices in a new class of locally pro-$p$-complete Kac-Moody groups of rank 2, revealing their well-behaved structure and classifying certain types of these lattices.

Contribution

It introduces the study of lattices in locally pro-$p$-complete Kac-Moody groups and classifies edge-transitive cocompact lattices in rank 2 cases.

Findings

Cocompact lattices in rank 2 have no elements of order p under mild assumptions.

Classification of edge-transitive cocompact lattices.

Identification of a cocompact lattice with minimal covolume.

Abstract

We initiate an investigation of lattices in a new class of locally compact groups, so called locally pro-$p$-complete Kac-Moody groups. We discover that in rank 2 their cocompact lattices are particularly well-behaved: under mild assumptions, a cocompact lattice in this completion contains no elements of order $p$. This statement is still an open question for the Caprace-R\'emy-Ronan completion. Using this, modulo results of Capdeboscq and Thomas, we classify edge-transitive cocompact lattices and describe a cocompact lattice of minimal covolume.