Montreal Geometric & Combinatorial Group Theory Seminar

Speaker: Frederic Haglund (Orsay)

Title : "Commensurability of lattices in buildings".

Date: 3:30pm Wednesday, December 4.

Room: 920 Burnside

Abstract : A classical construction (the graph-product of finite groups) provides uniform lattices of well-known geometric objects : regular buildings of right-angled type. Using a result of D. Wise, we prove that, in dimension 2, all uniform lattices of a hyperbolic regular building of right-angled type are commensurable. In the case of graph product, we also generalize Wise's result to buildings of any dimension: all quasi-convex subgroups of a hyperbolic graph product of finite groups are separable.