2000/05/17 by Benson Farb, Lee Mosher · 1 citation
Mathematics · #math.GR #msc:20F65 #msc:20F69
published as Acta Mathematica 184 no. 2 (2000), 145--202 · 65 pages, 2 figures. To appear in Acta Mathematica
arxiv created 2000/05/17 · arxiv updated 2009/11/30
A finitely presented, torsion free, abelian-by-cyclic group can always be written as an ascending HNN extension GammaM of Zn, determined by an n x n integer matrix M with det(M) ≠ 0. The group GammaM is polycyclic if and only if |det(M)|=1. We give a complete classification of the nonpolycyclic groups GammaM up to quasi-isometry: given n x n integer matrices M,N with |det(M)|, |det(N)| > 1, the groups GammaM, GammaN are quasi-isometric if and only if there exist positive integers r,s such that Mr, Ns have the same absolute Jordan form. We also prove quasi-isometric rigidity: if GammaM is an abelian-by-cyclic group determined by an n x n integer matrix M with |det(M)| > 1, and if G is any finitely generated group quasi-isometric to GammaM, then there is a finite normal subgroup K of G such that G/K is abstractly commensurable to GammaN, for some n x n integer matrix N with |det(N)| > 1.