New York Journal of Mathematics
Volume 13 (2007) 437-481

  

Claire Wladis

Thompson's group F(n) is not minimally almost convex


Published: December 13, 2007
Keywords: Thompson's group, almost convexity
Subject: 20F65

Abstract
We prove that Thompson's group F(n) is not minimally almost convex with respect to the standard finite generating set. A group G with Cayley graph Γ is not minimally almost convex if for arbitrarily large values of m there exist elements g,h∈ Bm such that dΓ(g,h)=2 and dBm(g,h)=2m. (Here Bm is the ball of radius m centered at the identity.) We use tree-pair diagrams to represent elements of F(n) and then use Fordham's metric to calculate geodesic length of elements of F(n). Cleary and Taback have shown that F(2) is not almost convex and Belk and Bux have shown that F(2) is not minimally almost convex; we generalize these results to show that F(n) is not minimally almost convex for all n∈{2,3,4,...}.

Author information

Department of Mathematics, Borough of Manhattan Community College/City University of New York, 199 Chambers St., New York, NY 10007
cwladis@gmail.com