Topological entropy of automorphisms of free groups

Geometry Topology Student Seminar
Wednesday, September 5, 2012 - 2:00pm
1 hour (actually 50 minutes)
Skiles 006
School of Mathematics
The main goal is to characterize the dilatation of an outer automorphisms of free groups. It is known that for any automorphism, its dilatation is a weak Perron number. The converse was recently shown by Thurston; for every weak Perron number, there is an automorphism represented by a train track map. We will discuss Thurston's theorem and its proof.