Videos

Fiberations of free-by-cyclic groups, lecture 2

Presenter
August 19, 2016
Keywords:
  • automorphism groups
  • Out(F_n)
  • free-by-cyclic groups
  • free groups
  • geometric group theory
  • fibrations
  • dilations
  • train-track maps
  • Dowdall-Kapovich-Leininger's construction
MSC:
  • 20F65
  • 20F67
  • 20Fxx
  • 20-xx
  • 14Dxx
Abstract
There is a beautiful and well developed theory (due to Thurston, Fried and McMullen) classifying all of the fiberations over the circle of a given 3-manifold. These fibrations have common characteristics in particular if one fibration has a monodromy that is pseudo-Anosov then all fibrations have this property, and the dilatations are related via an element in the group ring of the first homology of the manifold. We will discuss a theory of fiberations of free-by-cyclic groups that was developed in analogy to the 3-manifold case. In particular we will discuss Dowdall-Kapovich-Leininger's construction of an open cone of fiberations of a free-by-cyclic group, and their theorem that if the original outer automorphism was fully irreducible then the monodromy of each element in this cone is an irreducible train-track map. We then describe a polynomial that packages all of the dilatations of all of these train-track maps (by joint work with Hironaka and Rafi).
Supplementary Materials