The Lipschitz metric on deformation spaces of G–trees

For a finitely generated group $G$ , we introduce an asymmetric pseudometric on projectivized deformation spaces of $G$ –trees, using stretching factors of $G$ –equivariant Lipschitz maps, that generalizes the Lipschitz metric on Outer space and is an analogue of the Thurston metric on Teichmüller space. We show that in the case of irreducible $G$ –trees distances are always realized by minimal stretch maps, can be computed in terms of hyperbolic translation lengths and geodesics exist. We then study displacement functions on projectivized deformation spaces of $G$ –trees and classify automorphisms of $G$ . As an application, we prove the existence of train track representatives for irreducible automorphisms of virtually free groups and nonelementary generalized Baumslag–Solitar groups that contain no solvable Baumslag–Solitar group $BS (1, n)$ with $n \geq 2$ .

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Keywords

Lipschitz metric, deformation spaces, $G$–trees, outer automorphisms, train tracks, virtually free groups, generalized Baumslag–Solitar groups

Mathematical Subject Classification 2010

Primary: 20F65, 20E08

Secondary: 20E36

References

Publication

Received: 9 May 2014

Revised: 20 September 2014

Accepted: 25 September 2014

Published: 22 April 2015

Authors

Sebastian Meinert
Freie Universität Berlin Institut für Mathematik Arnimallee 7, 14195 Berlin Germany
http://meinert-online.de/personal/

Volume 15, issue 2 (2015)

Sebastian Meinert

Abstract