On the bordification of outer space

Kai-Uwe Bux, Peter Smillie, Karen Vogtmann

Published 2017-09-05Version 1

We give a simple construction of an equivariant deformation retract of Outer space which is homeomorphic to the Bestvina-Feighn bordification. This results in a much easier proof that the bordification is (2n-5)-connected at infinity, and hence that $Out(F_n)$ is a virtual duality group.