On the bordification of outer space

Abstract

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.

Accepted version, to appear in the Journal of the London MS. Section 7, giving the homeomorphism to the Bestvina-Feighn bordification, has been substantially revised

References in corpus (1)

• Topology of the tropical moduli spaces $M_{2,n}$

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