The Euler characteristic of Out()
Michael BorinskyNational Institute for Subatomic Physics, Amsterdam, Netherlands
Karen VogtmannUniversity of Warwick, Coventry, UK
We prove that the rational Euler characteristic of Out() is always negative and its asymptotic growth rate is . This settles a 1987 conjecture of J. Smillie and the second author. We establish connections with the Lambert -function and the zeta function.
Cite this article
Michael Borinsky, Karen Vogtmann, The Euler characteristic of Out(). Comment. Math. Helv. 95 (2020), no. 4, pp. 703–748DOI 10.4171/CMH/501