Texas A&M University, Department of
Mathematics, 317 Milner Hall, 14th of November 2003, 12:00-1:00
Groups and Dynamcs Seminar
Hypertrees and the
l2 Betti numbers of the pure symmetric
automorphism group
Jon McCammond of University of
California at Santa Barbara
In this talk I will give explicit formulae for the Euler characteristic
and l2-cohomology of the group of
motions of the trivial link, or isomorphically the group of free group
automorphisms that send each standard generator to a conjugate of
itself. The method is primarily combinatorial and ultimately relies on
a computation of the Mobius function for the poset of labelled
hypertrees.