Babytop

Student seminar in topology

Fall 2004






Mark Behrens
Buildings, elliptic curves, and the stable homotopy groups of spheres

Abstract:

Fix a prime p. I will describe a dense arithmetic subgroup of the second Morava stabilizer group at p. This group can be realized as a group of quasi-endomorphisms of an elliptic curve. It acts naturally on the Bruhat-Tits building for GL_2(Q_l) for l different than p. This action has finite stabilizers, which coincide with the automorphism groups of elliptic curves. The homotopy fixed points of this group acting on Morava E-theory produces half of the K(2)-local sphere, and the whole sphere is recovered using Gross-Hopkins duality. This work generalizes the resolution of Goerss-Henn-Mahowald-Rezk to all primes. Some of this work is joint work with Tyler Lawson.