Speaker: Dev Sinha

Title: The Lie coalgebra model of rational homotopy 
theory and Hopf invariants.

Abstract: In joint work with Ben Walter, we use the 
configuration pairing between graphs and trees to give 
a very explicit model for Lie coalgebras. We then 
define Quillen functors between Lie coalgebras and
(graded-)commutative algebras. This gives a new 
combinatorial/algebraic approach to rational homotopy 
theory. Hopf invariants seem to fit very naturally 
into this context. We give progress on this front.