Speaker: Urmie Ray
Date: March 03, 2011
Affiliation: University of Reims, France

Abstract: For finite dimensional simple and affine Lie algebras, the roots of positive norm are all real, i.e. act locally finitely on integrable modules, whereas the roots of non-positive norm do not, and the non-diagonal entries of the Cartan matrices are non-positive. For most finite dimensional and affine Lie superalgebras there are roots both positive, negative and isotropic (norm 0) that are real and there are both positive and negative non-diagonal entries in the Cartan matrices. Hence the usual proofs of the character formula do not work and computing these characters in all cases has remained an open problem for the last twenty years. The greater the dimension of the maximal isotropic subspace of the set of roots, the greater the complication. In this talk, I will explain my recent proof of these formulae.