The University of Michigan Combinatorics Seminar
Young tableaux provide a combinatorial model for the irreducible characters of the Lie algebra of type A. A simple combinatorial model for the irreducible characters of an arbitrary semisimple Lie algebra (and, more generally, of a symmetrizable Kac-Moody algebra) was recently developed in joint work with A. Postnikov. This model is based on the combinatorics of the corresponding Weyl group and, in the finite case, of the affine Weyl group, and it leads to an extensive generalization of the combinatorics of Young tableaux. In this talk, we present recent results in this direction. We use the setup of crystal graphs, which are colored directed graphs on the canonical basis of a representation. In this context, we present an explicit combinatorial description (generalizing Schützenberger's "evacuation" procedure for tableaux) of the involution which realizes the crystals as self-dual posets. We also discuss combinatorial aspects related to the product of crystals. The talk will be largely self-contained.