The University of Michigan Combinatorics Seminar
Winter 2010
February 19, 4:10-5:00, 3866 East Hall



Cyclage, catabolism, and the affine Hecke algebra

Jonah Blasiak

University of Chicago


Abstract

It is classically known that the ring of coinvariants C[y1,...,yn]/(e1,...,en), thought of as an Sn-module with Sn acting by permuting the variables, is a graded version of the regular representation of Sn. However, how a decomposition of the coinvariants into irreducibles is compatible with its ring structure remains a mystery. In particular, there are difficult combinatorial conjectures for the graded characters of certain subquotients of this ring. We describe a promising approach to understanding such subquotients using the canonical basis of the extended affine Hecke algebra. We show that a subalgebra of this Hecke algebra has a cellular subquotient which is a q-analog of the ring of coinvariants and, further, that this subquotient has cellular quotients which are q-analogs of the Garsia-Procesi modules. This cellular picture gives a clear explanation of the appearance of cyclage and catabolism in the combinatorial description of these modules.