Characters of Reductive Groups over Finite Fields

Let E be a connected reductive algebraic group over C and let W be its Weyl group. The Springer correspondence allows us to parametrize the irreducible representations E of W as F = F^^ where u is a unipotent element in G (up to conjugacy) and <p is an irreducible representation of the group of components AH(u) = ZH(u)IZ°H(u). (However, not all <p arise in the parametrization.) For F = F^Uttp) let aE be the dimension of the variety SSU of Borei subgroups containing u and let aE be the integer defined by the requirement: the irreducible representation of the Hecke