Iulian Simion (Kolozsvár): Refinements of Bruhat cells

Refinements of Bruhat cells, in the sense of C. Curtis and V. Deodhar, are combinatorial devices for describing intersections of the form HxH.HyH\cap HzH where H can be a Borel subgroup B of a simple algebraic group G, the unipotent radical of B or their analogues in a finite group of Lie type. One motivation, in the case of finite groups, comes from the possibility of obtaining structure constants for the endomorphism algebra of a Gelfand-Graev representation - this is work in progress with A. Paolini.