SPEAKER: Nicholas Proudfoot

TITLE: Sheaves on posets, or: the insane rigidity of hypertoric intersection cohomology

ABSTRACT: It is sometimes possible to compute various cohomology groups of stratified spaces in terms of sheaves on the poset that indexes the stratification. I'll explain how this works, focusing on a concrete example coming from the theory of hyperplane arrangements. Along the way, I will touch on such subjects as moment graphs, Poisson homology, and matroid complexes.