Sheaves on Triangulated Spaces and Koszul Duality
Abstract
Description
Let $X$ be a finite connected simplicial complex, and let $δ$ be a perversity (i.e., some function from integers to integers). One can consider two categories: (1) the category of perverse sheaves cohomologically constructible with respect to the triangulation, and (2) the category of sheaves constant along the perverse simplices ($δ$-sheaves). We interpret the categories (1) and (2) as categories of modules over certain quadratic (and even Koszul) algebras $A(X,δ)$ and $B(X,δ)$ respectively, and we prove that $A(X,δ)$ and $B(X,δ)$ are Koszul dual to each other. We define the $δ$-perverse topology on $X$ and prove that the category of sheaves on perverse topology is equivalent to the category of $δ$ sheaves. Finally, we study the relationship between the Koszul duality functor and the Verdier duality functor for simplicial sheaves and cosheaves.
41 page, AMSTEX. Minor improvements, new section 4.2.12
41 page, AMSTEX. Minor improvements, new section 4.2.12