We investigate the abelian category which is the target of intersection homology.
Recall that, given a stratified space X, we get intersection homology groups IpHnX
depending on the choice of an n–perversity p. The n–perversities form a lattice, and
we can think of IHnX as a functor from this lattice to abelian groups, or more
generally R–modules. Such perverse R–modules form a closed symmetric monoidal
abelian category. We study this category and its associated homological
algebra.
