Equivariantization and de-equivariantization

This is the second in a series of talks on "two realizations." We discuss equivariantization and de-equivariantization for a group GG, which relate categories with GG-actions and categories with RepG-actions, and how this relates to the notion of category over a stack. We will deduce a "deequivariantization principle" will be helpful in understanding the proof strategy of Arkhipov-Bezrukavnikov and the full "two realizations," to be explained in future talks.