20250220 Differentiable Stacks II

This second talk will be the necessary categorical prologue to stalks. We will first introduce a generalization of a topology to arbitrary categories, which will allow us to talk about sheaves on a category. We will then spend some time studying fibered categories, which are the basis for the first definition of a stack. Finally, we will introduce the basics of (strict) 2-categories as a prerequisite for the second definition of a stack. Examples will be sprinkled throughout the talk.