mathlib3 documentation


Stalks for presheaved spaces #

THIS FILE IS SYNCHRONIZED WITH MATHLIB4. Any changes to this file require a corresponding PR to mathlib4.

This file lifts constructions of stalks and pushforwards of stalks to work with the category of presheafed spaces. Additionally, we prove that restriction of presheafed spaces does not change the stalks.


The stalk at x of a PresheafedSpace.

For an open embedding f : U ⟶ X and a point x : U, we get an isomorphism between the stalk of X at f x and the stalk of the restriction of X along f at t x.


If α = β and x = x', we would like to say that stalk_map α x = stalk_map β x'. Unfortunately, this equality is not well-formed, as their types are not definitionally the same. To get a proper congruence lemma, we therefore have to introduce these eq_to_hom arrows on either side of the equality.