Documentation

Mathlib.Geometry.RingedSpace.PresheafedSpace

Presheafed spaces #

Introduces the category of topological spaces equipped with a presheaf (taking values in an arbitrary target category C.)

We further describe how to apply functors and natural transformations to the values of the presheaves.

structure AlgebraicGeometry.PresheafedSpace (C : Type u_1) [CategoryTheory.Category.{u_2, u_1} C] :
Type (max (max u_1 u_2) (u_3 + 1))

A PresheafedSpace C is a topological space equipped with a presheaf of Cs.

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    theorem AlgebraicGeometry.PresheafedSpace.mk_coe {C : Type u_1} [CategoryTheory.Category.{u_3, u_1} C] (carrier : TopCat) (presheaf : TopCat.Presheaf C carrier) :
    { carrier := carrier, presheaf := presheaf } = carrier

    The constant presheaf on X with value Z.

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      A morphism between presheafed spaces X and Y consists of a continuous map f between the underlying topological spaces, and a (notice contravariant!) map from the presheaf on Y to the pushforward of the presheaf on X via f.

      • base : X Y
      • c : Y.presheaf self.base _* X.presheaf
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        The category of PresheafedSpaces. Morphisms are pairs, a continuous map and a presheaf map from the presheaf on the target to the pushforward of the presheaf on the source.

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        Sometimes rewriting with comp_c_app doesn't work because of dependent type issues. In that case, erw comp_c_app_assoc might make progress. The lemma comp_c_app_assoc is also better suited for rewrites in the opposite direction.

        theorem AlgebraicGeometry.PresheafedSpace.congr_app {C : Type u_1} [CategoryTheory.Category.{u_2, u_1} C] {X : AlgebraicGeometry.PresheafedSpace C} {Y : AlgebraicGeometry.PresheafedSpace C} {α : X Y} {β : X Y} (h : α = β) (U : (TopologicalSpace.Opens Y)ᵒᵖ) :
        α.c.app U = CategoryTheory.CategoryStruct.comp (β.c.app U) (X.presheaf.toPrefunctor.map (CategoryTheory.eqToHom (_ : (TopologicalSpace.Opens.map β.base).op.toPrefunctor.obj U = (TopologicalSpace.Opens.map α.base).op.toPrefunctor.obj U)))

        The forgetful functor from PresheafedSpace to TopCat.

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          An isomorphism of PresheafedSpaces is a homeomorphism of the underlying space, and a natural transformation between the sheaves.

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            The restriction of a presheafed space along an open embedding into the space.

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              theorem AlgebraicGeometry.PresheafedSpace.ofRestrict_c_app {C : Type u_1} [CategoryTheory.Category.{u_2, u_1} C] {U : TopCat} (X : AlgebraicGeometry.PresheafedSpace C) {f : U X} (h : OpenEmbedding f) (V : (TopologicalSpace.Opens X)ᵒᵖ) :
              (AlgebraicGeometry.PresheafedSpace.ofRestrict X h).c.app V = X.presheaf.toPrefunctor.map ((IsOpenMap.adjunction (_ : IsOpenMap f)).counit.app V.unop).op

              The map from the restriction of a presheafed space.

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                The map to the restriction of a presheafed space along the canonical inclusion from the top subspace.

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                  The isomorphism from the restriction to the top subspace.

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                    theorem AlgebraicGeometry.PresheafedSpace.Γ_obj {C : Type u_1} [CategoryTheory.Category.{u_2, u_1} C] (X : (AlgebraicGeometry.PresheafedSpace C)ᵒᵖ) :
                    AlgebraicGeometry.PresheafedSpace.Γ.toPrefunctor.obj X = X.unop.presheaf.toPrefunctor.obj (Opposite.op )
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                    theorem AlgebraicGeometry.PresheafedSpace.Γ_map {C : Type u_1} [CategoryTheory.Category.{u_2, u_1} C] :
                    ∀ {X Y : (AlgebraicGeometry.PresheafedSpace C)ᵒᵖ} (f : X Y), AlgebraicGeometry.PresheafedSpace.Γ.toPrefunctor.map f = f.unop.c.app (Opposite.op )

                    The global sections, notated Gamma.

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                      theorem AlgebraicGeometry.PresheafedSpace.Γ_obj_op {C : Type u_1} [CategoryTheory.Category.{u_2, u_1} C] (X : AlgebraicGeometry.PresheafedSpace C) :
                      AlgebraicGeometry.PresheafedSpace.Γ.toPrefunctor.obj (Opposite.op X) = X.presheaf.toPrefunctor.obj (Opposite.op )
                      theorem AlgebraicGeometry.PresheafedSpace.Γ_map_op {C : Type u_1} [CategoryTheory.Category.{u_2, u_1} C] {X : AlgebraicGeometry.PresheafedSpace C} {Y : AlgebraicGeometry.PresheafedSpace C} (f : X Y) :
                      AlgebraicGeometry.PresheafedSpace.Γ.toPrefunctor.map f.op = f.c.app (Opposite.op )

                      We can apply a functor F : C ⥤ D to the values of the presheaf in any PresheafedSpace C, giving a functor PresheafedSpace C ⥤ PresheafedSpace D

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                        A natural transformation induces a natural transformation between the map_presheaf functors.

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