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Mathlib.CategoryTheory.Sites.LeftExact

Left exactness of sheafification #

In this file we show that sheafification commutes with finite limits.

An auxiliary definition to be used in the proof of the fact that J.diagramFunctor D X preserves limits.

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      Auxiliary definition for liftToDiagramLimitObj.

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          @[reducible, inline]

          An auxiliary definition to be used in the proof of the fact that J.diagramFunctor D X preserves limits.

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              def CategoryTheory.GrothendieckTopology.liftToPlusObjLimitObj {C : Type u} [Category.{v, u} C] {J : GrothendieckTopology C} {D : Type w} [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [∀ (X : C), Small.{t, max u v} (J.Cover X)ᵒᵖ] {K : Type s} [SmallCategory K] [FinCategory K] [Limits.HasLimitsOfShape K D] [Limits.PreservesLimitsOfShape K (forget D)] [Limits.ReflectsLimitsOfShape K (forget D)] (F : Functor K (Functor Cᵒᵖ D)) (X : C) (S : Limits.Cone (F.comp ((J.plusFunctor D).comp ((evaluation Cᵒᵖ D).obj (Opposite.op X))))) :

              An auxiliary definition to be used in the proof that J.plusFunctor D commutes with finite limits.

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                  theorem CategoryTheory.GrothendieckTopology.liftToPlusObjLimitObj_fac {C : Type u} [Category.{v, u} C] {J : GrothendieckTopology C} {D : Type w} [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [∀ (X : C), Small.{t, max u v} (J.Cover X)ᵒᵖ] {K : Type s} [SmallCategory K] [FinCategory K] [Limits.HasLimitsOfShape K D] [Limits.PreservesLimitsOfShape K (forget D)] [Limits.ReflectsLimitsOfShape K (forget D)] (F : Functor K (Functor Cᵒᵖ D)) (X : C) (S : Limits.Cone (F.comp ((J.plusFunctor D).comp ((evaluation Cᵒᵖ D).obj (Opposite.op X))))) (k : K) :
                  def CategoryTheory.plusPlusSheafIsoPresheafToSheaf {C : Type u} [Category.{v, u} C] (J : GrothendieckTopology C) (D : Type w) [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [(forget D).ReflectsIsomorphisms] [∀ {X : C} (S : J.Cover X), Limits.PreservesLimitsOfShape (Limits.WalkingMulticospan S.shape) (forget D)] :

                  plusPlusSheaf is isomorphic to an arbitrary choice of left adjoint.

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                      def CategoryTheory.plusPlusFunctorIsoSheafification {C : Type u} [Category.{v, u} C] (J : GrothendieckTopology C) (D : Type w) [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [(forget D).ReflectsIsomorphisms] [∀ {X : C} (S : J.Cover X), Limits.PreservesLimitsOfShape (Limits.WalkingMulticospan S.shape) (forget D)] :

                      plusPlusFunctor is isomorphic to sheafification.

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                          def CategoryTheory.plusPlusIsoSheafify {C : Type u} [Category.{v, u} C] (J : GrothendieckTopology C) (D : Type w) [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [(forget D).ReflectsIsomorphisms] [∀ {X : C} (S : J.Cover X), Limits.PreservesLimitsOfShape (Limits.WalkingMulticospan S.shape) (forget D)] (P : Functor Cᵒᵖ D) :

                          plusPlus is isomorphic to sheafify.

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                              theorem CategoryTheory.toSheafify_plusPlusIsoSheafify_hom {C : Type u} [Category.{v, u} C] (J : GrothendieckTopology C) (D : Type w) [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [(forget D).ReflectsIsomorphisms] [∀ {X : C} (S : J.Cover X), Limits.PreservesLimitsOfShape (Limits.WalkingMulticospan S.shape) (forget D)] (P : Functor Cᵒᵖ D) :
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                              theorem CategoryTheory.toSheafify_plusPlusIsoSheafify_hom_assoc {C : Type u} [Category.{v, u} C] (J : GrothendieckTopology C) (D : Type w) [Category.{t, w} D] [∀ (P : Functor Cᵒᵖ D) (X : C) (S : J.Cover X), Limits.HasMultiequalizer (S.index P)] [∀ (X : C), Limits.HasColimitsOfShape (J.Cover X)ᵒᵖ D] {FD : DDType u_1} {CD : DType t} [(X Y : D) → FunLike (FD X Y) (CD X) (CD Y)] [ConcreteCategory D FD] [∀ (X : C), Limits.PreservesColimitsOfShape (J.Cover X)ᵒᵖ (forget D)] [(forget D).ReflectsIsomorphisms] [∀ {X : C} (S : J.Cover X), Limits.PreservesLimitsOfShape (Limits.WalkingMulticospan S.shape) (forget D)] (P : Functor Cᵒᵖ D) {Z : Functor Cᵒᵖ D} (h : sheafify J P Z) :