Documentation

Mathlib.CategoryTheory.Functor.Derived.RightDerived

Right derived functors #

In this file, given a functor F : C ⥤ H, and L : C ⥤ D that is a localization functor for W : MorphismProperty C, we define F.totalRightDerived L W : D ⥤ H as the left Kan extension of F along L: it is defined if the type class F.HasRightDerivedFunctor W asserting the existence of a left Kan extension is satisfied. (The name totalRightDerived is to avoid name-collision with Functor.rightDerived which are the right derived functors in the context of abelian categories.)

Given RF : D ⥤ H and α : F ⟶ L ⋙ RF, we also introduce a type class F.IsRightDerivedFunctor α W saying that α is a left Kan extension of F along the localization functor L.

TODO #

References #

A functor RF : D ⥤ H is a right derived functor of F : C ⥤ H if it is equipped with a natural transformation α : F ⟶ L ⋙ RF which makes it a left Kan extension of F along L, where L : C ⥤ D is a localization functor for W : MorphismProperty C.

  • isLeftKanExtension' : RF.IsLeftKanExtension α
Instances
    theorem CategoryTheory.Functor.IsRightDerivedFunctor.isLeftKanExtension' {C : Type u_1} {D : Type u_2} {H : Type u_3} :
    ∀ {inst : CategoryTheory.Category.{u_4, u_1} C} {inst_1 : CategoryTheory.Category.{u_5, u_2} D} {inst_2 : CategoryTheory.Category.{u_6, u_3} H} {RF : CategoryTheory.Functor D H} {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} {α : F L.comp RF} (W : CategoryTheory.MorphismProperty C) {inst_3 : L.IsLocalization W} [self : RF.IsRightDerivedFunctor α W], RF.IsLeftKanExtension α
    theorem CategoryTheory.Functor.IsRightDerivedFunctor.isLeftKanExtension {C : Type u_1} {D : Type u_2} {H : Type u_5} [CategoryTheory.Category.{u_3, u_1} C] [CategoryTheory.Category.{u_4, u_2} D] [CategoryTheory.Category.{u_6, u_5} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] :
    RF.IsLeftKanExtension α
    theorem CategoryTheory.Functor.isRightDerivedFunctor_iff_isLeftKanExtension {C : Type u_1} {D : Type u_2} {H : Type u_5} [CategoryTheory.Category.{u_3, u_1} C] [CategoryTheory.Category.{u_4, u_2} D] [CategoryTheory.Category.{u_6, u_5} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] :
    RF.IsRightDerivedFunctor α W RF.IsLeftKanExtension α
    theorem CategoryTheory.Functor.isRightDerivedFunctor_iff_of_iso {C : Type u_1} {D : Type u_6} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_6} D] [CategoryTheory.Category.{u_2, u_3} H] {RF : CategoryTheory.Functor D H} {RF' : CategoryTheory.Functor D H} {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] (e : RF RF') (comm : CategoryTheory.CategoryStruct.comp α (CategoryTheory.whiskerLeft L e.hom) = α') :
    RF.IsRightDerivedFunctor α W RF'.IsRightDerivedFunctor α' W
    noncomputable def CategoryTheory.Functor.rightDerivedDesc {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (G : CategoryTheory.Functor D H) (β : F L.comp G) :
    RF G

    Constructor for natural transformations from a right derived functor.

    Equations
    • RF.rightDerivedDesc α W G β = RF.descOfIsLeftKanExtension α G β
    Instances For
      @[simp]
      theorem CategoryTheory.Functor.rightDerived_fac {C : Type u_5} {D : Type u_3} {H : Type u_4} [CategoryTheory.Category.{u_6, u_5} C] [CategoryTheory.Category.{u_1, u_3} D] [CategoryTheory.Category.{u_2, u_4} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (G : CategoryTheory.Functor D H) (β : F L.comp G) :
      CategoryTheory.CategoryStruct.comp α (CategoryTheory.whiskerLeft L (RF.rightDerivedDesc α W G β)) = β
      @[simp]
      theorem CategoryTheory.Functor.rightDerived_fac_app_assoc {C : Type u_5} {D : Type u_3} {H : Type u_4} [CategoryTheory.Category.{u_6, u_5} C] [CategoryTheory.Category.{u_1, u_3} D] [CategoryTheory.Category.{u_2, u_4} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (G : CategoryTheory.Functor D H) (β : F L.comp G) (X : C) {Z : H} (h : G.obj (L.obj X) Z) :
      CategoryTheory.CategoryStruct.comp (α.app X) (CategoryTheory.CategoryStruct.comp ((RF.rightDerivedDesc α W G β).app (L.obj X)) h) = CategoryTheory.CategoryStruct.comp (β.app X) h
      @[simp]
      theorem CategoryTheory.Functor.rightDerived_fac_app {C : Type u_5} {D : Type u_3} {H : Type u_4} [CategoryTheory.Category.{u_6, u_5} C] [CategoryTheory.Category.{u_1, u_3} D] [CategoryTheory.Category.{u_2, u_4} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (G : CategoryTheory.Functor D H) (β : F L.comp G) (X : C) :
      CategoryTheory.CategoryStruct.comp (α.app X) ((RF.rightDerivedDesc α W G β).app (L.obj X)) = β.app X
      noncomputable def CategoryTheory.Functor.rightDerivedNatTrans {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (τ : F F') :
      RF RF'

      The natural transformation RF ⟶ RF' on right derived functors that is induced by a natural transformation F ⟶ F'.

      Equations
      Instances For
        @[simp]
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatTrans_fac {C : Type u_1} {D : Type u_6} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_6} D] [CategoryTheory.Category.{u_2, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (τ : F F') :
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatTrans_app_assoc {C : Type u_1} {D : Type u_6} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_6} D] [CategoryTheory.Category.{u_2, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (τ : F F') (X : C) {Z : H} (h : RF'.obj (L.obj X) Z) :
        CategoryTheory.CategoryStruct.comp (α.app X) (CategoryTheory.CategoryStruct.comp ((RF.rightDerivedNatTrans RF' α α' W τ).app (L.obj X)) h) = CategoryTheory.CategoryStruct.comp (τ.app X) (CategoryTheory.CategoryStruct.comp (α'.app X) h)
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatTrans_app {C : Type u_1} {D : Type u_6} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_6} D] [CategoryTheory.Category.{u_2, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (τ : F F') (X : C) :
        CategoryTheory.CategoryStruct.comp (α.app X) ((RF.rightDerivedNatTrans RF' α α' W τ).app (L.obj X)) = CategoryTheory.CategoryStruct.comp (τ.app X) (α'.app X)
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatTrans_id {C : Type u_5} {D : Type u_1} {H : Type u_3} [CategoryTheory.Category.{u_6, u_5} C] [CategoryTheory.Category.{u_4, u_1} D] [CategoryTheory.Category.{u_2, u_3} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] :
        RF.rightDerivedNatTrans RF α α W (CategoryTheory.CategoryStruct.id F) = CategoryTheory.CategoryStruct.id RF
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatTrans_comp_assoc {C : Type u_1} {D : Type u_5} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_6, u_5} D] [CategoryTheory.Category.{u_2, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) (RF'' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {F'' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (α'' : F'' L.comp RF'') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] [RF'.IsRightDerivedFunctor α' W] (τ : F F') (τ' : F' F'') {Z : CategoryTheory.Functor D H} (h : RF'' Z) :
        CategoryTheory.CategoryStruct.comp (RF.rightDerivedNatTrans RF' α α' W τ) (CategoryTheory.CategoryStruct.comp (RF'.rightDerivedNatTrans RF'' α' α'' W τ') h) = CategoryTheory.CategoryStruct.comp (RF.rightDerivedNatTrans RF'' α α'' W (CategoryTheory.CategoryStruct.comp τ τ')) h
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatTrans_comp {C : Type u_1} {D : Type u_5} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_6, u_5} D] [CategoryTheory.Category.{u_2, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) (RF'' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {F'' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (α'' : F'' L.comp RF'') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] [RF'.IsRightDerivedFunctor α' W] (τ : F F') (τ' : F' F'') :
        CategoryTheory.CategoryStruct.comp (RF.rightDerivedNatTrans RF' α α' W τ) (RF'.rightDerivedNatTrans RF'' α' α'' W τ') = RF.rightDerivedNatTrans RF'' α α'' W (CategoryTheory.CategoryStruct.comp τ τ')
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatIso_hom {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] [RF'.IsRightDerivedFunctor α' W] (τ : F F') :
        (RF.rightDerivedNatIso RF' α α' W τ).hom = RF.rightDerivedNatTrans RF' α α' W τ.hom
        @[simp]
        theorem CategoryTheory.Functor.rightDerivedNatIso_inv {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] [RF'.IsRightDerivedFunctor α' W] (τ : F F') :
        (RF.rightDerivedNatIso RF' α α' W τ).inv = RF'.rightDerivedNatTrans RF α' α W τ.inv
        noncomputable def CategoryTheory.Functor.rightDerivedNatIso {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {F' : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α' : F' L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] [RF'.IsRightDerivedFunctor α' W] (τ : F F') :
        RF RF'

        The natural isomorphism RF ≅ RF' on right derived functors that is induced by a natural isomorphism F ≅ F'.

        Equations
        • RF.rightDerivedNatIso RF' α α' W τ = { hom := RF.rightDerivedNatTrans RF' α α' W τ.hom, inv := RF'.rightDerivedNatTrans RF α' α W τ.inv, hom_inv_id := , inv_hom_id := }
        Instances For
          @[reducible, inline]
          noncomputable abbrev CategoryTheory.Functor.rightDerivedUnique {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) (RF' : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (α'₂ : F L.comp RF') (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] [RF'.IsRightDerivedFunctor α'₂ W] :
          RF RF'

          Uniqueness (up to a natural isomorphism) of the right derived functor.

          Equations
          Instances For
            theorem CategoryTheory.Functor.isRightDerivedFunctor_iff_isIso_rightDerivedDesc {C : Type u_5} {D : Type u_3} {H : Type u_4} [CategoryTheory.Category.{u_6, u_5} C] [CategoryTheory.Category.{u_1, u_3} D] [CategoryTheory.Category.{u_2, u_4} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) (W : CategoryTheory.MorphismProperty C) [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] (G : CategoryTheory.Functor D H) (β : F L.comp G) :
            G.IsRightDerivedFunctor β W CategoryTheory.IsIso (RF.rightDerivedDesc α W G β)

            A functor F : C ⥤ H has a right derived functor with respect to W : MorphismProperty C if it has a left Kan extension along W.Q : C ⥤ W.Localization (or any localization functor L : C ⥤ D for W, see hasRightDerivedFunctor_iff).

            • hasLeftKanExtension' : W.Q.HasLeftKanExtension F
            Instances
              theorem CategoryTheory.Functor.HasRightDerivedFunctor.hasLeftKanExtension' {C : Type u_1} {H : Type u_2} :
              ∀ {inst : CategoryTheory.Category.{u_3, u_1} C} {inst_1 : CategoryTheory.Category.{u_4, u_2} H} {F : CategoryTheory.Functor C H} {W : CategoryTheory.MorphismProperty C} [self : F.HasRightDerivedFunctor W], W.Q.HasLeftKanExtension F
              theorem CategoryTheory.Functor.HasRightDerivedFunctor.mk' {C : Type u_1} {D : Type u_2} {H : Type u_3} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.Category.{u_6, u_3} H] (RF : CategoryTheory.Functor D H) {F : CategoryTheory.Functor C H} {L : CategoryTheory.Functor C D} (α : F L.comp RF) {W : CategoryTheory.MorphismProperty C} [L.IsLocalization W] [RF.IsRightDerivedFunctor α W] :
              F.HasRightDerivedFunctor W

              Given a functor F : C ⥤ H, and a localization functor L : D ⥤ H for W, this is the right derived functor D ⥤ H of F, i.e. the left Kan extension of F along L.

              Equations
              Instances For

                The canonical natural transformation F ⟶ L ⋙ F.totalRightDerived L W.

                Equations
                Instances For