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Mathlib.CategoryTheory.Triangulated.Functor

Triangulated functors #

In this file, when C and D are categories equipped with a shift by ℤ and F : C ⥤ D is a functor which commutes with the shift, we define the induced functor F.mapTriangle : Triangle C ⥤ Triangle D on the categories of triangles. When C and D are pretriangulated, a triangulated functor is such a functor F which also sends distinguished triangles to distinguished triangles: this defines the typeclass Functor.IsTriangulated.

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The functor Triangle C ⥤ Triangle D that is induced by a functor F : C ⥤ D which commutes with shift by ℤ.

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    The functor F.mapTriangle commutes with the shift.

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      • F.instCommShiftTriangleMapTriangleInt = { iso := F.mapTriangleCommShiftIso, zero := ⋯, add := ⋯ }

      F.mapTriangle commutes with the rotation of triangles.

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        F.mapTriangle commutes with the inverse of the rotation of triangles.

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          The canonical isomorphism (F ⋙ G).mapTriangle ≅ F.mapTriangle ⋙ G.mapTriangle.

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            def CategoryTheory.Functor.mapTriangleIso {C : Type u_1} {D : Type u_2} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.HasShift C ℤ] [CategoryTheory.HasShift D ℤ] {F₁ : CategoryTheory.Functor C D} {F₂ : CategoryTheory.Functor C D} (e : F₁ ≅ F₂) [F₁.CommShift ℤ] [F₂.CommShift ℤ] [CategoryTheory.NatTrans.CommShift e.hom ℤ] :
            F₁.mapTriangle ≅ F₂.mapTriangle

            Two isomorphic functors F₁ and F₂ induce isomorphic functors F₁.mapTriangle and F₂.mapTriangle if the isomorphism F₁ ≅ F₂ is compatible with the shifts.

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              A functor which commutes with the shift by ℤ is triangulated if it sends distinguished triangles to distinguished triangles.

              • map_distinguished : ∀ T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles, F.mapTriangle.obj T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles
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                theorem CategoryTheory.Functor.IsTriangulated.map_distinguished {C : Type u_1} {D : Type u_2} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.HasShift C ℤ] [CategoryTheory.HasShift D ℤ] {F : CategoryTheory.Functor C D} [F.CommShift ℤ] [CategoryTheory.Limits.HasZeroObject C] [CategoryTheory.Limits.HasZeroObject D] [CategoryTheory.Preadditive C] [CategoryTheory.Preadditive D] [∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [∀ (n : ℤ), (CategoryTheory.shiftFunctor D n).Additive] [CategoryTheory.Pretriangulated C] [CategoryTheory.Pretriangulated D] [self : F.IsTriangulated] (T : CategoryTheory.Pretriangulated.Triangle C) :
                T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles → F.mapTriangle.obj T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles
                theorem CategoryTheory.Functor.map_distinguished {C : Type u_1} {D : Type u_2} [CategoryTheory.Category.{u_4, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [CategoryTheory.HasShift C ℤ] [CategoryTheory.HasShift D ℤ] (F : CategoryTheory.Functor C D) [F.CommShift ℤ] [CategoryTheory.Limits.HasZeroObject C] [CategoryTheory.Limits.HasZeroObject D] [CategoryTheory.Preadditive C] [CategoryTheory.Preadditive D] [∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [∀ (n : ℤ), (CategoryTheory.shiftFunctor D n).Additive] [CategoryTheory.Pretriangulated C] [CategoryTheory.Pretriangulated D] [F.IsTriangulated] (T : CategoryTheory.Pretriangulated.Triangle C) (hT : T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles) :
                F.mapTriangle.obj T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles
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                theorem CategoryTheory.Triangulated.Octahedron.map_m₃ {C : Type u_1} {D : Type u_2} [CategoryTheory.Category.{u_3, u_1} C] [CategoryTheory.Category.{u_4, u_2} D] [CategoryTheory.HasShift C ℤ] [CategoryTheory.HasShift D ℤ] [CategoryTheory.Limits.HasZeroObject C] [CategoryTheory.Limits.HasZeroObject D] [CategoryTheory.Preadditive C] [CategoryTheory.Preadditive D] [∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [∀ (n : ℤ), (CategoryTheory.shiftFunctor D n).Additive] [CategoryTheory.Pretriangulated C] [CategoryTheory.Pretriangulated D] {X₁ : C} {X₂ : C} {X₃ : C} {Z₁₂ : C} {Z₂₃ : C} {Z₁₃ : C} {u₁₂ : X₁ ⟶ X₂} {u₂₃ : X₂ ⟶ X₃} {u₁₃ : X₁ ⟶ X₃} {comm : CategoryTheory.CategoryStruct.comp u₁₂ u₂₃ = u₁₃} {v₁₂ : X₂ ⟶ Z₁₂} {w₁₂ : Z₁₂ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₁} {h₁₂ : CategoryTheory.Pretriangulated.Triangle.mk u₁₂ v₁₂ w₁₂ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} {v₂₃ : X₃ ⟶ Z₂₃} {w₂₃ : Z₂₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₂} {h₂₃ : CategoryTheory.Pretriangulated.Triangle.mk u₂₃ v₂₃ w₂₃ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} {v₁₃ : X₃ ⟶ Z₁₃} {w₁₃ : Z₁₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₁} {h₁₃ : CategoryTheory.Pretriangulated.Triangle.mk u₁₃ v₁₃ w₁₃ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} (h : CategoryTheory.Triangulated.Octahedron comm h₁₂ h₂₃ h₁₃) (F : CategoryTheory.Functor C D) [F.CommShift ℤ] [F.IsTriangulated] :
                (h.map F).m₃ = F.map h.m₃
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                theorem CategoryTheory.Triangulated.Octahedron.map_m₁ {C : Type u_1} {D : Type u_2} [CategoryTheory.Category.{u_3, u_1} C] [CategoryTheory.Category.{u_4, u_2} D] [CategoryTheory.HasShift C ℤ] [CategoryTheory.HasShift D ℤ] [CategoryTheory.Limits.HasZeroObject C] [CategoryTheory.Limits.HasZeroObject D] [CategoryTheory.Preadditive C] [CategoryTheory.Preadditive D] [∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [∀ (n : ℤ), (CategoryTheory.shiftFunctor D n).Additive] [CategoryTheory.Pretriangulated C] [CategoryTheory.Pretriangulated D] {X₁ : C} {X₂ : C} {X₃ : C} {Z₁₂ : C} {Z₂₃ : C} {Z₁₃ : C} {u₁₂ : X₁ ⟶ X₂} {u₂₃ : X₂ ⟶ X₃} {u₁₃ : X₁ ⟶ X₃} {comm : CategoryTheory.CategoryStruct.comp u₁₂ u₂₃ = u₁₃} {v₁₂ : X₂ ⟶ Z₁₂} {w₁₂ : Z₁₂ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₁} {h₁₂ : CategoryTheory.Pretriangulated.Triangle.mk u₁₂ v₁₂ w₁₂ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} {v₂₃ : X₃ ⟶ Z₂₃} {w₂₃ : Z₂₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₂} {h₂₃ : CategoryTheory.Pretriangulated.Triangle.mk u₂₃ v₂₃ w₂₃ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} {v₁₃ : X₃ ⟶ Z₁₃} {w₁₃ : Z₁₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₁} {h₁₃ : CategoryTheory.Pretriangulated.Triangle.mk u₁₃ v₁₃ w₁₃ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} (h : CategoryTheory.Triangulated.Octahedron comm h₁₂ h₂₃ h₁₃) (F : CategoryTheory.Functor C D) [F.CommShift ℤ] [F.IsTriangulated] :
                (h.map F).m₁ = F.map h.m₁
                def CategoryTheory.Triangulated.Octahedron.map {C : Type u_1} {D : Type u_2} [CategoryTheory.Category.{u_3, u_1} C] [CategoryTheory.Category.{u_4, u_2} D] [CategoryTheory.HasShift C ℤ] [CategoryTheory.HasShift D ℤ] [CategoryTheory.Limits.HasZeroObject C] [CategoryTheory.Limits.HasZeroObject D] [CategoryTheory.Preadditive C] [CategoryTheory.Preadditive D] [∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [∀ (n : ℤ), (CategoryTheory.shiftFunctor D n).Additive] [CategoryTheory.Pretriangulated C] [CategoryTheory.Pretriangulated D] {X₁ : C} {X₂ : C} {X₃ : C} {Z₁₂ : C} {Z₂₃ : C} {Z₁₃ : C} {u₁₂ : X₁ ⟶ X₂} {u₂₃ : X₂ ⟶ X₃} {u₁₃ : X₁ ⟶ X₃} {comm : CategoryTheory.CategoryStruct.comp u₁₂ u₂₃ = u₁₃} {v₁₂ : X₂ ⟶ Z₁₂} {w₁₂ : Z₁₂ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₁} {h₁₂ : CategoryTheory.Pretriangulated.Triangle.mk u₁₂ v₁₂ w₁₂ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} {v₂₃ : X₃ ⟶ Z₂₃} {w₂₃ : Z₂₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₂} {h₂₃ : CategoryTheory.Pretriangulated.Triangle.mk u₂₃ v₂₃ w₂₃ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} {v₁₃ : X₃ ⟶ Z₁₃} {w₁₃ : Z₁₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj X₁} {h₁₃ : CategoryTheory.Pretriangulated.Triangle.mk u₁₃ v₁₃ w₁₃ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles} (h : CategoryTheory.Triangulated.Octahedron comm h₁₂ h₂₃ h₁₃) (F : CategoryTheory.Functor C D) [F.CommShift ℤ] [F.IsTriangulated] :

                The image of an octahedron by a triangulated functor.

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                • h.map F = { m₁ := F.map h.m₁, m₃ := F.map h.m₃, comm₁ := ⋯, comm₂ := ⋯, comm₃ := ⋯, comm₄ := ⋯, mem := ⋯ }
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                  If F : C ⥤ D is a triangulated functor from a triangulated category, then D is also triangulated if tuples of composables arrows in D can be lifted to C.