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Mathlib.CategoryTheory.Triangulated.TStructure.ETrunc

Truncations for a t-structure #

Let t be a t-structure on a triangulated category C. In this file, we extend the definition of the truncation functors truncLT and truncGE for indices in to EInt, as t.eTruncLT : EInt ⥤ C ⥤ C and t.eTruncGE : EInt ⥤ C ⥤ C.

The functor EInt ⥤ C ⥤ C which sends to the zero functor, n : ℤ to t.truncLT n and to 𝟭 C.

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    The functor EInt ⥤ C ⥤ C which sends to 𝟭 C, n : ℤ to t.truncGE n and to the zero functor.

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      The connecting homomorphism from t.eTruncGE to the shift by 1 of t.eTruncLT.

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        @[reducible, inline]

        The natural transformation t.eTruncLT.obj i ⟶ 𝟭 C for all i : EInt.

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          @[reducible, inline]

          The natural transformation 𝟭 C ⟶ t.eTruncGE.obj i for all i : EInt.

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            The (distinguished) triangles given by the natural transformations t.eTruncLT.obj i ⟶ 𝟭 C ⟶ t.eTruncGE.obj i ⟶ ... for all i : EInt.

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              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.eTriangleLTGE_obj_map_hom₃ {C : Type u_1} [Category.{v_1, u_1} C] [Preadditive C] [Limits.HasZeroObject C] [HasShift C ] [∀ (n : ), (shiftFunctor C n).Additive] [Pretriangulated C] (t : TStructure C) (i : EInt) {X✝ Y✝ : C} (φ : X✝ Y✝) :
              ((t.eTriangleLTGE.obj i).map φ).hom₃ = (t.eTruncGE.obj i).map φ
              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.eTriangleLTGE_map_app_hom₃ {C : Type u_1} [Category.{v_1, u_1} C] [Preadditive C] [Limits.HasZeroObject C] [HasShift C ] [∀ (n : ), (shiftFunctor C n).Additive] [Pretriangulated C] (t : TStructure C) {X✝ Y✝ : EInt} (f : X✝ Y✝) (j : C) :
              ((t.eTriangleLTGE.map f).app j).hom₃ = (t.eTruncGE.map f).app j
              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.eTriangleLTGE_obj_map_hom₁ {C : Type u_1} [Category.{v_1, u_1} C] [Preadditive C] [Limits.HasZeroObject C] [HasShift C ] [∀ (n : ), (shiftFunctor C n).Additive] [Pretriangulated C] (t : TStructure C) (i : EInt) {X✝ Y✝ : C} (φ : X✝ Y✝) :
              ((t.eTriangleLTGE.obj i).map φ).hom₁ = (t.eTruncLT.obj i).map φ
              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.eTriangleLTGE_obj_map_hom₂ {C : Type u_1} [Category.{v_1, u_1} C] [Preadditive C] [Limits.HasZeroObject C] [HasShift C ] [∀ (n : ), (shiftFunctor C n).Additive] [Pretriangulated C] (t : TStructure C) (i : EInt) {X✝ Y✝ : C} (φ : X✝ Y✝) :
              ((t.eTriangleLTGE.obj i).map φ).hom₂ = φ
              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.eTriangleLTGE_map_app_hom₁ {C : Type u_1} [Category.{v_1, u_1} C] [Preadditive C] [Limits.HasZeroObject C] [HasShift C ] [∀ (n : ), (shiftFunctor C n).Additive] [Pretriangulated C] (t : TStructure C) {X✝ Y✝ : EInt} (f : X✝ Y✝) (j : C) :
              ((t.eTriangleLTGE.map f).app j).hom₁ = (t.eTruncLT.map f).app j

              The natural transformation t.eTruncGE.obj b ⟶ t.eTruncGE.obj a ⋙ t.eTruncGE.obj b for all a and b in EInt.

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                The natural isomorphism t.eTruncGE.obj b ≅ t.eTruncGE.obj a ⋙ t.eTruncGE.obj b when a and b in EInt satisfy a ≤ b.

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                  The natural transformation t.eTruncLT.obj a ⋙ t.eTruncLT.obj b ⟶ t.eTruncLT.obj b for all a and b in EInt.

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                    The natural isomorphism t.eTruncLT.obj a ⋙ t.eTruncLT.obj b ⟶ t.eTruncLT.obj b when a and b in EInt satisfy b ≤ a.

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                      The natural transformation from t.eTruncLT.obj b ⋙ t.eTruncGE.obj a ⋙ t.eTruncLT.obj b to t.eTruncGE.obj a ⋙ t.eTruncLT.obj b. (This is an isomorphism.)

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                        The natural transformation from t.eTruncLT.obj b ⋙ t.eTruncGE.obj a ⋙ t.eTruncLT.obj b to t.eTruncLT.obj b ⋙ t.eTruncGE.obj a. (This is an isomorphism.)

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                          The commutation natural isomorphism t.eTruncGE.obj a ⋙ t.eTruncLT.obj b ≅ t.eTruncLT.obj b ⋙ t.eTruncGE.obj a for all a and b in EInt.

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