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Mathlib.CategoryTheory.Triangulated.TStructure.TruncLEGT

Truncations for a t-structure #

Let t be a t-structure on a (pre)triangulated category C. In this file, for any n : ℤ, we introduce the truncation functors t.truncLE n : C ⥤ C and t.truncGT n : C ⥤ C, as variants of the functors t.truncLT n : C ⥤ C and t.truncGE n : C ⥤ C introduced in the file Mathlib/CategoryTheory/Triangulated/TStucture/TruncLTGE.lean.

Given a t-structure t on a pretriangulated category C and n : ℤ, this is the ≤ n-truncation functor. See also the natural transformation truncLEι.

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    theorem CategoryTheory.Triangulated.TStructure.isLE_truncLE_obj {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 : C) (a b : ) (hn : a b := by lia) :
    t.IsLE ((t.truncLE a).obj X) b

    Given a t-structure t on a pretriangulated category C and n : ℤ, this is the > n-truncation functor. See also the natural transformation truncGTπ.

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      theorem CategoryTheory.Triangulated.TStructure.isGE_truncGT_obj {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 : C) (a b : ) (hn : b a + 1 := by lia) :
      t.IsGE ((t.truncGT a).obj X) b

      The isomorphism t.truncLE a ≅ t.truncLT b when a + 1 = b.

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        The isomorphism t.truncGT a ≅ t.truncGE b when a + 1 = b.

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          The natural transformation t.truncLE n ⟶ 𝟭 C when t is a t-structure on a category C and n : ℤ.

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            The natural transformation t.truncLE a ⟶ t.truncLE b when a ≤ b.

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              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.natTransTruncLEOfLE_ι_app {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) (n₀ n₁ : ) (h : n₀ n₁) (X : C) :
              CategoryStruct.comp ((t.natTransTruncLEOfLE n₀ n₁ h).app X) ((t.truncLEι n₁).app X) = (t.truncLEι n₀).app X
              @[simp]
              theorem CategoryTheory.Triangulated.TStructure.natTransTruncLEOfLE_ι_app_assoc {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) (n₀ n₁ : ) (h : n₀ n₁) (X : C) {Z : C} (h✝ : X Z) :

              The natural transformation 𝟭 C ⟶ t.truncGT n when t is a t-structure on a category C and n : ℤ.

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                The connecting homomorphism (t.truncGE b).obj X ⟶ ((t.truncLE a).obj X)⟦1⟧ when a + 1 = b, as a natural transformation.

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                  The distinguished triangle (t.truncLE a).obj A ⟶ A ⟶ (t.truncGE b).obj A ⟶ ... as a functor C ⥤ Triangle C when t is a t-structure on a pretriangulated category C and a + 1 = b.

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                    @[simp]
                    @[simp]
                    theorem CategoryTheory.Triangulated.TStructure.triangleLEGE_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) (a b : ) (h : a + 1 = b) {X✝ Y✝ : C} (φ : X✝ Y✝) :
                    ((t.triangleLEGE a b h).map φ).hom₁ = (t.truncLE a).map φ
                    @[simp]
                    theorem CategoryTheory.Triangulated.TStructure.triangleLEGE_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) (a b : ) (h : a + 1 = b) {X✝ Y✝ : C} (φ : X✝ Y✝) :
                    ((t.triangleLEGE a b h).map φ).hom₃ = (t.truncGE b).map φ
                    @[simp]
                    theorem CategoryTheory.Triangulated.TStructure.triangleLEGE_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) (a b : ) (h : a + 1 = b) {X✝ Y✝ : C} (φ : X✝ Y✝) :
                    ((t.triangleLEGE a b h).map φ).hom₂ = φ

                    The natural isomorphism of triangles t.triangleLEGE a b h ≅ t.triangleLTGE b when a + 1 = b.

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                      The connecting homomorphism (t.truncGT n).obj X ⟶ ((t.truncLE n).obj X)⟦1⟧ for n : ℤ, as a natural transformation.

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                        The distinguished triangle (t.truncLE n).obj A ⟶ A ⟶ (t.truncGT n).obj A ⟶ ... as a functor C ⥤ Triangle C when t is a t-structure on a pretriangulated category C and n : ℤ.

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                          @[simp]
                          theorem CategoryTheory.Triangulated.TStructure.triangleLEGT_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) (n : ) {X✝ Y✝ : C} (φ : X✝ Y✝) :
                          ((t.triangleLEGT n).map φ).hom₃ = (t.truncGT n).map φ
                          @[simp]
                          theorem CategoryTheory.Triangulated.TStructure.triangleLEGT_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) (n : ) {X✝ Y✝ : C} (φ : X✝ Y✝) :
                          ((t.triangleLEGT n).map φ).hom₂ = φ
                          @[simp]
                          theorem CategoryTheory.Triangulated.TStructure.triangleLEGT_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) (n : ) {X✝ Y✝ : C} (φ : X✝ Y✝) :
                          ((t.triangleLEGT n).map φ).hom₁ = (t.truncLE n).map φ

                          The natural isomorphism t.triangleLEGT a ≅ t.triangleLEGE a b h when a + 1 = b.

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                            theorem CategoryTheory.Triangulated.TStructure.isGE_iff_isIso_truncGTπ_app {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) (n₀ n₁ : ) (hn₁ : n₀ + 1 = n₁) (X : C) :
                            t.IsGE X n₁ IsIso ((t.truncGTπ n₀).app X)
                            theorem CategoryTheory.Triangulated.TStructure.isGE_iff_isZero_truncLE_obj {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) (n₀ n₁ : ) (h : n₀ + 1 = n₁) (X : C) :
                            t.IsGE X n₁ Limits.IsZero ((t.truncLE n₀).obj X)
                            theorem CategoryTheory.Triangulated.TStructure.isZero_truncLE_obj_of_isGE {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) (n₀ n₁ : ) (h : n₀ + 1 = n₁) (X : C) [t.IsGE X n₁] :
                            theorem CategoryTheory.Triangulated.TStructure.to_truncLE_obj_ext {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) {n : } {Y X : C} {f₁ f₂ : Y (t.truncLE n).obj X} (h : CategoryStruct.comp f₁ ((t.truncLEι n).app X) = CategoryStruct.comp f₂ ((t.truncLEι n).app X)) [t.IsLE Y n] :
                            f₁ = f₂
                            theorem CategoryTheory.Triangulated.TStructure.liftTruncLE_aux {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 : C} (f : X Y) (n : ) [t.IsLE X n] :
                            ∃ (f' : X (t.truncLE n).obj Y), f = CategoryStruct.comp f' ((t.truncLEι n).app Y)
                            noncomputable def CategoryTheory.Triangulated.TStructure.liftTruncLE {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 : C} (f : X Y) (n : ) [t.IsLE X n] :
                            X (t.truncLE n).obj Y

                            Constructor for morphisms to (t.truncLE n).obj Y.

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                              theorem CategoryTheory.Triangulated.TStructure.descTruncGT_aux {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 : C} (f : X Y) (n₀ n₁ : ) (h : n₀ + 1 = n₁) [t.IsGE Y n₁] :
                              ∃ (f' : (t.truncGT n₀).obj X Y), f = CategoryStruct.comp ((t.truncGTπ n₀).app X) f'
                              noncomputable def CategoryTheory.Triangulated.TStructure.descTruncGT {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 : C} (f : X Y) (n₀ n₁ : ) (h : n₀ + 1 = n₁) [t.IsGE Y n₁] :
                              (t.truncGT n₀).obj X Y

                              Constructor for morphisms from (t.truncGT n₀).obj Y.

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                                @[simp]
                                theorem CategoryTheory.Triangulated.TStructure.π_descTruncGT {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 : C} (f : X Y) (n₀ n₁ : ) (h : n₀ + 1 = n₁) [t.IsGE Y n₁] :
                                CategoryStruct.comp ((t.truncGTπ n₀).app X) (t.descTruncGT f n₀ n₁ h) = f
                                @[simp]
                                theorem CategoryTheory.Triangulated.TStructure.π_descTruncGT_assoc {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 : C} (f : X Y) (n₀ n₁ : ) (h : n₀ + 1 = n₁) [t.IsGE Y n₁] {Z : C} (h✝ : Y Z) :
                                @[reducible, inline]

                                The composition t.truncGE a ⋙ t.truncGE b.

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                                  @[reducible, inline]

                                  The composition t.truncLE b ⋙ t.truncGE a.

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                                    The natural isomorphism t.truncGELE a b ≅ t.truncGELT a b' when b + 1 = b'.

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                                      The natural isomorphism t.truncGELE a b ≅ t.truncLEGE a b.

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