Triangulated Categories #
This file contains the definition of triangulated categories, which are pretriangulated categories which satisfy the octahedron axiom.
An octahedron is a type of datum whose existence is asserted by the octahedron axiom (TR 4), see https://stacks.math.columbia.edu/tag/05QK
- m₁ : Z₁₂ ⟶ Z₁₃
- m₃ : Z₁₃ ⟶ Z₂₃
- comm₁ : CategoryTheory.CategoryStruct.comp v₁₂ self.m₁ = CategoryTheory.CategoryStruct.comp u₂₃ v₁₃
- comm₂ : CategoryTheory.CategoryStruct.comp self.m₁ w₁₃ = w₁₂
- comm₃ : CategoryTheory.CategoryStruct.comp v₁₃ self.m₃ = v₂₃
- comm₄ : CategoryTheory.CategoryStruct.comp w₁₃ ((CategoryTheory.shiftFunctor C 1).map u₁₂) = CategoryTheory.CategoryStruct.comp self.m₃ w₂₃
- mem : CategoryTheory.Pretriangulated.Triangle.mk self.m₁ self.m₃ (CategoryTheory.CategoryStruct.comp w₂₃ ((CategoryTheory.shiftFunctor C 1).map v₁₂)) ∈ CategoryTheory.Pretriangulated.distinguishedTriangles
Instances For
The triangle Z₁₂ ⟶ Z₁₃ ⟶ Z₂₃ ⟶ Z₁₂⟦1⟧
given by an octahedron.
Equations
- h.triangle = CategoryTheory.Pretriangulated.Triangle.mk h.m₁ h.m₃ (CategoryTheory.CategoryStruct.comp w₂₃ ((CategoryTheory.shiftFunctor C 1).map v₁₂))
Instances For
The first morphism of triangles given by an octahedron.
Equations
- h.triangleMorphism₁ = { hom₁ := CategoryTheory.CategoryStruct.id X₁, hom₂ := u₂₃, hom₃ := h.m₁, comm₁ := ⋯, comm₂ := ⋯, comm₃ := ⋯ }
Instances For
The second morphism of triangles given an octahedron.
Equations
- h.triangleMorphism₂ = { hom₁ := u₁₂, hom₂ := CategoryTheory.CategoryStruct.id X₃, hom₃ := h.m₃, comm₁ := ⋯, comm₂ := ⋯, comm₃ := ⋯ }
Instances For
When two diagrams are isomorphic, an octahedron for one gives an octahedron for the other.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A triangulated category is a pretriangulated category which satisfies the octahedron axiom (TR 4), see https://stacks.math.columbia.edu/tag/05QK
- octahedron_axiom {X₁ X₂ X₃ Z₁₂ Z₂₃ 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) : Nonempty (CategoryTheory.Triangulated.Octahedron comm h₁₂ h₂₃ h₁₃)
the octahedron axiom (TR 4)
Instances
A choice of octahedron given by the octahedron axiom.
Equations
- CategoryTheory.Triangulated.someOctahedron' comm = ⋯.some
Instances For
A choice of octahedron given by the octahedron axiom.
Equations
- CategoryTheory.Triangulated.someOctahedron comm h₁₂ h₂₃ h₁₃ = CategoryTheory.Triangulated.someOctahedron' comm
Instances For
Constructor for IsTriangulated C
which shows that it suffices to obtain an octahedron
for a suitable isomorphic diagram instead of the given diagram.