Triangles #
This file contains the definition of triangles in an additive category with an additive shift. It also defines morphisms between these triangles.
TODO: generalise this to n-angles in n-angulated categories as in https://arxiv.org/abs/1006.4592
A triangle in C
is a sextuple (X,Y,Z,f,g,h)
where X,Y,Z
are objects of C
,
and f : X ⟶ Y
, g : Y ⟶ Z
, h : Z ⟶ X⟦1⟧
are morphisms in C
.
See https://stacks.math.columbia.edu/tag/0144.
- mk' :: (
- obj₁ : C
the first object of a triangle
- obj₂ : C
the second object of a triangle
- obj₃ : C
the third object of a triangle
- mor₁ : self.obj₁ ⟶ self.obj₂
the first morphism of a triangle
- mor₂ : self.obj₂ ⟶ self.obj₃
the second morphism of a triangle
- mor₃ : self.obj₃ ⟶ (CategoryTheory.shiftFunctor C 1).obj self.obj₁
the third morphism of a triangle
- )
Instances For
A triangle (X,Y,Z,f,g,h)
in C
is defined by the morphisms f : X ⟶ Y
, g : Y ⟶ Z
and h : Z ⟶ X⟦1⟧
.
Equations
- CategoryTheory.Pretriangulated.Triangle.mk f g h = { obj₁ := X, obj₂ := Y, obj₃ := Z, mor₁ := f, mor₂ := g, mor₃ := h }
Instances For
Equations
- CategoryTheory.Pretriangulated.instInhabitedTriangle = { default := { obj₁ := 0, obj₂ := 0, obj₃ := 0, mor₁ := 0, mor₂ := 0, mor₃ := 0 } }
For each object in C
, there is a triangle of the form (X,X,0,𝟙 X,0,0)
Equations
Instances For
A morphism of triangles (X,Y,Z,f,g,h) ⟶ (X',Y',Z',f',g',h')
in C
is a triple of morphisms
a : X ⟶ X'
, b : Y ⟶ Y'
, c : Z ⟶ Z'
such that
a ≫ f' = f ≫ b
, b ≫ g' = g ≫ c
, and a⟦1⟧' ≫ h = h' ≫ c
.
In other words, we have a commutative diagram:
f g h
X ───> Y ───> Z ───> X⟦1⟧
│ │ │ │
│a │b │c │a⟦1⟧'
V V V V
X' ───> Y' ───> Z' ───> X'⟦1⟧
f' g' h'
See https://stacks.math.columbia.edu/tag/0144.
- hom₁ : T₁.obj₁ ⟶ T₂.obj₁
the first morphism in a triangle morphism
- hom₂ : T₁.obj₂ ⟶ T₂.obj₂
the second morphism in a triangle morphism
- hom₃ : T₁.obj₃ ⟶ T₂.obj₃
the third morphism in a triangle morphism
- comm₁ : CategoryTheory.CategoryStruct.comp T₁.mor₁ self.hom₂ = CategoryTheory.CategoryStruct.comp self.hom₁ T₂.mor₁
the first commutative square of a triangle morphism
- comm₂ : CategoryTheory.CategoryStruct.comp T₁.mor₂ self.hom₃ = CategoryTheory.CategoryStruct.comp self.hom₂ T₂.mor₂
the second commutative square of a triangle morphism
- comm₃ : CategoryTheory.CategoryStruct.comp T₁.mor₃ ((CategoryTheory.shiftFunctor C 1).map self.hom₁) = CategoryTheory.CategoryStruct.comp self.hom₃ T₂.mor₃
the third commutative square of a triangle morphism
Instances For
The identity triangle morphism.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
Composition of triangle morphisms gives a triangle morphism.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Triangles with triangle morphisms form a category.
Equations
- CategoryTheory.Pretriangulated.triangleCategory = CategoryTheory.Category.mk ⋯ ⋯ ⋯
Equations
- A.homMk B hom₁ hom₂ hom₃ comm₁ comm₂ comm₃ = { hom₁ := hom₁, hom₂ := hom₂, hom₃ := hom₃, comm₁ := comm₁, comm₂ := comm₂, comm₃ := comm₃ }
Instances For
Equations
- One or more equations did not get rendered due to their size.
Instances For
The obvious triangle X₁ ⟶ X₁ ⊞ X₂ ⟶ X₂ ⟶ X₁⟦1⟧
.
Equations
- CategoryTheory.Pretriangulated.binaryBiproductTriangle X₁ X₂ = CategoryTheory.Pretriangulated.Triangle.mk CategoryTheory.Limits.biprod.inl CategoryTheory.Limits.biprod.snd 0
Instances For
The obvious triangle X₁ ⟶ X₁ ⨯ X₂ ⟶ X₂ ⟶ X₁⟦1⟧
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The canonical isomorphism of triangles
binaryProductTriangle X₁ X₂ ≅ binaryBiproductTriangle X₁ X₂
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The product of a family of triangles.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A projection from the product of a family of triangles.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The fan given by productTriangle T
.
Equations
Instances For
A family of morphisms T' ⟶ T j
lifts to a morphism T' ⟶ productTriangle T
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The triangle productTriangle T
satisfies the universal property of the categorical
product of the triangles T
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The functor C ⥤ Triangle C
which sends X
to contractibleTriangle X
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The first projection Triangle C ⥤ C
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The second projection Triangle C ⥤ C
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The third projection Triangle C ⥤ C
.
Equations
- One or more equations did not get rendered due to their size.