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
.
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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Equations
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 (𝟭 C).mapTriangle ≅ 𝟭 (Triangle C)
.
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The canonical isomorphism (F ⋙ G).mapTriangle ≅ F.mapTriangle ⋙ G.mapTriangle
.
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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 : Pretriangulated.Triangle C) : T ∈ Pretriangulated.distinguishedTriangles → F.mapTriangle.obj T ∈ Pretriangulated.distinguishedTriangles
Instances
The image of an octahedron by a triangulated functor.
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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
.