Naturality of the preserved-colimit comparison #
The canonical comparison from a functor applied to a colimit to the colimit of its
image is natural also in the preserving functor. Mathlib's preservesColimitNatIso
records naturality in the diagram; this file records the other variable.
theorem
CategoryTheory.preservesColimitIso_naturality
{J : Type w}
[Category.{w', w} J]
{C : Type u}
[Category.{v, u} C]
{D : Type u'}
[Category.{v', u'} D]
[Limits.HasColimitsOfShape J D]
{H H' : Functor C D}
(α : H ⟶ H')
(F : Functor J C)
[Limits.HasColimit F]
[Limits.PreservesColimit F H]
[Limits.PreservesColimit F H']
:
CategoryStruct.comp (α.app (Limits.colimit F)) (preservesColimitIso H' F).hom = CategoryStruct.comp (preservesColimitIso H F).hom (Limits.colim.map (F.whiskerLeft α))
Naturality in the preserving functor complements Mathlib's diagram naturality
for preservesColimitIso. Compare both sides on each colimit injection.
theorem
CategoryTheory.preservesColimitIso_naturality_assoc
{J : Type w}
[Category.{w', w} J]
{C : Type u}
[Category.{v, u} C]
{D : Type u'}
[Category.{v', u'} D]
[Limits.HasColimitsOfShape J D]
{H H' : Functor C D}
(α : H ⟶ H')
(F : Functor J C)
[Limits.HasColimit F]
[Limits.PreservesColimit F H]
[Limits.PreservesColimit F H']
{Z : D}
(h : Limits.colimit (F.comp H') ⟶ Z)
:
CategoryStruct.comp (α.app (Limits.colimit F)) (CategoryStruct.comp (preservesColimitIso H' F).hom h) = CategoryStruct.comp (preservesColimitIso H F).hom (CategoryStruct.comp (Limits.colim.map (F.whiskerLeft α)) h)
Naturality in the preserving functor complements Mathlib's diagram naturality
for preservesColimitIso. Compare both sides on each colimit injection.