Oplax natural transformations #
Just as there are natural transformations between functors, there are oplax natural transformations
between oplax functors. The equality in the naturality of natural transformations is replaced by a
specified 2-morphism F.map f ≫ app b ⟶ app a ≫ G.map f
in the case of oplax natural
transformations.
Main definitions #
OplaxNatTrans F G
: oplax natural transformations between oplax functorsF
andG
OplaxNatTrans.vcomp η θ
: the vertical composition of oplax natural transformationsη
andθ
OplaxNatTrans.category F G
: the category structure on the oplax natural transformations betweenF
andG
If η
is an oplax natural transformation between F
and G
, we have a 1-morphism
η.app a : F.obj a ⟶ G.obj a
for each object a : B
. We also have a 2-morphism
η.naturality f : F.map f ≫ app b ⟶ app a ≫ G.map f
for each 1-morphism f : a ⟶ b
.
These 2-morphisms satisfies the naturality condition, and preserve the identities and
the compositions modulo some adjustments of domains and codomains of 2-morphisms.
- app : (a : B) → (↑F.toPrelaxFunctor).obj a ⟶ (↑G.toPrelaxFunctor).obj a
- naturality : {a b : B} → (f : a ⟶ b) → CategoryTheory.CategoryStruct.comp ((↑F.toPrelaxFunctor).map f) (self.app b) ⟶ CategoryTheory.CategoryStruct.comp (self.app a) ((↑G.toPrelaxFunctor).map f)
- naturality_naturality : ∀ {a b : B} {f g : a ⟶ b} (η : f ⟶ g), CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.whiskerRight (F.toPrelaxFunctor.map₂ η) (self.app b)) (self.naturality g) = CategoryTheory.CategoryStruct.comp (self.naturality f) (CategoryTheory.Bicategory.whiskerLeft (self.app a) (G.toPrelaxFunctor.map₂ η))
- naturality_id : ∀ (a : B), CategoryTheory.CategoryStruct.comp (self.naturality (CategoryTheory.CategoryStruct.id a)) (CategoryTheory.Bicategory.whiskerLeft (self.app a) (G.mapId a)) = CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.whiskerRight (F.mapId a) (self.app a)) (CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.leftUnitor (self.app a)).hom (CategoryTheory.Bicategory.rightUnitor (self.app a)).inv)
- naturality_comp : ∀ {a b c : B} (f : a ⟶ b) (g : b ⟶ c), CategoryTheory.CategoryStruct.comp (self.naturality (CategoryTheory.CategoryStruct.comp f g)) (CategoryTheory.Bicategory.whiskerLeft (self.app a) (G.mapComp f g)) = CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.whiskerRight (F.mapComp f g) (self.app c)) (CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.associator ((↑F.toPrelaxFunctor).map f) ((↑F.toPrelaxFunctor).map g) (self.app c)).hom (CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.whiskerLeft ((↑F.toPrelaxFunctor).map f) (self.naturality g)) (CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.associator ((↑F.toPrelaxFunctor).map f) (self.app b) ((↑G.toPrelaxFunctor).map g)).inv (CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.whiskerRight (self.naturality f) ((↑G.toPrelaxFunctor).map g)) (CategoryTheory.Bicategory.associator (self.app a) ((↑G.toPrelaxFunctor).map f) ((↑G.toPrelaxFunctor).map g)).hom))))
Instances For
The identity oplax natural transformation.
Equations
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Instances For
Equations
Vertical composition of oplax natural transformations.
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A modification Γ
between oplax natural transformations η
and θ
consists of a family of
2-morphisms Γ.app a : η.app a ⟶ θ.app a
, which satisfies the equation
(F.map f ◁ app b) ≫ θ.naturality f = η.naturality f ≫ (app a ▷ G.map f)
for each 1-morphism f : a ⟶ b
.
- app : (a : B) → η.app a ⟶ θ.app a
- naturality : ∀ {a b : B} (f : a ⟶ b), CategoryTheory.CategoryStruct.comp (CategoryTheory.Bicategory.whiskerLeft ((↑F.toPrelaxFunctor).map f) (self.app b)) (θ.naturality f) = CategoryTheory.CategoryStruct.comp (η.naturality f) (CategoryTheory.Bicategory.whiskerRight (self.app a) ((↑G.toPrelaxFunctor).map f))
Instances For
The identity modification.
Equations
Instances For
Equations
Vertical composition of modifications.
Equations
- CategoryTheory.OplaxNatTrans.Modification.vcomp Γ Δ = CategoryTheory.OplaxNatTrans.Modification.mk fun (a : B) => CategoryTheory.CategoryStruct.comp (Γ.app a) (Δ.app a)
Instances For
Category structure on the oplax natural transformations between OplaxFunctors.
Equations
- CategoryTheory.OplaxNatTrans.category F G = CategoryTheory.Category.mk
Construct a modification isomorphism between oplax natural transformations by giving object level isomorphisms, and checking naturality only in the forward direction.
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