Braiding coherence and naturality lemmas #
In a braided monoidal category, braiding an object Z past a morphism f : A ⊗ A' ⟶ 𝟙_ C
or g : 𝟙_ C ⟶ A ⊗ A' moves Z from one side of the morphism to the other. Splitting the
braiding of Z with A ⊗ A' into crossings with A and A' by the hexagon identities, the
crossing with one factor can be traded for the inverse crossing with the other factor. These
identities are used to move objects past evaluations and coevaluations of exact pairings, for
which no rigidity is needed.
This file also records naturality of the re-associated crossing
(α_ X Y Z).inv ≫ (β_ X Y).hom ▷ Z ≫ (α_ Y X Z).hom : X ⊗ (Y ⊗ Z) ⟶ Y ⊗ (X ⊗ Z) of the first
two factors of a right-bracketed triple with respect to whiskered and tensor-product morphisms,
and the unitor identity (λ_ X).hom ▷ 𝟙_ C ≫ (ρ_ X).hom expressed through the braiding
β_ X (𝟙_ C) of X past the tensor unit.
It also records that the inverse tensorator δ of a braided functor commutes with the braiding
(CategoryTheory.Functor.δ_braiding), the δ-form of Functor.map_braiding.
Braiding A past Z and then applying f : A ⊗ A' ⟶ 𝟙_ C after Z is braiding A' back
under Z and then applying f before Z.
Braiding A past Z and then applying f : A ⊗ A' ⟶ 𝟙_ C after Z is braiding A' back
under Z and then applying f before Z.
Braiding Z past A and then applying f : A' ⊗ A ⟶ 𝟙_ C before Z is braiding Z back
under A' and then applying f after Z.
Braiding Z past A and then applying f : A' ⊗ A ⟶ 𝟙_ C before Z is braiding Z back
under A' and then applying f after Z.
Applying g : 𝟙_ C ⟶ A ⊗ A' after Z and then braiding Z past A is applying g before
Z and then braiding Z back under A'.
Applying g : 𝟙_ C ⟶ A ⊗ A' after Z and then braiding Z past A is applying g before
Z and then braiding Z back under A'.
Applying g : 𝟙_ C ⟶ A' ⊗ A before Z and then braiding A past Z is applying g after
Z and then braiding A' back under Z.
Applying g : 𝟙_ C ⟶ A' ⊗ A before Z and then braiding A past Z is applying g after
Z and then braiding A' back under Z.
Whiskering a morphism on the first factor of X ⊗ (Y ⊗ Z) commutes with swapping the first
two factors via (α_ _ Y Z).inv ≫ (β_ _ Y).hom ▷ Z ≫ (α_ Y _ Z).hom, moving the morphism onto
the middle factor.
Whiskering a morphism on the first factor of X ⊗ (Y ⊗ Z) commutes with swapping the first
two factors via (α_ _ Y Z).inv ≫ (β_ _ Y).hom ▷ Z ≫ (α_ Y _ Z).hom, moving the morphism onto
the middle factor.
Whiskering f ⊗ₘ g on the right two factors of X ⊗ (Y ⊗ Z) commutes with swapping the first
two factors via (α_ X _ _).inv ≫ (β_ X _).hom ▷ _ ≫ (α_ _ X _).hom, moving f onto the first
factor and g onto the third factor.
Whiskering f ⊗ₘ g on the right two factors of X ⊗ (Y ⊗ Z) commutes with swapping the first
two factors via (α_ X _ _).inv ≫ (β_ X _).hom ▷ _ ≫ (α_ _ X _).hom, moving f onto the first
factor and g onto the third factor.
Unitors through the braiding with the unit. The two ways of mapping
(𝟙_ C ⊗ X) ⊗ 𝟙_ C to X agree: whiskering the left unitor and applying the right unitor, or
reassociating, braiding X past the unit, reassociating back, and applying the unitors.
Unitors through the braiding with the unit. The two ways of mapping
(𝟙_ C ⊗ X) ⊗ 𝟙_ C to X agree: whiskering the left unitor and applying the right unitor, or
reassociating, braiding X past the unit, reassociating back, and applying the unitors.
The inverse tensorator δ of a braided functor intertwines the braiding of the images with the
image of the braiding. This is the δ counterpart of Functor.map_braiding.
The inverse tensorator δ of a braided functor intertwines the braiding of the images with the
image of the braiding. This is the δ counterpart of Functor.map_braiding.