Pseudofunctors #
A pseudofunctor is an oplax (or lax) functor whose mapId and mapComp are isomorphisms.
We provide several constructors for pseudofunctors:
- Pseudofunctor.mk: the default constructor, which requires- map₂_whiskerLeftand- map₂_whiskerRightinstead of naturality of- mapComp.
- Pseudofunctor.mkOfOplax: construct a pseudofunctor from an oplax functor whose- mapIdand- mapCompare isomorphisms. This constructor uses- Isoto describe isomorphisms.
- pseudofunctor.mkOfOplax': similar to- mkOfOplax, but uses- IsIsoto describe isomorphisms.
- Pseudofunctor.mkOfLax: construct a pseudofunctor from a lax functor whose- mapIdand- mapCompare isomorphisms. This constructor uses- Isoto describe isomorphisms.
- pseudofunctor.mkOfLax': similar to- mkOfLax, but uses- IsIsoto describe isomorphisms.
Main definitions #
- CategoryTheory.Pseudofunctor B C: a pseudofunctor between bicategories- Band- C
- CategoryTheory.Pseudofunctor.comp F G: the composition of pseudofunctors
A pseudofunctor F between bicategories B and C consists of a function between objects
F.obj, a function between 1-morphisms F.map, and a function between 2-morphisms F.map₂.
Unlike functors between categories, F.map do not need to strictly commute with the compositions,
and do not need to strictly preserve the identity. Instead, there are specified 2-isomorphisms
F.map (𝟙 a) ≅ 𝟙 (F.obj a) and F.map (f ≫ g) ≅ F.map f ≫ F.map g.
F.map₂ strictly commute with compositions and preserve the identity. They also preserve the
associator, the left unitor, and the right unitor modulo some adjustments of domains and codomains
of 2-morphisms.
- obj : B → C
- map₂_comp {a b : B} {f g h : a ⟶ b} (η : f ⟶ g) (θ : g ⟶ h) : self.map₂ (CategoryStruct.comp η θ) = CategoryStruct.comp (self.map₂ η) (self.map₂ θ)
- mapComp {a b c : B} (f : a ⟶ b) (g : b ⟶ c) : self.map (CategoryStruct.comp f g) ≅ CategoryStruct.comp (self.map f) (self.map g)
- map₂_whisker_left {a b c : B} (f : a ⟶ b) {g h : b ⟶ c} (η : g ⟶ h) : self.map₂ (Bicategory.whiskerLeft f η) = CategoryStruct.comp (self.mapComp f g).hom (CategoryStruct.comp (Bicategory.whiskerLeft (self.map f) (self.map₂ η)) (self.mapComp f h).inv)
- map₂_whisker_right {a b c : B} {f g : a ⟶ b} (η : f ⟶ g) (h : b ⟶ c) : self.map₂ (Bicategory.whiskerRight η h) = CategoryStruct.comp (self.mapComp f h).hom (CategoryStruct.comp (Bicategory.whiskerRight (self.map₂ η) (self.map h)) (self.mapComp g h).inv)
- map₂_associator {a b c d : B} (f : a ⟶ b) (g : b ⟶ c) (h : c ⟶ d) : self.map₂ (Bicategory.associator f g h).hom = CategoryStruct.comp (self.mapComp (CategoryStruct.comp f g) h).hom (CategoryStruct.comp (Bicategory.whiskerRight (self.mapComp f g).hom (self.map h)) (CategoryStruct.comp (Bicategory.associator (self.map f) (self.map g) (self.map h)).hom (CategoryStruct.comp (Bicategory.whiskerLeft (self.map f) (self.mapComp g h).inv) (self.mapComp f (CategoryStruct.comp g h)).inv)))
- map₂_left_unitor {a b : B} (f : a ⟶ b) : self.map₂ (Bicategory.leftUnitor f).hom = CategoryStruct.comp (self.mapComp (CategoryStruct.id a) f).hom (CategoryStruct.comp (Bicategory.whiskerRight (self.mapId a).hom (self.map f)) (Bicategory.leftUnitor (self.map f)).hom)
- map₂_right_unitor {a b : B} (f : a ⟶ b) : self.map₂ (Bicategory.rightUnitor f).hom = CategoryStruct.comp (self.mapComp f (CategoryStruct.id b)).hom (CategoryStruct.comp (Bicategory.whiskerLeft (self.map f) (self.mapId b).hom) (Bicategory.rightUnitor (self.map f)).hom)
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The oplax functor associated with a pseudofunctor.
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The Lax functor associated with a pseudofunctor.
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The identity pseudofunctor.
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Composition of pseudofunctors.
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More flexible variant of mapId. (See the file Bicategory.Functor.Strict
for applications to strict bicategories.)
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More flexible variant of mapComp. (See Bicategory.Functor.Strict
for applications to strict bicategories.)
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Construct a pseudofunctor from an oplax functor whose mapId and mapComp are isomorphisms.
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Construct a pseudofunctor from an oplax functor whose mapId and mapComp are isomorphisms.
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Construct a pseudofunctor from a lax functor whose mapId and mapComp are isomorphisms.
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Construct a pseudofunctor from a lax functor whose mapId and mapComp are isomorphisms.
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