Whiskering #
Given a functor F : C ⥤ D
and functors G H : D ⥤ E
and a natural transformation α : G ⟶ H
,
we can construct a new natural transformation F ⋙ G ⟶ F ⋙ H
,
called whiskerLeft F α
. This is the same as the horizontal composition of 𝟙 F
with α
.
This operation is functorial in F
, and we package this as whiskeringLeft
. Here
(whiskeringLeft.obj F).obj G
is F ⋙ G
, and
(whiskeringLeft.obj F).map α
is whiskerLeft F α
.
(That is, we might have alternatively named this as the "left composition functor".)
We also provide analogues for composition on the right, and for these operations on isomorphisms.
We show the associators an unitor natural isomorphisms satisfy the triangle and pentagon identities.
If α : G ⟶ H
then
whiskerLeft F α : (F ⋙ G) ⟶ (F ⋙ H)
has components α.app (F.obj X)
.
Equations
- CategoryTheory.whiskerLeft F α = { app := fun (X : C) => α.app (F.obj X), naturality := ⋯ }
Instances For
If α : G ⟶ H
then
whiskerRight α F : (G ⋙ F) ⟶ (G ⋙ F)
has components F.map (α.app X)
.
Equations
- CategoryTheory.whiskerRight α F = { app := fun (X : C) => F.map (α.app X), naturality := ⋯ }
Instances For
Left-composition gives a functor (C ⥤ D) ⥤ ((D ⥤ E) ⥤ (C ⥤ E))
.
(whiskeringLeft.obj F).obj G
is F ⋙ G
, and
(whiskeringLeft.obj F).map α
is whiskerLeft F α
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Right-composition gives a functor (D ⥤ E) ⥤ ((C ⥤ D) ⥤ (C ⥤ E))
.
(whiskeringRight.obj H).obj F
is F ⋙ H
, and
(whiskeringRight.obj H).map α
is whiskerRight α H
.
Equations
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Instances For
If F : D ⥤ E
is fully faithful, then so is
(whiskeringRight C D E).obj F : (C ⥤ D) ⥤ C ⥤ E
.
Equations
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Instances For
The isomorphism between left-whiskering on the identity functor and the identity of the functor between the resulting functor categories.
Equations
Instances For
The isomorphism between left-whiskering on the composition of functors and the composition of two left-whiskering applications.
Equations
- CategoryTheory.whiskeringLeftObjCompIso F G = CategoryTheory.Iso.refl ((CategoryTheory.whiskeringLeft C D' E).obj (F.comp G))
Instances For
The isomorphism between right-whiskering on the identity functor and the identity of the functor between the resulting functor categories.
Equations
Instances For
Alias of CategoryTheory.whiskeringRightObjIdIso
.
The isomorphism between right-whiskering on the identity functor and the identity of the functor between the resulting functor categories.
Instances For
The isomorphism between right-whiskering on the composition of functors and the composition of two right-whiskering applications.
Equations
- CategoryTheory.whiskeringRightObjCompIso F G = CategoryTheory.Iso.refl (((CategoryTheory.whiskeringRight E C D).obj F).comp ((CategoryTheory.whiskeringRight E D D').obj G))
Instances For
If α : G ≅ H
is a natural isomorphism then
isoWhiskerLeft F α : (F ⋙ G) ≅ (F ⋙ H)
has components α.app (F.obj X)
.
Equations
- CategoryTheory.isoWhiskerLeft F α = ((CategoryTheory.whiskeringLeft C D E).obj F).mapIso α
Instances For
If α : G ≅ H
then
isoWhiskerRight α F : (G ⋙ F) ≅ (H ⋙ F)
has components F.map_iso (α.app X)
.
Equations
- CategoryTheory.isoWhiskerRight α F = ((CategoryTheory.whiskeringRight C D E).obj F).mapIso α
Instances For
The obvious functor (C₁ ⥤ D₁) ⥤ (C₂ ⥤ D₂) ⥤ (D₁ ⥤ D₂ ⥤ E) ⥤ (C₁ ⥤ C₂ ⥤ E)
.
Equations
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Instances For
Auxiliary definition for whiskeringLeft₃
.
Equations
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Auxiliary definition for whiskeringLeft₃
.
Equations
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Instances For
Auxiliary definition for whiskeringLeft₃
.
Equations
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Instances For
Auxiliary definition for whiskeringLeft₃
.
Equations
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Instances For
Auxiliary definition for whiskeringLeft₃
.
Equations
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Instances For
Auxiliary definition for whiskeringLeft₃
.
Equations
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Instances For
The obvious functor
(C₁ ⥤ D₁) ⥤ (C₂ ⥤ D₂) ⥤ (C₃ ⥤ D₃) ⥤ (D₁ ⥤ D₂ ⥤ D₃ ⥤ E) ⥤ (C₁ ⥤ C₂ ⥤ C₃ ⥤ E)
.
Equations
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Instances For
The "postcomposition" with a functor E ⥤ E'
gives a functor
(E ⥤ E') ⥤ (C₁ ⥤ C₂ ⥤ E) ⥤ C₁ ⥤ C₂ ⥤ E'
.
Equations
- CategoryTheory.Functor.postcompose₂ = (CategoryTheory.whiskeringRight C₂ E E').comp (CategoryTheory.whiskeringRight C₁ (CategoryTheory.Functor C₂ E) (CategoryTheory.Functor C₂ E'))
Instances For
The "postcomposition" with a functor E ⥤ E'
gives a functor
(E ⥤ E') ⥤ (C₁ ⥤ C₂ ⥤ C₃ ⥤ E) ⥤ C₁ ⥤ C₂ ⥤ C₃ ⥤ E'
.
Equations
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