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Mathlib.CategoryTheory.GradedObject.Unitor

The left and right unitors #

Given a bifunctor F : C ⥤ D ⥤ D, an object X : C such that F.obj X ≅ 𝟭 D and a map p : I × J → J such that hp : ∀ (j : J), p ⟨0, j⟩ = j, we define an isomorphism of J-graded objects for any Y : GradedObject J D. mapBifunctorLeftUnitor F X e p hp Y : mapBifunctorMapObj F p ((single₀ I).obj X) Y ≅ Y.

TODO (@joelriou): define similarly a right unitor isomorphism and get the triangle identity.

Given F : C ⥤ D ⥤ D, X : C, e : F.obj X ≅ 𝟭 D and Y : GradedObject J D, this is the isomorphism ((mapBifunctor F I J).obj ((single₀ I).obj X)).obj Y a ≅ Y a.2 when a : I × J is such that a.1 = 0.

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    Given F : C ⥤ D ⥤ D, X : C and Y : GradedObject J D, ((mapBifunctor F I J).obj ((single₀ I).obj X)).obj Y a is an initial when a : I × J is such that a.1 ≠ 0.

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      Given F : C ⥤ D ⥤ D, X : C, e : F.obj X ≅ 𝟭 D, Y : GradedObject J D and p : I × J → J such that p ⟨0, j⟩ = j for all j, this is the (colimit) cofan which shall be used to construct the isomorphism mapBifunctorMapObj F p ((single₀ I).obj X) Y ≅ Y, see mapBifunctorLeftUnitor.

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        The cofan mapBifunctorLeftUnitorCofan F X e p hp Y j is a colimit.

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          Given F : C ⥤ D ⥤ D, X : C, e : F.obj X ≅ 𝟭 D, Y : GradedObject J D and p : I × J → J such that p ⟨0, j⟩ = j for all j, this is the left unitor isomorphism mapBifunctorMapObj F p ((single₀ I).obj X) Y ≅ Y.

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            theorem CategoryTheory.GradedObject.mapBifunctorLeftUnitor_inv_naturality_assoc {C : Type u_1} {D : Type u_2} {I : Type u_3} {J : Type u_4} [CategoryTheory.Category.{u_6, u_1} C] [CategoryTheory.Category.{u_5, u_2} D] [Zero I] [DecidableEq I] [CategoryTheory.Limits.HasInitial C] (F : CategoryTheory.Functor C (CategoryTheory.Functor D D)) (X : C) (e : F.obj X CategoryTheory.Functor.id D) [(Y : D) → CategoryTheory.Limits.PreservesColimit (CategoryTheory.Functor.empty C) ((CategoryTheory.Functor.flip F).obj Y)] (p : I × JJ) (hp : ∀ (j : J), p (0, j) = j) {Y : CategoryTheory.GradedObject J D} {Y' : CategoryTheory.GradedObject J D} (φ : Y Y') [CategoryTheory.GradedObject.HasMap (((CategoryTheory.GradedObject.mapBifunctor F I J).obj ((CategoryTheory.GradedObject.single₀ I).obj X)).obj Y) p] [CategoryTheory.GradedObject.HasMap (((CategoryTheory.GradedObject.mapBifunctor F I J).obj ((CategoryTheory.GradedObject.single₀ I).obj X)).obj Y') p] {Z : CategoryTheory.GradedObject J D} (h : CategoryTheory.GradedObject.mapBifunctorMapObj F p ((CategoryTheory.GradedObject.single₀ I).obj X) Y' Z) :