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Mathlib.CategoryTheory.Enriched.Ordinary.Basic

Enriched ordinary categories #

If V is a monoidal category, a V-enriched category C does not need to be a category. However, when we have both Category C and EnrichedCategory V C, we may require that the type of morphisms X ⟶ Y in C identify to šŸ™_ V ⟶ EnrichedCategory.Hom X Y. This data shall be packaged in the typeclass EnrichedOrdinaryCategory V C.

In particular, if C is a V-enriched category, it is shown that the "underlying" category ForgetEnrichment V C is equipped with a EnrichedOrdinaryCategory V C instance.

Simplicial categories are implemented in AlgebraicTopology.SimplicialCategory.Basic using an abbreviation for EnrichedOrdinaryCategory SSet C.

An enriched ordinary category is a category C that is also enriched over a category V in such a way that morphisms X ⟶ Y in C identify to morphisms šŸ™_ V ⟶ (X ⟶[V] Y) in V.

Instances

    The bijection (X ⟶ Y) ā‰ƒ (šŸ™_ V ⟶ (X ⟶[V] Y)) given by a EnrichedOrdinaryCategory instance.

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      def CategoryTheory.eHomWhiskerRight (V : Type u') [Category.{v', u'} V] [MonoidalCategory V] {C : Type u} [Category.{v, u} C] [EnrichedOrdinaryCategory V C] {X X' : C} (f : X ⟶ X') (Y : C) :
      (X' ⟶[V] Y) ⟶ X ⟶[V] Y

      The morphism (X' ⟶[V] Y) ⟶ (X ⟶[V] Y) induced by a morphism X ⟶ X'.

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        Whiskering commutes with the enriched composition.

        def CategoryTheory.eHomWhiskerLeft (V : Type u') [Category.{v', u'} V] [MonoidalCategory V] {C : Type u} [Category.{v, u} C] [EnrichedOrdinaryCategory V C] (X : C) {Y Y' : C} (g : Y ⟶ Y') :
        (X ⟶[V] Y) ⟶ X ⟶[V] Y'

        The morphism (X ⟶[V] Y) ⟶ (X ⟶[V] Y') induced by a morphism Y ⟶ Y'.

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          Whiskering commutes with the enriched composition.

          Given an isomorphism α : Y ≅ Y₁ in C, the enriched composition map eComp V X Y Z : (X ⟶[V] Y) āŠ— (Y ⟶[V] Z) ⟶ (X ⟶[V] Z) factors through the V object (X ⟶[V] Y₁) āŠ— (Y₁ ⟶[V] Z) via the map defined by whiskering in the middle with α.hom and α.inv.

          The bifunctor Cįµ’įµ– ℤ C ℤ V which sends X : Cįµ’įµ– and Y : C to X ⟶[V] Y.

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            @[simp]
            theorem CategoryTheory.eHomFunctor_obj_map (V : Type u') [Category.{v', u'} V] [MonoidalCategory V] (C : Type u) [Category.{v, u} C] [EnrichedOrdinaryCategory V C] (X : Cįµ’įµ–) {Xāœ Yāœ : C} (φ : Xāœ ⟶ Yāœ) :
            ((eHomFunctor V C).obj X).map φ = eHomWhiskerLeft V (Opposite.unop X) φ
            @[simp]
            theorem CategoryTheory.eHomFunctor_map_app (V : Type u') [Category.{v', u'} V] [MonoidalCategory V] (C : Type u) [Category.{v, u} C] [EnrichedOrdinaryCategory V C] {Xāœ Yāœ : Cįµ’įµ–} (φ : Xāœ ⟶ Yāœ) (Y : C) :
            ((eHomFunctor V C).map φ).app Y = eHomWhiskerRight V φ.unop Y
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            If D is already an enriched ordinary category, there is a canonical functor from D to ForgetEnrichment V D.

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              @[simp]
              theorem CategoryTheory.ForgetEnrichment.equivInverse_map (V : Type u') [Category.{v', u'} V] [MonoidalCategory V] (D : Type u') [Category.{v', u'} D] [EnrichedOrdinaryCategory V D] {Xāœ Yāœ : D} (f : Xāœ ⟶ Yāœ) :
              (equivInverse V D).map f = homOf V ((eHomEquiv V) f)

              If D is already an enriched ordinary category, there is a canonical functor from ForgetEnrichment V D to D.

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                @[simp]

                If D is already an enriched ordinary category, it is equivalent to ForgetEnrichment V D.

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                  @[reducible, inline]

                  enriched coyoneda functor (X ⟶[V] _) : C ℤ V.

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                    If C is an ordinary enriched category, the category structure on TransportEnrichment F C is trivially equivalent to the one on C itself.

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                      If for a lax monoidal functor F : V ℤ W the canonical function (šŸ™_ V ⟶ v) → (šŸ™_ W ⟶ F.obj v) is bijective, and C is an enriched ordinary category on V, then F induces the structure of a W-enriched ordinary category on TransportEnrichment F C, i.e. on the same underlying category C.

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                        The inverse functor that makes up TransportEnrichment.forgetEnrichmentEquiv.

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                          If D is a V-enriched category, then forgetting the enrichment and transporting the resulting enriched ordinary category along a functor F : V ℤ W, for which f ↦ Functor.LaxMonoidal.ε F ≫ F.map f has an inverse, results in a category equivalent to transporting along F and then forgetting about the resulting W-enrichment.

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