Documentation

Mathlib.CategoryTheory.Enriched.HomCongr

Congruence of enriched homs #

Recall that when C is both a category and a V-enriched category, we say it is an EnrichedOrdinaryCategory if it comes equipped with a sufficiently compatible equivalence between morphisms X ⟶ Y in C and morphisms 𝟙_ V ⟶ (X ⟶[V] Y) in V.

In such a V-enriched ordinary category C, isomorphisms in C induce isomorphisms between hom-objects in V. We define this isomorphism in CategoryTheory.Iso.eHomCongr and prove that it respects composition in C.

The treatment here parallels that for unenriched categories in Mathlib/CategoryTheory/HomCongr.lean and that for sorts in Mathlib/Logic/Equiv/Defs.lean (cf. Equiv.arrowCongr). Note, however, that they construct equivalences between Types and Sorts, respectively, while in this file we construct isomorphisms between objects in V.

Given isomorphisms α : X ≅ X₁ and β : Y ≅ Y₁ in C, we can construct an isomorphism between V objects X ⟶[V] Y and X₁ ⟶[V] Y₁.

Equations
  • One or more equations did not get rendered due to their size.
Instances For
    theorem CategoryTheory.Iso.eHomCongr_trans (V : Type u') [CategoryTheory.Category.{v', u'} V] [CategoryTheory.MonoidalCategory V] {C : Type u} [CategoryTheory.Category.{v, u} C] [CategoryTheory.EnrichedOrdinaryCategory V C] {X₁ Y₁ X₂ Y₂ X₃ Y₃ : C} (α₁ : X₁ X₂) (β₁ : Y₁ Y₂) (α₂ : X₂ X₃) (β₂ : Y₂ Y₃) :

    eHomCongr respects composition of morphisms. Recall that for any composable pair of arrows f : X ⟶ Y and g : Y ⟶ Z in C, the composite f ≫ g in C defines a morphism 𝟙_ V ⟶ (X ⟶[V] Z) in V. Composing with the isomorphism eHomCongr V α γ yields a morphism in V that can be factored through the enriched composition map as shown: 𝟙_ V ⟶ 𝟙_ V ⊗ 𝟙_ V ⟶ (X₁ ⟶[V] Y₁) ⊗ (Y₁ ⟶[V] Z₁) ⟶ (X₁ ⟶[V] Z₁).