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 Type
s and Sort
s, 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
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)
.
The inverse map defined by eHomCongr
respects composition of morphisms.