English
A Lawful structure on the Day convolution gives a monoidal category on D via an induced construction.
Русский
Законная структура Day-конволюции задаёт моноидальную категорию на D через индуцированную конструкцию.
LaTeX
$$$ \text{lawful}_{C,V,D} \Rightarrow \text{MonoidalCategory } D $$$
Lean4
theorem ι_map_associator_hom_eq_associator_hom (d d' d'')
[∀ (v : V) (d : C), Limits.PreservesColimitsOfShape (CostructuredArrow (tensor C) d) (tensorLeft v)]
[∀ (v : V) (d : C), Limits.PreservesColimitsOfShape (CostructuredArrow (tensor C) d) (tensorRight v)] :
(ι C V D).map (α_ d d' d'').hom =
(DayConvolution.associator (ι C V D |>.obj d) (ι C V D |>.obj d') (ι C V D |>.obj d'')).hom :=
by
apply corepresentableBy₂' (ι C V D |>.obj d) (ι C V D |>.obj d') (ι C V D |>.obj d'') |>.homEquiv.injective
dsimp
ext ⟨⟨x, y⟩, z⟩
simp only [externalProductBifunctor_obj_obj, Functor.comp_obj, Functor.prod_obj, tensor_obj, Functor.id_obj,
Functor.homEquivOfIsLeftKanExtension_apply_app, externalProductBifunctor_map_app, Functor.leftUnitor_inv_app,
whiskerLeft_id, Category.comp_id, corepresentableBy_homEquiv_apply_app, DayConvolution.associator_hom_unit_unit]
exact associator_hom_unit_unit V _ _ _ _ _ _