English
In the category of commutative group objects, there exists an initial object (the trivial one).
Русский
В категории коммутативных групп существует начальный объект (тривиальный).
LaTeX
$$$\\text{HasInitial }(\\text{CommGrp}_C)$$$
Lean4
/-- Construct an isomorphism of commutative group objects by giving a monoid isomorphism between the
underlying objects. -/
@[simps!]
def mkIso' {G H : C} (e : G ≅ H) [GrpObj G] [IsCommMonObj G] [GrpObj H] [IsCommMonObj H] [IsMonHom e.hom] :
mk G ≅ mk H :=
(fullyFaithfulForget₂Grp_ C).preimageIso (Grp_.mkIso' e)