English
The forgetful functor from GrpCat to MonCat is fully faithful; it induces bijections on Hom-sets.
Русский
Функтор забывания из GrpCat в MonCat полностью полно; он задаёт биекции между множествами мороморфизмов.
LaTeX
$$$ (\\mathrm{forget}_{\\mathrm GrpCat\\to MonCat}).\\mathrm{FullyFaithful}$$$
Lean4
/-- The forgetful functor from groups to monoids is fully faithful. -/
@[to_additive fullyFaihtfulForget₂ToAddMonCat /--
The forgetful functor from additive groups to additive monoids is fully faithful. -/
]
def fullyFaithfulForget₂ToMonCat : (forget₂ GrpCat.{u} MonCat).FullyFaithful where preimage f := ofHom f.hom