English
There is a canonical algebra structure on S over R' induced from A via the inclusion S → A.
Русский
Существует каноническая структура алгебры на S над R', наследуемая от A через включение S ↪ A.
LaTeX
$$$\text{Algebra}(R', S)$$$
Lean4
instance (priority := 500) algebra' [CommSemiring R'] [SMul R' R] [Algebra R' A] [IsScalarTower R' R A] : Algebra R' S
where
algebraMap :=
(algebraMap R' A).codRestrict S fun x =>
by
rw [Algebra.algebraMap_eq_smul_one, ← smul_one_smul R x (1 : A), ← Algebra.algebraMap_eq_smul_one]
exact algebraMap_mem S _
commutes' := fun _ _ => Subtype.eq <| Algebra.commutes _ _
smul_def' := fun _ _ => Subtype.eq <| Algebra.smul_def _ _