English
There is a finite instance ensuring that a Span over R' is controlled by Span over R.
Русский
Существует конечный пример, обеспечивающий контроль над span над R' знаменем над R.
LaTeX
$$$\\operatorname{Finite}\\;\\operatorname{Localization}\\;\\operatorname{Span}$$$
Lean4
/-- If `S` is an `R' = M⁻¹R` algebra, and `x ∈ adjoin R' s`,
then `t • x ∈ adjoin R s` for some `t : M`. -/
theorem multiple_mem_adjoin_of_mem_localization_adjoin [Algebra R' S] [Algebra R S] [IsScalarTower R R' S]
[IsLocalization M R'] (s : Set S) (x : S) (hx : x ∈ Algebra.adjoin R' s) : ∃ t : M, t • x ∈ Algebra.adjoin R s :=
by
change ∃ t : M, t • x ∈ Subalgebra.toSubmodule (Algebra.adjoin R s)
change x ∈ Subalgebra.toSubmodule (Algebra.adjoin R' s) at hx
simp_rw [Algebra.adjoin_eq_span] at hx ⊢
exact multiple_mem_span_of_mem_localization_span M R' _ _ hx