English
There is a natural isomorphism between the multivariate polynomial ring on Option ι and the polynomial ring over the algebra generated by an algebraically independent family.
Русский
Существует естественный изоморфизм между кольцом многочленов по Option ι и кольцом многочленов над порожденной алгеброй алгебраически независимой семьи.
LaTeX
$$$\MvPolynomial (Option \ ι) R \cong_*\ Polynomial (\operatorname{adjoin} R (\operatorname{range} x))$$$
Lean4
/-- The isomorphism between `MvPolynomial (Option ι) R` and the polynomial ring over
the algebra generated by an algebraically independent family. -/
def mvPolynomialOptionEquivPolynomialAdjoin (hx : AlgebraicIndependent R x) :
MvPolynomial (Option ι) R ≃+* Polynomial (adjoin R (Set.range x)) :=
(MvPolynomial.optionEquivLeft _ _).toRingEquiv.trans (Polynomial.mapEquiv hx.aevalEquiv.toRingEquiv)