Every unital -subalgebra is a Noetherian ring. If or , a nonconstant element makes that ambient polynomial ring a finitely generated module over . Otherwise contains an with both positive and negative exponents, and both and are integral elements over . In either case is a submodule of a finite module over the Noetherian ring , and every ideal of is finitely generated over , hence over .
Noetherian scheme Created 2026-09-24 Updated 2026-09-24
A Noetherian scheme has a finite cover by affine schemes with each a Noetherian ring. Equivalently, it is quasi-compact and locally Noetherian.