Exercise 6, § 3
Commutative Algebra, V, 372
An integral domain is called integrally Noetherian if it is Noetherian and if, for every finite sequence of elements of an extension field of the field of fractions of , the integral closure of is a finitely generated -module. Every finitely generated integral algebra over a field is an integrally Noetherian domain (no. 2, Theorem 2).
(a) Every finitely generated integral algebra over an integrally Noetherian domain is an integrally Noetherian domain. Every ring of fractions of an integrally Noetherian domain not reduced to 0 is an integrally Noetherian domain.
(b) Let be an integrally Noetherian domain a finite sequence of elements of an extension field of the field of fractions of and a subring of containing and integral over . Then is a finitely generated -module. (Note that the field of fractions of is a finite algebraic extension of , using Algebra, Chapter V, § 5, no. 7.)
Solution
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