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Height-one localizations of normal Noetherian domains are DVRs
Statement
Let be a Noetherian integrally closed domain, and let be a prime ideal of height . Then the localisation is a discrete valuation ring.
Facts & Assumptions
Given: A Noetherian integrally closed domain and a height-one prime ideal .
The height of is (The height of a prime ideal).
Localisation at a prime means inverting (Localisation at a prime ideal: ).
The ring is local with maximal ideal ( is local with unique maximal ideal ).
A domain is integrally closed when every element of its fraction field integral over it already lies in the domain (Integral closure in an extension ring and integrally closed domains).
Localisations of Noetherian rings are Noetherian (Every quotient and every localisation of a Noetherian ring is Noetherian).
A nonfield domain is a DVR exactly when it is a one-dimensional Noetherian local integrally closed domain (Equivalent characterizations of a DVR).
Proof
By [L1] and [L3], the ring is a Noetherian local domain. By [F1], its Krull dimension is .
The localisation remains integrally closed. Let lie in the fraction field of and be integral over . Write a monic equation with each . Put . Then is integral over , so [F3] gives . Since , we conclude . Thus is integrally closed.
The maximal ideal of is nonzero. Choose . If in , then some satisfies , impossible in the domain . Hence is nonzero, so is not a field.
Steps 1.1, 1.2, and 1.3 verify condition 3 of [L4] for the ring . Therefore is a discrete valuation ring.
Depends on
The height of a prime ideal
Localisation at a prime ideal:
is local with unique maximal ideal
Prime ideals of a localization are exactly the primes disjoint from the denominator set
Integral closure in an extension ring and integrally closed domains
Left and right Noetherian rings
Equivalent characterizations of a DVR
Every quotient and every localisation of a Noetherian ring is Noetherian