Gorenstein ring
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In commutative algebra, a Gorenstein local ring is a Noetherian commutative local ring R with finite injective dimension, as an R-module. There are many equivalent conditions, some of them listed below, most dealing with some sort of duality condition.
A Gorenstein commutative ring is a commutative ring such that each localization at a prime ideal is a Gorenstein local ring. The Gorenstein ring concept is a special case of the more general Cohen-Macaulay ring.
A noteworthy occurrence of the concept is as one ingredient (among many) of the solution by Andrew Wiles to the Fermat Conjecture.
Examples
- Every complete intersection ring is Gorenstein.
- Every regular local ring is a complete intersection ring, so is Gorenstein.
See also Daniel Gorenstein.
The classical definition reads:
A local Cohen--Macaulay ring R is called Gorenstein if there is a maximal R--regular sequence in the maximal ideal generating an irreducible ideal.