Published online by Cambridge University Press: 18 May 2009
The concept of reduction and integral closure of ideals relative to Artinian modules were introduced in [7]; and we summarize some of the main aspects now.
Let A be a commutative ring (with non-zero identity) and let a, b be ideals of A. Suppose that M is an Artinian module over A. We say that a is a reduction of b relative to M if a ⊆ b and there is a positive integer s such that
)O:Mabs)=(O:Mbs+l).
An element x of A is said to be integrally dependent on a relative to M if there exists n y ℕ(where ℕ denotes the set of positive integers) such that
It is shown that this is the case if and only if a is a reduction of a+Ax relative to M; moreover
ᾱ={x ɛ A: xis integrally dependent on a relative to M}
is an ideal of A called the integral closure of a relative to M and is the unique maximal member of
℘ = {b: b is an ideal of A which has a as a reduction relative to M}.