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Studies in Rings generalised Unique Factorisation Rings

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-100-<br />

Lemma 4 019.<br />

An <strong>in</strong>vertible ideal <strong>in</strong> a<br />

(right) Noetherian r<strong>in</strong>g<br />

has the (right) AR<br />

property.<br />

Let R be a Noetherian r<strong>in</strong>g with a quotient r<strong>in</strong>g Q.<br />

, J<br />

Let P = aR = ha be a prime ideal with a regularo Then<br />

R has a partial quotient r<strong>in</strong>g S obta<strong>in</strong>ed by localis<strong>in</strong>g<br />

R at the Ore set {l,a,a 2 •.• J It is easy to see that<br />

P = aR = Ra is S-<strong>in</strong>vertible and<br />

hence P has the (right<br />

and left) AR property. Us<strong>in</strong>g <strong>in</strong>duction and regularity<br />

of a, it is easy to see that C(p) ~ C(pn) for every n.<br />

Now by [28, proposition 2 0 1 ] , P is localisable which gives<br />

the proof of lemma 2.17.<br />

Given a prime ideal P,<br />

any right localisation at P<br />

must be found by <strong>in</strong>vert<strong>in</strong>g a right Ore set C ~ C R<br />

(p) ·<br />

Thus, <strong>in</strong> fact, C ~ () [CR(Q) IQ , rt cl p} by corollary 4 07.<br />

Let X != Spec R and def<strong>in</strong>e C(X) = () { C ( Q ) R<br />

IQ' XJ. If X<br />

is a right clique and if we want to localise at X, then<br />

c(x) must be a right Ore set. We also want some nice<br />

properties for the quotient r<strong>in</strong>g.<br />

Def<strong>in</strong>ition 4 0 20 .<br />

Let R be a Noetherian r<strong>in</strong>g and X < Spec R. Then

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