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localization (Definition)

Let $R$ be a commutative ring and let $S$ be a nonempty multiplicative subset of $R$ . The localization of $R$ at $S$ is the ring $S^{-1} R$ whose elements are equivalence classes of $R \times S$ under the equivalence relation $(a,s) \sim (b,t)$ if $r(at - bs) = 0$ for some $r \in S$ . Addition and multiplication in $S^{-1}R$ are defined by:

  • $(a,s) + (b,t) = (at+bs,st)$
  • $(a,s) \cdot (b,t) = (a \cdot b,s \cdot t)$
The equivalence class of $(a,s)$ in $S^{-1}R$ is usually denoted $a/s$ . For $a \in R$ , the localization of $R$ at the minimal multiplicative set containing $a$ is written as $R_a$ . When $S$ is the complement of a prime ideal $\mathfrak{p}$ in $R$ , the localization of $R$ at $S$ is written $R_{\mathfrak{p}}$ .




"localization" is owned by djao.
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See Also: fraction field

Other names:  ring of fractions

Attachments:
extension by localization (Definition) by pahio
localization of a module (Definition) by CWoo
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Cross-references: prime ideal, complement, multiplicative set, minimal, multiplication, addition, equivalence relation, equivalence classes, ring, multiplicative subset, commutative ring
There are 32 references to this entry.

This is version 6 of localization, born on 2001-10-19, modified 2003-04-02.
Object id is 391, canonical name is Localization.
Accessed 8607 times total.

Classification:
AMS MSC13B30 (Commutative rings and algebras :: Ring extensions and related topics :: Quotients and localization)

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correction by nerdy2 on 2001-11-08 00:58:26
$R_a$ denotes the localization at the set $\{ a^n \vert n \in Z {\mathrm and } n \geq 0 \}$. The ideal $(a)$ has too many elements.
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non-commutative version by antizeus on 2001-10-19 22:55:05
There's a lovely theory devoted to localization over sets in non-commutative rings that I think deserves some treatment. I'm not up to it at this second though,
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