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ideal generated by a subset of a ring (Definition)

Let $X$ be a subset of a ring $R$ . Let $S=\{I_k\}$ be the collection of all left ideals of $R$ that contain $X$ (note that the set is nonempty since $X\subset R$ and $R$ is an ideal in itself). The intersection

$\displaystyle I=\bigcap_{I_k\in S} I_k$    

is called the left ideal generated by $X$ , and is denoted by $(X)$ . We say that $X$ generates $I$ as an ideal.

The definition is symmetrical for right ideals.

Alternatively, we can constructively form the set of elements that constitutes this ideal: The left ideal $(X)$ consists of finite $R$ -linear combinations of elements of $X$ :

$\displaystyle (X)=\left\{\sum_\lambda (r_\lambda a_\lambda + n_\lambda a_\lambda)\mid a_\lambda\in X, r_\lambda\in R, n_\lambda\in\mathbb{Z}\right\}.$    




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See Also: generators of inverse ideal, prime ideals by Artin are prime ideals

Also defines:  ideal generated by, left ideal generated by, right ideal generated by, generate as an ideal, generates as an ideal, generates

Attachments:
entries on finitely generated ideals (Topic) by pahio
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Cross-references: combinations, finite, right ideals, intersection, ideal, contain, left ideals, collection, ring, subset
There are 56 references to this entry.

This is version 6 of ideal generated by a subset of a ring, born on 2004-09-28, modified 2004-09-29.
Object id is 6242, canonical name is IdealGeneratedByASet.
Accessed 11929 times total.

Classification:
AMS MSC16D25 (Associative rings and algebras :: Modules, bimodules and ideals :: Ideals)

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