“Irreducible ideal”的意思、由来-开放百科全书

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Irreducible ideal

释义

Examples
Properties
See also
References

In mathematics, a proper ideal of a commutative ring is said to be irreducible if it cannot be written as the intersection of two strictly larger ideals.^[1]

Examples

Every prime ideal is irreducible.^[2] Let two ideals be contained in some commutative ring . If the intersection is a non-trivial ideal, then there exists some elements and , where neither is in the intersection but the product is, which means a reducible ideal is not prime. A concrete example of this are the ideals and contained in . The intersection is , and is not a prime ideal.
Every irreducible ideal of a Noetherian ring is a primary ideal,^[1] and consequently for Noetherian rings an irreducible decomposition is a primary decomposition.^[3]
Every primary ideal of a principal ideal domain is an irreducible ideal.
Every irreducible ideal is a primal ideal.^[4]

Properties

An element of an integral domain is prime if, and only if, an ideal generated by it is a nonzero prime ideal. This is not true for irreducible ideals: an irreducible ideal may be generated by an element that is not an irreducible element, as is the case in for the ideal : It is not the intersection of two strictly greater ideals.

An ideal I of a ring A can be irreducible only if the algebraic set it defines is irreducible (that is, any open subset is dense) for the Zariski topology, or equivalently if the closed space of spec A consisting of prime ideals containing I is irreducible for the spectral topology.

The converse is not correct, for example the ideal of polynomials in two variables with vanishing terms of first and second order is not irreducible.

If k is an algebraically closed field, choosing the radical of an irreducible ideal of a polynomial ring over k is the same thing as choosing an embedding of the affine variety of its Nullstelle in the affine space.

References

1. ^¹{{citation|title=Algebraic Geometry|volume=136|series=Translations of mathematical monographs|first=Masayoshi|last=Miyanishi|publisher=American Mathematical Society|year=1998|isbn=9780821887707|page=13|url=https://books.google.com/books?id=1reGWSo8XIsC&pg=PA13}}.
2. ^{{citation|title=Advanced Algebra|first=Anthony W.|last=Knapp|series=Cornerstones|publisher=Springer|year=2007|isbn=9780817645229|page=446|url=https://books.google.com/books?id=25JfJAgqC8sC&pg=PA446}}.
3. ^{{cite book|last1=Dummit|first1=David S.|last2=Foote|first2=Richard M.|title=Abstract Algebra|date=2004|publisher=John Wiley & Sons, Inc.|location=Hoboken, NJ|isbn=0-471-43334-9|pages=683-685|edition=Third}}
4. ^{{citation | last = Fuchs | first = Ladislas | doi = 10.2307/2032421 | journal = Proceedings of the American Mathematical Society | mr = 0032584 | pages = 1–6 | title = On primal ideals | volume = 1 | year = 1950}}. Theorem 1, p. 3.

2 : Ring theory|Algebraic topology

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Examples

Properties

See also

References