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词条 Correspondence theorem (group theory)
释义

  1. See also

  2. Notes

  3. References

In the area of mathematics known as group theory, the correspondence theorem,[1][2][3][4][5][6][7][8] sometimes referred to as the fourth isomorphism theorem[6][9][10][11] or the lattice theorem,[12] states that if is a normal subgroup of a group , then there exists a bijection from the set of all subgroups of containing , onto the set of all subgroups of the quotient group . The structure of the subgroups of is exactly the same as the structure of the subgroups of containing , with collapsed to the identity element.

Specifically, if

G is a group,

N is a normal subgroup of G,

is the set of all subgroups A of G such that , and

is the set of all subgroups of G/N,

then there is a bijective map such that

for all

One further has that if A and B are in , and A' = A/N and B' = B/N, then

  • if and only if ;
  • if then , where is the index of A in B (the number of cosets bA of A in B);
  • where is the subgroup of generated by
  • , and
  • is a normal subgroup of if and only if is a normal subgroup of .

This list is far from exhaustive. In fact, most properties of subgroups are preserved in their images under the bijection onto subgroups of a quotient group.

More generally, there is a monotone Galois connection between the lattice of subgroups of (not necessarily containing ) and the lattice of subgroups of : the lower adjoint of a subgroup of is given by and the upper adjoint of a subgroup of is a given by . The associated closure operator on subgroups of is ; the associated kernel operator on subgroups of is the identity.

Similar results hold for rings, modules, vector spaces, and algebras.

See also

  • Modular lattice

Notes

1. ^{{cite book|author=Derek John Scott Robinson|title=An Introduction to Abstract Algebra|year=2003|publisher=Walter de Gruyter|isbn=978-3-11-017544-8|page=64}}
2. ^{{cite book|author=J. F. Humphreys|title=A Course in Group Theory|year=1996|publisher=Oxford University Press|isbn=978-0-19-853459-4|page=65}}
3. ^{{cite book|author=H.E. Rose|title=A Course on Finite Groups|year=2009|publisher=Springer|isbn=978-1-84882-889-6|page=78}}
4. ^{{cite book|author1=J.L. Alperin|author2=Rowen B. Bell|title=Groups and Representations|year=1995|publisher=Springer|isbn=978-1-4612-0799-3|page=11}}
5. ^{{cite book|author=I. Martin Isaacs|title=Algebra: A Graduate Course|year=1994|publisher=American Mathematical Soc.|isbn=978-0-8218-4799-2|page=35}}
6. ^{{cite book|author=Joseph Rotman|title=An Introduction to the Theory of Groups|year=1995|publisher=Springer|isbn=978-1-4612-4176-8|pages=37–38|edition=4th}}
7. ^{{cite book|author=W. Keith Nicholson|title=Introduction to Abstract Algebra|year=2012|publisher=John Wiley & Sons|isbn=978-1-118-31173-8|page=352|edition=4th}}
8. ^{{cite book|author=Steven Roman|title=Fundamentals of Group Theory: An Advanced Approach|year=2011|publisher=Springer Science & Business Media|isbn=978-0-8176-8301-6|pages=113–115}}
9. ^{{cite book|author1=Jonathan K. Hodge|author2=Steven Schlicker|author3=Ted Sundstrom|title=Abstract Algebra: An Inquiry Based Approach|year=2013|publisher=CRC Press|isbn=978-1-4665-6708-5|page=425}}
10. ^Some authors use "fourth isomorphism theorem" to designate the Zassenhaus lemma; see for example by Alperin & Bell (p. 13) or {{cite book|author=Robert Wilson|title=The Finite Simple Groups|year=2009|publisher=Springer|isbn=978-1-84800-988-2|page=7}}
11. ^Depending how one counts the isomorphism theorems, the correspondence theorem can also be called the 3rd isomorphism theorem; see for instance H.E. Rose (2009), p. 78.
12. ^W.R. Scott: Group Theory, Prentice Hall, 1964, p. 27.

References

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1 : Isomorphism theorems

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