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In the area of mathematics known as group theory, the correspondence theorem, sometimes referred to as the fourth isomorphism theorem〔〔Some authors use "fourth isomorphism theorem" to designate the Zassenhaus lemma; see for example by Alperin & Bell (p. 13) or 〕〔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.〕 or the lattice theorem,〔W.R. Scott: ''Group Theory'', Prentice Hall, 1964, p. 27.〕 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. This establishes a monotone Galois connection between the lattice of subgroups of and the lattice of subgroups of , where the associated closure operator on subgroups of is 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. Similar results hold for rings, modules, vector spaces, and algebras. == See also == * Modular lattice 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Correspondence theorem (group theory)」の詳細全文を読む スポンサード リンク
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