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In mathematics, a Young symmetrizer is an element of the group algebra of the symmetric group, constructed in such a way that, for the homomorphism from the group algebra to the endomorphisms of a vector space obtained from the action of on by permutation of indices, the image of the endomorphism determined by that element corresponds to an irreducible representation of the symmetric group over the complex numbers. A similar construction works over any field, and the resulting representations are called Specht modules. The Young symmetrizer is named after British mathematician Alfred Young. ==Definition== Given a finite symmetric group ''S''''n'' and specific Young tableau λ corresponding to a numbered partition of ''n'', define two permutation subgroups and of ''S''''n'' as follows: : and : Corresponding to these two subgroups, define two vectors in the group algebra as : and : where is the unit vector corresponding to ''g'', and is the sign of the permutation. The product : is the Young symmetrizer corresponding to the Young tableau λ. Each Young symmetrizer corresponds to an irreducible representation of the symmetric group, and every irreducible representation can be obtained from a corresponding Young symmetrizer. (If we replace the complex numbers by more general fields the corresponding representations will not be irreducible in general.) 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「Young symmetrizer」の詳細全文を読む スポンサード リンク
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