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In the mathematical field of representation theory, a highest-weight category is a ''k''-linear category C (here ''k'' is a field) that *is ''locally artinian''〔In the sense that it admits arbitrary direct limits of subobjects and every object is a union of its subobjects of finite length.〕 *has enough injectives *satisfies :: :for all subobjects ''B'' and each family of subobjects of each object ''X'' and such that there is a locally finite poset Λ (whose elements are called the weights of C) that satisfies the following conditions: * The poset Λ indexes an exhaustive set of non-isomorphic simple objects in C. * Λ also indexes a collection of objects of objects of C such that there exist embeddings ''S''(''λ'') → ''A''(''λ'') such that all composition factors ''S''(''μ'') of ''A''(''λ'')/''S''(''λ'') satisfy ''μ'' < ''λ''.〔Here, a composition factor of an object ''A'' in C is, by definition, a composition factor of one of its finite length subobjects.〕 * For all ''μ'', ''λ'' in Λ, :: :is finite, and the multiplicity〔Here, if ''A'' is an object in C and ''S'' is a simple object in C, the multiplicity () is, by definition, the supremum of the multiplicity of ''S'' in all finite length subobjects of ''A''.〕 :: :is also finite. *Each ''S''(''λ'') has an injective envelope ''I''(''λ'') in C equipped with an increasing filtration :: :such that :# :# for ''n'' > 1, for some ''μ'' = ''μ''(''n'') > ''λ'' :# for each ''μ'' in Λ, ''μ''(''n'') = ''μ'' for only finitely many ''n'' :# == Examples == * The module category of the -algebra of upper triangular matrices over . * This concept is named after the category of highest-weight modules of Lie-algebras. * A finite-dimensional -algebra is quasi-hereditary iff its module category is a highest-weight category. In particular all module-categories over semisimple and hereditary algebras are highest-weight categories. * A cellular algebra over a field is quasi-hereditary (and hence its module category a highest-weight category) iff its Cartan-determinant is 1. 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「Highest-weight category」の詳細全文を読む スポンサード リンク
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