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In mathematics, algebras ''A'', ''B'' over a field ''k'' inside some field extension of ''k'' (e.g., universal field) are said to be linearly disjoint over ''k'' if the following equivalent conditions are met: *(i) The map induced by is injective. *(ii) Any ''k''-basis of ''A'' remains linearly independent over ''B''. *(iii) If are ''k''-bases for ''A'', ''B'', then the products are linearly independent over ''k''. Note that, since every subalgebra of is a domain, (i) implies is a domain (in particular reduced). One also has: ''A'', ''B'' are linearly disjoint over ''k'' if and only if subfields of generated by , resp. are linearly disjoint over ''k''. (cf. tensor product of fields) Suppose ''A'', ''B'' are linearly disjoint over ''k''. If , are subalgebras, then and are linearly disjoint over ''k''. Conversely, if any finitely generated subalgebras of algebras ''A'', ''B'' are linearly disjoint, then ''A'', ''B'' are linearly disjoint (since the condition involves only finite sets of elements.) == See also == *Tensor product of fields 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「linearly disjoint」の詳細全文を読む スポンサード リンク
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