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In commutative algebra, an étale or separable algebra is a special type of algebra, one that is isomorphic to a finite product of separable extensions. == Definitions == Let be a field and let be a -algebra. Then is called étale or separable if , where is an algebraically closed extension of and is an integer . Equivalently, is étale if it is isomorphic to a finite product of separable extensions of . When these extensions are all of finite degree, is said to be finite étale; in this case one can replace with a finite separable extension of in the definition above. A third definition says that an étale algebra is a finite dimensional commutative algebra whose trace form (''x'',''y'') = Tr(''xy'') is non-degenerate The name "étale algebra" comes from the fact that a finite dimensional commutative algebra over a field is étale if and only if is an étale morphism. 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「Étale algebra」の詳細全文を読む スポンサード リンク
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