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In algebra, an analytically irreducible ring is a local ring whose completion has no zero divisors. Geometrically this corresponds to a variety with only one analytic branch at a point. proved that if a local ring of an algebraic variety is a normal ring, then it is analytically irreducible. There are many examples of reduced and irreducible local rings that are analytically reducible, such as the local ring of a node of an irreducible curve, but it is hard to find examples that are also normal. gave such an example of a normal Noetherian local ring that is analytically reducible. ==Nagata's example== Suppose that ''K'' is a field of characteristic not 2, and ''K'' is the formal power series ring over ''K'' in 2 variables. Let ''R'' be the subring of ''K'' generated by ''x'', ''y'', and the elements ''z''''n'' and localized at these elements, where : is transcendental over ''K''(''x'') : :. Then ''R''()/(''X'' 2–''z''1) is a normal Noetherian local ring that is analytically reducible. 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「Analytically irreducible ring」の詳細全文を読む スポンサード リンク
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