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In mathematics, the Bourbaki–Witt theorem in order theory, named after Nicolas Bourbaki and Ernst Witt, is a basic fixed point theorem for partially ordered sets. It states that if ''X'' is a non-empty chain complete poset, and : such that : for all then ''f'' has a fixed point. Such a function ''f'' is called ''inflationary'' or ''progressive''. == Special case of a finite poset == If the poset ''X'' is finite then the statement of the theorem has a clear interpretation that leads to the proof. The sequence of successive iterates, : where ''x''0 is any element of ''X'', is monotone increasing. By the finiteness of ''X'', it stabilizes: : for ''n'' sufficiently large. It follows that ''x''∞ is a fixed point of ''f''. 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「Bourbaki–Witt theorem」の詳細全文を読む スポンサード リンク
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