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In set theory, a mathematical discipline, a reflecting cardinal is a cardinal number κ for which there is a normal ideal ''I'' on κ such that for every ''X''∈''I''+, the set of α∈κ for which ''X'' reflects at α is in ''I''+. (A stationary subset ''S'' of κ is said to reflect at α<κ if ''S''∩α is stationary in α.) Reflecting cardinals were introduced by . Every weakly compact cardinal is a reflecting cardinal, and is also a limit of reflecting cardinals. Every reflecting cardinal is a greatly Mahlo cardinal, and is also a limit of greatly Mahlo cardinals, where a cardinal κ is called greatly Mahlo if it is κ+-Mahlo. ==References== * * 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「Reflecting cardinal」の詳細全文を読む スポンサード リンク
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