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In mathematics, a rank ring is a ring with a real-valued rank function behaving like the rank of an endomorphism. introduced rank rings in his work on continuous geometry, and showed that the ring associated to a continuous geometry is a rank ring. ==Definition== defined a ring to be a rank ring if it is regular and has a real-valued rank function ''R'' with the following properties: *0 ≤ ''R''(''a'') ≤ 1 for all ''a'' *''R''(''a'') = 0 if and only if ''a'' = 0 *''R''(1) = 1 *''R''(''ab'') ≤ ''R''(''a''), ''R''(''ab'') ≤ ''R''(''b'') *If ''e''2 = ''e'', ''f''2 = ''f'', ''ef'' = ''fe'' = 0 then ''R''(''e'' + ''f'') = ''R''(''e'') + ''R''(''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「Rank ring」の詳細全文を読む スポンサード リンク
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