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Rouché's theorem, named after , states that if the complex-valued functions ''f'' and ''g'' are holomorphic inside and on some closed contour ''K'', with |''g''(''z'')| < |''f''(''z'')| on ''K'', then ''f'' and ''f'' + ''g'' have the same number of zeros inside ''K'', where each zero is counted as many times as its multiplicity. This theorem assumes that the contour ''K'' is simple, that is, without self-intersections. Rouché's theorem is an easy consequence of a stronger symmetric Rouché's theorem described below. == Symmetric version == Theodor Estermann (1902–1991) proved in his book ''Complex Numbers and Functions'' the following statement: Let be a bounded region with continuous boundary . Two holomorphic functions have the same number of roots (counting multiplicity) in , if the strict inequality : holds on the boundary . The original Rouché's theorem then follows by setting and . 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「Rouché's theorem」の詳細全文を読む スポンサード リンク
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