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In mathematics, the Drazin inverse, named after Michael P. Drazin, is a kind of generalized inverse of a matrix. Let ''A'' be a square matrix. The index of ''A'' is the least nonnegative integer ''k'' such that rank(''A''''k''+1) = rank(''A''''k''). The Drazin inverse of ''A'' is the unique matrix ''A''''D'' which satisfies : * If ''A'' is invertible with inverse , then . * The Drazin inverse of a matrix of index 0 or 1 is called the group inverse or -inverse and denoted ''A''#. The group inverse can be defined, equivalently, by the properties ''AA''#''A'' = ''A'', ''A''#''AA''# = ''A''#, and ''AA''# = ''A''#''A''. * A projection matrix ''P'', defined as a matrix such that ''P''2 = ''P'', has index 1 (or 0) and has Drazin inverse ''P''''D'' = ''P''. * If A is a nilpotent matrix (for example a shift matrix), then The hyper-power sequence is : for convergence notice that For or any regular with chosen such that the sequence tends to its Drazin inverse, : == See also== * Constrained generalized inverse * Inverse element * Moore–Penrose inverse 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「Drazin inverse」の詳細全文を読む スポンサード リンク
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