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Colin de Verdière's invariant is a graph parameter for any graph ''G,'' introduced by Yves Colin de Verdière in 1990. It was motivated by the study of the maximum multiplicity of the second eigenvalue of certain Schrödinger operators.〔 ==Definition== Let be a loopless simple graph. Assume without loss of generality that . Then is the largest corank of any symmetric matrix such that: * (M1) for all with : if ''i'' and ''j'' are adjacent, and if ''i'' and ''j'' are nonadjacent; * (M2) ''M'' has exactly one negative eigenvalue, of multiplicity 1; * (M3) there is no nonzero matrix such that and such that whenever or .〔〔 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「Colin de Verdière graph invariant」の詳細全文を読む スポンサード リンク
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