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In matroid theory, the dual of a matroid is another matroid that has the same elements as , and in which a set is independent if and only if has a basis set disjoint from it.〔.〕〔.〕〔.〕 Matroid duals go back to the original paper by Hassler Whitney defining matroids.〔. Reprinted in , pp. 55–79. See in particular section 11, "Dual matroids", pp. 521–524.〕 They generalize to matroids the notions of planar graph duality and of dual spaces in linear algebra. ==Basic properties== Duality is an involution: for all , .〔〔〔 An alternative definition of the dual matroid is that its basis sets are the complements of the basis sets of . The basis exchange axiom, used to define matroids from their bases, is self-complementary, so the dual of a matroid is necessarily a matroid.〔 The flats of are complementary to the cycles (unions of circuits) of , and vice versa.〔 If is the rank function of a matroid on ground set , then the rank function of the dual matroid is .〔〔〔 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「Dual matroid」の詳細全文を読む スポンサード リンク
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