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In geometric topology, the de Rham invariant is a mod 2 invariant of a (4''k''+1)-dimensional manifold, that is, an element of – either 0 or 1. It can be thought of as the simply-connected ''symmetric'' L-group and thus analogous to the other invariants from L-theory: the signature, a 4''k''-dimensional invariant (either symmetric or quadratic, ), and the Kervaire invariant, a (4''k''+2)-dimensional ''quadratic'' invariant It is named for Swiss mathematician Georges de Rham, and used in surgery theory.〔Morgan & Sullivan, ''The transversality characteristic class and linking cycles in surgery theory,'' 1974〕〔John W. Morgan, ''(A product formula for surgery obstructions ),'' 1978〕 == Definition == The de Rham invariant of a (4''k''+1)-dimensional manifold can be defined in various equivalent ways: * the rank of the 2-torsion in as an integer mod 2; * the Stiefel–Whitney number ; * the (squared) Wu number, where is the Wu class of the normal bundle of and is the Steenrod square ; formally, as with all characteristic numbers, this is evaluated on the fundamental class: ; * in terms of a semicharacteristic. 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「De Rham invariant」の詳細全文を読む スポンサード リンク
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