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In algebraic topology, a complex-orientable cohomology theory is a multiplicative cohomology theory ''E'' such that the restriction map is surjective. An element of that restricts to the canonical generator of the reduced theory is called a complex orientation. The notion is central to Quillen's work relating cohomology to formal group laws. If , then ''E'' is complex-orientable. Examples: *An ordinary cohomology with any coefficient ring ''R'' is complex orientable, as . *A complex ''K''-theory, denoted by ''K'', is complex-orientable, as (Bott periodicity theorem) *Complex cobordism, whose spectrum is denoted by MU, is complex-orientable. A complex orientation, call it ''t'', gives rise to a formal group law as follows: let ''m'' be the multiplication : where denotes a line passing through ''x'' in the underlying vector space of . Viewing :, let be the pullback of ''t'' along ''m''. It lives in : and one can show it is a formal group law (e.g., satisfies associativity). == See also == *Chromatic homotopy theory 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「Complex-oriented cohomology theory」の詳細全文を読む スポンサード リンク
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