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In mathematics, a quasitoric manifold is a topological analogue of the nonsingular projective toric variety of algebraic geometry. A smooth -dimensional manifold is a quasitoric manifold if it admits a smooth, locally standard action of an -dimensional torus, with orbit space an -dimensional simple convex polytope. Quasitoric manifolds were introduced in 1991 by M. Davis and T. Januszkiewicz,〔M. Davis and T. Januskiewicz, 1991.〕 who called them "toric manifolds". However, the term "quasitoric manifold" was eventually adopted to avoid confusion with the class of compact smooth toric varieties, which are known to algebraic geometers as toric manifolds.〔V. Buchstaber and T. Panov, 2002.〕 Quasitoric manifolds are studied in a variety of contexts in algebraic topology, such as complex cobordism theory, and the other oriented cohomology theories.〔V. Buchstaber and N. Ray, 2008.〕 ==Definitions== Denote the -th subcircle of the -torus by so that . Then coordinate-wise multiplication of on is called the standard representation. Given open sets in and in , that are closed under the action of , a -action on is defined to be locally isomorphic to the standard representation if , for all in , in , where is a homeomorphism , and is an automorphism of . Given a simple convex polytope with facets, a -manifold is a quasitoric manifold over if, # the -action is locally isomorphic to the standard representation, # there is a projection that maps each -dimensional orbit to a point in the interior of an -dimensional face of , for . The definition implies that the fixed points of under the -action are mapped to the vertices of by , while points where the action is free project to the interior of the polytope. 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「Quasitoric manifold」の詳細全文を読む スポンサード リンク
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