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In mathematics, in particular in differential geometry, the minimal volume is a number that describes one aspect of a Riemannian manifold's topology. This topological invariant was introduced by Mikhail Gromov. ==Definition== Consider a closed orientable connected smooth manifold with a smooth Riemannian metric , and define to be the volume of a manifold with the metric . Let represent the sectional curvature. The minimal volume of is a smooth invariant defined as : that is, the infimum of the volume of over all metrics with bounded sectional curvature. Clearly, any manifold may be given an arbitrarily small volume by selecting a Riemannian metric and scaling it down to , as . For a meaningful definition of minimal volume, it is thus necessary to prevent such scaling. The inclusion of bounds on sectional curvature suffices, as . If , then can be "collapsed" to a manifold of lower dimension (and thus one with -dimensional volume zero) by a series of appropriate metrics; this manifold may be considered the Hausdorff limit of the related sequence, and the bounds on sectional curvature ensure that this convergence takes place in a topologically meaningful fashion. 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「Minimal volume」の詳細全文を読む スポンサード リンク
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