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In mathematics, a universal space is a certain metric space that contains all metric spaces whose dimension is bounded by some fixed constant. A similar definition exists in topological dynamics. ==Definition== Given a class of topological spaces, is universal for if each member of embeds in . Menger stated and proved the case of the following theorem. The theorem in full generality was proven by Nöbeling. Theorem: The -dimensional cube is universal for the class of compact metric spaces whose Lebesgue covering dimension is less than . Nöbeling went further and proved: Theorem: The subspace of consisting of set of points, at most of whose coordinates are rational, is universal for the class of separable metric spaces whose Lebesgue covering dimension is less than . The last theorem was generalized by Lipscomb to the class of metric spaces of (weight ) , : There exist a one-dimensional metric space such that the subspace of consisting of set of points, at most of whose coordinates are "rational"'' (suitably defined), ''is universal for the class of metric spaces whose Lebesgue covering dimension is less than and whose weight is less than . 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「Universal space (topology)」の詳細全文を読む スポンサード リンク
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