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In mathematics, the mean (topological) dimension of a topological dynamical system is a non-negative extended real number that is a measure of the complexity of the system. Mean dimension was first introduced in 1999 by Gromov. Shortly after it was developed and studied systematically by Lindenstrauss and Weiss. In particular they proved the following key fact: a system with finite topological entropy has zero mean dimension. For various topological dynamical systems with infinite topological entropy, the mean dimension can be calculated or at least bounded from below and above. This allows mean dimension to be used to distinguish between systems with infinite topological entropy. ==General definition== A topological dynamical system consists of a compact Hausdorff topological space and a continuous self-map . Let denote the collection of open finite covers of . For define its order by : An open finite cover refines , denoted , if for every , there is so that . Let : Note that in terms of this definition the Lebesgue covering dimension is defined by of any finite collection of open covers of . The mean dimension is the non-negative extended real number: : where 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「Mean dimension」の詳細全文を読む スポンサード リンク
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