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Busemann functions were introduced by Busemann to study the large-scale geometry of metric spaces in his seminal ''The Geometry of Geodesics''.〔Busemann, Herbert. The geometry of geodesics. Vol. 6. DoverPublications. com, 1985.〕 More recently, Busemann functions have been used by probabilists to study asymptotic properties in models of first-passage percolation.〔Hoffman, Christopher. "Coexistence for Richardson type competing spatial growth models." The Annals of Applied Probability 15.1B (2005): 739-747.〕〔Damron, Michael, and Jack Hanson. "Busemann functions and infinite geodesics in two-dimensional first-passage percolation." arXiv preprint arXiv:1209.3036 (2012).〕 == Definition == Let be a metric space. A ray is a path which minimizes distance everywhere along its length. i.e., for all , :. Equivalently, a ray is an isometry from the "canonical ray" (the set equipped with the Euclidean metric) into the metric space ''X''. Given a ray ''γ'', the Busemann function is defined by : That is, when ''t'' is very large, the distance is approximately equal to . Given a ray ''γ'', its Busemann function is always well-defined. Loosely speaking, a Busemann function can be thought of as a "distance to infinity" along the ray ''γ''. 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「Busemann function」の詳細全文を読む スポンサード リンク
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