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arXiv 1104.0759math.DGmath.AP
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曲线缩短流等周剖面的比较定理

A comparison theorem for the isoperimetric profile under curve shortening flow

Ben Andrews, Paul Bryan

摘要:

我们证明了一个比较定理的简单闭曲线的等周轮廓演变的归一化曲线缩短流:如果由初始曲线包围的区域的等周轮廓是大于,一些“模型”凸区域正好有四个顶点,并在两个轴上的反射对称,然后不等式仍然为真的演变区域的等周轮廓。我们应用此使用的Angenent的解决方案作为模型区域推导出尖锐的时间依赖的曲率上界任意嵌入闭曲线演变的归一化曲线缩短流。一个稍微不同的比较也给出了曲率的下界,其结果是格雷森定理的一个简单而直接的证明,而不使用任何爆破或紧性参数,Harnack估计,或自相似解的分类。

英文摘要:

We prove a comparison theorem for the isoperimetric profiles of simple closed curves evolving by the normalized curve shortening flow: If the isoperimetric profile of the region enclosed by the initial curve is greater than that of some `model' convex region with exactly four vertices and with reflection symmetry in both axes, then the inequality remains true for the isoperimetric profiles of the evolved regions. We apply this using the Angenent solution as the model region to deduce sharp time-dependent upper bounds on curvature for arbitrary embedded closed curves evolving by the normalized curve shortening flow. A slightly different comparison also gives lower bounds on curvature, and the result is a simple and direct proof of Grayson's theorem without use of any blowup or compactness arguments, Harnack estimates, or classification of self-similar solutions.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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