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arXiv 1709.04002math.AP
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经典障碍问题自由边界的精细结构

On the fine structure of the free boundary for the classical obstacle problem

Alessio Figalli, Joaquim Serra

摘要:

在经典障碍问题中,自由边界可以分解为“正则”点和“奇异”点。正如卡法雷利在他的开创性论文\cite{C77,C98}中所示,正则点由光滑超曲面组成,而奇点则包含在不同维度的$C^1$流形的分层联合中。在二维中,这个$C^1$结果已经由Weiss \cite{W99}改进为$C^{1,α}$。本文证明了对于$n=2$,奇点局部包含在$C^2$曲线中.在高维$n\ge 3$中,我们证明了相同的结果适用于$C^{1,1}$流形(或可数多个$C^2$流形),直到存在一些更高余维的“异常”点。此外,我们还证明了$C^{1,α}$流形中总是包含高维层,从而将\cite{W99}中的结果推广到所有维.我们注意到,在接触集的密度衰减估计方面,我们的结果是最优的。此外,对于$n\ge3$,我们构造的例子非常对称的解决方案,表现出线性空间的异常点,证明我们的界限上的Hausdorff维数是尖锐的。

英文摘要:

In the classical obstacle problem, the free boundary can be decomposed into "regular" and "singular" points. As shown by Caffarelli in his seminal papers \cite{C77,C98}, regular points consist of smooth hypersurfaces, while singular points are contained in a stratified union of $C^1$ manifolds of varying dimension. In two dimensions, this $C^1$ result has been improved to $C^{1,α}$ by Weiss \cite{W99}. In this paper we prove that, for $n=2$ singular points are locally contained in a $C^2$ curve. In higher dimension $n\ge 3$, we show that the same result holds with $C^{1,1}$ manifolds (or with countably many $C^2$ manifolds), up to the presence of some "anomalous" points of higher codimension. In addition, we prove that the higher dimensional stratum is always contained in a $C^{1,α}$ manifold, thus extending to every dimension the result in \cite{W99}. We note that, in terms of density decay estimates for the contact set, our result is optimal. In addition, for $n\ge3$ we construct examples of very symmetric solutions exhibiting linear spaces of anomalous points, proving that our bound on their Hausdorff dimension is sharp.

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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