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arXiv math/0608746math.AP
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一个在自由边界上具有Bernoulli型条件的抛物型自由边界问题

A parabolic free boundary problem with Bernoulli type condition on the free boundary

J. Andersson, G. S. Weiss

摘要:

考虑抛物型自由边界问题$$ Δu - \partial_t u = 0 \textrm{in} \{u>0\}, |\nabla u|=1 \textrm{on} \partial\{u>0\} . $$对于一类现实的解决方案,包含例如{ \em所有}限制的奇异扰动问题$$Δu_ε- \partial_t u_ε= β_ε(u_ε) \textrm{as} ε\to 0,$$我们证明,单侧平坦的自由边界意味着正则性。特别地,我们证明了拓扑自由边界$\partial\{u>0\}$可以分解为一个{ \em开}正则集(相对于$\partial\{u>0\}$)和一个闭奇异集,其中正则集是局部具有Hölder连续空间法线的曲面.我们的结果推广了H.W. Alt-洛杉矶Caffarelli(1981)对更一般的解以及与时间相关的情况进行了讨论。我们的证明使用H.W. Alt-洛杉矶Caffarelli(1981),但是我们用基于标度差异的论证取代了那篇论文的核心,它依赖于奇点处的非正中曲率,这有望适用于更一般的自由边界或自由不连续性问题。

英文摘要:

Consider the parabolic free boundary problem $$ Δu - \partial_t u = 0 \textrm{in} \{u>0\}, |\nabla u|=1 \textrm{on} \partial\{u>0\} . $$ For a realistic class of solutions, containing for example {\em all} limits of the singular perturbation problem $$Δu_ε- \partial_t u_ε= β_ε(u_ε) \textrm{as} ε\to 0,$$ we prove that one-sided flatness of the free boundary implies regularity. In particular, we show that the topological free boundary $\partial\{u>0\}$ can be decomposed into an {\em open} regular set (relative to $\partial\{u>0\}$) which is locally a surface with Hölder-continuous space normal, and a closed singular set. Our result extends the main theorem in the paper by H.W. Alt-L.A. Caffarelli (1981) to more general solutions as well as the time-dependent case. Our proof uses methods developed in H.W. Alt-L.A. Caffarelli (1981), however we replace the core of that paper, which relies on non-positive mean curvature at singular points, by an argument based on scaling discrepancies, which promises to be applicable to more general free boundary or free discontinuity problems.

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