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arXiv 1902.04066math.AP
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一个模拟坏死肿瘤生长的自由边界问题分析

Analysis of a free boundary problem modeling the growth of necrotic tumors

Shangbin Cui

摘要:

本文对一个模拟坏死肿瘤生长的自由边界问题进行了严格的数学分析。这个自由边界问题的一个显著特点是它包含两个不同类型的自由表面:一个是肿瘤表面,其发展受发展方程控制;另一个是肿瘤的活壳和坏死核之间的界面,它是一个障碍型自由表面,即,它的演化不是由发展方程控制的,而是由某种定常型方程决定的。在数学上,内自由面是由该模型中非线性反力函数的不连续性引起的,这是分析该自由边界问题的主要困难。以往的工作研究的是球对称情况,其实质是一维自由边界问题。本文的目的是在一般的球非对称情况下进行严格的分析。应用Nash-Moser隐函数定理,证明了当球面为小扰动时,内自由曲面是光滑的,且光滑地依赖于外自由曲面.应用这个结果和巴拿赫流形上抛物型微分方程的一些抽象结果,我们证明了这个自由边界问题的唯一径向定常解在小的非径向扰动下是渐近稳定的.

英文摘要:

In this paper we make rigorous mathematical analysis to a free boundary problem modeling the growth of necrotic tumors. A remarkable feature of this free boundary problem is that it contains two different-type free surfaces: One is the tumor surface whose evolution is governed by an evolution equation and the other is the interface between the living shell of the tumor and the necrotic core which is an obstacle-type free surface, i.e., its evolution is not governed by an evolution equation but instead is determined by some stationary-type equation. In mathematics, the inner free surface is induced by discontinuity of the nonlinear reaction functions in this model, which causes the main difficulty of analysis of this free boundary problem. Previous work on this model studies spherically symmetric situation which is in essence an one-dimension free boundary problem. The purpose of this paper is to make rigorous analysis in general spherically asymmetric situation. By applying the Nash-Moser implicit function theorem, we prove that the inner free surface is smooth and depends on the outer free surface smoothly when it is a small perturbation of the surface of a sphere. By applying this result and some abstract results for parabolic differential equations in Banach manifolds we prove that the unique radial stationary solution of this free boundary problem is asymptotically stable under small non-radial perturbations.

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