This paper is devoted to the study of some nonlinear parabolic equations with discontinuous diffusion intensities. Such problems appear naturally in physical and biological models. Our analysis is based on variational techniques and in particular on gradient flows in the space of probability measures equipped with the distance arising in the Monge–Kantorovich optimal transport problem. The associated internal energy functionals in general fail to be differentiable, therefore classical results do not apply directly in our setting. We study the combination of both linear and porous medium type diffusions and we show the existence and uniqueness of the solutions in the sense of distributions in suitable Sobolev spaces. Our notion of solution allows us to give a fine characterization of the emerging critical regions, observed previously in numerical experiments. A link to a three phase free boundary problem is also pointed out.

中文翻译：

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具有不连续扩散系数的退化非线性抛物方程

本文致力于研究具有不连续扩散强度的非线性抛物方程。这些问题自然出现在物理和生物学模型中。我们的分析基于变分技术，尤其是基于概率测度空间中的梯度流，该概率流配备了蒙格–坎托罗维奇最优输运问题中出现的距离。通常，相关的内部能量功能无法区分，因此经典结果不适用于我们的环境。我们研究了线性和多孔介质类型扩散的组合，并在合适的Sobolev空间中的分布意义上证明了解的存在性和唯一性。我们的解决方案概念使我们能够对新兴的关键区域进行精细描述，以前在数值实验中观察到。还指出了与三相自由边界问题的联系。