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arXiv 2006.09200math.AP
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关于存在奇点时输运方程的解

On solutions of the transport equation in the presence of singularities

Evelyne Miot, Nicholas Sharples

摘要:

本文考虑了向量场为$BV$偏离一个集合$S\subset [0,T]\times \mathbb{R}^n$的情况下$[0,T]\times \mathbb{R}^n$上的输运方程。我们证明了解决方案的存在,是唯一的,提供了一组奇点具有足够小的各向异性分形维数和正常的向量场的分量是充分可积附近的奇点。这一结果改进了Ambrosio最近的结果,Ambrosio要求向量场处处有界变化。此外,我们证明,在这些条件下,几乎每一个相关的定期拉格朗日流的轨迹不相交的$S$集的奇点。最后,我们考虑的特殊情况下,初始的一组奇点,演变的时间,所以奇点组成的曲线在相空间,这是典型的应用,如涡动力学。我们证明了输运方程的解的存在性和唯一性,只要奇异点的盒维数是有界的曲线的Hölder指数。

英文摘要:

We consider the transport equation on $[0,T]\times \mathbb{R}^n$ in the situation where the vector field is $BV$ off a set $S\subset [0,T]\times \mathbb{R}^n$. We demonstrate that solutions exist and are unique provided that the set of singularities has a sufficiently small anisotropic fractal dimension and the normal component of the vector field is sufficiently integrable near the singularities. This result improves upon recent results of Ambrosio who requires the vector field to be of bounded variation everywhere. In addition, we demonstrate that under these conditions almost every trajectory of the associated regular Lagrangian flow does not intersect the set $S$ of singularities. Finally, we consider the particular case of an initial set of singularities that evolve in time so the singularities consists of curves in the phase space, which is typical in applications such as vortex dynamics. We demonstrate that solutions of the transport equation exist and are unique provided that the box-counting dimension of the singularities is bounded in terms of the Hölder exponent of the curves.

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