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arXiv 1508.07613math.AP
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修正的SQG贴片方程有限时间奇异性的形成

Finite time singularity formation for the modified SQG patch equation

Alexander Kiselev, Lenya Ryzhik, Yao Yao, Andrej Zlatos

摘要:

众所周知,二维不可压Euler方程存在整体正则解。无粘面准地转方程的毕奥-萨伐尔定律比欧拉方程少一阶导数,其解的整体正则性问题至今尚未解决。我们在这里研究补丁动力学的半平面的一个家庭的积极标量这两个方程之间的插值,通过一个参数$α\in[0,\frac 12]$出现在他们的毕奥-萨伐尔定律的内核。值$α=0$和$α=\frac 12$分别对应于2D Euler和SQG情况。我们证明了全球的时间规律的二维欧拉补丁模型,即使补丁最初接触的半平面的边界。另一方面,对于任何足够小的$α>0$,我们展示了初始数据,导致在有限时间内的奇异性。因此,这些结果显示了这些方程的解的行为中的相变,并且为将2D欧拉方程分类为临界提供了严格的基础。

英文摘要:

It is well known that the incompressible Euler equations in two dimensions have globally regular solutions. The inviscid surface quasi-geostrophic (SQG) equation has a Biot-Savart law which is one derivative less regular than in the Euler case, and the question of global regularity for its solutions is still open. We study here the patch dynamics in the half-plane for a family of active scalars which interpolates between these two equations, via a parameter $α\in[0,\frac 12]$ appearing in the kernels of their Biot-Savart laws. The values $α=0$ and $α=\frac 12$ correspond to the 2D Euler and SQG cases, respectively. We prove global in time regularity for the 2D Euler patch model, even if the patches initially touch the boundary of the half-plane. On the other hand, for any sufficiently small $α>0$, we exhibit initial data which lead to a singularity in finite time. Thus, these results show a phase transition in the behavior of solutions to these equations, and provide a rigorous foundation for classifying the 2D Euler equations as critical.

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