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arXiv 2307.09189math.APmath-phmath.MP
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Onsager临界类中的耗散与$BV\cap L^\infty$中有无边界时的能量守恒

Dissipation in Onsager's critical classes and energy conservation in $BV\cap L^\infty$ with and without boundary

Luigi De Rosa, Marco Inversi

AI总结:

本文研究不可压Euler方程,在Onsager临界类中给出Duchon-Robert测度显式公式,并证明$L^\infty\cap BV$解在有无边界下的能量守恒,引入法向Lebesgue迹概念将边界分析推广至任意Lipschitz有界域。

摘要:

本文研究不可压Euler方程。在Onsager临界类中,我们给出了Duchon-Robert测度的显式公式,用正则化核和一族向量值测度$\{μ_z\}_z$表示,该族测度关于方向$z\in B_1$具有一定的Hölder正则性。然后,我们证明了$L^\infty_{x,t}\cap L^1_t BV_x$解的能量守恒,无论是否存在物理边界。该结果推广了先前已知的Vortex Sheets情形,表明能量守恒源于$L^\infty\cap BV$不可压向量场的结构,而非流具有“组织奇点”。内部能量守恒利用了Ambrosio的卷积核各向异性优化,与通常的能量守恒论证不同,它严重依赖于向量场的不可压性。这是首个针对给定解类的能量守恒证明,无法同时适用于可压和不可压模型,这与具有非平凡熵产生的可压激波相一致。为进行边界分析,我们为一般向量场引入了“法向Lebesgue迹”的概念,非常类似于$BV$函数的迹。我们证明了具有这种零法向迹基本等价于边界能量通量消失。这超越了以往方法,建立了一个适用于每个Lipschitz有界域的框架。允许任意Lipschitz边界给证明引入了一些技术细节,带有很强的几何/测度论色彩。

英文摘要:

This paper is concerned with the incompressible Euler equations. In Onsager's critical classes we provide explicit formulas for the Duchon-Robert measure in terms of the regularization kernel and a family of vector-valued measures $\{μ_z\}_z$, having some Hölder regularity with respect to the direction $z\in B_1$. Then, we prove energy conservation for $L^\infty_{x,t}\cap L^1_t BV_x$ solutions, in both the absence or presence of a physical boundary. This result generalises the previously known case of Vortex Sheets, showing that energy conservation follows from the structure of $L^\infty\cap BV$ incompressible vector fields rather than the flow having "organized singularities". The interior energy conservation features the use of Ambrosio's anisotropic optimization of the convolution kernel and it differs from the usual energy conservation arguments by heavily relying on the incompressibility of the vector field. This is the first energy conservation proof, for a given class of solutions, which fails to simultaneously apply to both compressible and incompressible models, coherently with compressible shocks having non-trivial entropy production. To run the boundary analysis we introduce a notion of "normal Lebesgue trace" for general vector fields, very reminiscent of the one for $BV$ functions. We show that having such a null normal trace is basically equivalent to have vanishing boundary energy flux. This goes beyond the previous approaches, laying down a setup which applies to every Lipschitz bounded domain. Allowing any Lipschitz boundary introduces several technicalities to the proof, with a quite geometrical/measure-theoretical flavour.

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