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arXiv 0709.1670math.APmath-phmath.MP
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关于半线性发展方程II的近似解Navier-斯托克斯方程的推广及其应用

On approximate solutions of semilinear evolution equations II. Generalizations, and applications to Navier-Stokes equations

Carlo Morosi, Livio Pizzocchero

摘要:

在我们以前的论文[12](Rev. Math. Phys. 16,383-420(2004))中,概述了处理半线性发展方程的近似解的一般框架;更准确地说,提出了一种方案,从近似解推断精确解的存在性(时间上的局部或全局),并估计它们的距离。在本工作的前半部分,\cite{uno}的抽象框架进行了扩展,以便适用于演化偏微分方程的非线性包含衍生物的空间变量。在本文的后半部分,我们将这种扩展的框架应用于任意维环面T^d上的不可压Navier-斯托克斯方程。这样,在索伯列夫空间H^n(T^d)的背景下,用不同的方法选择近似解,得到了一些结果.通过最简单的选择,我们恢复了任意数据和外力的精确解的局部存在性,以及小数据和力的全局存在性。在力随时间指数衰减的补充假设下,对于具有小(零均值)数据和力的精确解,导出了相同的衰减规律。任意数据的存在区间、数据和力的整体存在上界以及精确解的指数衰减的所有估计都是以完全定量的方式导出的(即,给出所有必要常数的值;这与以前的大多数文献不同)。其次,考虑了Galerkin近似解,并推导了它们与精确解的H^n距离的精确定量估计;对于小数据和力,这些估计在时间上是全局的(如果力类似地衰减,则上述距离具有指数时间衰减)。

英文摘要:

In our previous paper [12] (Rev. Math. Phys. 16, 383-420 (2004)), a general framework was outlined to treat the approximate solutions of semilinear evolution equations; more precisely, a scheme was presented to infer from an approximate solution the existence (local or global in time) of an exact solution, and to estimate their distance. In the first half of the present work the abstract framework of \cite{uno} is extended, so as to be applicable to evolutionary PDEs whose nonlinearities contain derivatives in the space variables. In the second half of the paper this extended framework is applied to theincompressible Navier-Stokes equations, on a torus T^d of any dimension. In this way a number of results are obtained in the setting of the Sobolev spaces H^n(T^d), choosing the approximate solutions in a number of different ways. With the simplest choices we recover local existence of the exact solution for arbitrary data and external forces, as well as global existence for small data and forces. With the supplementary assumption of exponential decay in time for the forces, the same decay law is derived for the exact solution with small (zero mean) data and forces. The interval of existence for arbitrary data, the upper bounds on data and forces for global existence, and all estimates on the exponential decay of the exact solution are derived in a fully quantitative way (i.e., giving the values of all the necessary constants; this makes a difference with most of the previous literature). Nextly, the Galerkin approximate solutions are considered and precise, still quantitative estimates are derived for their H^n distance from the exact solution; these are global in time for small data and forces (with exponential time decay of the above distance, if the forces decay similarly).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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