arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2009.04102math-phmath.MPnlin.SI
收藏

一般微分方程的修正形式拉格朗日公式

A modified formal Lagrangian formulation for general differential equations

Linyu Peng

摘要:

本文通过引入虚拟因变量,提出了一种修正的形式拉格朗日公式,并证明了这种公式对任何微分方程组的存在性。相应的欧拉-拉格朗日方程,由原系统和它的伴随系统的虚拟变量,减少到原系统通过一个简单的替代虚拟变量。利用Noether定理将该公式应用于微分方程的守恒律研究,特别是利用Fornberg-Whitham方程的Lie点对称性得到了它的一个非平凡的守恒定律.最后,不可压缩欧拉方程的守恒律和相关的修改形式拉格朗日变分对称性之间的对应关系。

英文摘要:

In this paper, we propose a modified formal Lagrangian formulation by introducing dummy dependent variables and prove the existence of such a formulation for any system of differential equations. The corresponding Euler--Lagrange equations, consisting of the original system and its adjoint system about the dummy variables, reduce to the original system via a simple substitution for the dummy variables. The formulation is applied to study conservation laws of differential equations through Noether's Theorem and in particular, a nontrivial conservation law of the Fornberg--Whitham equation is obtained by using its Lie point symmetries. Finally, a correspondence between conservation laws of the incompressible Euler equations and variational symmetries of the relevant modified formal Lagrangian is shown.

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。

↑