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arXiv 2008.07476math-phmath.MP
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伴随对称的对称作用和括号。一、主要结果及应用

Symmetry actions and brackets for adjoint-symmetries. I: Main results and applications

Stephen C. Anco

摘要:

偏微分方程(PDE)的无穷小对称可以用代数的方法定义为线性化(Frechet导数)方程的解在PDE的解空间上保持不变,并且它们构成具有李代数结构的线性空间,伴随线性化方程的解在PDE的解空间上保持不变,称为伴随对称。本文研究了一般偏微分方程系统的代数结构。这是由变分对称性和守恒律之间的对应关系所激发的诺特定理,该定理对非变分偏微分方程有一个众所周知的推广,其中无穷小对称性被伴随对称性取代,变分对称性被乘数(满足一定欧拉-拉格朗日条件的伴随对称性)取代。得到了几个主要结果。对称被证明有三个不同的线性作用在伴随对称的线性空间。这些线性作用被用来构造双线性伴随对称括号,其中之一是对称交换子括号的拉回,并具有李括号的性质。括号不使用或要求存在任何局部变分结构(哈密顿量或拉格朗日量),因此适用于一般PDE系统。其中一个对称性的行动是编码的前辛(Noether)运营商和辛2-形式,导致建设的辛2-形式和泊松括号的发展系统。用势形式的广义KdV方程来说明所有结果。

英文摘要:

Infinitesimal symmetries of a partial differential equation (PDE) can be defined algebraically as the solutions of the linearization (Frechet derivative) equation holding on the space of solutions to the PDE, and they are well-known to comprise a linear space having the structure of a Lie algebra.Solutions of the adjoint linearization equation holding on the space of solutions to the PDE are called adjoint-symmetries. Their algebraic structure for general PDE systems is studied herein. This is motivated by the correspondence between variational symmetries and conservation laws arising from Noether's theorem, which has a well-known generalization to non-variational PDEs, where infinitesimal symmetries are replaced by adjoint-symmetries, and variational symmetries are replaced by multipliers (adjoint-symmetries satisfying a certain Euler-Lagrange condition). Several main results are obtained. Symmetries are shown to have three different linear actions on the linear space of adjoint-symmetries. These linear actions are used to construct bilinear adjoint-symmetry brackets, one of which is a pull-back of the symmetry commutator bracket and has the properties of a Lie bracket. The brackets do not use or require the existence of any local variational structure (Hamiltonian or Lagrangian) and thus apply to general PDE systems. One of the symmetry actions is shown to encode a pre-sympletic (Noether) operator and a symplectic 2-form, which lead to the construction of a symplectic 2-form and Poisson bracket for evolution systems. The generalized KdV equation in potential form is used to illustrate all of the results.

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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