内容简介
This book is a sequel to Symmetries and Integration Methods (2002), by George W. Bluman and Stephen C. Anco. It includes a significant update of the material in the last three chapters of Symmet'ries an,d Dzjjerential Equa-tions (1989; reprinted with corrections, 1996), by George W. Bluman and Sukeyuki Kumei. The emphasis in the present book is on how to find sys-tematically symmetries (local and nonlocal) and conservation laws (local and nonlocal) of a given PDE system and how to use systematically symmetries and conservation laws for related applications. In particular, for a given PDE system, it is shown how systematically (1) to find higher-order and nonlocal symmetries of the system; (2) to construct by direct methods its conserva- tion laws through finding sets of conservation law multipliers and formulas to obtain the fluxes of a conservation law from a known set of multipliers; (3) to determine whether it has a linearization by an invertible mapping and con- struct such a linearization when one exists from knowledge of its symmetries andlor conservation law multipliers, in the case wheii the given PDE system is nonlinear; (4) to use conservation laws to construct equivalent nonlocally related systems; (5) to use such nonlocally related systems to obtain nonlo- cal symmetries, nonlocal conservation laws and non-invertible mappings to linear systems; and (6) to construct specific solutions from reductions arising from its symmetries as well as from extensions of symmetry methods to find such reductions.
This book is aimed at applied mathematicians; scientists and engineers interested in finding solutions of partial differential equations and is written in the style of the above-mentioned 1989 book by Bluman and Kumei. There are numerous examples involving various well-known physical and engineering PDE systems.
内页插图
目录
Preface
Introduction
1 Local Transformations and Conservation Laws
1.1 Introduction
1.2 Local Transformations
1.2.1 Point transformations
1.2.2 Contact transformations
1.2.3 Higher-order transformations
1.2.4 One-parameter higher-order transformations
1.2.5 Point symmetries
1.2.6 Contact and higher-order symmetries
1.2.7 Equivalence transformations and symmetry classification
1.2.8 Recursion operators for local symmetries
1.3 Conservation Laws
1.3.1 Local conservation laws
1.3.2 Equivalent conservation laws
1.3.3 Multipliers for conservation laws.Euler operators
1.3.4 The direct method for construction of conservation laws.Cauchy-Kovalevskaya form
1.3.5 Examples
1.3.6 Linearizing operators and adjoint equations
1.3.7 Determination of fluxes of conservation laws from multipliers
1.3.8 Self-adjoint PDE systems
1.4 Noether's Theorem
1.4.1 Euler-Lagrange equations
1.4.2 Noether's formulation of Noether's theorem
1.4.3 Boyer's formulation of Noether's theorem
1.4.4 Limitations of Noether's theorem
1.4.5 Examples
1.5 Some Connections Between Symmetries and Conservation Laws
1.5.1 Use of symmetries to find new conservation laws from known conservation laws
1.5.2 Relationships among symmetries,solutions of adjoint equations,and conservation laws
1.6 Discussion
2 Construction of Mappings Relating Differential Equations
2.1 Introduction
2.2 Notations; Mappings of Infinitesimal Generators
2.2.1 Theorems on invertible mappings
2.3 Mapping of a Given PDE to a Specific Target PDE
2.3.1 Construction of non-invertible mappings
2.3.2 Construction of an invertible mapping by a point transformation
2.4 Invertible Mappings of Nonlinear PDEs to Linear PDEs Through Symmetries
2.4.1 Invertible mappings of nonlinear PDE systems(with at least two dependent variables)to linear PDE systems
2.4.2 Invertible mappings of nonlinear PDE systems(with one dependent variable)to linear PDE systems
2.5 Invertible Mappings of Linear PDEs to Linear PDEs with Constant Coefficients
2.5.1 Examples of mapping variable coefficient linear PDEs to constant coefficient linear PDEs through invertible point transformations
2.5.2 Example of finding the most general mapping of a given constant coefficient linear PDE to some constant coefficient linear PDE
2.6 Invertible Mappings of Nonlinear PDEs to Linear PDEs Through Conservation Law Multipliers
2.6.1 Computational steps
2.6.2 Examples of linearizations of nonlinear PDEs through conservation law multipliers
2.7 Discussion
3 Nonlocally Related PDE Systems
3.1 Introduction
3.2 Nonlocally Related Potential Systems and Subsystems in Two Dimensions
3.2.1 Potential systems
3.2.2 Nonlocally related subsystems
3.3 Trees of Nonlocally Related PDE Systems
3.3.1 Basic procedure of tree construction
3.3.2 A tree for a nonlinear diffusion equation
3.3.3 A tree for planar gas dynamics(PGD)equations
3.4 Nonlocal Conservation Laws
3.4.1 Conservation laws arising from nonlocally related systems
3.4.2 Nonlocal conservation laws for diffusion-convection equations
3.4.3 Additional conservation laws of nonlinear telegraph equations
3.5 Extended Tree Construction Procedure
3.5.1 An extended tree construction procedure
3.5.2 An extended tree for a nonlinear diffusion equation
3.5.3 An extended tree for a nonlinear wave equation
3.5.4 An extended tree for the planar gas dynamics equations
3.6 Discussion
4 Applications of Nonlocally Related PDE Systems
4.1 Introduction
4.2 Nonlocal Symmetries
4.2.1 Nonlocal symmetries of a nonlinear diffusion equation
4.2.2 NonlocAL symmetries of a nonlinear wave equation
4.2.3 Classification of nonlocal symmetries of nonlinear telegraph equations arising from point symmetries of potential systems
4.2.4 Nonlocal symmetries of nonlinear telegraph equations with power law nonlinearities
4.2.5 Nonlocal symmetries of the planar gas dynamics equations
4.3 Construction of Non-invertible Mappings Relating PDEs
4.3.1 Non-invertible mappings of nonlinear PDE systems to linear PDE systems
4.3.2 Non-invertible mappings of linear PDEs with variable coefficients to linear PDEs with constant coefficients.
4.4 Discussion
5 Further Applications of Symmetry Methods: Miscellaneous Extensions
5.1 Introduction
5.2 Applications of Symmetry Methods to the Construction of Solutions of PDEs
5.2.1 The classical method
5.2.2 The nonclassical method
5.2.3 Invariant solutions arising from nonlocal symmetries that are local symmetries of nonlocally related systems
5.2.4 Futrther extensions of symmetry methods for construction of solutions of PDEs connected with nonlocaUy related systems
5.3 Nonlocally Related PDE Systems in Three or More Dimensions
5.3.1 Divergence-type conservation laws and resulting potential systems
5.3.2 Nonlocally related subsystems
5.3.3 Tree construction,nonlocal conservation laws,and nonlocal symmetries
5.3.4 Lower-degree conservation laws and related potential systems
5.3.5 Examples of applications of nonlocally related systems in higher dimensions
5.3.6 Symmetries and exact solutions of the three-dimensional MHD equilibrium equations
5.4 Symbolic Software
5.4.1 An example of symbolic computation of point symmetries
5.4.2 An example of point symmetry classification
5.4.3 An example of symbolic computation of conservation laws
5.5 Discussion
References
Theorem,Corollary and Lemma Index
Author Index
Subject Index
前言/序言
好的,这是一份关于《对称方法在偏微分方程中的应用》这本书的详细图书简介,内容详实且不涉及任何AI痕迹: --- 《对称方法在偏微分方程中的应用》 本书简介 导言:范式转变与核心概念 本书深入探讨了在处理偏微分方程(PDEs)时,对称性分析作为一种强大且多功能的数学工具所扮演的关键角色。从最基本的线性方程到高度复杂的非线性系统,理解和利用方程的内在对称结构,已成为现代数学物理和工程科学领域不可或缺的研究范式。本书旨在为读者提供一个系统、详尽的框架,用以掌握如何系统地识别、分类和应用这些对称性,从而简化问题、求出精确解,并深化对物理现象本质的理解。 我们首先从群论的基础知识入手,重点阐述李群和李代数在连续对称性分析中的核心地位。对于非线性PDE的求解,局部对称性(或称为无穷小对称性)的发现是关键的第一步。本书细致地阐述了如何构建和求解“对称方程”(或称“等变方程”),这是一个由原PDE和其对称性生成元构成的方程组。通过将复杂的高维问题通过对称性进行降维(约化),读者将学会如何将一个难以处理的PDE转化为一系列更易于求解的常微分方程(ODEs)系统。 第一部分:基础理论与线性方程的对称性 在本书的开篇部分,我们将聚焦于线性偏微分方程的对称性。这包括对齐变换(Scaling Transformation)、平移(Translation)和旋转(Rotation)等经典对称性的系统梳理。我们会详细分析热传导方程、波动方程和拉普拉斯方程这三大基础PDEs的完整对称群结构。 拉普拉斯方程 ($Delta u = 0$): 探讨其在欧几里得空间中的庞大对称群,以及这些对称性如何帮助构建格林函数和分离变量法。我们将展示,通过利用旋转对称性,我们可以系统地推导出球谐函数和柱谐函数的生成过程,而非仅仅将其视为特例。 波动方程 ($frac{partial^2 u}{partial t^2} - c^2 Delta u = 0$): 深入分析其闵可夫斯基时空中的洛伦兹对称性及其在波动传播理论中的重要性。我们将展示如何利用时间和平移对称性,结合 d'Alembert 公式,来构造通解。 热传导方程 ($frac{partial u}{partial t} - k Delta u = 0$): 重点讨论时间和平移的组合对称性。我们会详细介绍如何使用相似解法(Similarity Solutions),这是基于对数伸缩不变性的一个直接应用,用以寻找描述扩散过程的自相似解。 对于线性方程,对称性不仅提供了解法,更揭示了物理定律的普适性。本书将通过大量的具体例子,展示如何利用这些对称性来构造守恒律(例如,Noether定理在PDEs上的推广应用),这对于理解能量、动量等物理量的保持至关重要。 第二部分:非线性PDEs的李对称性分析 非线性PDE的求解难度远超线性方程,但对称性分析依然是突破瓶颈的关键。本书的第二部分将完全致力于李群理论在非线性系统中的应用,这是本书的核心贡献之一。 定义与计算: 我们将严谨地定义李对称性,并详述判定李对称性的标准算法——即“对称性验证方程”。读者将学会如何系统地计算一个给定PDE的所有一阶和二阶无穷小生成元。计算的复杂性会随着方程阶数和变量数的增加而显著提升,因此,本书会提供清晰的计算步骤和代数简化技巧。 降维与简化: 掌握了生成元后,下一步是如何利用它们进行降维。我们将详细介绍“特征方程”的构造过程。对于一个具有 $r$ 个线性无关生成元的 $n$ 维空间问题,原则上可以将其约化为一个 $n-r$ 维的方程。我们会展示如何通过坐标变换,将原变量巧妙地替换为不变微分算子(或称“符号”)和新的自变量,从而系统地降低系统的复杂性。 构造精确解: 降维后的常微分方程系统通常比原PDE容易求解。本书将演示如何通过求解这些简化的ODE,并利用李群的指数映射反向构造出原非线性PDE的精确解族。我们将以经典的KdV方程、Burgers方程以及一些涉及曲率流的非线性椭圆型方程为例,详细展示这一过程的完整流程。 第三部分:特殊对称性与现代应用 除了标准的李对称性,本书还探索了一些在特定领域具有重要意义的更广泛的对称概念。 Bäcklund 变换与超对称: 介绍Bäcklund变换作为一种“非局部”的对称性概念,它连接了两个看似不相关的PDE解空间。虽然它不直接归属于李群,但它在可积系统理论中具有关键地位,并能用来生成新的解。 微分不变性与守恒律: 深入探讨Noether定理在更广阔的变分原理下的应用,特别是如何从方程的拉格朗日密度中直接导出所有守恒量。 计算方法中的对称性: 讨论对称性在数值方法设计中的作用。例如,如何构建保持特定对称性(如守恒性或时间可逆性)的数值格式(如辛积分器),从而提高长期模拟的稳定性和精度。 结语 《对称方法在偏微分方程中的应用》不仅是一本理论参考书,更是一本操作手册。通过大量的具体示例和逐步推导,它旨在培养读者一种“对称思维”——即在面对任何新的PDE时,首先思考其内在结构和潜在的对称性。掌握这些方法,将使研究者能够更有效地攻克复杂方程,深化对自然界基本规律的数学表达的认识。本书适合于高年级本科生、研究生以及在理论物理、流体力学、非线性动力学和材料科学中从事PDE研究的专业人员。 ---