一般非齐次非线性扩散方程的等价变换和高维不变子空间

结合压力变换和不变子空间方法中的等价变换,给出了一般非齐次非线性扩散方程的等价方程,并给出了等价方程的高维不变子空间.由此构造了一般非齐次非线性扩散方程的广义分离变量解,并给出了几个例子解释这个过程.     

对一般非齐次非线性扩散方程的变换

通过欧拉方程中的变换,将一般非齐次非线性扩散方程转化为常系数非线性演化方程,并给出两个非齐次非线性扩散方程的同形变换.     

一类非线性耗散方程组的不变子空间及其精确解

利用不变子空间方法研究一类在孤立子理论中具有广泛应用的非线性耗散方程组,确定出非线性耗散方程组在它所容许的不变子空间W_3~1×W_2~2中的完全分类,构造了方程组的精确解或者将方程组约化为有限维动力系统.文中的结果进一步推广了不变子空间理论在非线性偏微分方程中的应用.     

一类Camassa-Holm型方程的不变子空间及其精确解

研究一类三阶CH型方程的解的问题.利用不变子空间理论,讨论了方程在不同参变量取值情况下所允许的不变子空间,从而得出了此类方程的两个特殊的精确解.所得结果不仅描述了该方程的一些特性,而且丰富了文献中关于此类CH型方程的内容.     

非线性扩散方程广义解的有限传播速度性质

本文考虑具强退缩性的非线性扩散方程的第一初边值问题。在一定的结构条件下证明了广义解具有有限传播速度。该条件在某种意义下不可改进。     

分数阶非线性薄膜方程的不变子空间和精确解

方程的精确解是方程的非线性现象以及它本身所蕴含的物理意义的一种具体表现,而不变子空间则可以理解为方程的稳定区域.在给出一类非线性薄膜方程所对应的几种不变子空间后,通过两边系数比较得到了其相应的有限维动力系统.再借助Mittag-Leffler函数的一些基本性质以及拉普拉斯变换等求解该系统,从而构造得到了分数阶非线性薄膜...     

H~2(S_n)的不变子空间的酉等价

本文给出了Ｈ２（Ｓｎ）的两个不变子空间酉等价的必要条件．并证明了Ｈ２（Ｓｎ）的任何两个不变子空间经某种扩张后仅相差一个幺模函数．还讨论了Ｈ２（Ｓｎ）的两个不变子空间相差一个内函数因子的条件．     

带幂非线性项变系数非线性波动方程的李对称分类与等价性变换

从微分方程群理论分析角度,研究了一类含有3个任意函数和2个幂非线性项的变系数非线性波动方程.由于方程具有很强的任意性和非线性项,可通过等价性变换寻找方程的不变对称分类.首先给出了等价性变换的一般结果,其中包括一些包含任意元的非局部变换.然后对所研究的方程,利用广义扩展等价群和条件等价群给出了方程的完全对称分类.最后获得并分析了方程的特殊类相似解.     

奇异扩散方程的非线性边值问题

本文讨论具有非线性边界条件的奇异扩散方程混合边值问题整体光滑解的存在性,唯一性和关于初值的连续依赖性。     

Constructive approximations to the invariant densities of higher-dimensional transformations

Let τ be a piecewiseC ² transformation on a rectangular partition of then-dimensional cube which has a unique absolutely continuous invariant measure. An approximation to τ by a sequence of Jablonski transformations is presented and it is shown that the associated sequence of invariant density functions converges to the density function invariant under τ. An example is presented.     

A nonlinear characterization of stable invariant subspaces

A nonlinear characterization of stable invariant subspaces for an operator on Hilbert space is given. The characterization involves the solutions to a certain quadratic operator equation. The characterization is used to give information about the stability of certain invariant subspaces of an operator.     

New invariant sets to nonlinear diffusion equations with x-dependent convection and absorption

In this paper, we introduce a new invariant set

     

Positive periodic solutions of higher-dimensional nonlinear functional difference equations

By using a well-known fixed point index theorem, we study the existence, multiplicity and nonexistence of positive T-periodic solution(s) to the higher-dimensional nonlinear functional difference equations of the form

     

A method for calculating invariant subspaces of symmetric hyperbolic equations

An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations.     

Quasiaffinity and invariant subspaces

Special classes of intertwining transformations between Hilbert spaces are introduced and investigated, whose purposes are to provide partial answers to some classical questions on the existence of nontrivial invariant subspaces for operators acting on separable Hilbert spaces. The main result ensures that if an operator is \({{\mathcal D}}\)-intertwined to a normal operator, then it has a nontrivial invariant subspace.     

Perturbation of invariant subspaces of the equations of elasticity: Spectral theory

This paper is a discussion of the perturbation of operators in certain of their invariant subspaces. The program is carried out by the study of the simple nontrivial example, the equations of linear elasticity.