多维Landau-Lifshitz方程的δ-黏性解

本文引入δ-黏性上解,δ-黏性下解和δ-黏性解的概念,给出一些相关性质,利用这些性质证明取值于三维单位球面的多维Landau-Lifshitz方程的δ-黏性上解和δ-黏性下解的存在性,揭示存在两个不相交的开子集M和N,使得δ-黏性上解和δ-黏性下解在M内任一紧子集上趋于(0,1,0),在N内任一紧子集上趋于(0,-1,0)．     

一类迭代函数方程的Cm解的存在性、唯一性和稳定性

讨论了较为广泛的一类迭代函数方程G(x,f(x) ,… ,fⁿ(x) ) =0 (对任意x∈J) ,在此J为实数轴R的连通闭子集 , G∈C^m(Jⁿ⁺¹> +1,R) ,n≥ 2 .通过采用小挪动映射逼近不动点的办法 ,借助于函数空间中的度量的选择 ,经过对一般空间映射的不动点的唯一性与稳定性之间的关系的讨论 ,对任一整数m≥ 0 ,在较弱的条件下证明了该方程的C^m解的存在性、唯一性和稳定性 ,从多个方面推广了有关文献中的已有结果     

广义态空间中Krein-Milman定理的算子类似

讨论在C^*-凸理论下C^*-代数A的广义态空间S_Cⁿ(A)中的Krein-Milman型问题.证明了S_Cⁿ(A)的任意一个BW-紧的C^*-凸子集K都具有一个C^*-端点,而且K是其C^*-端点的C^*-凸包.     

一个求极值问题(Ⅰ)

对于给定的正整数n,N(N>n>1)与实数δ(0≤δ≤1/2),要求在k₁+k₂+…+k_n=N,k_i≥1(i=1,2,…,n)都是整数 (1)的条件下,求出一组使文中定义的目标函数L_{k¹k²…kⁿ}(δ)取最大值的整数组(k₁k₂…k_n),这整数组称为方程(1)的最优解。在本文中,将要证明:对于任何N>n>1与0≤δ≤1/2,一定能从适合(ⅰ)k₁为偶数;(ⅱ)|k_i-k_j|≤2(1≤i,j≤n);(ⅲ)在k₂,…,k_n中出现的偶数k都有相同的数值等条件的那些(k₁k₂…k_n)中找到方程(1)的一组最优解。特别对于δ=0与δ=1/2这两个重要的情形,给出了当N=n(e-1),而e≥4为一偶数时方程(1)的一组最优解。文中还证明了:对于δ=0与δ=1/2,以及N=nk(k≥2),从极限的观点看,(k,k,…,k)都是方程(1)的一个“相当不好”的解。     

解在QK 型及Dirichlet 型空间中的线性微分方程

对于单位圆盘上系数函数是解析函数的复微分方程
f⁽ⁿ⁾+A_n-1(z)f^(n-1)+…+A₁(z)f''+A₀(z)f=0,
给出了方程的系数函数和解函数之间的关系, 即当系数函数A_j 满足给定的条件时, 方程的所有解属于Q_K型空间和Dirichlet 型空间.     

广义Landau-Lifshitz方程组和调和映射

证明了广义Landau-Lifshitz铁磁链方程组从Riemann流形到单位球面S^n-1(?)Rⁿ整体弱解和光滑解的存在性,并建立了调和映射和广义Landau-Lifshitz方程的解的紧密联系.     

R~n中有界区域上调和函数的积分平均值估计

设={x∈Rⁿ;λ(x<0}是一具有光滑边界的有界区域.给定x₀∈,0-1,m∈N及ε>0足够小,就上的调和函数f证明了和其中M_p(f,r)是f在上的积分平均,grad_jf为f的j次梯度.     

KdV方程的特征速度的Lax猜想的证明

本文证明Lax提出的对KdV方程u_l+6uu_x+u_xxx=0的如下猜想:存在N个正常数ci,j=1,2,…,N和2N个常数θ_i^±,j=1,2,…N对方程的任一解u(x,t)有其中S为一孤立波。     

非线性不适定单调算子方程正则解的收敛率

讨论非线性不适定单调算子方程正则解的收敛率问题.给出了保证收敛率分别为O(δ^1/2),O(δ^2/3)和O(δ^n/(n+1))的条件,这里δ为近似数据的误差界.     

l p值Gauss过程的增量有多大

设{Y(t),t≥0}={X_k(t),t≥0}^∞_k=1是独立的Gauss过程序列,σ²_k(h)=E(X_k(t+h)-X_k(t))².记σ(p,h)=(sum from k=1 to ∞ σ^p_k(h))^1/p,P≥1.考察σ(P,h)有界时Y(·)的大增量.作为一个例子,给出了无穷维分数Ornstein-Uhlenbeck过程在l^p空间中的大增量.所建立的方法适用于某些其它类型的平稳增量过程.     

Multiple Nontrivial Solutions for a Class of p-Laplacian Equations

In this paper a class of p-Laplacian equations are considered. The existence of five nontrivial solutions is stated. By the standard supersolution and subsolution method, we prove the existence of minimal positive solution and maximal negative solution in L ^∞(Ω). Furthermore, in virtue of the well-known Mountain-Pass Theorem and Second Deformation Theorem, we can give additional three nontrivial solutions, i.e., one positive solution, one negative solution and one sign-changing solution.     

The Carnot-Carathéodory Distance and the Infinite Laplacian

In ℝ ⁿ equipped with the Euclidean metric, the distance from the origin is smooth and infinite harmonic everywhere except the origin. Using geodesics, we find a geometric characterization for when the distance from the origin in an arbitrary Carnot-Carathéodory space is a viscosity infinite harmonic function at a point outside the origin. We show that at points in the Heisenberg group and Grushin plane where this condition fails, the distance from the origin is not a viscosity infinite harmonic subsolution. In addition, the distance function is not a viscosity infinite harmonic supersolution at the origin.     

Existence results for some quasilinear parabolic problems

We first give an existence theorem, for some equations associated with Leray-Lions operators, assuming the existence of a subsolution smaller than a supersolution. Then we prove, with an additional hypothesis on the operator, that in the previous theorem, we can replace the subsolution by two subsolutions and the supersolution by two supersolutions. Finally, we deduce the existence of a smallest and a greatest solution.     

Banach空间半线性发展方程的周期解

把上、下解方法引入到有序Ｂａｎａｃｈ空间中的半线性发展方程周期解问题，利用正算子半群特征与单调迭代程序，获得了最大周期解与最小周期解的存在性．所得的结果概括和推广了常微分方程与偏微分方程中的有关结论     

Nonlinear Elliptic Variational Inequalities

We consider the problem of finding a solution to a class of nonlinear elliptic variational inequalities. These inequalities may be defined on bounded or unbounded domains Ω, and the nonlinearity can depend on gradient terms. Appropriate definitions of sub-and supersolutions relative to the constraint sets are given. By using a mixture of maximal monotone operator theory and compactness arguments we prove the existence of a H²(Ω) solution lying between a given subsolution φ₁ and a given supersolution φ₂≧φ₁, when Ω is bounded, and a H¹(Ω) solution when Ω is unbounded.     

Existence and global stability of traveling curved fronts in the Allen-Cahn equations

This paper is concerned with existence and stability of traveling curved fronts for the Allen-Cahn equation in the two-dimensional space. By using the supersolution and the subsolution, we construct a traveling curved front, and show that it is the unique traveling wave solution between them. Our supersolution can be taken arbitrarily large, which implies some global asymptotic stability for the traveling curved front.     

Maximum principle and existence of <Emphasis Type="Italic">L</Emphasis><Superscript><Emphasis Type="Italic">p</Emphasis></Superscript>-viscosity solutions for fully nonlinear uniformly elliptic equations with measurable and quadratic terms

We study L^p-viscosity solutions of fully nonlinear, second-order, uniformly elliptic partial differential equations (PDE) with measurable terms and quadratic nonlinearity. We present a sufficient condition under which the maximum principle holds for L^p-viscosity solution. We also prove stability and existence results for the equations under consideration.     

Convergence theorem for the common solution for a finite family of ?-strongly accretive operator equations

The purpose of this paper is to study a strong convergence of multi-step iterative scheme to a common solution for a finite family of uniformly continuous ?-strongly accretive operator equations in an arbitrary Banach space. As a consequence, the strong convergence theorem for the multi-step iterative sequence to a common fixed point for finite family of ?-strongly pseudocontractive mappings is also obtained. The results presented in this paper thus improve and extend the corresponding results of Inchan [6], Kang [8] and [9] and many others.     

Perron's method for second order hyperbolic PDE. Part I

In parts I, II, and III combined of this paper, we define a notion of viscosity solution for these equations and existence is proved by a Perron-like method. Here, in part I, we prove useful identities, and a maximum-like principle for smooth sub(super) solutions of the standard wave equation. We define a new potential theoretic (P) notion of solution, subsolution and supersolution, and a related potential type (P) Cauchy problem for semilinear second order hyperbolic equations.