Parabolic and Elliptic Equations with VMO Coefficients

An L_p-theory of divergence and non-divergence form elliptic and parabolic equations is presented. The main coefficients are supposed to belong to the class VMO_x, which, in particular, contains all functions independent of x. Weak uniqueness of the martingale problem associated with such equations is obtained.     

带VMO系数的拟线性抛物型方程斜微商问题

本文给出了拟线性抛物型方程Cu=ut-aij(x,t,u)Diju+a(x,t,u,Du)=0在正则斜微商边界条件Bu=biDiu=g下的强解u∈Wq2,1(QT)(q＞n+1)的存在、唯一性.这里我们假设系数aij是Caratheodory函数,且关于(x,t),aij∈VMO∩L∞;而函数a(x,t,u,Du)关于Du至多是二次增长.     

The Lp - Lq Estimates for the Wave Equation with A nonnegative Potential

In this paper, some Fredholm properties of the Dirichlet problem for the Laplace operator in an exterior domain are given in weighted Hölder spaces. These results extend the corresponding approach in weighted L ^p -Sobolev spaces.     

Pointwise Estimates for a Class of Oscillatory Integrals and Related Lp–Lq Estimates

In this article we establish pointwise estimates for a class of oscillatory integrals related to the fundamental solution of the dispersive equation ∂_t u − iP (D_x)u = 0, where P(D_x) is a differential operator whose symbol P(ξ) is a real polynomial in one variable. Then we use such pointwise estimates to establish L^p–L^q estimates for the solution of this equation.     

Pointwise Estimates for Oscillatory Integrals and Related Lp–Lq Estimates II: Multidimensional Case

In this article we first establish some pointwise estimates for a class of multidimensional oscillatory integrals, and then use such estimates to establish L^p – L^q estimates for a class of dispersive equations of the form D_tu − P(D_x)u = 0, where D_t = −i∂_t, D_x = −i∇_x, and P(D_x) is a partial differential operator whose symbol P(ξ) (ξ ∈ Rⁿ) is an inhomogeneous real nondegenerate elliptic polynomial. These estimates not only improve, but also extend some known results in the related topics. Tools used to obtain such results are the Van der Corput lemma, integration by parts, Young’s inequality and the interpolation theory.     

Lp – Lq Decay Estimates fo the Solutions of Strictly Hyperbolic Equations of Second Order with Increasing in Time Coefficients

One of the most important questions in the theory of nonlinear wave equations is that for global existence of solutions. An essential tool is the Strichartz inequality for special solutions of the wave equation.In the last time different results were proved generalizing the classical one of Strichartz. In the present paper L_p – L_q estimates are proved for the solutions of strictly hyperbolic equations of second order with time dependent coefficients where these are unbounded at infinity. In the first step the WKB method is applied to the construction of a fundamental system of solutions for ordinary differential equations depending on a parameter. In a second step the method of stationary phase yields the asymptotical behaviour of Fourier multipliers with nonstandard phase functions depending on a parameter.     

Morrey Estimates for Nondivergence Parabolic Operators with Discontinuous Coefficients on Homogeneous Groups

In this paper, by establishing the boundedness of singular integral operators with variable kernels and their commutators with BMO functions on Morrey spaces of homogeneous groups, we prove a local a prior estimate in Sobolev-Morrey space for solutions to the nondivergence parabolic equation with discontinuous coefficients.     

The Caffarelli Alternative in Measure for the Nondivergence Form Elliptic Obstacle Problem with Principal Coefficients in VMO

We study the obstacle problem with an elliptic operator in nondivergence form with principal coefficients in VMO. We develop all of the basic theory of existence, uniqueness, optimal regularity, and nondegeneracy of the solutions. These results, in turn, allow us to begin the study of the regularity of the free boundary, and we show existence of blowup limits, a basic measure stability result, and a measure-theoretic version of the Caffarelli alternative proven in [3 Caffarelli , L.A. ( 1977 ). The regularity of free boundaries in higher dimensions . Acta Math. 139 : 155 – 184 .[Crossref], [Web of Science ®] , [Google Scholar]].     

一类系数依赖于时间的抛物系统解的全局存在性及爆破现象

研究了系数依赖于时间的抛物系统解的爆破现象.应用微分不等式技术,得到了一类系数依赖于时间的抛物系统存在全局解的条件.当系统的数据项满足不同的适当约束条件时,推导了爆破时间的上下界.     

Parabolic Type Decay Rates for 1-D-Thermoelastic Systems with Time-Dependent Coefficients

 The purpose of this paper is to derive L ^p − L ^q decay estimates for linear thermoelastic systems with time-dependent coefficient in one space variable. When all coefficients in the system have the same growth speed with small oscillations, we obtain a parabolic type decay estimate. For the system with time-dependent coefficients, we need to investigate the delicate asymptotic behaviour of characteristic roots and the remainder of diagonalization, which will be treated by dividing the phase space into three regions. Received September 15, 2001; in revised form April 20, 2002     

Parabolic equations with VMO coefficients in generalized Morrey spaces

In this paper, the authors establish the regularity in generalized Morrey spaces of solutions to parabolic equations with VMO coefficients by means of the theory of singular integrals and linear commutators.     

一类半线性变系数抛物型方程的紧差分格式

对一类半线性变系数抛物型方程初边值问题建立了紧差分格式,用能量分析方法证明了差分格式解的存在唯一性、关于初值的无条件稳定性和在L_∞范数下阶数为O(τ~2+h~4)的收敛性,最后给出的数值算例验证了理论结果.     

Random Walks Associated with Non-Divergence Form Elliptic Equations

This paper is concerned with the study of the diffusion process associated with a nondivergence form elliptic operator in d dimensions, d2. The authors introduce a new technique for studying the diffusion, based on the observation that the probability of escape from a d–1 dimensional hyperplane can be explicitly calculated. They use the method to estimate the probability of escape from d–1 dimensional manifolds which are C ^1, , and also d–1 dimensional Lipschitz manifolds. To implement their method the authors study various random walks induced by the diffusion process, and compare them to the corresponding walks induced by Brownian motion.     

Parabolic equations with VMO coefficients in Sobolev spaces with mixed norms

An L_q(L_p)-theory of divergence and non-divergence form parabolic equations is presented. The main coefficients are supposed to belong to the class VMO_x, which, in particular, contains all measurable functions depending only on t. The method of proving simplifies the methods previously used in the case p=q.     

General Linear Boundary Value Problems for Elliptic Operators with VMO Coefficients

We prove a priori estimates in Sobolev spaces for general linear elliptic boundary value problems with VMO coefficients.We give also results of existence and uniqueness of a solution.     

Regularity of Solutions to Elliptic Equations with VMO Coefficients

The aim of this paper is to study the regularity of solutions to the Dirichlet problems for general second-order elliptic equations in Lebesgue and Morrey spaces. We consider both nondivergence and divergence forms and the coefficients of principle terms are assumed to be in VMO.     

Lp(·)−Lq(·) Estimates for Some Convolution Operators with Singular Finite Measures

Analysis Mathematica - Let μ be the surface measure on ℝn+1 supported on the graph of $$varphi ({y_1}, ldots ,{y_n}) = {left| {{y_1}} right|^{{beta _1}}} + cdots + {left| {{y_n}}...     

Parabolic Equations with Measurable Coefficients

We investigate the unique solvability of second order parabolic equations in non-divergence form in , p ≥ 2. The leading coefficients are only measurable in either one spatial variable or time and one spatial variable. In addition, they are VMO (vanishing mean oscillation) with respect to the remaining variables. The second author was partially supported by NSF Grant DMS-0140405.     

Very Weak Solutions of p-Laplacian Type Equations with VMO Coefficients

In this note we obtain a new a priori estimate for the very weak solutions of p-Laplacian type equations with VMO coefficients when p is close to 2, and then prove that the very weak solutions of such equations are the usual weak solutions. Our approath is based on the Hodge decomposition and the L^p-estimate for the corresponding linear equations. And this also provides a simpler proof for the results in [1].