广义拟线性双曲型方程的对称势及其守恒定律

基于Lie群方法,研究广义拟线性双曲型方程的对称势和不变解.为了得到显式的不变解,关注物理上有趣的有对称势的情况.然后,利用局部的Lagrange函数逼近,在3种物理上引起注意的情况下,得到该方程的守恒定律.     

Wave Front Tracking in Systems of Conservation Laws

This paper contains several recent results about nonlinear systems of hyperbolic conservation laws obtained through the technique of Wave Front Tracking.     

非线性对流扩散方程的守恒律

利用直接方法研究了非线性对流扩散方程的守恒律,得到了关于非线性对流扩散方程的守恒律乘子性质的一个定理.利用这个定理,可以简化守恒律乘子的确定方程.随后通过对确定方程中的变量函数进行分析,发现在四种情况下乘子的确定方程是可解的.最后解出这些守恒律乘子,利用积分公式法分别得到了四种情况下对应于各个守恒律乘子的守恒律.     

Essential Conservation Laws for Equations with Infinite Symmetries

We consider partial differential equations of variational problems with infinite symmetry groups. We study local conservation laws associated with arbitrary functions of one variable in the group generators. We show that only symmetries with arbitrary functions of dependent variables lead to an infinite number of conservation laws. We also calculate local conservation laws for the potential Zabolotskaya-Khokhlov equation for one of its infinite subgroups.__________Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 1, pp. 190–198, July, 2005.     

Classification of Local Conservation Laws of Maxwell's Equations

A complete and explicit classification of all independent local conservation laws of Maxwell's equations in four dimensional Minkowski space is given. Besides the elementary linear conservation laws, and the well-known quadratic conservation laws associated to the conserved stress-energy and zilch tensors, there are also chiral quadratic conservation laws which are associated to a new conserved tensor. The chiral conservation laws possess odd parity under the electric–magnetic duality transformation of Maxwell's equations, in contrast to the even parity of the stress-energy and zilch conservation laws. The main result of the classification establishes that every local conservation law of Maxwell's equations is equivalent to a linear combination of the elementary conservation laws, the stress-energy and zilch conservation laws, the chiral conservation laws, and their higher order extensions obtained by replacing the electromagnetic field tensor by its repeated Lie derivatives with respect to the conformal Killing vectors on Minkowski space. The classification is based on spinorial methods and provides a direct, unified characterization of the conservation laws in terms of Killing spinors.     

具有非凸标量守恒律的解的衰减性

我们研究了具有周期初值数据的标量守恒律的方程的解的大时间行为,在很弱的非线性条件下,我们证明了当时间趋于无穷时其解收敛于一常数,本文的结果改进了以前的结果,因为我们只需在初值数据的平均值处流量是非线性的。     

二维双曲守恒律的大时间步长Godunov方法(英文)

考虑了关于二维守恒律的大时间步长Godunov方法.该方法是关于一维问题的自然推广.证明了文中给出的数值流函数下,该方法是守恒的.进一步还给出了近似Riemann解应满足的条件,并且证明了利用满足这些条件的近似Riemann解的大时间步长Godunov方法守恒.最后,补充证明了满足这些条件的近似Riemann解是满足熵条件的.     

Partition of Waves in a System of Conservation Laws

The aim of this paper is to give a simple proof of the classical Liu estimate on the decay of positive waves in a solution of a n×n system of conservation laws. In the first part, we transcribe the wave partition technique introduced in Comm. Math. Phys. 57 (1977), 135–148 (by means of the Glimm scheme) to the case of approximate solutions constructed by the wave front tracking scheme. Then, we use a decoupling argument on the characteristic speeds to establish the desired estimate.     

J积分在多层介质中的守恒性和其应用

首先证明和讨论了当裂纹平行于多层介质界面时,其裂纹尖端J积分的守恒性;然后建立了具有界面裂纹的由4种介质构成的材料分析模型,根据J积分在多层介质中的守恒性原理,提出了该模型的I型断裂能量释放率守恒假设,并经过了数值实验的验证,通过能量分析和量纲分析,用渐近分析方法得到了计算该模型结构界面裂纹尖端能量释放率和复应力强度因子的分析公式,并且进行了讨论。     

Polynomial Conservation Laws in Quantum Systems

We consider systems with a finite number of degrees of freedom and potential energy that is a finite sum of exponentials with purely imaginary or real exponents. Such systems include the generalized Toda chains and systems with a toric configuration space. We consider the problem of describing all the quantum conservation laws, i.e., the differential operators that are polynomial in the derivatives and commute with the Hamiltonian operator. We prove that in the case where the potential energy spectrum is invariant under reflection with respect to the origin, such nontrivial operators exist only if the system under consideration decomposes into a direct sum of decoupled subsystems. In the general case (without the spectrum symmetry assumption), we prove that the existence of a complete set of independent conservation laws implies the complete integrability of the corresponding classical system.     

Boundary value problems in queueing theory

Recently complex function techniques have been developed for the analysis of queueing systems which need for their modelling a two dimensional state space. A variety of computer- and communication networks gives rise to such two-dimensional queueing systems and their analysis is needed for the performance evaluation of these aggregates. The present study reviews these developments     

二阶非Четаев型非完整系统的守恒律

研究二阶非ЧｅＴａｅＢ型完整系统的守恒律,引入Ｊｏｕｒｄａｉｎ生成元,给出无限小变换下Ｊｏｕｒ－ｄａｉｎ原理的不变性条件,在一定条件下得到系统的守恒律,并举例说明结果的应用。     

一维单个守恒律的一类二阶、几乎熵耗散的格式

本文考虑一维单个守恒律方程，对其设计了一个基于熵耗散的非线性守恒型差分格式．本格式的数值流函数是Lax-Freidrichs格式和Lax-Wendroff格式数值流函数的凸组合，凸组合中的系数是由考虑耗散熵来决定的．这样在解的光滑区域内，格式几乎、甚至完全是Lax-Wendroff格式，而在解的间断处，格式几乎、甚至完全是Lax—Freidrichs格式．从而消除了间断附近的非物理振荡，实现了计算的非线性稳定性．理论分析表明本格式在解的非极值点处是二阶精度的，而在解的极值点处至少有一阶精度．数值试验表明格式是有效的．     

Equipartition of energy in geometric scattering theory

In this note, we use an elementary argument to show that the existence and unitarity of radiation fields implies asymptotic partition of energy for the corresponding wave equation. This argument establishes the equipartition of energy for the wave equation on scattering manifolds, asymptotically hyperbolic manifolds, asymptotically complex hyperbolic manifolds, and the Schwarzschild spacetime. It also establishes equipartition of energy for the energy-critical semilinear wave equation on ?³.     

具张弛的拟线性双曲守恒律方程组

In this paper,we investigate the relaxation phenomenon for quasilinear hyper- bolic conservation laws,and obtain global smooth solutions and the life span of classical solutions to its Canchy problem.These results shows that the relaxation admits the effects of dissipation.     

一类微分差分方程的无穷守恒律及Backlund变换

In this paper, with the help of the Lax representation, we show the existence of infinitely many conservation laws for a differential-difference equation,which is one of the Ladic-Ablowitz hierarchy, and the conservation density and the associated flux are given for- mularlly. We also demonstrate the relation between a continuous partial differential equation and the differential-difference equation, and give Backlund transformation for the former.     

Conservation Laws for Single-Server Fluid Networks

We consider single-server fluid networks with feedback and arbitrary input processes. The server has to be scheduled in order to minimize a linear holding cost. This model is the fluid analogue of the so-called Klimov problem. Using the achievable-region approach, we show that the Gittins index rule is optimal in a strong sense: it minimizes the linear holding cost for arbitrary input processes and for all time points t0.