一类耦合非线性Klein-Gordon方程组解的稳定集和不稳定集

利用势井理论的构造方程un-△u u-|v|^ρ 2|u|^ρ△ρu=0;vu-△v v-|u|^ρ＋2|v|^ρv=0的初边值问题的稳定集和不稳定集。证明了当初值属于稳定集时，整体弱解存在，当初值在不稳定集时，解将爆破。     

带竞争势的非线性Klein-Gordon方程的稳定集和不稳定集

收稿研究带竞争势的非线性Klein-Gordon方程的柯西问题.首先定义了新的稳定集和不稳定集.其次证明了如果初值进入不稳定集,该柯西问题的解在有限时间内爆破;如果初值进入稳定集,该柯西问题的整体解存在.最后运用势井讨论,我们回答了当初值在什么范围时,该柯西问题的整体解存在这个问题.     

一类Boussinesq方程的整体解的存在性与不存在性

主要考察Boussinesq方程v_(tt)-v_(xx)+v_(xxx)=σ(v)_(xx),x∈R的整体解的存在性和blow-up问题,当σ(v)=-β(|v|~p v),β0,p0时,通过采用构造稳定集(位势井)W={v∈H~1(R)|||v_x||~2+||v||~22(p+2)/p d}和不稳定集V={v∈H~1(R)|||v_x||~2+||v||~22(p+2)/p d}的方法,得到了W和V在上述方程的流下是不变的,并证明了如果初始能量E(0)≤d,那么当初值v_0∈(?)时,问题存在惟一整体解;当初值v_0∈V时,问题的解在有限时刻T_1∈(t_1,t_1+4φ(t_1)/pφ′(t_1))发生爆破.     

动态边界条件下一类阻尼波动方程解的研究

本文研究了一类动态边界条件下阻尼波动方程解的问题.利用位势井理论,通过构造稳定集和不稳定集,并结合能量分析的方法,获得了如下结果.首先,当初值属于稳定集时该问题存在整体解,且E(0)相似文献   

带势的非线性Klein-Gordon方程柯西问题的稳定和不稳定集

对带势的非线性Klein-Gordon方程柯西问题,我们定义了新的对于初值的稳定和不稳定集.我们证明了如果发展进入了不稳定集,解在有限时间内爆破;如果发展进入了稳定集,解整体存在.运用势并讨论,我们回答了当初值为多少时,柯西问题的整体解存在.     

带线性坍塌项和竞争势的非线性波动方程柯西问题的稳定集和不稳定集(英文)

本文考虑带线性坍塌项和竞争势的非线性波动方程柯西问题,定义了新的稳定集和不稳定集,证明了如果初值进入不稳定集,则解在有限时间爆破;如果初值进入稳定集,则整体解存在.运用势井讨论,回答了当初值在多么小的时候,该柯西问题的整体解存在.     

关于非齐次线性方程组解的结构的进一步讨论

一、子空间的陪集定义1.设V是数域F上的向量空间,W是V的子空间。若v是V中任意向量,把和v w(w∈W)组成的集记作v W,即v W={v w|w∈W},则这些集称为V中W的陪集。 容易证明下面定理 定理1.V中W的陪集将V分成互不相交的集,即:(ⅰ)任何两个陪集u W与v W或重合或不相交;(ⅱ)每个v∈V属于一个陪集,事实上v∈v W     

含奇异势和记忆项的四阶抛物方程解的整体存在性与爆破

本文研究一类具有奇异势和记忆项的四阶抛物方程在有界域上的初边值问题.当初值在稳定集中,初始能量在正有界范围内,根据Faedo-Galerkin方法结合Hardy-Sobolev不等式得到了问题解的整体存在性并建立了能量泛函的衰减估计;当初始能量为负时,利用凸方法证明了问题的解在有限时刻爆破并估计了爆破时间上界,该上界依赖于初始能量;当初值位于不稳定集,初始能量有上界时,通过构造辅助泛函获得了一个与初始能量无关的爆破时间上界.     

广义函数的集值导数

本文应用广义函数的调和表示,引进了一维广义函数的集值导数,并给出了连续函数的集值导数的几种等价定义.局部Lipschitz函数的集值导数同Clarke定义的广义梯度一致;广义函数在一点附近是Lipschitz 函数之充要条件是它在该点的集值导数是有限的.当广义函数在某点的集值导数不同时包含+∞和-∞时,它的广义导函数在该点的某邻域上是Radon测度.利用一阶集值导数,给出了连续函数的逆函数存在定理;应用高阶集值导数,得到了广义函数取极值的两种非常一般的充分条件.广义函数在一个开区间上成为凸函数的充要条件是它在该区间内每点处的二阶集值导数都包含在[0,+∞]之中.于是,本文建立起一元非可微函数的一套令人满意的微分理论.     

动态控制下Euler-Bernoulli梁的多项式镇定

考虑动态输出反馈控制下Euler-Bernoulli梁的振动抑制问题,证明了系统算子生成的C0-半群,不指数稳定但渐近稳定.且当初值充分光滑时,利用Riesz基方法估计出系统能量多项式衰减.     

Stable and unstable sets for the Cauchy problem for a nonlinear wave equation with nonlinear damping and source terms

For the Cauchy problem for the nonlinear wave equation with nonlinear damping and source terms we define stable and unstable sets for the initial data. We prove that, if during the evolution the solution enters into the stable set, the solution is global and we are able to estimate the decay rate of the energy. If during the evolution the solution enters into the unstable set, the solution blows up in finite time.     

Rotation intervals for chaotic sets

Chaotic invariant sets for planar maps typically contain periodic orbits whose stable and unstable manifolds cross in grid-like fashion. Consider the rotation of orbits around a central fixed point. The intersections of the invariant manifolds of two periodic points with distinct rotation numbers can imply complicated rotational behavior. We show, in particular, that when the unstable manifold of one of these periodic points crosses the stable manifold of the other, and, similarly, the unstable manifold of the second crosses the stable manifold of the first, so that the segments of these invariant manifolds form a topological rectangle, then all rotation numbers between those of the two given orbits are represented. The result follows from a horseshoe-like construction.

     

Stable and Unstable Solitary-Wave Solutions of the Generalized Regularized Long-Wave Equation

Summary. Investigated here are interesting aspects of the solitary-wave solutions of the generalized Regularized Long-Wave equation For p>5 , the equation has both stable and unstable solitary-wave solutions, according to the theory of Souganidis and Strauss. Using a high-order accurate numerical scheme for the approximation of solutions of the equation, the dynamics of suitably perturbed solitary waves are examined. Among other conclusions, we find that unstable solitary waves may evolve into several, stable solitary waves and that positive initial data need not feature solitary waves at all in its long-time asymptotics. Received March 28, 2000; accepted August 24, 2000 %%Online publication November 15, 2000 Communicated by Thanasis Fokas     

On decay and blow-up of solutions for a system of nonlinear wave equations

The initial boundary value problem for a system of viscoelastic wave equations of Kirchhoff type with the nonlinear damping and the source terms in a bounded domain is considered. We prove that, under suitable conditions on the nonlinearity of the damping and the source terms and certain initial data in the stable set and for a wider class of relaxation functions, the decay estimates of the energy function is exponential or polynomial depending on the exponents of the damping terms in both equations by using Nakao’s method. Conversely, for certain initial data in the unstable set, we obtain the blow-up of solutions in finite time when the initial energy is nonnegative. This improves earlier results in the literature.     

Open-Loop Viable Control Under Uncertain Initial State Information

We consider the problem of open-loop viable control of a nonlinear system in Rⁿ in the case of a nonexactly known initial state. We characterize the family of those initial sets for which the problem is solvable. The characterization employs the notion of a contingent field to a given collection of sets introduced in the paper. It also involves an appropriate set-dynamic equation that describes the evolution of the state estimation within a prescribed collection of sets. An extension of the classical concept of viability kernel with respect to this set-dynamic equation is the key tool. We present an approximation scheme for the viability kernel which is numerically realizable in the case of low dimension and simple collections of sets chosen for state estimation (balls, ellipsoids, polyhedrons, etc.). As an application, we consider a viability differential game, where the uncertainty may enter also in the dynamics of the system as an input which is not known in advance. The control is then sought as a nonanticipative strategy depending on the uncertain input.     

A model equation for nonlinear wavelength selection and amplitude evolution of frontal waves

Summary We study a model equation describing the temporal evolution of nonlinear finite-amplitude waves on a density front in a rotating fluid. The linear spectrum includes an unstable interval where exponential growth of the amplitude is expected. It is shown that the length scale of the waves in the nonlinear situation is determined by the linear instabilities; the effect of the nonlinearities is to limit the amplitude's growth, leaving the wavelength unchanged. When linearly stable waves are prescribed as initial data, a short interval of rapid decrease in amplitude is encountered first, followed by a transfer of energy to the unstable part of the spectrum, where the fastest growing mode starts to dominate. A localized disturbance is broken up into its Fourier components, the linearly unstable modes grow at the expense of all other modes, and final amplitudes are determined by the nonlinear term. Periodic evolution of linearly unstable waves in the nonlinear situation is also observed. Based on the numerical results, the existence of low-order chaos in the partial differential equation governing weakly nonlinear wave evolution is conjectured.