Finite-Time Blow-Up of Solutions to Semilinear Wave Equations

This work studies the finite-time blow-up of solutions to the equation u_tt−Δu=F(u) in Minkowski space. We develop a new technique which simplifies some of the existing arguments. The approach we use is a modification of the so-called method of conformal compactification. In this we are motivated by the work of Christodoulou, and Baez, Segal, and Zhou on nonlinear wave equations, as well as the recent developments in the rigorous theory of nonlinear quantum fields.     

Blow-Up of Solutions to Semilinear Nonautonomous Wave Equations with Robin Boundary Conditions

Mathematical Notes - The problem of the blow-up of solutions to the initial boundary value problem for a nonautonomous semilinear wave equation with damping and accelerating terms under the Robin...     

Generalized Solutions of Semilinear Parabolic Equations

It is well-known that a semilinear parabolic equation has no unique solution in the classical sense. We study such equations from the viewpoint of generalized functions. By using approximations for generalized functions, we obtain results on existence and uniqueness of generalized solutions. Furthermore, we establish the relationship between generalized solutions and classical solutions. Current address: Institute of Mathematics, University of Tsukuba, Tsukuba 305-8571, Japan     

半线性椭圆方程的正解

本文用特征理论及上下解方法,证明了一类半线性椭圆方程边值问题的正解的存在性,同时给出了解的估计.     

Exact Controllability for Semilinear Wave Equations

In this note, we prove the exact controllability for the semilinear wave equations in any space dimensions under the condition that the nonlinearity behaves like as s → ∞.     

Solutions of Semilinear Elliptic Equations in Tubes

Given a smooth compact k-dimensional manifold Λ embedded in ? ^m , with m≥2 and 1≤k≤m?1, and given ?>0, we define B _? (Λ) to be the geodesic tubular neighborhood of radius ? about Λ. In this paper, we construct positive solutions of the semilinear elliptic equation $$\begin{cases} \Delta u + u^p = 0 &\mbox{in } B_{\epsilon}(\varLambda) \\ u = 0 & \mbox{on } \partial B_{\epsilon}(\varLambda) , \end{cases} $$ when the parameter ? is chosen small enough. In this equation, the exponent p satisfies either p>1 when n:=m?k≤2 or $p\in(1, \frac{n+2}{n-2})$ when n>2. In particular, p can be critical or supercritical in dimension m≥3. As ? tends to 0, the solutions we construct have Morse index tending to infinity. Moreover, using a Pohozaev type argument, we prove that our result is sharp in the sense that there are no positive solutions for $p>\frac{n+2}{n-2}$ , n≥3, if ? is sufficiently small.     

Singularities of Solutions to Cauchy Problems for Semilinear Wave Equations in Two Space Dimensions

This paper concerns the Cauchy problem for semilinear wave equations with two space variables, of which the initial data have conormal singularities on finite curves intersecting at one point on the initial plane. It is proved that the solution is of conormal distribution type, and its singularities are contained in the union of the characteristic surfaces through these curves and the characteristic cone issuing from the intersection point.     

半线性波动方程的振荡波

对于一类二维和三维的半线性波动方程,当其振荡初值具有一个非退化性相时,给出了双位相振荡解的任意阶的有效几何光学展开,同时给出了层面的清晰结构。     

半线性波动方程柯西问题解的生命跨度的上界估计

主要研究了在n(n≥1)维空间下,半线性波动方程在次临界情形时的柯西问题,通过构造一个测试函数ψ(x,t)证明不论正初值多么小,其解都会在有限时间内破裂,并给出其解的生命跨度上界估计.     

On the Multiplicity of Solutions of Semilinear Equations

We study uniqueness and exact multiplicity of solutions of semilinear equations for both balls and annular domains. We assume the annular domains to be “thin ”, but allow them to be wider than in the previous works.     

半线性抛物型泛函微分方程的周期解

本文应用上下解的概念及schauder不动点定理,在较广泛的条件下,解决了半线性抛物型泛函数微分方程周期解的存在性问题.所得结果推广了文献[3]的定理1.2.     

全空间上一类半线性椭圆方程的正解

本文研究Rn(n≥ 3)上的半线性椭圆方程 -Δu=f(u)的C2 正解 .如果f(u)在 ( 0 ,∞ )上局部有界并且对某个α 1 <α相似文献   

Nonradial Entire Large Solutions of Semilinear Elliptic Equations

We consider the problem of whether the equation △u = p（x）f（u） on RN, N ≥ 3, has a positive solution for which lim ｜x｜→∞（x） = ∞ where f is locally Lipschitz continuous, positive, and nondecreasing on （0,oo） and satisfies ∫1∞[F （t）]^- 1/2dt = ∞ where F（t） = ∫0^tf（s）ds. The nonnegative function p is assumed to be asymptotically radial in a certain sense. We show that a sufficient condition to ensure such a solution u exists is that p satisfies ∫0∞ r min｜x｜=r P （x） dr = ∞. Conversely, we show that a necessary condition for the solution to exist is that p satisfies ∫0∞r1＋ε min ｜x｜=rp（x）dr =∞ for all ε〉0.     

Stability of Semilinear Delay Equations with Positive Solutions

We prove stability for a semilinear delay equation, whose nonlinearity is majorized by a linear positive operator. The key ingredients are a spectral condition, positivity of solutions to the linear problem, and lattice properties of the Banach space.     

Existence for Semilinear Wave Equations with Low Regularity

In this paper, we study how much regularity of initial data is needed to ensure existence of a local solution to the following semilinear wave equations utt-Δu=F(u, Du), u(0, x)=f(x)∈HS,(?)tu(0, x)=g(x)∈HS-1, where F is quadratic in Du with D = ((?)t,(?)x1,…,(?)xn). We proved that the range of s is s≥n 1/2 δ, respectively, withδ>1/4 if n = 2, andδ>0 if n = 3, andδ≥0 if n≥4. Which is consistent with Lindblad's counterexamples [3] for n = 3, and the main ingredient is the use of the Strichartz estimates and the refinement of these.     

(2+1)维Broer-Kaup-Kupershmidt方程组的行波解

借助于计算机代数系统Mathematica,利用推广的简单方程方法构造了(2+1)维Broer-Kaup-Kupershmidt方程组的新的精确行波解,分别以含有双参数的用双曲函数,三角函数和有理函数表示,其中双曲函数表.示的行波解中参数取特殊值时可得到文献已有的孤波解.方法也适用于其它非线性发展方程(组).     

Almost Automorphic Solutions for Hyperbolic Semilinear Evolution Equations

In the present paper, we deal with mild solutions for the semilinear evolution equation \begin{displaymath} \frac{d}{dt}x(t)=Ax(t)+f(t,x(t)),\qquad t\in \R, \end{displaymath} under the sectoriality of $A$, a linear operator with not necessarily dense domain, in a Banach space $X$ and $\sigma(A)\cap i\R=\emptyset$. We prove the existence and uniqueness of an almost automorphic solution in an intermediate space $X_{\alpha}$, when the function $f\colon \ \R\times X_{\alpha}\longrightarrow X$ is almost automorphic. An example illustrating the obtained result is given.     

Interaction of Three Conormal Waves for Semilinear Wave Equations

In this paper, we consider the interaction of triple of conormal waves with different singularities for semilinear wave equations. We will show that if three characteristic hyperplanes carrying different conormal singularities intersect transversally at the origin, then the solution will be conormal with respect to the three hyperplanes, and a new singularity will be produced on the surface of the light cone at later times. We can also prove here that the strength of the new singularity will be dependent only on the weakest one and strongest one in the three hyperplanes.