On the global attraction to solitary waves for the Klein–Gordon equation coupled to a nonlinear oscillator

The long-time asymptotics are analyzed for all finite energy solutions to a model $\mathbf{U}(1)$-invariant nonlinear Klein–Gordon equation in one dimension, with the nonlinearity concentrated at a point. Our main result is that each finite energy solution converges as $t\to \pm \infty$ to the set of ‘nonlinear eigenfunctions’ $\psi (x){\mathrm{e}}^{?\mathrm{i}\omega t}$. To cite this article: A.I. Komech, A.A. Komech, C. R. Acad. Sci. Paris, Ser. I 343 (2006).     

The initial value problem for the cubic nonlinear Klein–Gordon equation

We study the initial value problem for the cubic nonlinear Klein–Gordon equation

Blowup behaviour for the nonlinear Klein–Gordon equation

We analyze the blowup behaviour of solutions to the focusing nonlinear Klein–Gordon equation in spatial dimensions $d\ge 2$ . We obtain upper bounds on the blowup rate, both globally in space and in light cones. The results are sharp in the conformal and sub-conformal cases. The argument relies on Lyapunov functionals derived from the dilation identity. We also prove that the critical Sobolev norm diverges near the blowup time.     

Hydrodynamic limits of the nonlinear Klein–Gordon equation

We perform the mathematical derivation of the compressible and incompressible Euler equations from the modulated nonlinear Klein–Gordon equation. Before the formation of singularities in the limit system, the nonrelativistic-semiclassical limit is shown to be the compressible Euler equations. If we further rescale the time variable, then in the semiclassical limit (the light speed kept fixed), the incompressible Euler equations are recovered. The proof involves the modulated energy introduced by Brenier (2000) [1].     

Solitary waves for the perturbed nonlinear Klein–Gordon equation

In this work, we study the perturbed nonlinear Klein–Gordon equation. We shall use the sech-ansätze method to derive the solitary wave solutions of this equation.     

Spectral and modulational stability of periodic wavetrains for the nonlinear Klein–Gordon equation

This paper is a detailed and self-contained study of the stability properties of periodic traveling wave solutions of the nonlinear Klein–Gordon equation _utt−_uxx+V^′(u)=0$u_{tt}-u_{xx}+V^{\prime }(u)=0$, where u is a scalar-valued function of x and t  , and the potential V(u)$V(u)$ is of class C²$C^2$ and periodic. Stability is considered both from the point of view of spectral analysis of the linearized problem (spectral stability analysis) and from the point of view of wave modulation theory (the strongly nonlinear theory due to Whitham as well as the weakly nonlinear theory of wave packets). The aim is to develop and present new spectral stability results for periodic traveling waves, and to make a solid connection between these results and predictions of the (formal) modulation theory, which has been developed by others but which we review for completeness.     

Modulation of localized solutions for the Schrödinger equation with logarithm nonlinearity

We investigate the presence of localized analytical solutions of the Schrödinger equation with logarithm nonlinearity. After including inhomogeneities in the linear and nonlinear coefficients, we use similarity transformation to convert the nonautonomous nonlinear equation into an autonomous one, which we solve analytically. In particular, we study stability of the analytical solutions numerically.     

Existence and nonexistence to exterior Dirichlet problem for Monge–Ampère equation

We consider the exterior Dirichlet problem for Monge–Ampère equation with prescribed asymptotic behavior. Based on earlier work by Caffarelli and the first named author, we complete the characterization of the existence and nonexistence of solutions in terms of their asymptotic behaviors.     

High-order linear compact conservative method for the nonlinear Schrödinger equation coupled with the nonlinear Klein–Gordon equation

In this paper, we design a linear-compact conservative numerical scheme which preserves the original conservative properties to solve the Klein–Gordon–Schrödinger equation. The proposed scheme is based on using the finite difference method. The scheme is three-level and linear-implicit. Priori estimate and the convergence of the finite difference approximate solutions are discussed by the discrete energy method. Numerical results demonstrate that the present scheme is conservative, efficient and of high accuracy.     

Approximate damped oscillatory solutions and error estimates for the perturbed Klein–Gordon equation

The influence of perturbation on traveling wave solutions of the perturbed Klein–Gordon equation is studied by applying the bifurcation method and qualitative theory of dynamical systems. All possible approximate damped oscillatory solutions for this equation are obtained by using undetermined coefficient method. Error estimates indicate that the approximate solutions are meaningful. The results of numerical simulations also establish our analysis.     

On global solutions to the initial–boundary value problem for the nonlinear Schrödinger equations in exterior domains

We consider the initial–boundary value problem for the nonlinear Schr‐dinger equations in an exterior domain. Global existence theorem of smooth solutions is established by using a–priori decay estimates of solutions which are obtained by the pseudoconformal indentity     

Existence and uniqueness of positive solutions to?m-point boundary value problem for?nonlinear fractional differential equation

In this paper, we consider the following nonlinear fractional m-point boundary value problem where $D_{0+}^{\alpha}$ is the standard Riemann-Liouville fractional derivative. By the properties of the Green function, the lower and upper solution method and fixed-point theorem in partially ordered sets, some new existence and uniqueness of positive solutions to the above boundary value problem are established. As applications, examples are presented to illustrate the main results.