On positive multi-lump bound states of nonlinear Schrödinger equations under multiple well potential

In this paper, we first construct multi-lump (nonlinear) bound states of the nonlinear Schrödinger equation for sufficiently small >0, in which sense we call them semiclassical bound states. We assume that 1p< forn=1,2 and 1p<1+4/(n–2) forn3, and thatV is in the class(V) _a in the sense of Kato for somea. For any finite collection {x ₁,...,x _N} of nondegenerate critical points ofV, we construct a solution of the forme ^–iEt/v(x) forE<a, wherev is real and it is a small perturbation of a sum of one-lump solutions concentrated nearx ₁,...,x _N respectively. The concentration gets stronger as 0. And we also prove these solutions are positive, and unstable with respect to perturbations of initial conditions for possibly smaller >0. Indeed, for each such collection of critical points we construct 2 ^N–1 distinct unstable bound states which may have nodes in general, and the above positive bound state is just one of them.     

Stability of semiclassical bound states of nonlinear Schrödinger equations with potentials

In this paper, we study the Lyapunov stabilities of some semiclassical bound states of the (nonhomogeneous) nonlinear Schrödinger equation, We prove that among those bound states, those which are concentrated near local minima (respectively maxima) of the potentialV are stable (respectively unstable). We also prove that those bound states are positive if is sufficiently small.     

On the finite-time behaviour for nonlinear Schrödinger equations

Consider the nonlinear Schrödinger equationu _t –iu=f(u). Forf(u)=±|u|^1+p , ±i|u|^1+p , ±u|u| ^p (p>0), and the Dirichlet boundary or nonlinear boundary (including the Neumann boundary and the Robin boundary) conditions, we establish the local estimates for the timet to the solutions of the initial-boundary value problems. Being based up on these estimates, we investigate the blowing-up properties of the solutions.Research supported in part by the Youth Foundation of Sichuan Education Committee and the Natural Science Foundation of China     

On the integration of some classes of weakly deformed nonlinear Schrödinger equations

A method is proposed for constructing the solutions of a nonlinear Schrödinger equation with small corrections arising as a result of the introduction of arbitrary functions of the time and coordinates into the operator that dresses the kernel of a local $\bar \partial $ problem.     

Self-similar solutions of equations of the nonlinear Schrödinger type

Experimental data are presented for the temperature dependence of the conductivity of Cu: SiO₂ metal-insulator composite films containing 3-nm Cu granules. At low temperatures in the concentration range 17–33 vol % Cu, all of the conductivity curves have a temperature dependence of the form σ ∝ exp{ (T ₀/T)^1/2}, while at higher temperatures a transition is observed to an activational dependence. A numerical simulation of the conduction in a composite material shows that an explanation of the observed temperature dependence must include the Coulomb interaction and the presence of a rather large random potential. The simulation also yields the size dependence and temperature dependence of the mesoscopic scatter of the conductivities of composite conductors. It is shown that a self-selecting percolation channel of current flow is formed in the region of strong mesoscopic scatter.     

A bound on the number of bound states in the Schrödinger equation

A boundS _l is given for the number of bound statesn _i in thelth partial wave corresponding to a spherically symmetric potential in non-relativistic quantum mechanics. This bound is given by whereV _a(l, r) is the attractive part of the effective potentialV(r)+l(l+1)/r ². Extensive comparative study ofS _i and the Bargmann inequality is made.     

Nature of transitions in augmented discrete nonlinear Schrödinger equations

We investigate the nature of the transitions between free and self-trapping states occurring in systems described by augmented forms of the discrete nonlinear Schr?dinger equation. These arise from an interaction between a moving quasiparticle (such as an electron or an exciton) and lattice vibrations, when the effects of nonlinearities in interaction potential and restoring force are included. We derive analytic conditions for the stability of the free state and the crossover between first- and second-order transitions. We demonstrate our results for different types of nonlinearities in the interaction potential and restoring force. We find that, depending on the type of nonlinearity, it is possible to have both first- and second-order transitions. We discuss possible hysteresis effects.     

Periodic wavetrains for systems of coupled nonlinear Schrödinger equations

Exact, periodic wavetrains for systems of coupled nonlinear Schrödinger equations are obtained by the Hirota bilinear method and theta functions identities. Both the bright and dark soliton regimes are treated, and the solutions involve products of elliptic functions. The validity of these solutions is verified independently by a computer algebra software. The long wave limit is studied. Physical implications will be assessed.     

New bounds on the number of bound states for Schrödinger operators

We consider the Schrödinger operatorH = – +V(|x|) onR ³. Letn denote the number of bound states with angular momentum (not counting the 2 + 1 degeneracy). We prove the following bounds onn . LetV 0 and d/dr r ^1-2p (-V)^{1 –p} 0 for somep [1/2, 1) then

Šilnikov manifolds in coupled nonlinear Schrödinger equations

We consider two coupled nonlinear Schrödinger equations with even, periodic boundary conditions, that are damped and quasiperiodically forced. We prove the existence of invariant manifolds with Šilnikov-type dynamics that are homoclinic to a spatially independent invariant torus. Such manifolds appear to induce complex behavior in numerical experiments.     

Coupled nonlinear Schrödinger equations in optic fibers theory

In this paper a detailed derivation and numerical solutions of Coupled Nonlinear Schrödinger Equations for pulses of polarized electromagnetic waves in cylindrical fibers has been reviewed. Our recent work has been compared with some previous ones and the advantage of our new approach over other methods has been assessed. The novelty of our approach lies is an attempt to proceed without loss of information within the frame of basic approximations. In our work we focused on the multimode The eigen mode definition is based on complete linearized Maxwell equations and Hondros-Debye boundary conditions, which depend on the geometry of the dielectric waveguide. We proved both stability and convergence in the L ₂ space of an explicit finite-difference scheme for the Coupled Nonlinear Schrödinger Equations and those estimations are used for an implicit scheme. To test our hypothesis we compare numerical solutions for Manakov system with known analytical solitonic solutions. We also consider an important example of the general system - an evolution of two pulses with different group velocity which can serve as a model of pulses interaction in multimode optic fibers. Last case, a nonlinear dispersion of rectangular pulse, exhibits an asymptotic behavior similar to Nonlinear Schrödinger Equation solution asymptotics for the rectangular initial condition. Finally, we compared theoretical results with specially arranged experiments employing a photonic crystal fiber.     

Semiclassical trajectory-coherent states of the nonlinear Schrödinger equation with unitary nonlinearity

Semiclassically concentrated states of the nonlinear Schrödinger equation (NLSE) with unitary nonlinearity, representing multidimensional localized wave packets, are constructed on the basis of the Maslov complex germ theory. A system of ordinary differential equations of Hamilton-Ehrenfest (HE) type, describing the motion of the wave packet centroid, is derived. The structure of the HE system is strongly influenced by the initial conditions of the Cauchy problem for the NLSE. Wave packets of Gaussian type are constructed in an explicit form. Possible use of the solutions constructed in the problem of optical pulse propagation in a nonlinear medium with nonstationary dispersion is discussed.     

On the nonlinear Schrödinger limit of the Korteweg-de Vries equation

Using the multiscale approach of Zakharov and Kuznetsov it is shown that the nonlinear Schrödinger periodic scattering data is related to the Korteweg-de Vries periodic scattering data via an average over the Korteweg-de Vries carrier oscillation. This allows a complete elucidation of the physical meaning of the nonlinear Schrödinger scattering data, conservation laws, theta function solutions and reality constraint.     

Dynamics of three nonisospectral nonlinear Schrdinger equations

Dynamics of three nonisospectral nonlinear Schrdinger equations(NNLSEs), following different time dependencies of the spectral parameter, are investigated. First, we discuss the gauge transformations between the standard nonlinear Schrdinger equation(NLSE) and its first two nonisospectral counterparts, for which we derive solutions and infinitely many conserved quantities. Then, exact solutions of the three NNLSEs are derived in double Wronskian terms. Moreover,we analyze the dynamics of the solitons in the presence of the nonisospectral effects by demonstrating how the shapes,velocities, and wave energies change in time. In particular, we obtain a rogue wave type of soliton solutions to the third NNLSE.     

The nonlinear Schrödinger limit of the Zakharov equations governing Langmuir turbulence

We consider the initial value problem for the Zakharov equations $$\begin{gathered} \left( Z \right)\frac{1}{{\lambda ^2 }}n_{tt} - \Delta (n + \left| {\rm E} \right|^2 ) = 0n(x,0) = n_0 (x) \hfill \\ n_t (x,0) = n_1 (x) \hfill \\ iE_t + \Delta E - nE = 0E(x,0) = E_0 (x) \hfill \\ \end{gathered} $$ (x∈? ^k ,k=2, 3,t ≧0) which model the propagation of Langmuir waves in plasmas. For suitable initial data solutions are shown to exist for a time interval independent of λ, a parameter proportional to the ion acoustic speed. For such data, solutions of (Z) converge as λ → ∞ to a solution of the cubic nonlinear Schrödinger equation (CSE)iE _t +ΔE+|E|² E=0. We consider both weak and strong solutions. For the case of strong solutions the results are analogous to previous results on the incompressible limit of compressible fluids.     

Stationary dark localized modes: discrete nonlinear Schrödinger equations

Various kinds of stationary dark localized modes in discrete nonlinear Schr?dinger equations are considered. A criterion for the existence of such excitations is introduced and an estimation of a localization region is provided. The results are illustrated in examples of the deformable discrete nonlinear Schr?dinger equation, of the model of Frenkel excitons in a chain of two-level atoms, and of the model of a one-dimensional Heisenberg ferromagnetic in the stationary phase approximation. The three models display essentially different properties. It is shown that at an arbitrary amplitude of the background it is impossible to reach strong localization of dark modes. In the meantime, in the model of Frenkel excitons, exact dark compacton solutions are found.     

The surfboard Schrödinger equations

We study the large time behavior of solutions of time dependent Schrödinger equationsiu/t=–(1/2)u+t V(x/t)u with bounded potentialV(x). We show that (1) if>–1, all solutions are asymptotically free ast, (2) if–1 a solution becomes asymptotically free if and only if it has the momentum support outside of suppV for large time, (3) if –1 <0 all solutions are still asymptotically modified free ast and that (4) if 0 <2, for each local minimumx ₀ ofV(x), there exist solutions which are asymptotically Gaussians centered atx=tx ₀ and spreading slowly ast.     

On the Born-Oppenheimer approximation for excited states of polyatomic Schrödinger operators

In this Letter, excited states of polyatomic molecular Schrödinger operators are investigated with the help of the Born-Oppenheimer approximation. The ratio of electronic and nuclear mass plays the role of a semi-classical parameter h ². Asymptotic series of eigenvalues at the bottom of the spectrum are constructed up to any order in h. Mathematically, this leads to the discussion of the semi-classical limit of pseudo-differential operators with the principal symbol po(x,) = ² + , where has a degenerate minimum (a whole manifold).     

On the exact solutions of nonlinear Schrödinger equation with spin current

An integrable nonlinear Schrödinger (NLS) equation driven by spin polarized current governing the magnetization dynamics of a ferromagnetic nanowire is considered. The exact soliton solution of the NLS equation propagating along the direction of wire axis which is also the current direction along which nonuniform magnetization occurs is obtained through the application of exponential function method. The solution of the system admits a class of solitons such as kink and periodic solitons in the nanowire along the direction of the electric current.