Double-pole soliton solutions of the defocusing nonlinear Schrödinger equation with local and nonlocal nonlinearities under nonzero boundary conditions

formula omitted]-double poles solutions for nonlocal Hirota equation with nonzero boundary conditions using Riemann–Hilbert method and PINN algorithm

Optical solitons and their propagations in a time-varying coefficient modified nonlinear Schrödinger equation with non-zero boundary conditions via Riemann–Hilbert method

We analyze the existence, bifurcations, and shape transformations of one-dimensional gap solitons (GSs) in the first finite band gap induced by a periodic potential built into materials with local self-focusing and nonlocal self-defocusing nonlinearities. Originally stable on-site GS modes become unstable near the upper edge of the band gap with the introduction of the nonlocal self-defocusing nonlinearity with a small nonlocality radius. Unstable off-site GSs bifurcate into a new branch featuring single-humped, double-humped, and flat-top modes due to the competition between local and nonlocal nonlinearities. The mechanism underlying the complex bifurcation pattern and cutoff effects (termination of some bifurcation branches) is illustrated in terms of the shape transformation under the action of the varying degree of the nonlocality. The results of this work suggest a possibility of optical-signal processing by means of the competing nonlocal and local nonlinearities.

We study dipolar Bose–Einstein condensate (BEC) solitons in a one-dimensional optical lattice with the combined effect of local and nonlocal nonlinearities. The local nonlinearity is imposed by a magnetic or optical field via the Feshbach (FB) resonance. In contrast, the nonlocal nonlinearity is created by the long-range dipole–dipole interaction among the condensates. The orientations of the dipoles are directed by a rotatable uniform external field, which gives rise to a controllable nonlocal nonlinearity resulting from the angle θ between the direction of the dipole and the elongation of the lattice. If the lattice is sufficiently deep, this model can be described by the Gross–Pitaevskii equation (GPE) with tunable local and nonlocal nonlinear strengths (\(g\) and θ respectively). The formation, motion, and collision of the solitons in this system are studied by numerical simulations. The combined effect of the local and nonlocal nonlinearities gives a controllable scheme for all these characteristics ...

In this work, the double and triple pole soliton solutions for the Gerdjikov–Ivanov type of the derivative nonlinear Schrödinger equation with zero boundary conditions (ZBCs) and nonzero boundary conditions (NZBCs) are studied via the Riemann–Hilbert (RH) method. With spectral problem analysis, we first obtain the Jost function and scattering matrix under ZBCs and NZBCs. Then, according to the analyticity, symmetry, and asymptotic behavior of the Jost function and scattering matrix, the RH problem (RHP) with ZBCs and NZBCs is constructed. Furthermore, the obtained RHP with ZBCs and NZBCs can be solved in the case that reflection coefficients have double or triple poles. Finally, we derive the general precise formulas of N-double and N-triple pole solutions corresponding to ZBCs and NZBCs, respectively. In addition, the asymptotic states of the one-double pole soliton solution and the one-triple pole soliton solution are analyzed when t tends to infinity. The dynamical behaviors for these solutions are further discussed by image simulation.

On the two nonzero boundary problems of the AB system with multiple poles

We study numerically the dynamics of an initially localized wave packet in one-dimensional nonlinear Schrodinger lattices with both local and nonlocal nonlinearities. Using the discrete nonlinear Schrodinger equation generalized by including a nonlocal nonlinear term, we calculate four different physical quantities as a function of time, which are the return probability to the initial excitation site, the participation number, the root-mean-square displacement from the excitation site and the spatial probability distribution. We investigate the influence of the nonlocal nonlinearity on the delocalization to self-trapping transition induced by the local nonlinearity. In the non-self-trapping region, we find that the nonlocal nonlinearity compresses the soliton width and slows down the spreading of the wave packet. In the vicinity of the delocalization to self-trapping transition point and inside the self-trapping region, we find that a new kind of self-trapping phenomenon, which we call partial self-trapping, takes place when the nonlocal nonlinearity is sufficiently strong.

Focusing and defocusing mKdV equations with nonzero boundary conditions: Inverse scattering transforms and soliton interactions

We systematically report a rigorous theory of the inverse scattering transforms (ISTs) for the derivative nonlinear Schrodinger (DNLS) equation with both zero boundary condition (ZBC)/non-zero boundary conditions (NZBCs) at infinity and double poles of analytical scattering coefficients. The scattering theories for both ZBC and NZBCs are addressed. The direct problem establishes the analyticity, symmetries and asymptotic behavior of the Jost solutions and scattering matrix, and properties of discrete spectra. The inverse problems are formulated and solved with the aid of the matrix Riemann-Hilbert problems, and the reconstruction formulae, trace formulae and theta conditions are also posed. In particular, the IST with NZBCs at infinity is proposed by a suitable uniformization variable, which allows the scattering problem to be solved on a standard complex plane instead of a two-sheeted Riemann surface. The reflectionless potentials with double poles for the ZBC and NZBCs are both carried out explicitly by means of determinants. Some representative semi-rational bright-bright soliton, dark-bright soliton, and breather-breather solutions are examined in detail. These results will be useful to further explore and apply the related nonlinear wave phenomena.

Under investigation in this work is the inverse scattering transform of the general fifth-order nonlinear Schr\"{o}dinger equation with nonzero boundary conditions (NZBCs), which can be reduced to several integrable equations. Firstly, a matrix Riemann-Hilbert problem for the equation with NZBCs at infinity is systematically investigated.Then the inverse problems are solved through the investigation of the matrix Riemann-Hilbert problem. Thus, the general solutions for the potentials, and explicit expressions for the reflection-less potentials are well constructed. Furthermore, the trace formulae and theta conditions are also presented. In particular, we analyze the simple-pole and double-pole solutions for the equation with NZBCs. Finally, the dynamics of the obtained solutions are graphically discussed. These results provided in this work can be useful to enrich and explain the related nonlinear wave phenomena in nonlinear fields.

In this paper, the Riemann-Hilbert approach is applied to study a third-order flow equation of derivative nonlinear Schrödinger-type equation with nonzero boundary conditions. By utilizing the analytical, symmetric, and asymptotic properties of eigenfunctions, a generalized Riemann-Hilbert problem is formulated for the third-order flow equation of derivative nonlinear Schrödinger-type equation with nonzero boundary conditions. The formulas of N-soliton solutions for cases of single pole and double poles are given. We present some kinds of soliton solutions of these two cases according to different distributions of spectral parameters to study the dynamical behavior of them.

We consider initial boundary value problems for one-dimensional diffusion equation with time-fractional derivative of order which are subject to non-zero Neumann boundary conditions. We prove the uniqueness for an inverse coefficient problem of determining a spatially varying potential and the order of the time-fractional derivative by Dirichlet data at one end point of the spatial interval. The imposed Neumann conditions are required to be within the correct Sobolev space of order α. Our proof is based on a representation formula of solution to an initial boundary value problem with non-zero boundary data. Moreover, we apply such a formula and prove the uniqueness in the determination of boundary value at another end point by Cauchy data at one end point.

Mixed single, double, and triple poles solutions for the space-time shifted nonlocal DNLS equation with nonzero boundary conditions via Riemann–Hilbert approach

We study systematically a matrix Riemann-Hilbert problem for the modified Landau-Lifshitz (mLL) equation with nonzero boundary conditions at infinity. Unlike the zero boundary conditions case, there occur double-valued functions during the process of the direct scattering. In order to establish the Riemann-Hilbert (RH) problem, it is necessary to make appropriate modification, that is, to introduce an affine transformation that can convert the Riemann surface into a complex plane. In the direct scattering problem, the analyticity, symmetries, asymptotic behaviors of Jost functions and scattering matrix are presented in detail. Furthermore, the discrete spectrum, residual conditions, trace foumulae and theta conditions are established with simple and double poles. The inverse problems are solved via a matrix RH problem formulated by Jost function and scattering coefficients. Finally, the dynamic behavior of some typical soliton solutions of the mLL equation with reflection-less potentials are given to further study the structure of the soliton waves. In addition, some remarkable characteristics of these soliton solutions are analyzed graphically. According to analytic solutions, the influences of each parameters on dynamics of the soliton waves and breather waves are discussed, and the method of how to control such nonlinear phenomena are suggested.

In this report we discuss the problem of approximating nonlinear delta-interactions in dimensions one and three with regular, local or non-local nonlinearities. Concerning the one dimensional case, we discuss a recent result proved in [10], on the derivation of nonlinear delta-interactions as limit of scaled, local nonlinearities. For the three dimensional case, we consider an equation with scaled, non-local nonlinearity. We conjecture that such an equation approximates the nonlinear delta-interaction, and give an heuristic argument to support our conjecture.