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The intimate connection between discrete and continuous integrable systems may yield deep insight into some inherent discreteness of physical phenomena. In this paper, a spatially discrete Boussinesq equation is investigated. The integrability of the spatially discrete model is confirmed by showing the existence of Lax pair and infinite number of conservation laws. The Darboux transformation is expressed in terms of Casorati type determinant. Further, by combining the Darboux transformation with different solutions of eigenfunction, we provide a comprehensive approach to construct various types of exact solutions to the spatially discrete Boussinesq equation, such as multi-soliton solutions, periodic solutions, rational solutions and more generally their interaction solutions. Lastly, we prove that the theory of spatially discrete Boussinesq equation including the Lax pair, the conservation laws, the Darboux transformation and the exact solutions converges to the corresponding theory of the Boussinesq equation in the continuum limit.

A nonlocal matrix nonlinear Schrödinger equation with the self-induced parity-time $\mathcal{PT}$-symmetric potentials and its Darboux transformation have been studied. We obtain several types of solutions as taking different spectral parameter and seeds, include localized soliton solutions, dark-antidark soliton solutions, exact solutions which describe the onset and nonlinear development of the modulational instability of continuous wave states, parallel traveling wave solution, and rogue wave solutions. Besides, the Infinite conservation laws have been derived.

In this work, we consider a nonlinear Schrodinger equation with stimulated Raman scattering and quintic nonlinearity, which works as a model for the propagation of ultrashort pulse in optical fiber and also corresponds to one-dimensional anisotropic Heisenberg ferromagnetic spin chain. Introducing a Galilean transformation, we transform the model into a fifth-order complex modified KdV equation, the integrability of which has been considered in the AKNS technique framework. The N-fold Darboux transformation for the model is derived in terms of the gauge transformation of the associated $$3 \times 3$$ matrix spectral problem. As applications, abundant intriguing types of nonlinear waves are obtained in zero and nonzero boundary conditions. The dynamical evolution of these nonlinear waves can be well controlled under stimulated Raman scattering and quintic nonlinearity management. Beside that, we also find some novel and interesting conversion phenomena, where a high-order term plays a pivotal role.

The integrability of the reverse space–time nonlocal Sasa–Satsuma equation in the Liouville sense is established by showing the existence of infinitely many conservation laws and putting into a bi-Hamiltonian form. Further, we show that the nonlocal Sasa–Satsuma equation for focusing case and defocusing case is, respectively, gauge equivalent to a generalized Heisenberg-like equation and a modified generalized Heisenberg-like equation. Finally, by using of special variable transformations, various kinds of nonlinear waves are obtained from those of the classical counterpart.

To get more insight into the relation between discrete model and continuous counterpart, a new integrable semi-discrete Kundu–Eckhaus equation is derived from the reduction in an extended Ablowitz–Ladik hierarchy. The integrability of the semi-discrete model is confirmed by showing the existence of Lax pair and infinite number of conservation laws. The dynamic characteristics of the breather and rational solutions have been analyzed in detail for our semi-discrete Kundu–Eckhaus equation to reveal some new interesting phenomena which was not found in continuous one. It is shown that the theory of the discrete system including Lax pair, Darboux transformation and explicit solutions systematically yields their continuous counterparts in the continuous limit.

A three-component integrable differential-difference dynamic system is introduced. It is interesting that the model includes the modified Volterra lattice, the two-component modified Volterra lattice, the relativistic Volterra lattice and the relativistic Toda lattice as special reductions. In this report, we (I) obtain a Lax pair, (II) use the Lax pair to derive the first three conservations laws, (III) present Darboux transformations. and (IV) construct various kinds of exact solutions.

In this paper, we present a new coupled modified (1 + 1)-dimensional Toda equation of BKP type (Kadomtsev-Petviashvilli equation of B-type), which is a reduction of the (2 + 1)-dimensional Toda equation. Two-soliton and three-soliton solutions to the coupled system are derived. Furthermore, the N-soliton solution is presented in the form of Pfaffian. The asymptotic analysis of two-soliton solutions is studied to explain their collision properties. It is shown that the coupled system exhibit richer interaction phenomena including soliton fission, fusion, and mixed collision. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, a spatial discrete complex modified Korteweg-de Vries equation is investigated. The Lax pair, conservation laws, Darboux transformations, and breather and rational wave solutions to the semi-discrete system are presented. The distinguished feature of the model is that the discrete rational solution can possess new W-shape rational periodic-solitary waves that were not reported before. In addition, the first-order rogue waves reach peak amplitudes which are at least three times of the background amplitude, whereas their continuous counterparts are exactly three times the constant background. Finally, the integrability of the discrete system, including Lax pair, conservation laws, Darboux transformations, and explicit solutions, yields the counterparts of the continuous system in the continuum limit.

In this paper, we give a coupled lattice equation with the help of Hirota operators, which comes from a special BKP lattice. Two-soliton and three-soliton solutions to the coupled system are constructed. Furthermore, resonant interaction of the two-soliton solution is analyzed in detail. Under some special resonant condition, it is shown that low soliton can propagate faster than high one. Finally, the N-soliton solution is presented in the Pfaffian form.

In this Letter, we propose a new coupled higher-order Ito equation and present its N -soliton solutions in Pfaffian form. Furthermore, some interesting examples of soliton resonance related to two solitons near the resonant state are pointed out.

In this paper, we study a coupled modified Volterra lattice equation which is an integrable semidiscrete version of the coupled KdV and the coupled mKdV equation. By using the Darboux transformation, we obtain its new explicit solutions including multi-soliton and multi-positon. Furthermore, an integrable discretization of the coupled modified Volterra lattice equation is constructed.

A broad set of sufficient conditions consisting of systems of linear partial differential equations are presented which guarantee that the Wronskian determinant is the solutions of the integrable variable-coefficient Korteweg-de Vries model from Bose–Einstein condensates and fluid dynamics. The generalized Wronskian solutions provide us with a comprehensive approach to construct many exact solutions including rational solutions, solitons, negatons, positons, and complexitons.

We show here that rational, positon, negaton, breather solutions of some discrete nonlinear evolution equations are presented via long wave limiting method. The discrete nonlinear evolution equations concerned are 1D Toda lattice, differential-difference KdV, differential-difference analogue KdV equations.

In this Letter, Wronskian solutions for the complex KdV equation are obtained by Hirota's bilinear method. Moreover, starting from the bilinear Backlund transformation, multi-soliton solutions are presented for the same equation. At the same time, it is also shown that these two kinds of solutions are equivalent.

The Boussinesq equation usually arises in a physical problem as a long wave equation. The present work extends the search of periodic wave solutions for it. The Hirota bilinear method and Riemann theta function are employed in the process. We also analyse the asymptotic property of periodic waves in detail. Furthermore, it is of interest to note that well-known soliton solutions can be reduced from the periodic wave solutions.

In this paper, we propose a new semidiscrete Hirota equation which yields the Hirota equation in the continuum limit. We focus on the topic of how the discrete space step δ affects the simulation for the soliton solution to the Hirota equation. The Darboux transformation and explicit solution for the semidiscrete Hirota equation are constructed. We show that the continuum limit for the semidiscrete Hirota equation, including the Lax pair, the Darboux transformation and the explicit solution, yields the corresponding results for the Hirota equation as δ → 0 .

A new integrable semi-discrete version is proposed for the multi-component coherently coupled nonlinear Schrodinger equation. The integrability of the semi-discrete system is confirmed by existence of Lax pair and infinite number of conservation laws. With the aid of gauge transformations, explicit formulas for N-fold Darboux transformations are derived whereby some physically important solutions of the system are presented. Furthermore, the theory of the semi-discrete system including Lax pair, Darboux transformations, exact solutions and infinite number of conservation laws are shown for their continuous counterparts in the continuous limit.

The Darboux transformation for a three‐field lattice equation is constructed. As an application of the obtained Darboux transformation, explicit exact solutions of the lattice equation are given. We also discuss some properties for these new explicit solutions. Our analysis shows that the explicit solutions possess new characters.

With the help of a property of Hirota bilinear operators, a new coupled Volterra lattice system is presented based on its bilinear form. Using the perturbational method, we obtain two-soliton solution and three-soliton solution to the coupled Volterra lattice system. Furthermore, resonant interactions of the solitons are analyzed in detail to reveal several new features. A explanation of the mechanism of the resonant properties of the solution is proposed. Finally, the \(N\)-soliton solution is expressed in the form of Pfaffian.

In this paper, we obtain the coupled bright-bright and the coupled dark-dark soliton solutions for an integrable coupled semidiscrete Hirota equation (ICDHE) using the bilinear method. These solutions have both singular and nonsingular behaviors depending upon the choice of the parameters. The distinguishing feature of the ICDHE is that the singular solution can possess some nonsingular characteristics in the discrete space at some time. The asymptotic behavior of these coupled bright-bright and the coupled dark-dark solitons is studied in order to explain their collision properties.

Coupled Korteweg-de Vries (KdV) systems have many important physical applications. By considering a 4 × 4 spectral problem, we derive a discrete coupled KdV-type equation hierarchy. Our hierarchy includes the coupled Volterra system proposed by Lou et al. (e-print arXiv:0711.0420) as the first member which is a discrete version of the coupled KdV equation. We also investigate the integrability in the Liouville sense and the multi-Hamiltonian structures for the obtained hierarchy.

In this paper, we aim to get more insight on the relation between semidiscrete coupled mKdV system (where “semidiscrete” means that the system is discrete in the space variable and continuous in time) and the coupled mKdV equations; to this purpose, we propose a new coupled semidiscrete mKdV system. The Lax pairs, the Darboux transformation, soliton solutions and conservation laws for the coupled semidiscrete mKdV system are given. The coupled mKdV theory including the Lax pairs, the Darboux transformation, soliton solutions, and conservation laws is recovered through the continuous limits of corresponding theory for the new semidiscrete mKdV system.

This paper aims to find new explicit solutions including multisoliton, multipositon, multinegaton, and multiperiodic for a coupled Volterra lattice system. This coupled lattice system is an integrable discrete version of the coupled Korteweg-deVries (KdV) equation which has many physical applications. The dynamical properties of these new solutions are discussed in detail. We also prove that the theory of the coupled Volterra lattice system including the Lax pair, the Darboux transformation, and explicit solutions yield the corresponding theory of the coupled KdV equation in the continuous limit.