Soliton, Positon and Negaton Solutions of Extended KdV Equation

Darboux transformation （DT） provides us with a comprehensive approach to construct the exact and explicit solutions to the negative extended KdV （eKdV） equation, by which some new solutions such as singular soliton, negaton, and positon solutions are computed for the eKdV equation. We rediscover the soliton solution with finiteamplitude in [A.V. Slyunyaev and E.N. Pelinovskii, J. Exp. Theor. Phys. 89 （1999） 173] and discuss the difference between this soliton and the singular soliton. We clarify the relationship between the exact solutions of the eKdV equation and the spectral parameter. Moreover, the interactions of singular two solitons, positon and negaton, positon and soliton, and two positons are studied in detail.     

Zakharov-Shabat Equations for Dark Soliton Solutions to the NLS Equation

For dark soliton solutions of the NLS equation, an inverse scattering transform is redeveloped. Deductions are essentially simplified in terms of an auxiliary spectral parameter from the beginning. Equations of inverse scattering transform in the form of Zakharov-Shabat are found to be simpler than those in the form of Marchenko. An explicate expression for the dark N-soliton solution and its asymptotic behaviors in the limits as t →±∞ are simply derived.     

Conservation Laws and Soliton Solutions for Generalized Seventh Order KdV Equation

With the assistance of the symbolic computation system Maple, rich higher order polynomial-type conservation laws and a sixth order t/x-dependent conservation law are constructed for a generalized seventh order nonlinear evolution equation by using a direct algebraic method. From the compatibility conditions that guaranteeing the existence of conserved densities, an integrable unnamed seventh order KdV-type equation is found. By introducing some nonlinear transformations, the one-, two-, and three-solition solutions as well as the solitary wave solutions are obtained.     

Classification of Dark Modified KdV Equation

The dark Korteweg-de Vries(KdV) systems are defined and classified by Kupershmidt sixteen years ago. However, there is no other classifications for other kinds of nonlinear systems. In this paper, a complete scalar classification for dark modified KdV(MKdV) systems is obtained by requiring the existence of higher order differential polynomial symmetries. Different to the nine classes of the dark KdV case, there exist twelve independent classes of the dark MKdV equations. Furthermore, for the every class of dark MKdV system, there is a free parameter. Only for a fixed parameter, the dark MKdV can be related to dark KdV via suitable Miura transformation. The recursion operators of two classes of dark MKdV systems are also given.     

Two Types of New Solutions to KdV Equation

It is common knowledge that the soliton solutions u（x, t） defined by the bell-shape form is required to satisfy the following condition lira u（x, t） = u（±∞, t） = 0. However, we think that the above condition can be modified as lim u（x, t） = u（±∞, t）^x→ = c, where c is a constant, which is called as a stationary height of u（x, t） in the present paper.^x→∞ If u（x, t） is a bell-shape solitary solution, then the stationary height of each solitary wave is just c. Under the constraint c = 0, all the solitary waves coming from the N-bell-shape-sollton solutions of the KdV equation are the same-oriented travelling. A new type of N-soliton solution with the bell shape is obtained in the paper, whose stationary height is an arbitrary constant c. Taking c ≥ 0, the resulting solitary wave is bound to be the same-oriented travelling. Otherwise, the resulting solitary wave may travel at the same orientation, and also at the opposite orientation. In addition, another type of singular rational travelling solution to the KdV equation is worked out.     

Soliton Perturbation Theory for the Compound KdV Equation

The soliton perturbation theory is used to study the solitons that are governed by the compound Korteweg de-Vries equation in presence of perturbation terms. The adiabatic parameter dynamics of the solitons in presence of the perturbation terms are obtained. AMS Codes: 35Q51; 35Q53; 37K10. PACS Codes: 02.30.Jr; 02.30.Ik.     

New Optical Soliton Solutions of the Perturbed Fokas-Lenells Equation

In this article, we employ the perturbed Fokas-Lenells equation(FLE), which represents recent electronic communications. The Riccati-Bernoulli Sub-ODE method which does not depend on the balance rule is used for thefirst time to obtain the new exact and solitary wave solutions of this equation. This technique is direct, effective and reduces the large volume of calculations.     

Higher-Dimensional KdV Equations and Their Soliton Solutions

A (2+1)-dimensional KdV equation is obtained by use of Hirota method, which possesses N-soliton solution, specially its exact two-soliton solution is presented. By employing a proper algebraic transformation and the Riccati equation, a type of bell-shape soliton solutions are produced via regarding the variable in the Riccati equation as the independent variable. Finally, we extend the above (2+1)-dimensional KdV equation into (3+1)-dimensional equation, the two-soliton solutions are given.     

Novel Solutions of KdV Equation

Some novel solutions of the KdV equation are obtained through the modified bilinear B\"{a}cklund transformation.     

New Exact Solutions to the Combined KdV and mKdV Equation

The modified mapping method is developed to obtain new exact solutions to the combined KdV and mKdV equation. The method is applicable to a large variety of nonlinear evolution equations, as long as odd- and even-order derivative terms do not coexist in the equation under consideration.     

New Soliton-like Solutions for Combined KdV and mKdV Equation

By the application of the extended tanh method and the symbolic computation system Mathematica, new soliton-like solutions are obtained for the combined KdV and mKdV (KdV-mKdV) equation.     

The Bi-Hamiltonian Structure and New Solutions of KdV6 Equation

We show that the KdV6 equation and the nonholonomic perturbation of bi-Hamiltonian system of KdV hierarchy recently studied in Karasu-Kalkanli et al. (J Math Phys 49:073516, 2008) and Kupershmidt (Phys Lett A 372:2634–2639, 2008) are equivalent to the Rosochatius deformation of KdV equation and KdV hierarchy with self-consistent sources (RD-KdVESCS, RD-KdVHSCS), respectively, recently presented in Yao and Zeng (J Phys A Math Theor 41:295205, 2008). The t-type bi-Hamiltonian formalisms of KdV6 equation and RD-KdVHSCS are constructed by taking x as evolution parameter. Some new solutions of KdV6 equation, such as soliton, positon and negaton solution, are presented.     

New Double-Periodic Soliton Solutions for the (2+1)-Dimensional Breaking Soliton Equation

Under investigation is the (2+1)-dimensional breaking soliton equation. Based on a special ansätz functions and the bilinear form, some entirely new double-periodic soliton solutions for the (2+1)-dimensional breaking soliton equation are presented. With the help of symbolic computation software Mathematica, many important and interesting properties for these obtained solutions are revealed with some figures.     

Analytic Solutions to Forced KdV Equation

The Korteweg-de Vries equation with a forcing term is established by recentstudies as a simple mathematical model of describing the physics of a shallow layerof fluid subject to external forcing. In the present paper, we study the analytic solutions to the KdV equation with forcing term by using Hirota's direct method. Several exact solutions are given as examples, from which one can see thatthe same type soliton solutions can be excited by different forced term.     

Analytic Solutions to Forced KdV Equation

The Korteweg-de Vries equation with a forcing term is established by recent studies as a simple mathematical model of describing the physics of a shallow layer of fluid subject to external forcing. In the present paper, we study the analytic solutions to the KdV equation with forcing term by using Hirota＇s direct method. Several exact solutions are given as examples, from which one can see that the same type soliton solutions can be excited by different forced term.     

Interactions of Soliton Waves for a Generalized Discrete KdV Equation

It is well known that soliton interactions in discrete integrable systems often possess new properties which are different from the continuous integrable systems, e.g., we found that there are such discrete solitons in a semidiscrete integrable system(the time variable is continuous and the space one is discrete) that the shorter solitary waves travel faster than the taller ones. Very recently, this kind of soliton was also observed in a full discrete generalized Kd V system(the both of time and space variables are discrete) introduced by Kanki et al. In this paper, for the generalized discrete Kd V(gd Kd V) equation, we describe its richer structures of one-soliton solutions. The interactions of two-soliton waves to the gd Kd V equation are studied. Some new features of the soliton interactions are proposed by rigorous theoretical analysis.     

Generalized Variational Iteration Solution of Soliton for Disturbed KdV Equation

The corresponding solution for a class of disturbed KdV equation is considered using the analytic method. From the generalized variational iteration theory, the problem of solving soliton for the corresponding equation translates into the problem of variational iteration. And then the approximate solution of the soliton for the equation is obtained.     

New Jacobian Elliptic Function Solutions of Modified KdV Equation: II

Recently, we obtained thirteen families of Jacobian elliptic function solutions of mKdV equation by using our extended Jacobian elliptic function expansion method. In this note, the mKdV equation is investigated and another three families of new doubly periodic solutions (Jacobian elliptic function solutions) are found again by using a new transformation, which and our extended Jacobian elliptic function expansion method form a new method still called the extended Jacobian elliptic function expansion method. The new method can be more powerful to be applied to other nonlinear differential equations.     

New Jacobian Elliptic Function Solutions of Modified KdV Equation: Ⅱ

Recently, we obtained thirteen families of Jacobian elliptic function solutions of mKdV equation by usingour extended Jacobian elliptic function expansion method. In this note, the mKdV equation is investigated and anotherthree families of new doubly periodic solutions (Jacobian elliptic function solutions) are fbund again by using a newtransformation, which and our extended Jacobian elliptic function expansion method form a new method still called theextended Jacobian elliptic function expansion method. The new method can be more powertul to be applied to othernonlinear differential equations.