New Exact Jacobi Elliptic Function Solutions for the Coupled Schrödinger-Boussinesq Equations

A general algebraic method based on the generalized Jacobi elliptic functions expansion method, the improved general mapping deformation method, and the extended auxiliary function method with computerized symbolic computation is proposed to construct more new exact solutions for coupled Schrödinger-Boussinesq equations. As a result, several families of new generalized Jacobi elliptic function wave solutions are obtained by using this method, some of them are degenerated to solitary wave solutions and trigonometric function solutions in the limited cases, which shows that the general method is more powerful than plenty of traditional methods and will be used in further works to establish more entirely new solutions for other kinds of nonlinear partial differential equations arising in mathematical physics.


Introduction
Nonlinear partial differential equations (NLPDEs) are widely used to describe complex physical phenomena arising in the world around us and various fields of science. The investigation of exact solutions of NLPDEs plays an important role in the study of these phenomena such as the nonlinear dynamics and the mechanism behind the phenomena. With the development of soliton theory, many powerful methods for obtaining exact solutions of NLPDEs have been presented, such as homotopy perturbation method [1], nonperturbative method [2], homogeneous balance method [3], Bäcklund transformation [4], Darboux transformation [5], extended tanh-function method [6], extended -expansion method [7], / method [8], exp-function method [9], sine-cosine method [10], Jacobi elliptic function method [11], extended Riccati equation rational expansion method [12], extended auxiliary function method [13], and other methods [14,15].
In [16,17], Hong proposed a generalized Jacobi elliptic functions expansion method to obtain generalized exact solutions of NLPDEs. In [18], Hong and Lu proposed an improved general mapping deformation method which is more general than many other algebraic expansion methods [19,20]. The solution procedure of this method, by the help of Matlab or Mathematica, is of utmost simplicity, and this method can be easily extended to all kinds of NLPDEs. In this work, we will propose the general algebraic method which contained the two methods [16][17][18] to obtain several new families of exact solutions for the coupled Schrödinger-Boussinesq equations.

Summary of the General Algebraic Method
We seek the following formal solutions of the given system by a new intermediate transformation: where are constants to be determined later. = ( , ) are arbitrary functions with the variables and . The parameter 2 Journal of Applied Mathematics can be determined by balancing the highest order derivative terms with the nonlinear terms in (1). And ( ) is a solution of the following ordinary differential equation: Substituting (3) and (2) into (1) and setting the coefficients of ( ) ( = 0, 1, 2, . . .) and ( ) √ ∑ 4 =0 ( ) ( = . . . , −2, −1, 0, 1, 2, . . .) to zero yield a set of algebraic equations for , , and . Using the Mathematica to solve the algebraic equations and substituting each of the solutions of the set, that is, each of the expressions of ( ) into (2), we can get the solutions of (1). In order to obtain some new general solutions of (3), we assume that (3) has the following solutions: where , , , and are arbitrary constants which ensure the denominator unequal to zero, and = ( ) is a solution of the following equations: where " " denotes / , " " denotes 2 / 2 , , , , , and are arbitrary constants, and the four functions , , , and ℎ satisfy the following relations: And , , , and ℎ satisfy one of the following relations at the same time.

Remark 2. Equations
where can be an arbitrary positive integer. is usually a positive integer. If is a fraction or a negative integer, we make the following transformation: (a) when = / is a fraction, we let ( ) = V / ( ), then return to determine the balance constant again; (b) when is a negative integer, we suppose ( ) = V ( ), then return to determine the balance constant again.
In the following, we will use this method to solve the Schrödinger-Boussinesq equations.

Exact Solutions to the Coupled Schrödinger-Boussinesq Equations
We consider the coupled Schrödinger-Boussinesq equations [21][22][23][24][25][26][27][28] These equations are known to describe various physical processes in laser and plasma, such as formation, Langmuir field amplitude, intense electromagnetic waves, and modulational instabilities [22][23][24][25]. The problem of the complete integrability of this system has been studied by Chowdhury et al. from the point of view of Painlevé analysis [25]. The solitary wave solutions for system (11) have been obtained in [26,27]. The Jacobi doubly periodic wave solutions and a range of other solutions for this system have been investigated in [21,28]. We are interested in searching new generalized Jacobi elliptic function solutions for (11) by using our method.
Journal of Applied Mathematics Case 5.
Remark 5. The seven types of explicit solutions we obtained here to (11) are not shown in the previous literature to our knowledge. They are new exact solutions of (11). Notice that sn → tanh , cn → sech , and dn → sech when the modulus → 1, and sn → sin , cn → cos , and dn → 1 when the modulus → 0. Solutions , ( = 1, . . . , 6) are degenerated to solitary wave solutions when the modulus → 1 and to triangular functions solutions when the modulus → 0.
We can give the numerical simulation of 6 to show their physical properties (see Figures 1, 2, and 3).

Conclusion
In this paper, we succeed to propose a general algebraic method approach for finding new exact solutions of the nonlinear evolution equations. By using this method and computerized symbolic computation, we have found abundant new exact solutions for the coupled Schrödinger-Boussinesq equations (11). More importantly, our method is much simpler and powerful to find new solutions to various kinds of nonlinear evolution equations, such as KdV equation, Boussinesq equation, and zakharov equation. We believe that this method should play an important role for finding exact solutions in the mathematical physics.