In this article, the generalized Riccati equation mapping together with the basic (G′/G)-expansion method is implemented which is advance mathematical tool to investigate nonlinear partial differential equations. Moreover, the auxiliary equation G′(ϕ) = h + f G(ϕ) + g G2(ϕ) is used with arbitrary constant coefficients and called the generalized Riccati equation. By applying this method, we have constructed abundant traveling wave solutions in a uniform way for the Sawada-Kotera equation. The obtained solutions of this equation have vital and noteworthy explanations for some practical physical phenomena.
I. INTRODUCTION
The rapid developments of nonlinear sciences, a wide range of straightforward and effective methods have been introduced to obtain traveling wave solutions of nonlinear PDEs. Such as, the truncated Painleve expansion method,1,2 the Hirota's bilinear transformation method,3 the weierstrass elliptic function method,4 the inverse scattering method,5 the Backlund transformation method,6–8 the Jacobi elliptic function expansion method,9–11 the tanh-coth method,12,13 the direct algebraic method,14 the Cole-Hopf transformation method,15 the homotopy perturbation method,16–19 the Exp-function method,20–25 the variational iteration method26–32 and others.33–41
Recently, Wang et al.42 presented a widely used simple and concise method which is called the (G′/G)-expansion method for constructing traveling wave solutions of some nonlinear evolution equations (NLEEs). In addition, in this method the second order linear ordinary differential equation G′′(ϕ) + λG′(ϕ) + μG(ϕ) = 0 is implemented, as an auxiliary equation, where λ and μ are arbitrary constants. Subsequently, many researchers studied many nonlinear PDEs to obtain exact traveling wave solutions via this powerful (G′/G)-expansion method.43–51
Zhu52 implemented the generalized Riccati equation mapping with the extended tanh-function method to investigate the (2+1)-dimensional Boiti-Leon-Pempinelle equation. Moreover, G′(ϕ) = h + f G(ϕ) + g G2(ϕ) is utilized as an auxiliary equation and called generalized Riccati equation, where f, g and h are arbitrary constants. Li et al.53 concerned about the generalized Riccati equation expansion method to study higher-dimensional Jimbo-Miwa equation. In Ref. 54 Bekir and Cevikel investigated nonlinear coupled equation in mathematical physics via the tanh-coth method combined with the Riccati equation while Salas55 applied the projective Riccati equation method to obtain some exact solutions for the Caudrey-Dodd-Gibbon equation. In Ref. 56 Guo et al. executed the extended Riccati equation mapping method to study the diffusion-reaction and the mKdV equation with variable coefficient whereas Naher and Abdullah57 established traveling wave solutions of the modified Benjamin-Bona-Mahony equation by applying the generalized Riccati equation mapping with the basic (G′/G)-expansion method and so on.
Many researchers constructed traveling wave solutions of the fifth order Sawada-Kotera equation by using different methods. Such as, Liu and Dai58 executed the Hirota's bilinear method to obtain exact solutions of the same equation. Feng and Zheng59 investigated this equation to establish traveling wave solutions via the (G′/G)-expansion method. In Ref. 60, Wazwaz implemented the extended tanh method for constructing analytical solutions of the same equation. Salas61 concerned about the projective Riccati equation method to obtain exact solutions of this equation. But, to the best of our knowledge, the fifth-order Sawada-Kotera equation is not investigated to construct exact solutions by applying the generalized Riccati equation mapping together with the(G′/G)-expansion method. The obtained traveling wave solutions in this article are new and have not been found in the previous literature.
The importance of our present work is, in order to construct abundant traveling wave solutions including solitons, periodic and rational solutions, and a Sawada-Kotera equation is considered by applying the extended generalized Riccati equation mapping method.
II. THE EXTENDED GENERALIZED RICCATI EQUATION MAPPING METHOD
Suppose the general nonlinear partial differential equation:
where u = u(x, t) is an unknown function, S is a polynomial in u(x, t) and the subscripts indicate the partial derivatives.
The most important steps of the generalized Riccati equation mapping together with the (G′/G)-expansion method42,52 are as follows:
Step 1. Consider the traveling wave variable:
where Q is the wave speed. Now using Eq. (2), Eq. (1) is converted into an ordinary differential equation for q(ϕ):
where the superscripts stand for the ordinary derivatives with respect to ϕ.
Step 2. Eq. (3) integrates term by term one or more times according to possibility, yields constant(s) of integration. The integral constant(s) may be zero for simplicity.
where bj (j = 0, 1, 2, ..., m) and bm ≠ 0, with G = G(ϕ) is the solution of the generalized Riccati equation:
where f, g, h are arbitrary constants and g ≠ 0.
Step 4. To decide the positive integer m, consider the homogeneous balance between the nonlinear terms and the highest order derivatives appearing in Eq. (3).
Step 5. Substitute Eq. (4) along with Eq. (5) into the Eq. (3), then collect all the coefficients with the same order, the left hand side of Eq. (3) converts into polynomials in G k(ϕ) and G−k(ϕ), (k = 0, 1, 2, ...). Then equating each coefficient of the polynomials to zero, yield a set of algebraic equations for bj (j = 0, 1, 2, ..., m), f, g, h and Q.
Step 6. Solve the system of algebraic equations which are found in Step 5 with the aid of algebraic software Maple to obtain values for bj (j = 0, 1, 2, ..., m), f, g, h and Q. Then, substitute obtained values in Eq. (4) along with Eq. (5) with the value of n, we obtain exact solutions of Eq. (1).
In the following, we have twenty seven solutions including four different families of Eq. (5).
Family 2.1: When f2 − 4gh < 0 and f g ≠ 0 or gh ≠ 0 , the solutions of Eq. (5) are:
where A and B are two non-zero real constants and satisfies A2 − B2 > 0.
Family 2.2: When f2 − 4gh > 0 and f g ≠ 0 or gh ≠ 0 , the solutions of Eq. (5) are:
where A and B are two non-zero real constants and satisfies A2 − B2 < 0.
Family 2.3: when h = 0 and gh ≠ 0, the solution Eq. (5) becomes:
where c1 is an arbitrary constant.
Family 2.4: when g ≠ 0 and h = f = 0, the solution of Eq. (5) becomes:
where l1 is an arbitrary constant.
III. APPLICATIONS OF THE METHOD
In this section, we have constructed new exact traveling wave solutions for the Sawada-Kotera equation by using the method.
A. The Sawada-Kotera equation
We consider the Sawada-Kotera equation followed by Liu and Dai:58
Eq. (7) is integrable, therefore, integrating with respect ϕ once yields:
where C is an integral constant which is to be determined later.
Taking the homogeneous balance between q3and q(4) in Eq. (8), we obtain m = 2.
Therefore, the solution of Eq. (8) is of the form:
where f, g and h are free parameters.
By substituting Eq. (10) into Eq. (8), collecting all coefficients of Gk and G−k (k = 0, 1, 2, ...) and setting them equal to zero, we obtain a set of algebraic equations for b0, b1, b2, f, g, h, C and Q (algebraic equations are not shown, for simplicity). Solving the system of algebraic equations with the help of algebraic software Maple, we obtain
Family 3.1: The periodic form solutions of Eq. (6) (when f2 − 4gh < 0 and f g ≠ 0 or g h ≠ 0) are:
where |$\Psi = \frac{1}{2}\sqrt {4gh - f^2 }$|, ϕ = x − (f4 − 8f2gh + 16g2h2)t and f, g, h are arbitrary constants.
where A and B are two non-zero real constants and satisfies A2 − B2 > 0.
Family 3.2: The soliton and soliton-like solutions of Eq. (6) (when f2 − 4gh > 0 and f g ≠ 0 or g h ≠ 0) are:
where |$\Phi = \frac{1}{2}\sqrt {f^2 - 4gh},$| ϕ = x − (f4 − 8f2gh + 16g2h2)t and f, g, h are arbitrary constants.
where A and B are two non-zero real constants and satisfies A2 − B2 < 0.
Family 3.3: The soliton and soliton-like solutions of Eq. (6) (when h = 0 and f g ≠ 0) are:
where ϕ = x − (f4 − 8f2gh + 16g2h2)t and c1, f, g, h are arbitrary constants.
Family 3.4: The rational function solution (when g ≠ 0 and h = f = 0) is:
where l1 is an arbitrary constant and ϕ = x − (f4 − 8f2gh + 16g2h2)t.
IV. GRAPHICAL PRESENTATIONS OF SOME TRAVELING WAVE SOLUTIONS
The graphical descriptions of some solutions are represented in figures 1–12 with the aid of commercial software Maple.
ACKNOWLEDGMENTS
This article is supported by the USM short term grant (Ref. No. 304/PMATHS/6310072) and authors would like to express their thanks to the School of Mathematical Sciences, USM for providing related research facilities.