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Various Heteroclinic Solutions for the Coupled Schrödinger-Boussinesq Equation
Various closed-form heteroclinic breather solutions including classical heteroclinic, heteroclinic breather and Akhmediev breathers solutions for coupled Schrödinger-Boussinesq equation are obtained using two-soliton and homoclinic test methods, respectively. Moreover, various heteroclinic structures of waves are investigated.
The existence of the homoclinic and heteroclinic orbits is very important for investigating the spatiotemporal chaotic behavior of the nonlinear evolution equations (NEEs). In recent years, exact homoclinic and heterclinic solutions were proposed for some NEEs like nonlinear Schrödinger equation, Sine-Gordon equation, Davey-Stewartson equation, Zakharov equation, and Boussinesq equation [1–7].
The coupled Schrödinger-Boussinesq equation is considered as with the periodic boundary condition where are real constants, is a complex function, and is a real function. Equation (1) has also appeared in  as a special case of general systems governing the stationary propagation of coupled nonlinear upper-hybrid and magnetosonic waves in magnetized plasma. The complete integrability of (1) was studied by Chowdhury et al. , and -soliton solution, homoclinic orbit solution, and rogue solution were obtained by Hu et al. , Dai et al. [11–13], and Mu and Qin .
2. Linear Stability Analysis
It is easy to see that is a fixed point of (1), and is an arbitrary constant. We consider a small perturbation of the form where , . Substituting (3) into (1), we get the linearized equations Assume that and have the following forms: where are complex constants, and is a real number; , and is the growth rate of the th modes.
3. Various Heterclinic Breather Solutions
By using the following transformation Equation (11) can be reduced into the following bilinear form: where is an unknown complex function and is a real function, is conjugate function of , and is an integration constant. The Hirota bilinear operators are defined by
We use three test functions to investigate the variation of the heterclinic solution for the coupled Schrödinger-Boussinesq equation (1).
(1) We seek the following forms of the heterclinic solution: where are complex numbers and are real numbers. will be determined later.
Choosing , then . Substituting (15) into the (13), we have the following relations among these constants: Therefore, we have the heterclinic solution for (1) as: It is easy to see that as and as . After giving some constants in (17), we find that the shape of the heterclinic orbit for Schrödinger-Boussinesq equation likes the hook, and the orbits are heterclinic to two different fixed points (see Figure 1 with , , , and ).
(2) We take ansatz of extended homoclinic test approach for (13) as follows: where the parameters will be determined later, and are complex numbers, and and are real numbers. Substituting (18) into (13) and choosing , we get the following relations among the parameters: From (19), we get the restrictive conditions with Denote that . Then, substituting (10) into (1) and employing (19), we obtain the solution of the coupled Schrödinger-Boussinesq equation as follows: where are arbitrary numbers.
Solution in (21) is a heteroclinic breather wave solution. It is easy to see that as and as . Given some constants in (21), this kind of the heterclinic orbit likes a spiral, and it is heterclinic to the points and (see Figure 2 with , , and ).
Note that and are two different fixed points of (21), which is a heteroclinic solution (see Figure 3). This wave also contains the periodic wave, and its amplitude periodically oscillates with the evolution of time, which shows that this wave has breather effect. The previous results combined with (21) show that interaction between a solitary wave and a periodic wave with the same velocity and opposite propagation direction can form a heteroclinic breather flow. This is a new phenomenon of physics in the stationary propagation of coupled nonlinear upper-hybrid and magnetosonic waves in magnetized plasma.
(3) Use the following forms of the heterclinic solution : where are complex numbers and are real numbers. will be determined later.
We also choose and substitute (22) into (13). We have the following relations among these constants: Solving (23), we get Therefore, we have the heterclinic solution for (1) as Giving some special parameters in (25), we see that the shape of the heterclinic orbits likes the arc (see Figure 4 with , , and ). The fixed points are as and as .
In this work, by using three special test functions in two-soliton method and homoclinic test method, we obtain three families of heteroclinic breather wave solution heteroclinic to two different fixed points, respectively. Moreover, we investigate different structures of these wave solutions. These results show that the Schrödinger-Boussinesq equation has the variety of heteroclinic structure. As the further work, we will consider whether there exist the spatiotemporal chaos for the coupled Schrödinger-Boussinesq equation or not.
This work was supported by Chinese Natural Science Foundation Grant nos. 11161055 and 11061028, as well as Yunnan NSF Grant no. 2008PY034.
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Copyright © 2013 Murong Jiang and Zhengde Dai. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.