Abstract
In this paper, based on similarity transformation and auxiliary equation method, we construct many exact solutions of N-coupled nonlinear Schrödinger equations with variable coefficients, which include soliton solutions, combined soliton solutions, triangular periodic solutions, Jacobi elliptic function solutions and combined Jacobi elliptic function solutions. These solutions may give insight into many considerable physical processes.
1 Introduction
In recent years, the N-coupled nonlinear Schrödinger (NLS) equations which are used to describe the simultaneous propagation of N nonlinear waves in a uniform medium have received considerable interest due to their numerous applications in the areas of plasma physics [1], nonlinear optics and quantum electronics [2], Bose–Einstein condensates [3], and hydrodynamics [4, 5]. For better understanding the complicated nonlinear physical phenomena, the solution is much involved. In the past, various methods have been used to handle nonlinear partial differential nonlinear equations, such as the variational iteration method [6, 7], homotopy perturbation method [8, 9], the Bäcklund transformation method [10], the subsidiary ordinary differential equation method (sub-ODE for short) [11, 12], F-expansion method [13–15], sine-cosine method [16, 17], sech-tanh method [18, 19], Exp-function method [20, 21], Jacobi elliptic function method [22–24], residual power series method (RPSM for short) [25, 26], and homotopy analysis method [27, 28].
It is well known that the nonlinear partial differential equations with variable-coefficients are more realistic in various physical situations than their constant coefficients counterparts. So the aim of this paper is to construct exact solutions of the following N-coupled NLS equations with variable coefficients using similarity reduction and auxiliary equation method:
where the physical field Ψk≡Ψk(x, t)(k=1, 2, …, N), the external potential vk(x, t)(k=1, 2, …, N) is a real-valued function of time and spatial coordinates, and the nonlinear coefficient gkj(t)(j, k=1, 2, …, N) and gain or loss coefficient γ(t) are real valued functions of time.
The rest of this paper is organised as follows: In Section 2, we study the similarity solutions by reducing (1) to the (1+1)-dimensional standard NLS equations with constant coefficients via the similarity transformation and auxiliary equation method. In Section 3, some conclusions are given.
2 Similarity Transformation and Solutions
In general, it is difficult to seek directly analytical solutions of (1). Here, we search for a similarity transformation connecting solutions of (1) with those of the (1+1)-dimensional standard NLS equations with constant coefficients
where the physical field Φk(η, τ)(k=1, 2, …, N) are functions of two variables η≡η(x, t) and τ≡τ(t), which are to be determined later, and Gkj(j, k=1, 2, …, N) are constants.
To do this, we write the solution of (1) as
Substituting transformation (3) into (1) and after relatively simple algebra obtain the system of partial differential equations
Solving (4), we can write the similarity variables η(x, t), τ(t), and the phase φ(x, t) in the following form
where k(t), c(t), w(t) are time-dependent functions and an overdot stands for the derivative with respect to time. Now, from (5) to (7), we obtain the functions ρ(t), vk(x, t), and gjk(t) as follows:
where ρ0 is a constant.
To obtain the solutions of (2), we make the complex transformation
where Ak(η, τ) and Bk(η, τ)(k=1, 2, …, N) are real functions of η and τ.
Substituting Φk(η, τ)(k=1, 2, …, N) into (2) and setting the real and imaginary parts of the resulting equations to zero lead to the following set of PDEs:
The solution of (15) and (16) is chosen in the following form:
where ak, bk, dk(k=1, 2, …, N), p, mk, and q(τ), h(τ) to be determined later, and
With the aid of Mathematica, substituting (17)–(19) along with (20) into (15) and (16), setting the coefficients of monomials of F(θ) and η of the resulting system numerator to zero, we obtain a set of ODEs with respect to unknowns ak, bk, dk, p, mk, and q(τ), lk(τ).
Solving the system, we get the following solution set:
Case 1:
where ξ0, ξk, p, and m are arbitrary constants, and the parameter ϵ can have the values ϵ=0, ±1.
Case 2:
where ak, ζ0, ζk, p, and m are arbitrary constants, and the parameter ϵ can have the values ϵ=0, ±1, the expression of D as following:
and Dk is the determinant formed by replacing the k-th column of D by the unit column vector.
Therefore, we obtain exact traveling wave solutions of (2)
where
where
Substituting (21) and (24) along with (8)–(11) into (3), we get exact traveling wave solutions of (1) in the following form:
where
where
Remark 2.1. As we know the more solutions of (20) we find, the more exact solutions of (1) may be obtained. However, the general solutions are difficult to be listed because of the complexity of (20). Some special solutions [29–33] are listed in Tables 1–3.
Solutions of (20) m (0<m<1) denotes the modulus of the Jacobi elliptic function.
| h0 | h2 | h4 | F(ξ) |
|---|---|---|---|
| 0 | >0 | <0 | |
| 0 | >0 | >0 | |
| <0 | >0 | ||
| 0 | <0 | >0 | |
| 0 | <0 | >0 | |
| >0 | >0 | ||
| 1 | –(1 +m2) | m2 | |
| (1–m2) | 2m2–1 | –m2 | cnξ |
| m2–1 | 2–m2 | –1 | dnξ |
| m2 | (–1+m2) | 1 | |
| nsξ±csξ | |||
| ncξ±scξ |
Solutions of (20) (continued) m (0<m<1) denotes the modulus of the Jacobi elliptic function.
| h0 | h2 | h4 | F(ξ) |
|---|---|---|---|
| –m2 | 2m2–1 | 1–m2 | ncξ |
| –1 | 2–m2 | m2–1 | ndξ |
| 1 | 2–m2 | 1–m2 | scξ |
| 1 | 2m2–1 | –m2(1–m2) | sdξ |
| 1–m2 | 2–m2 | 1 | csξ |
| –m2(1–m2) | 2m2–1 | 1 | dsξ |
| nsξ±dsξ | |||
| snξ±icnξ, | |||
| msnξ±idnξ, | |||
| mcn(ξ)±dn(ξ) |
Solutions of (20) (continued) m (0<m<1) denotes the modulus of the Jacobi elliptic function.
| h0 | h2 | h4 | F(ξ) |
|---|---|---|---|
| 1 | 2 –4m2 | 1 | |
| –2m3+m4+m2 | 6m–m2–1 | ||
| 2m3+m4+m2 | –6m–m2–1 | ||
| 2+2k1–m2 | 6k1–m2+2 | 4k1 | |
| 2–2k1–m2 | –6k1–m2+2 | –4k1 | |
| 2m2+2 | –B2m2–B2–2B2m | ||
| 2m2+2 | –B2m2–B2–2B2m | ||
| 0 | 1 | ||
| 0 | 0 | >0 |
For example, if we choose ϵ=0, we can obtain the following solutions using (25) and Table 1:
Case 2.1 Soliton and soliton-like solutions
where
where
where
where
Case 2.2 Triangular periodic solutions
where
where
where
where
Case 2.3 Jacobi elliptic function solutions and combined Jacobi elliptic function solutions
where
where
where
where
where
where
where
where
where
where
where
where
Since k(t) and c(t) are arbitrary functions, the solution (27) has abundant properties. We show some properties of the bright soliton intensity of Eq. (27) in Figure 1. And the wave propagation of the dark soliton intensity of Eq. (29) is illustrated in Figure 2.

Bright soliton intensity of (27) with

Dark soliton intensity of (29) with
Remark 2.2 We can obtain many other solutions using (25), (26), and Tables 1–3, but we omit them for simplicity.
Remark 2.3 There are some hyperbolic function solutions and trigonometric function solutions can be obtained at the limit case when m→1 and m→0, but we also omit them for simplicity.
3 Conclusion
In this paper, we have obtained many types of exact solutions for the N-coupled NLS equations with variable coefficients by means of the combination method of the similarity transformation and auxiliary equation method, which include soliton solutions, combined soliton solutions, triangular periodic solutions, Jacobi elliptic function solutions, and combined Jacobi elliptic function solutions. To the best of our knowledge, the solutions obtained in this letter have not been reported in the previous literature. These solutions may provide more information to further study the mechanisms of the complicated nonlinear physical phenomena.
Funding source: National Natural Science Foundation of China
Award Identifier / Grant number: 11526088
Award Identifier / Grant number: 11501186
Funding source: Natural Science Foundation of Hubei Province
Award Identifier / Grant number: 2014CFB640
Funding statement: This work is supported by the National Natural Science Foundation of China (11526088, 11501186) and Natural Science Foundation of Hubei Province (2014CFB640).
Acknowledgments:
This work is supported by the National Natural Science Foundation of China (11526088, 11501186) and Natural Science Foundation of Hubei Province (2014CFB640).
References
[1] K. H. Spatschek, Phys. Fluids 21, 1032 (1978).10.1063/1.862323Suche in Google Scholar
[2] A. K. Dhar and K. P. Das, Phys. Fluids 3, 3021 (1991).10.1063/1.858209Suche in Google Scholar
[3] A. Hasegawa and Y. Kodama, Solitons in Optical Communications, Oxford University Press, Oxford 1995.10.1093/oso/9780198565079.001.0001Suche in Google Scholar
[4] E. P. Bashkin and A. V. Vagov, Phys. Rev. B. 56, 6207 (1997).10.1103/PhysRevB.56.6207Suche in Google Scholar
[5] S. B. Leble, Nonlinear Waves in Waveguides with Stratification, Springer, Berlin 1991.10.1007/978-3-642-75420-3Suche in Google Scholar
[6] J. H. He, Int. J. Nonlinear Mech. 34, 699 (1999).10.1016/S0020-7462(98)00048-1Suche in Google Scholar
[7] E. Yusufoglu, Int. J. Nonlinear Sci. Numer. Simul. 8, 153 (2007).Suche in Google Scholar
[8] J. H. He and X. H. Wu, Comput. Math. Appl. 54, 881 (2007).10.1016/j.camwa.2006.12.083Suche in Google Scholar
[9] J. H. He, Comput. Methods Appl. Mech. Eng. 178, 257 (1999).10.1016/S0045-7825(99)00018-3Suche in Google Scholar
[10] M. R. Miurs, Bäcklund Transformation, Springer, Berlin 1978.Suche in Google Scholar
[11] X. Li and M. Wang, Phys. Lett. A. 361, 115 (2007).10.1016/j.physleta.2006.09.022Suche in Google Scholar
[12] D. Lu, and C. Liu, Appl. Math. Comput. 217, 1404 (2010).10.1016/j.amc.2009.05.049Suche in Google Scholar
[13] M. A. Abdou, Chaos Solitons Fract. 31, 95 (2007).10.1016/j.chaos.2005.09.030Suche in Google Scholar
[14] J. L. Zhang, M. L. Wang, Y. M. Wang, and Z. D. Fang, Phys. Lett. A. 350, 103 (2006).10.1016/j.physleta.2005.10.099Suche in Google Scholar
[15] M. L. Wang and X. Z. Li, Chaos Solitons Fract. 24, 1257 (2005).10.1016/j.chaos.2004.09.044Suche in Google Scholar
[16] A. M. Wazwaz, Comput. Math. Appl. 47, 583 (2004).10.1016/S0898-1221(04)90047-8Suche in Google Scholar
[17] A. M. Wazwaz, Math. Comput. Model. 40, 499 (2004).10.1016/j.mcm.2003.12.010Suche in Google Scholar
[18] W. Malfliet, Am. J. Phys. 60, 650 (1992).10.1119/1.17120Suche in Google Scholar
[19] A. M. Wazwaz, Appl. Math. Comput. 154, 713 (2004).10.1016/S0096-3003(03)00745-8Suche in Google Scholar
[20] J. H. He and X. H. Wu, Chaos Solitons Fract. 30, 700 (2006).10.1016/j.chaos.2006.03.020Suche in Google Scholar
[21] J. H. He and M. A. Abdou, Chaos Solitons Fract. 34, 1421 (2007).10.1016/j.chaos.2006.05.072Suche in Google Scholar
[22] S. Liu, Z. Fu, S. Liu, and Q. Zhao, Phys. Lett. A 289, 69 (2001).10.1016/S0375-9601(01)00580-1Suche in Google Scholar
[23] E. Fan and J. Zhang, Phys. Lett. A 305, 383 (2002).10.1016/S0375-9601(02)01516-5Suche in Google Scholar
[24] X. Q. Zhao, H. Y. Zhi, and H. Q. Zhang, Chaos Solitons Fract. 28, 112 (2006).10.1016/j.chaos.2005.05.016Suche in Google Scholar
[25] S. Kumar, A. Kumar, and D. Baleanu, Nonlinear Dynam. doi:10.1007/s11071-016-2716-2, (2016).Suche in Google Scholar
[26] J. Yao, A. Kumar, and S. Kumar, Adv. Mech. Eng. 7, 1 (2015).Suche in Google Scholar
[27] X. B. Yin, S. Kumar, and D. Kumar, Adv. Mech. Eng. 7, 1 (2015).10.1177/1687814015620330Suche in Google Scholar
[28] S. Kumar, D. Kumar, and J. Singh, Adv. Nonlinear Anal. DOI: 10.1515/anona-2013-0033, (2016).Suche in Google Scholar
[29] H. Triki, T. R. Taha, and A. M. Wazwaz, Math. Comput. Simul. 80, 1867 (2010).10.1016/j.matcom.2010.02.001Suche in Google Scholar
[30] H. T. Chen and H. Q. Zhang, Chaos Solitons Fract. 20, 765 (2004).10.1016/j.chaos.2003.10.030Suche in Google Scholar
[31] Y. Chen and Q. Wang, Appl. Math. Comput. 168, 1189 (2005).10.1016/j.amc.2004.10.012Suche in Google Scholar
[32] D. S. Wang and H. B. Li, Appl. Math. Comput. 188, 762 (2007).10.1016/j.amc.2006.10.026Suche in Google Scholar
[33] B. Tang, X. Wang, Y. Fan, and J. Qu, Math. Probl. Eng. 2016, Article ID 5274243, 10 pages, (2016).10.1155/2016/5274243Suche in Google Scholar
©2016 by De Gruyter
Artikel in diesem Heft
- Frontmatter
- Decay Mode Solutions for the Supersymmetric Cylindrical KdV Equation
- Cooling of Moving Wavy Surface through MHD Nanofluid
- Parallel Plate Flow of a Third-Grade Fluid and a Newtonian Fluid With Variable Viscosity
- Flow of a Micropolar Fluid Through a Channel with Small Boundary Perturbation
- Exact Solutions for Stokes’ Flow of a Non-Newtonian Nanofluid Model: A Lie Similarity Approach
- A New Reduction of the Self-Dual Yang–Mills Equations and its Applications
- Quasi-periodic Solutions to the K(−2, −2) Hierarchy
- Superposition of Solitons with Arbitrary Parameters for Higher-order Equations
- Elastic and Thermal Properties of Silicon Compounds from First-Principles Calculations
- Exact Solutions for N-Coupled Nonlinear Schrödinger Equations With Variable Coefficients
- Rapid Communication
- Electrical Conductivity of Molten CdCl2 at Temperatures as High as 1474 K
Artikel in diesem Heft
- Frontmatter
- Decay Mode Solutions for the Supersymmetric Cylindrical KdV Equation
- Cooling of Moving Wavy Surface through MHD Nanofluid
- Parallel Plate Flow of a Third-Grade Fluid and a Newtonian Fluid With Variable Viscosity
- Flow of a Micropolar Fluid Through a Channel with Small Boundary Perturbation
- Exact Solutions for Stokes’ Flow of a Non-Newtonian Nanofluid Model: A Lie Similarity Approach
- A New Reduction of the Self-Dual Yang–Mills Equations and its Applications
- Quasi-periodic Solutions to the K(−2, −2) Hierarchy
- Superposition of Solitons with Arbitrary Parameters for Higher-order Equations
- Elastic and Thermal Properties of Silicon Compounds from First-Principles Calculations
- Exact Solutions for N-Coupled Nonlinear Schrödinger Equations With Variable Coefficients
- Rapid Communication
- Electrical Conductivity of Molten CdCl2 at Temperatures as High as 1474 K