1
Introduction
Nonlinearity in nature is fascinating, and many researchers see nonlinear science as the most promising field for enhancing our understanding of the universe [1, 2]. The mathematical characterization of complex systems with time-varying parameters necessitates the examination of a variety of nonlinear partial differential equations (NLPDEs). Since the mid-18th century, scholars have endeavored to simplify intricate physical phenomena by employing NLPDEs. Researchers frequently use NLPDEs to reconstruct various dynamic phenomena [3]. As a result, the study of NLPDEs has continued to attract a substantial quantity of attention in recent years. To explore the exact solutions to nonlinear equations is a critical component of the investigation of nonlinear physical phenomena [4]. The significance of obtaining exact solutions for nonlinear equations is paramount, as these solutions are essential for numerical solution verification and stability analysis. A mathematical structure must be used to express the physical characteristics of any nonlinear physical system in order to obtain an exact solution. This mathematical structure is frequently represented by NLPDEs. Therefore, the investigation of NLPDEs is essential; these equations provide a fundamental framework that facilitates the highly precise understanding of a diverse array of nonlinear physical phenomena. NLPDEs are basic mathematical models that help us understand many different types of phenomena in physics, photonics, optics, fluid dynamics and nonlinear fiber optics. They are used in fields like plasma physics and nonlinear optics [5].
The soliton theory has garnered significant attention in trial designs due to its function as a research domain in the disciplines of media transmission, numerical physical science, designing, and various nonlinear sciences [6]. Specifically, the current period has seen a concentration of optical solitons. Optical solitons are waves that possess the ability to generate waves without dispersing over a significant distance, i.e., they maintain their shape over a significant distance [7, 8]. The basic role of solitons in the media communications society underscores their significance in nonlinear optics. In the system of single wave-based interchanges, optical pulse generators, fiber-optic amplifiers, and many others, solitons models are extensively useful. Examining the motion of solitons through nonlinear optical fibers, extreme laser radiation into plasmas, and the hypothesis of optical solitons are among the most interesting topics [9]. The scholars have adopted a variety of nonlinear models to predict and comprehend the nature of soliton waves.
Researchers have developed a number of approaches and methods to deal with these problems and get solutions in a wide range of systems. Among the most well-known and widely used techniques developed recently are: Darboux transformation [10], the enhanced modified extended tanh expansion method [11], the advanced F-expansion function approach [12], the truncated Painlevé approach [13], the modified F-expansion method [14], the modified simple equation method [15], the iterative transform method [16], Lie classical approach [17], the new sub equation approach [18], Adomian decomposition technique [19], the simplest equation technique [20], the
\tan ({\phi \over 2}) technique [21], the multiple exp-function approach [22], Bernoulli
{{{G^\prime }} \over G}-expansion method [23],
\left( {{{{G^\prime }} \over G}} \right)-expansion method [24], the tanh-coth method [25], the the inverse scattering approach [26], the Bäcklund transformation [27], Riccati equation mapping technique [28], bifurcation analysis [29, 30] and so on [31–36].
Moreover, the model under consideration has not been investigated using these novel sophisticated methodologies in the existing literature. So, this paper has the aim to study various kinds of soliton solutions of the M-fractional nonlinear ZSE by applying the new integration methods known as modified generalized Riccati equation mapping method (MGREMM) [37], KMM [38] and multivariate generalized exponential rational integral function method (MGERIFM) [39]. These methods can be employed to obtain novel and exact solutions, including exponential, trigonometric, and rational functions. The proposed solutions will markedly improve the comprehension of diverse physical processes in associated domains.
The rest of the article is organized as follows: The definition about the new truncated M-fractional derivative of
\hbar is presented in Section 2. In Section 3, the applications of methods together with graphs are presented in Section 3. The conclusion obtained in this paper is reported in Section 4.
3
Applications
In this section, we apply the powerful methods such as MGREMM, KMM, and MGERIFM to obtain desired solutions for the nonlinear ZSE [41–43] in truncated M-fractional derivative given as:
2
D_{M,xt}^{2\varepsilon,\;\beta }u + p{e^u} + q{e^{ - u}} + r{e^{ - 2u}} = 0,
where u = u(x,t) is an unknown function, while the parameters p, q, r are real constants. Eq.(2) transforms to sinh-Gordon equation by taking r = 0, while for q = r = 0 it transforms to the Liouville equation. Similarly, for q = 0, Eq.(2) transforms to the Dodd-Bullough-Mikhailov equation and for p = 0, q = –1, r = 1, it converts to the form of Tzitzeica-Dodd-Bullough equation. Moreover, the subscripts x and t are the partial derivatives and
{\cal D}_M^{,\;\varsigma } denote the M-fractional derivative with β ∈ (0,1) and ς > 0. Furthermore, the suggested model has been examined in the literature from different perspectives. In [41], various solitary wave solutions have been extracted by using tanh method, while a variety of new exact solutions have recovered in [42] by applying
\left( {{1 \over {{G^\prime }}}} \right) expansion method,
\left( {{{{G^\prime }} \over G}} \right) and
\left( {{1 \over G}} \right) methods. In [43], the existence of soliton solutions are derived by employing ansatz approach.
In this work, we study the exact solutions of the proposed model using the suggested techniques with truncated M-fractional derivatives. First of all, let’s consider the following transformation as:
3
u(x,t) = \Phi (\xi ),\xi = {{\Gamma (\beta + 1)} \over \varepsilon }\left( {{x^\varepsilon } - c{t^\varepsilon }} \right),
where c is the wave speed. On manipulating the Eq.(3) into Eq.(2) provides
4
p{e^u} + q{e^{ - u}} + r{e^{ - 2u}} - c{u^{\prime \prime }} = 0.
Furthermore, for solving the Eq.(4), the following assumption is used as:
5
v = {e^u}{\rm{or }}u = \ln v.
Manipulating Eq.(5) into Eq.(4), we get
6
c\left( {{{\left( {{v^\prime }} \right)}^2} - v{v^{\prime \prime }}} \right) + p{v^3} + qv + r = 0.
Now, applying the homogeneous balance principle between the terms v3 and vv″ in Eq.(6) gives n = 2.
3.1
Application of the MGREMM
The solution for MGREMM [37] is expressed as:
7
v(\xi ) = {\phi _0} + \sum\limits_{r = 1}^n {{\phi _r}} {\Omega ^r}(\xi ) + \sum\limits_{r = 1}^n {{\psi _r}} (\xi ){\left( {{{{\Omega ^\prime }(\xi )} \over {\Omega (\xi )}}} \right)^r}.
For n = 2, we get
8
v(\xi ) = {\phi _0} + {\phi _1}\Omega (\xi ) + {\phi _2}{\left( {\Omega (\xi )} \right)^2} + {\psi _1}(\xi ){{\Omega '(\xi )} \over {\Omega (\xi )}} + {\psi _2}(\xi ){\left( {{{\Omega '(\xi )} \over {\Omega (\xi )}}} \right)^2},
and
v(\xi ) = {\phi _0} + {\phi _1}\Omega (\xi ) + {\phi _2}{\left( {\Omega (\xi )} \right)^2} + {\psi _1}(\xi ){{\Omega '(\xi )} \over {\Omega (\xi )}} + {\psi _2}(\xi ){\left( {{{\Omega '(\xi )} \over {\Omega (\xi )}}} \right)^2},. On putting Eq.(8) into Eq.(6), the general solutions are given as: (I): When
\Delta = \delta _1^2 - 4{\delta _0}{\delta _2} > 0, δ1 δ2 ≠ 0, δ0 δ2 ≠ 0 and
{\phi _1} = - {\delta _1}{\delta _2}{\psi _2},p = {{2c} \over {{\psi _2}}},
q = {{c\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\left( {\left( {\delta _1^2 - 10{\delta _0}{\delta _2}} \right){\psi _2} - 6{\phi _0}} \right)} \over {{\psi _2}}},
r = {{c{{\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)}^2}\left( {4{\phi _0} - \left( {\delta _1^2 - 8{\delta _0}{\delta _2}} \right){\psi _2}} \right)} \over {{\psi _2}}},
{\phi _2} = - \delta _2^2{\psi _2},{\psi _1} = - {\delta _1}{\psi _2}, the soliton solutions are
9
{u_1}(x,t) = \ln \left( {{{{\delta _0}{\delta _2}{\psi _2}{\rm{sec}}{{\rm{h}}^2}\left( {{{\sqrt \Delta \xi } \over 2}} \right)\left( {{\delta _1}\sqrt \Delta \sinh \left( {\sqrt \Delta \xi } \right) + \left( {\delta _1^2 - 2{\delta _0}{\delta _2}} \right)\cosh \left( {\sqrt \Delta \xi } \right) - \delta _1^2 + 6{\delta _0}{\delta _2}} \right)} \over {{{\left( {{\delta _1} + \sqrt \Delta \tanh \left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right)}^2}}} + {\phi _0}} \right),
10
{u_2}(x,t) = \ln \left( {{{{\delta _0}{\delta _2}{\psi _2}{\rm{csc}}{{\rm{h}}^2}\left( {{{\sqrt \Delta \xi } \over 2}} \right)\left( {{\delta _1}\sqrt \Delta \sinh \left( {\sqrt \Delta \xi } \right) + \left( {\delta _1^2 - 2{\delta _0}{\delta _2}} \right)\cosh \left( {\sqrt \Delta \xi } \right) + \delta _1^2 - 6{\delta _0}{\delta _2}} \right)} \over {{{\left( {{\delta _1} + \Delta \coth \left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right)}^2}}} + {\phi _0}} \right),
11
{u_3}(x,t) = \ln \left( {{\phi _0} + {\delta _0}{\delta _2}{\psi _2}\left( {1 + {{i\left( {\delta _1^2 - 4{\delta _0}{\delta _2}} \right)} \over {\delta _1^2\sinh \left( {\sqrt \Delta \xi } \right) - 2{\delta _0}{\delta _2}\left( {\sinh \left( {\sqrt \Delta \xi } \right) + i} \right) + {\delta _1}\sqrt \Delta \cosh \left( {\sqrt \Delta \xi } \right)}}} \right)} \right),
12
{u_4}(x,t) = \ln \left( {{{{\delta _1}\sqrt \Delta \left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\sinh \left( {\sqrt \Delta \xi } \right) + \left( {\delta _1^2 - 2{\delta _0}{\delta _2}} \right)\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\cosh \left( {\sqrt \Delta \xi } \right) + {\delta _0}{\delta _2}\left( {\left( {\delta _1^2 - 6{\delta _0}{\delta _2}} \right){\psi _2} - 2{\phi _0}} \right)} \over {{{\left( {{\delta _1}\sinh \left( {{{\sqrt \Delta \xi } \over 2}} \right) + \sqrt \Delta \cosh \left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right)}^2}}}} \right).
When
{\phi _1} = {{2c{\delta _1}{\delta _2}} \over p},
q = - {{\left( {c\delta _1^2 + 2c{\delta _0}{\delta _2} - 3p{\phi _0}} \right)\left( {2c{\delta _0}{\delta _2} - p{\phi _0}} \right)} \over p},
r = {{{{\left( {p{\phi _0} - 2c{\delta _0}{\delta _2}} \right)}^2}\left( {2p{\phi _0} - c\delta _1^2} \right)} \over {{p^2}}}, ψ2 = 0,
{\phi _2} = {{2c\delta _2^2} \over p}, ψ1 = 0, we have the solitary wave solutions:
13
{u_5}(x,t) = \ln \left( {{{ - 4c{\delta _0}{\delta _2} + c\Delta {\rm{csc}}{{\rm{h}}^2}\left( {{{\sqrt \Delta \xi } \over 2}} \right) + 2p{\phi _0}} \over {2p}}} \right),
14
{u_6}(x,t) = \ln \left( {{1 \over {p{{(d + e s i n h (\sqrt \Delta \xi ))}^2}}}\left( {c\delta _1^2e(e - d\sinh (\sqrt \Delta \xi )) - c\sqrt \Delta e\sqrt {\Delta \left( {{d^2} + {e^2}} \right)} \cosh (\sqrt \Delta \xi )} \right.} \right.\left. {\left. {p{\phi _0}{{(d + e\sinh (\sqrt \Delta \xi ))}^2} - c{\delta _0}{\delta _2}\left( {2{d^2} + {e^2}\cosh (2\sqrt \Delta \xi ) + 3{e^2}} \right)} \right)} \right),
15
{u_7}(x,t) = \ln \left( { - {{4c{\delta _0}{\delta _1}{\delta _2}} \over {{\delta _1}p - \sqrt \Delta p\tanh \left( {{{\sqrt \Delta \xi } \over 2}} \right)}} + {{4c\delta _0^2\delta _2^2\left( {\cosh \left( {\sqrt \Delta \xi } \right) + 1} \right)} \over {p{{\left( {{\delta _1}\cosh \left( {{{\sqrt \Delta \xi } \over 2}} \right) - \sqrt \Delta \sinh \left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right)}^2}}} + {\phi _0}} \right).
When ϕ1 = –δ1 δ2 ψ2,
q = - {1 \over 2}p\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\left( {6{\phi _0} - \left( {\delta _1^2 - 10{\delta _0}{\delta _2}} \right){\psi _2}} \right),
r = {1 \over 2}p{\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)^2}\left( {4{\phi _0} - \left( {\delta _1^2 - 8{\delta _0}{\delta _2}} \right){\psi _2}} \right),
c = {{p{\psi _2}} \over 2},
{\phi _2} = - \delta _2^2{\psi _2}, ψ1 = –δ1 ψ2, we have the following solutions:
16
{u_8}(x,t) = \ln \left( {{1 \over 4}{\psi _2}\left( {4{\delta _0}{\delta _2} + \Delta {\rm{csc}}{{\rm{h}}^2}\left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right) + {\phi _0}} \right),
17
{u_9}(x,t) = \ln \left( {{\delta _0}{\delta _2}{\psi _2} - {{\Delta {\psi _2}} \over {2 + 2\sinh \left( {\sqrt \Delta \xi } \right)}} + {\phi _0}} \right),
18
{u_{10}}(x,t) = \ln \left( {{1 \over 4}{\psi _2}\left( {4{\delta _0}{\delta _2} + \Delta {\rm{csc}}{{\rm{h}}^2}\left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right) + {\phi _0}} \right).
(II): When
\Delta = \delta _1^2 - 4{\delta _0}{\delta _2} < 0,\;{\delta _1}{\delta _2} \ne 0,\;{\delta _0}{\delta _2} \ne 0 and
{\phi _1} = - {\delta _1}{\delta _2}{\psi _2},\;q = - {1 \over 2}p\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\left( {6{\phi _0} - \left( {\delta _1^2 - 10{\delta _0}{\delta _2}} \right){\psi _2}} \right),
r = {1 \over 2}p{\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)^2}\left( {4{\phi _0} - \left( {\delta _1^2 - 8{\delta _0}{\delta _2}} \right){\psi _2}} \right),
c = {{p{\psi _2}} \over 2},
{\phi _2} = - \delta _2^2{\psi _2}, ψ1 = –δ1 ψ2, we have the following periodic solutions:
19
{u_{11}}(x,t) = \ln \left( {{{{\phi _0}{{\left( {\sqrt { - \Delta } \tan \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right) - {\delta _1}} \right)}^2}} \over {4{\delta _0}{\delta _2}}} + {{{\delta _1}{\phi _0}\left( {\sqrt { - \Delta } \tan \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right) - {\delta _1}} \right)} \over {2{\delta _0}{\delta _2}}} + {\phi _0}} \right),
20
{u_{12}}(x,t) = \ln \left( {{{{\delta _0}{\delta _2}{\psi _2}{{\csc }^2}\left( {{{\sqrt { - \Delta } \xi } \over 2}} \right)\left( {{\delta _1}\sqrt { - \Delta } \sin \left( {\sqrt { - \Delta } \xi } \right) - \delta _1^2 + 6{\delta _0}{\delta _2} - \Delta \cos \left( {\sqrt { - \Delta } \xi } \right)} \right)} \over {{{\left( {{\delta _1} + \sqrt { - \Delta } \cot \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right)} \right)}^2}}} + {\phi _0}} \right),
21
{u_{13}}(x,t) = \ln \left( {{{{\delta _0}{\delta _1}{\delta _2}\sqrt { - \Delta } {\psi _2}\cosh (\sqrt \Delta \xi ) + {\delta _1}\sqrt { - \Delta } {\phi _0}\cos (\sqrt { - \Delta } \xi ) + \sin (\sqrt { - \Delta } \xi )} \over {\left( {\delta _1^2 - 2{\delta _0}{\delta _2}} \right)\sin (\sqrt { - \Delta } \xi ) + {\delta _1}\sqrt { - \Delta } \cos (\sqrt { - \Delta } \xi ) - 2{\delta _0}{\delta _2}}}} \right.\left. {\left( {\delta _1^2 - 2{\delta _0}{\delta _2}} \right)\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right) + {\delta _0}{\delta _2}\left( {\left( {\delta _1^2 - 6{\delta _0}{\delta _2}} \right){\psi _2} - 2{\phi _0}} \right)} \right),
22
{u_{14}}(x,t) = \ln \left( {{{{\delta _1}\sqrt \Delta \left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\sin \left( {\sqrt { - \Delta } \xi } \right) + \left( {\delta _1^2 - 2{\delta _0}{\delta _2}} \right)\left( {{\delta _0}{\delta _2}{\psi _2} + {\phi _0}} \right)\cosh \left( {\sqrt \Delta \xi } \right) + {\delta _0}{\delta _2}\left( {\left( {\delta _1^2 - 6{\delta _0}{\delta _2}} \right){\psi _2} - 2{\phi _0}} \right)} \over {{{\left( {{\delta _1}\sin \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right) + \sqrt \Delta \cosh \left( {{{\sqrt \Delta \xi } \over 2}} \right)} \right)}^2}}}} \right).
When
{\phi _1} = {{2c{\delta _1}{\delta _2}} \over p},
q = - {{\left( {c\delta _1^2 + 2c{\delta _0}{\delta _2} - 3p{\phi _0}} \right)\left( {2c{\delta _0}{\delta _2} - p{\phi _0}} \right)} \over p},
r = {{{{\left( {p{\phi _0} - 2c{\delta _0}{\delta _2}} \right)}^2}\left( {2p{\phi _0} - c\delta _1^2} \right)} \over {{p^2}}}, ψ2 = 0,
{\phi _2} = {{2c\delta _2^2} \over p}, ψ1 = 0, we have:
23
{u_{15}}(x,t) = \ln \left( { - {{2c{\delta _0}{\delta _2}} \over p} + {{c\Delta } \over {p\left( {\cos \left( {\sqrt { - \Delta } \xi } \right) - 1} \right)}} + {\phi _0}} \right),
24
{u_{16}}(x,t) = \ln \left( {{1 \over {p{{(d + e s i n (\sqrt { - \Delta } \xi ))}^2}}}\left( { - c\delta _1^2e(d\sin (\sqrt { - \Delta } \xi ) + e) - c\sqrt { - \Delta } e\sqrt {\Delta (d - e)(d + e)} \cos (\sqrt { - \Delta } \xi )} \right.} \right.\left. {\left. { + c{\delta _0}{\delta _2}\left( { - 2{d^2} + {e^2}\cosh (2\sqrt \Delta \xi ) + 3{e^2}} \right) + {1 \over 2}p{\phi _0}\left( {2{d^2} + 4de\sin (\sqrt { - \Delta \xi } ) - {e^2}\cos (2\sqrt { - \Delta \xi } ) + {e^2}} \right)} \right)} \right),
25
{u_{17}}(x,t) = \ln \left( { - {{4c{\delta _0}{\delta _1}{\delta _2}} \over {{\delta _1}p + \sqrt { - \Delta } p\tan \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right)}} + {{4c\delta _0^2\delta _2^2\left( {\cos \left( {\sqrt { - \Delta } \xi } \right) + 1} \right)} \over {p{{\left( {{\delta _1}\cos \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right) + \sqrt { - \Delta } \sin \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right)} \right)}^2}}} + {\phi _0}} \right),
26
{u_{18}}(x,t) = \ln \left( { - {{4c{\delta _0}{\delta _1}{\delta _2}} \over {{\delta _1}p - \sqrt { - \Delta } p\cot \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right)}} - {{4c\delta _0^2\delta _2^2\left( {\cos \left( {\sqrt { - \Delta } \xi } \right) - 1} \right)} \over {p{{\left( {{\delta _1}\sin \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right) - \sqrt { - \Delta } \cos \left( {{{\sqrt { - \Delta } \xi } \over 2}} \right)} \right)}^2}}} + {\phi _0}} \right),
we have:where ξ is expressed in Eq.(3). All the obtained solutions are written in the form of Eq.(5), such that u = In v. We simulate the wave behaviours of the solutions of the governing model.
3.2
Application of the KMM
For n = 2, the general solution forms in KMM [38] can be described as
27
v(\xi ) = {\rho _0} + {\rho _1}\Omega (\xi ) + {\rho _2}{\left( {\Omega (\xi )} \right)^2},
with
28
\Omega '(\xi ) = \sqrt {{\gamma _1}\Omega {{(\xi )}^4} + {\gamma _2}\Omega {{(\xi )}^3} + {\gamma _3}\Omega {{(\xi )}^2} + {\gamma _4}\Omega (\xi ) + {\gamma _5}}.
The following solutions are obtained by employing (27) along with (28) in (6):
• Case-1 For
\Omega '(\xi ) = \sqrt {{\gamma _1}\Omega {{(\xi )}^4} + {\gamma _2}\Omega {{(\xi )}^3} + {\gamma _3}\Omega {{(\xi )}^2} + {\gamma _4}\Omega (\xi ) + {\gamma _5}}. offers
{\gamma _5} = {{{{\left( {4{\gamma _1}{\gamma _3} - \gamma _2^2} \right)}^2}} \over {64\gamma _1^3}},\;{\gamma _4} = {{{\gamma _2}\left( {4{\gamma _1}{\gamma _3} - \gamma _2^2} \right)} \over {8\gamma _1^2}},
{\rho _2} = {{2{\gamma _1}{\rho _1}} \over {{\gamma _2}}},\;p = {{c{\gamma _2}} \over {{\rho _1}}},\;r = {{c\left( {8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \right){{\left( {\gamma _2^2{\rho _1} + 4{\gamma _1}{\gamma _2}{\rho _0} - 4{\gamma _1}{\gamma _3}{\rho _1}} \right)}^2}} \over {64\gamma _1^3{\gamma _2}{\rho _1}}}. As a result we have the following solutions:
When γ1 > 0 and
8{\gamma _1}{\gamma _3} - 3\gamma _2^2 < 0, we get the solutions as follows:
The dark type soliton solution
29
{u_1}(x,t) = \ln \left( {{{{{\left( {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \right){\rho _1}{{\tanh }^2}\left( {{{\sqrt {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \Gamma (\beta + 1)\left( {{x^} - c{t^}} \right)} \over {4\sqrt {{\gamma _1}} }}} \right)} \over {{\gamma _2}}} + 8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \over {8{\gamma _1}}}} \right).
The singular soliton solution
30
{u_2} = \ln \left( { - {{{\gamma _3}{\rho _1}{{\coth }^2}\left( {{{\sqrt {{\gamma _1}\left( {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \right)} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {4{\gamma _1}\varepsilon }}} \right)} \over {{\gamma _2}}} + {{{\gamma _2}{\rho _1}\left( {3{{\coth }^2}\left( {{{\sqrt {{\gamma _1}\left( {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \right)} \Gamma (\beta + 1)\left( {{x^{\rm{\varepsilon }}} - c{t^{\rm{\varepsilon }}}} \right)} \over {4{\gamma _1}\varepsilon }}} \right) - 1} \right)} \over {8{\gamma _1}}} + {\rho _0}} \right).
When γ1 > 0 and
8{\gamma _1}{\gamma _3} - 3\gamma _2^2 > 0, we get the periodic solutions as follows:
31
{u_3}(x,t) = \ln \left( {{{{{\left( {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \right){\rho _1}{{\tan }^2}\left( {{{\sqrt {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {4\sqrt {{\gamma _1}} \varepsilon }}} \right)} \over {{\gamma _2}}} + 8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \over {8{\gamma _1}}}} \right),
32
{u_4}(x,t) = \ln \left( {{{{\gamma _3}{\rho _1}{{\cot }^2}\left( {{{\sqrt {{\gamma _1}\left( {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \right)} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {4{\gamma _1}\varepsilon }}} \right)} \over {{\gamma _2}}} - {{{\gamma _2}{\rho _1}\left( {3{{\cot }^2}\left( {{{\sqrt {{\gamma _1}\left( {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \right)} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {4{\gamma _1}\varepsilon }}} \right) + 1} \right)} \over {8{\gamma _1}}} + {\rho _0}} \right).
• Case-2 For
{\gamma _5} = {{\gamma _2^2\left( {16{\gamma _1}{\gamma _3} - 5\gamma _2^2} \right)} \over {256\gamma _1^3}},\;{\gamma _4} = {{{\gamma _2}\left( {4{\gamma _1}{\gamma _3} - \gamma _2^2} \right)} \over {8\gamma _1^2}} offers
{\rho _2} = {{2{\gamma _1}{\rho _1}} \over {{\gamma _2}}},\;p = {{c{\gamma _2}} \over {{\rho _1}}},
r = - {{c{{\left( {8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \right)}^2}\left( { - 5\gamma _2^2{\rho _1} - 8{\gamma _1}{\gamma _2}{\rho _0} + 16{\gamma _1}{\gamma _3}{\rho _1}} \right)} \over {256\gamma _1^3{\rho _1}}},
q = {{c\left( {8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \right)\left( { - 9\gamma _2^2{\rho _1} - 24{\gamma _1}{\gamma _2}{\rho _0} + 32{\gamma _1}{\gamma _3}{\rho _1}} \right)} \over {64\gamma _1^2{\rho _1}}}.. As a result we have the following solutions:
When γ1 < 0 and
8{\gamma _1}{\gamma _3} - 3\gamma _2^2 < 0, we get: The bright soliton solution
33
{u_5}(x,t) = \ln \left( {{{{{2\left( {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \right){\rho _1}{\rm{sec}}{{\rm{h}}^2}\left( {{{\sqrt {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {2\sqrt 2 \sqrt {{\gamma _1}} \varepsilon }}} \right)} \over {{\gamma _2}}} + 8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \over {8{\gamma _1}}}} \right).
When γ > 0 and
8{\gamma _1}{\gamma _3} - 3\gamma _2^2 > 0, we get the hyperbolic solution as follows:
34
{u_6}(x,t) = \ln \left( {{{{{2\left( {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \right){\rho _1}{\rm{csc}}{{\rm{h}}^2}\left( {{{\sqrt {8{\gamma _1}{\gamma _3} - 3\gamma _2^2} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {2\sqrt 2 \sqrt {{\gamma _1}} }}} \right)} \over {{\gamma _2}}} + 8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \over {8{\gamma _1}}}} \right).
When γ > 0 and
8{\gamma _1}{\gamma _3} - 3\gamma _2^2 < 0, we get the periodic solutions as follows:
35
{u_7}(x,t) = \ln \left( {{{{{2\left( {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \right){\rho _1}{{\sec }^2}\left( {{{\sqrt {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {2\sqrt 2 {{\sqrt {{\gamma _1}} }^\varepsilon }}}} \right)} \over {{\gamma _2}}} + 8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \over {8{\gamma _1}}}} \right),
36
{u_8}(x,t) = \ln \left( {{{{{2\left( {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \right){\rho _1}{{\csc }^2}\left( {{{\sqrt {3\gamma _2^2 - 8{\gamma _1}{\gamma _3}} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {2\sqrt 2 \sqrt {{\gamma _1}} \varepsilon }}} \right)} \over {{\gamma _2}}} + 8{\gamma _1}{\rho _0} - {\gamma _2}{\rho _1}} \over {8{\gamma _1}}}} \right).
• Case-3 For γ2 = 0, γ4 = 0, γ5 = 0 and γ3 > 0, offers ρ1 = 0,
c = {{p{\rho _2}} \over {2{\gamma _1}}},\;r = {{2\left( {{\gamma _1}p\rho _0^3 - {\gamma _3}p\rho _0^2{\rho _2}} \right)} \over {{\gamma _1}}},\;q = {{2{\gamma _3}p{\rho _0}{\rho _2} - 3{\gamma _1}p\rho _0^2} \over {{\gamma _1}}}. As a result we have the following exponential solution:
37
{u_9}(x,t) = \ln \left( {{{16\gamma _3^2{\rho ^2}{\rho _2}{e^{{{2\sqrt {{\gamma _3}} \Gamma (\beta + 1)\left( {{x^\varepsilon } - {{p{\rho _2}{t^\varepsilon }} \over {2{\gamma _1}}}} \right)} \over \varepsilon }}}} \over {{{\left( {{\gamma _1}{\gamma _3} - 4{\rho ^2}{e^{{{2\sqrt {{\gamma _3}} \Gamma (\beta + 1)\left( {{x^\varepsilon } - {{p{\rho _2}{t^\varepsilon }} \over {2{\gamma _1}}}} \right)} \over \varepsilon }}}} \right)}^2}}} + {\rho _0}} \right).
Taking
{\gamma _1} = - {{4{\rho ^2}} \over {{\gamma _3}}} in Eq. (37), we have bright soliton solution
38
{u_{10}}(x,t) = \ln \left( {{{\gamma _3^2{\rho _2}{\rm{sec}}{{\rm{h}}^2}\left( {{{\sqrt {{\gamma _3}} \Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over \varepsilon }} \right)} \over {4{\rho ^2}}} + {\rho _0}} \right).
Similarly, taking
{\gamma _1} = {{4{\rho ^2}} \over {{\gamma _3}}} in Eq. (37), we have
39
{u_{11}}(x,t) = \ln \left( {{{\gamma _3^2{\rho _2}{{{\mathop{\rm csch}\nolimits} }^2}\left( {{{\sqrt {{\gamma _3}\Gamma } (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over \varepsilon }} \right)} \over {4{\rho ^2}}} + {\rho _0}} \right).
Remark:
All the obtained solutions are written in the form of Eq. (5), such that u = ln v.
3.3
Application of the MGERIFM
The solution via MGERIFM [39] is described as:
40
v(\xi ) = {c_0} + \sum\limits_{r = 1}^n {{c_i}} {\left( {\underbrace {\int\!\!\!\int \cdots \smallint }_rv(\xi )d\xi d\xi \cdots d\xi } \right)^r} + \sum\limits_{r = 1}^n {{d_r}} {\left( {\underbrace {\int\!\!\!\int \cdots \smallint }_rv(\xi )d\xi d\xi \cdots d\xi } \right)^{ - r}}.
The solution to equation (40) for n = 2 is as follows:
41
v(\xi ) = {c_0} + {c_1}\int \phi (\xi )d\xi + {d_1}{\left( {\int \phi (\xi )d\xi } \right)^{ - 1}} + {c_2}{\left( {\int \phi (\xi )d\xi } \right)^2} + {d_2}{\left( {\int \phi (\xi )d\xi } \right)^{ - 2}},
where v(ξ) is defined by
42
\phi (\xi ) = {{{\tau _1}{e^{\xi {s_1}}} + {\tau _2}{e^{\xi {s_2}}}} \over {{\tau _3}{e^{\xi {s_3}}} + {\tau _4}{e^{\xi {s_4}}}}}.
Moreover, we proceed as:
• Case-1: Choosing [τ1, τ2, τ3, τ4 = [–i, –i, –i, –i] and [s1, s2, s3, s4] = [1, –1,0,0], Eq. (42) takes the following form
43
\phi (\xi ) = \cosh (\xi ).
Inserting Eq. (43) into Eq. (41), implies that
44
v(\xi ) = {c_0} + {c_1}\sinh (\xi ) + {c_2}{\sinh ^2}(\xi ) + {{{d_1}} \over {\sinh (\xi )}} + {{{d_2}} \over {{{\sinh }^2}(\xi )}}.
The solutions are as follows when Eq. (44) is inserted into Eq. (6):
For d1 = 0, c1 = 0, c2 = 0,
c = {{{d_2}p} \over 2},
r = 2c_0^2p\left( {{c_0} - {d_2}} \right), q = c0p (2d2 – 3c0), we have:
45
{u_1}(x,t) = \ln \left( {{{2c{{{\mathop{\rm csch}\nolimits} }^2}\left( {{{\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over \varepsilon }} \right)} \over p} + {c_0}} \right).
• Case-2: Let [τ1, τ2, τ3, τ4] = [2i, –2i, 4i, 4i] and
\left[ {{s_1},{s_2},{s_3},{s_4}} \right] = \left[ {{1 \over 2}, - {1 \over 2},0,0} \right], Eq. (42) transforms to sine hyperbolic function
46
\phi (\xi ) = {1 \over 2}\sinh \left( {{\xi \over 2}} \right).
Plugging Eq. (46) into Eq. (41), offers
47
v(\xi ) = {c_0} + {c_1}\cosh \left( {{\xi \over 2}} \right) + {c_2}{\cosh ^2}\left( {{\xi \over 2}} \right) + {{{d_1}} \over {\cosh \left( {{\xi \over 2}} \right)}} + {{{d_2}} \over {{{\cosh }^2}\left( {{\xi \over 2}} \right)}}.
Applying Eq. (47) to Eq. (6), we get:
For d1 = 0, c1 = 0, c2 = 0, c = –2d2p,
r = 2c_0^2p\left( {{c_0} + {d_2}} \right), q = c0(–p) (3c0 + 2d2), we get the solution as follows:
48
{u_2}(x,t) = \ln \left( {{c_0} - {{c{{{\mathop{\rm sech}\nolimits} }^2}\left( {{{\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {2\varepsilon }}} \right)} \over {2p}}} \right).
• Case-3: Taking [τ1, τ2, τ3, τ4] = [1, –1, i, i] and [s1, s2, s3, s4] = [i, –i, 0, 0], Eq. (42) converts to the periodic function
49
\phi (\xi ) = \sin (\xi )
Putting Eq. (49) into Eq. (41), gives
50
v(\xi ) = {c_0} + {c_2}{( - \cos (\xi ))^2} + {c_1}( - \cos (\xi )) + {{{d_1}} \over { - \cos (\xi )}} + {{{d_2}} \over {{{( - \cos (\xi ))}^2}}}.
Incorporating Eq. (50) in Eq. (6), we have:
For d1 = 0, c1 = 0, c2 = 0,
c = {{{d_2}p} \over 2},
r = 2c_0^2p\left( {{c_0} + {d_2}} \right), q = c0(–p) (3c0 + 2d2), we obtain:
51
{u_3}(x,t) = \ln \left( {{{2c{{\sec }^2}\left( {{{\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over \varepsilon }} \right)} \over p} + {c_0}} \right).
• Case-4: Choosing the parameters [τ1, τ2, τ3, τ4] = [1,1,1,1] and [s1, s2, s3, s4] = [i, –i, 0, 0], Eq. (42) offers
52
\phi (\xi ) = \cos (\xi ).
Manipulating Eq. (52) and Eq. (41), we have
53
v(\xi ) = {c_0} + {c_1}\sin (\xi ) + {c_2}{\sin ^2}(\xi ) + {{{d_1}} \over {\sin (\xi )}} + {{{d_2}} \over {{{\sin }^2}(\xi )}}.
Plugging Eq. (53) into Eq. (6), give the following solutions:
When d1 = 0, c1 = 0, c2 = 0,
c = {{{d_2}p} \over 2}, q = c0(–p) (3c0 + 2d2),
r = 2c_0^2p\left( {{c_0} + {d_2}} \right), we get:
54
{u_4}(x,t) = \ln \left( {{{2c{{\csc }^2}\left( {{{\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over \varepsilon }} \right)} \over p} + {c_0}} \right).
• Case-5: Taking the parameters [τ1, τ2, τ3, τ4] = [2,2,2,2] and [s1, s2,
\left[ {{s_1},{s_2},{s_3},{s_4}} \right] = \left[ {{2 \over 5},{2 \over 5},0,0} \right], Eq. (42) gives
55
\phi (\xi ) = {e^{{{2\xi } \over 5}}}.
Manipulating Eq. (55) and Eq. (41), we have
56
v(\xi ) = {c_0} + {1 \over 2}{c_1}\left( {5{e^{{{2\xi } \over 5}}}} \right) + {c_2}{\left( {{5 \over 2}{e^{{{2\xi } \over 5}}}} \right)^2} + {{{d_1}} \over {{5 \over 2}{e^{{{2\xi } \over 5}}}}} + {{{d_2}} \over {{{\left( {{5 \over 2}{e^{{{2\xi } \over 5}}}} \right)}^2}}}.
Inserting Eq. (56) into Eq. (6), give the following solution:
When d1 = 0, c1 = 0, p = 0,
r = {1 \over {25}}( - 16)c\left( {c_0^2 - 4{c_2}{d_2}} \right),\;q = {{16c{c_0}} \over {25}}, we get:
57
{u_5}(x,t) = \ln \left( {{4 \over {25}}{d_2}{e^{ - {{4\Gamma (\beta + 1)\left( {{x^\varepsilon } - {\alpha ^\varepsilon }} \right)} \over {5\varepsilon }}}} + {{25} \over 4}{c_2}{e^{\left. {{{4\Gamma (\beta + 1)\left( {{x^\varepsilon } - {\alpha ^\varepsilon }} \right)} \over {5\varepsilon }}} \right)}} + {c_0}} \right).
Next, the hyperbolic solution is written as
58
{u_6}(x,t) = \ln \left( {{{25} \over 4}{c_2}\left( {\cosh \left( {{{4\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {5\varepsilon }}} \right) + \sinh \left( {{{4\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {5\varepsilon }}} \right)} \right) + {c_0}} \right.\left. { + {4 \over {25}}{d_2}\left( {\cosh \left( {{{4\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {5\varepsilon }}} \right) - \sinh \left( {{{4\Gamma (\beta + 1)\left( {{x^\varepsilon } - c{t^\varepsilon }} \right)} \over {5\varepsilon }}} \right)} \right)} \right).
Remark:
All the obtained solutions are written in the form of Eq. (5), such that u = lnv.