Applications of some transformations for several variable-coefficient nonlinear evolution equations from plasma physics,arterial mechanics,nonlinear optics and Bose–Einstein condensates

Variable-coefficient nonlinear evolution equations have occurred in such fields as plasma physics, arterial mechanics, nonlinear optics and Bose–Einstein condensates. This paper is devoted to giving some transformations to convert the original nonlinear evolution equations, e.g., the variable-coefficient nonlinear Schrödinger, generalized Gardner and variable-coefficient Sawada–Kotera equations to simpler ones or even constant-coefficient ones. Based on some constraints, we simplify the original equations and derive the associated chirp solitons, Lax pairs, and Bäcklund transformations from the original equations by means of the aforementioned transformations.     

Comment on: “Some exact solutions of KdV equation with variable coefficients” [Commun Nonlinear Sci Numer Simul 2011;16:1783–86]

It is shown that in the commented paper the exact solutions were found only for those variable-coefficient KdV equations which are reduced to the classical (constant-coefficient) KdV equation by point transformations, and these solutions are preimages of well-known traveling wave solutions of the KdV equation with respect to the corresponding point transformations. The equivalence-based approach suggested in [Popovych RO, Vaneeva OO. More common errors in finding exact solutions of nonlinear differential equations: Part I. Commun Nonlinear Sci Numer Simul 2010;15:3887–99] allows one to obtain more results. This disproves the relevance of the extended mapping transformation method for the class of equations under consideration.     

Analytic N-solitary-wave solution of a variable-coefficient Gardner equation from fluid dynamics and plasma physics

In this paper, the investigation is focused on a variable-coefficient Gardner equation with quadric and cubic nonlinearities from fluid dynamics and plasma physics. Using the Hirota bilinear method, the one-, two- and three-solitary-wave solutions of the variable-coefficient Gardner equation are derived, and the analytic N-solitary-wave solution is presented for the first time in this paper with the aid of symbolic computation. Figures are plotted to illustrate the solutions obtained in this paper.     

Symmetry classification of the Gardner equation with time-dependent coefficients arising in stratified fluids

We perform symmetry classification of a variable-coefficient combined KdV-mKdV equation. That is, the equation combining the Korteweg-de Vries (KdV) and modified Korteweg-de Vries (mKdV) equations, or also known as the Gardner equation. The direct method of group classification is utilized to specify the forms of these time-dependent coefficients.     

General propagation lattice Boltzmann model for a variable-coefficient compound KdV-Burgers equation

In this paper, a general propagation lattice Boltzmann model for a variable-coefficient compound Korteweg-de Vries-Burgers (vc-cKdVB) equation is investigated through selecting equilibrium distribution function and adding a compensation function, which can provide some more realistic models than their constant-coefficient counterparts in fluids or plasmas. Chapman–Enskog analysis shows that the vc-gKdVB equation can be recovered correctly from the present model. Numerical simulations in different situations of this equation are conducted, including the propagation and interaction of the bell-type, kink-type and periodic-depression solitons and the evolution of the shock-wave solutions. It is found that the numerical results match well with the analytical solutions, which demonstrates that the current lattice Boltzmann model is a satisfactory and efficient algorithm. In addition, it is also shown the present model could be more stable and more accurate than the standard lattice Bhatnagar–Gross–Krook model through adjusting the two free parameters introduced into the propagation step.     

Lattice Boltzmann model for a generalized Gardner equation with time-dependent variable coefficients

In this paper, lattice Boltzmann model for a generalized Gardner equation with time-dependent variable coefficients, which can provide some more realistic models than their constant-coefficient counterparts, is derived through selecting equilibrium distribution function and adding the compensate function, appropriately. Effects and approximate value range of the free parameters, which are introduced to adjust the single relaxation time and equilibrium distribution function, are discussed in detail, as well as the impact of the lattice space step and velocity. Numerical simulations in different situations of this equation are conducted, including the propagation and interaction of the solitons, the evolution of the non-propagating soliton and the propagation of the double-pole solutions. It is found that the numerical results match well with the analytical solutions, which demonstrates that the current lattice Boltzmann model is a satisfactory and efficient algorithm.     

The non-isospectral and variable-coefficient KP equation with self-consistent sources and new coupled system

The non-isospectral variable-coefficient KP equation with self-consistent sources and its Grammian solutions are obtained for the first time by using the source generation procedure. Moreover, a new coupled system of the non-isospectral variable-coefficient KP equation with self-consistent sources is constructed by applying the source generation procedure and the coupled non-isospectral variable-coefficient KP equation without sources. The novel coupled system with sources cannot only be reduced to the coupled non-isospectral variable-coefficient KP equation, but also reduced to the non-isospectral variable-coefficient KP equation with self-consistent sources.     

A semidiscrete Gardner equation

We construct the Darboux transformations, exact solutions, and infinite number of conservation laws for a semidiscrete Gardner equation. A special class of solutions of the semidiscrete equation, called table-top solitons, are given. The dynamical properties of these solutions are also discussed.     

The extended Riccati equation mapping method for variable-coefficient diffusion-reaction and mKdV equations

In this paper, the extended Riccati equation mapping method is proposed to seek exact solutions of variable-coefficient nonlinear evolution equations. Being concise and straightforward, this method is applied to certain type of variable-coefficient diffusion-reaction equation and variable-coefficient mKdV equation. By means of this method, hyperbolic function solutions and trigonometric function solutions are obtained with the aid of symbolic computation. It is shown that the proposed method is effective, direct and can be used for many other variable-coefficient nonlinear evolution equations.     

How to find solutions,Lie symmetries,and conservation laws of forced Korteweg–de Vries equations in optimal way

It is shown that the forced Korteweg–de Vries (KdV) equation studied in the recent papers [A.H. Salas, Computing solutions to a forced KdV equation, Nonlinear Anal. RWA 12 (2011) 1314–1320] and [M.L. Gandarias, M.S. Bruzón, Some conservation laws for a forced KdV equation, Nonlinear Anal. RWA 13 (2012) 2692–2700] is reduced to the classical (constant-coefficient) KdV equation by point transformations for all values of variable coefficients. The equivalence-based approach proposed in [R.O. Popovych, O.O. Vaneeva, More common errors in finding exact solutions of nonlinear differential equations: part I, Commun. Nonlinear Sci. Numer. Simul. 15 (2010) 3887–3899] allows one to obtain more results in a much simpler way.     

Superapproximation and Commutator Properties of Discrete Orthogonal Projections for Continuous Splines

This paper builds upon the L_p-stability results for discrete orthogonal projections on the spaces S_h of continuous splines of order r obtained by R. D. Grigorieff and I. H. Sloan in (1998, Bull. Austral. Math. Soc.58, 307–332). Properties of such projections were proved with a minimum of assumptions on the mesh and on the quadrature rule defining the discrete inner product. The present results, which include superapproximation and commutator properties, are similar to those derived by I. H. Sloan and W. Wendland (1999, J. Approx. Theory97, 254–281) for smoothest splines on uniform meshes. They are expected to have applications (as in I. H. Sloan and W. Wendland, Numer. Math. (1999, 83, 497–533)) to qualocation methods for non-constant-coefficient boundary integral equations, as well as to the wide range of other numerical methods in which quadrature is used to evaluate L₂-inner products. As a first application, we consider the most basic variable-coefficient boundary integral equation, in which the constant-coefficient operator is the identity. The results are also extended to the case of periodic boundary conditions, in order to allow appplication to boundary integral equations on closed curves.     

Solitonic solutions for a variable-coefficient variant Boussinesq system in the long gravity waves

Variable-coefficient variant Boussinesq (VCVB) system is able to describe the nonlinear and dispersive long gravity waves traveling in two horizontal directions with varying depth. In this paper, with symbolic computation, a Lax pair associated with the VCVB system under some constraints for variable coefficients is derived, and based on the Lax pair, two sorts of basic Darboux transformations are presented. By applying the Darboux transformations, some solitonic solutions are obtained, with the relevant constraints given in the text. In addition, the VCVB system is transformed to a variable-coefficient Broer-Kaup system. Solitonic solutions and procedure of getting them could be helpful to solve the nonlinear and dispersive problems in fluid dynamics.     

Exact solutions of nonlinear dispersive K(m, n) model with variable coefficients

The variable-coefficient Korteweg-de Vries (KdV) equation with additional terms contributed from the inhomogeneity in the axial direction and the strong transverse confinement of the condense was presented to describe the dynamics of nonlinear excitations in trapped quasi-one-dimensional Bose-Einstein condensates with repulsive atom-atom interactions. To understand the role of nonlinear dispersion in this variable-coefficient model, we introduce and study a new variable-coefficient KdV with nonlinear dispersion (called vc-K(m, n) equation). With the aid of symbolic computation, we obtain its compacton-like solutions and solitary pattern-like solutions. Moreover, we also present some conservation laws for both vc-K⁺(n, n) equation and vc-K⁻(n, n) equation.     

Lie group classifications and exact solutions for two variable-coefficient equations

In this paper, the Lie symmetry analysis and group classifications are performed for two variable-coefficient equations, the hanging chain equation and the bond pricing equation. The symmetries for the two equations are obtained, the exact explicit solutions generated from the similarity reductions are presented. Moreover, the exact analytic solutions are considered by the power series method.     

一类变系数KdV方程的Painlevé分析和自Bcklund变换

利用符号计算对一类系数函数是x和t的函数的变系数K dV方程进行了Pa in levé分析,得到了该方程具有Pa in levé性质时系数函数必须满足的约束条件.利用Pa in levé截断法给出了该方程的一个自B ck lund变换,作为例子根据得到的自B ck lund变换给出了两组精确解.     

Painlevé property, soliton-like solutions and complexitons for a coupled variable-coefficient modified Korteweg-de Vries system in a two-layer fluid model

As a model derived from a two-layer fluid system which describes the atmospheric and oceanic phenomena, a coupled variable-coefficient modified Korteweg-de Vries system is concerned in this paper. With the help of symbolic computation, its integrability in the Painlevé sense is investigated. Furthermore, Hirota’s bilinear method is employed to construct the bilinear forms through the dependent variable transformations, and soliton-like solutions and complexitons are derived. Finally, effects of variable coefficients are discussed graphically, and it is concluded that the variable coefficients control the propagation trajectories of solitons and complexitons.     

Grammian solutions and pfaffianization of a non-isospectral and variable-coefficient Kadomtsev-Petviashvili equation

In this paper, we first present the Grammian determinant solutions to the non-isospectral and variable-coefficient Kadomtsev-Petviashvili (vcKP) equation. Then, by using the pfaffianization procedure of Hirota and Ohta, a new non-isospectral and variable-coefficient integrable coupled system is generated. Moreover, Gramm-type pfaffian solutions of the pfaffianized system are proposed.     

Bäcklund transformation of variable-coefficient Boiti–Leon–Manna–Pempinelli equation

In this letter, we discuss a variable-coefficient Boiti–Leon–Manna–Pempinelli equation. We present its soliton solution and derive its new bilinear Bäcklund transformation through Bell polynomial technique and bilinear method. Finally, we show the variable-coefficient Boiti–Leon–Manna–Pempinelli equation is completely integrable.     

On existence of kink and antikink wave solutions of singularly perturbed Gardner equation

In this paper, we study the existence of kink and antikink wave solutions of singularly perturbed Gardner equation from the geometric perspective. We obtain the sufficient conditions to guarantee the existence of kink and antikink wave solutions of the singularly perturbed Gardner equation when the perturbation parameter is sufficiently small, by exploiting the geometric singular perturbation theory and the Melnikov function method.     

Lax pair,auto-Bäcklund transformation and conservation law for a generalized variable-coefficient KdV equation with external-force term

A generalized variable-coefficient KdV equation with perturbed and external-force terms is investigated in this Letter. Lax pair, Riccati-type auto-Bäcklund transformation and Wahlquist–Estabrook-type auto-Bäcklund transformation (WE–BT) are constructed. Based on the WE–BT, the nonlinear superposition formula is obtained and an infinite number of conservation laws are derived recursively, then the analytic solutions are provided including periodic, one-soliton-like and two-soliton-like solutions with inhomogeneous coefficients, external-force term and eigenvalue.