Classical Lie Symmetry Research Articles

A nonlocal Boussinesq equation: Multiple-soliton solutions and symmetry analysis

A nonlocal Boussinesq equation is deduced from the local one by using consistent correlated bang method. To study various exact solutions of the nonlocal Boussinesq equation, it is converted into two local equations which contain the local Boussinesq equation. From the N-soliton solutions of the local Boussinesq equation, the N-soliton solutions of the nonlocal Boussinesq equation are obtained, among which the (N = 2,3,4)-soliton solutions are analyzed with graphs. Some periodic and traveling solutions of the nonlocal Boussinesq equation are derived directly from the known solutions of the local Boussinesq equation. Symmetry reduction solutions of the nonlocal Boussinesq equation are also obtained by using the classical Lie symmetry method.

Symmetry classification and invariance of the Reynolds equation

In this essay, extensions to the results of Lie symmetry classification of Reynolds equation are proposed. The infinitesimal technique is used to derive symmetry groups of the Reynolds equation. Onedimensional optimal system is constructed for symmetry sub-algebras gained through Lie point symmetry. At the end, the general symmetry group of the non-conservative generalized thin-film equation are determined.

A reaction–diffusion system with cross-diffusion: Lie symmetry, exact solutions and their applications in the pandemic modelling

A non-linear reaction–diffusion system with cross-diffusion describing the COVID-19 outbreak is studied using the Lie symmetry method. A complete Lie symmetry classification is derived and it is shown that the system with correctly specified parameters admits highly non-trivial Lie symmetry operators, which do not occur for all known reaction–diffusion systems. The symmetries obtained are also applied for finding exact solutions of the system in the most interesting case from applicability point of view. It is shown that the exact solutions derived possess typical properties for describing the pandemic spread under 1D approximation in space and lead to the distributions, which qualitatively correspond to the measured data of the COVID-19 spread in Ukraine.

Lie symmetry reductions, abound exact solutions and localized wave structures of solitons for a (2 + 1)-dimensional Bogoyavlenskii equation

By applying the two efficient mathematical methods particularly with regard to the classical Lie symmetry approach and generalized exponential rational function method, numerous exact solutions are constructed for a (2 + 1)-dimensional Bogoyavlenskii equation, which describes the interaction of Riemann wave propagation along the spatial axes. Moreover, we obtain the infinitesimals, all the possible vector fields, optimal system, and Lie symmetry reductions. The governing Bogoyavlenskii equation is converted into various nonlinear ordinary differential equations through two stages of Lie symmetry reductions. Accordingly, abundant exact closed-form solutions are obtained explicitly in terms of independent arbitrary functions, rational functions, trigonometric functions, and hyperbolic functions with arbitrary free parameters. The dynamical behavior of the resulting soliton solutions is presented through 3D-plots via numerical simulation. Eventually, single solitons, multi-solitons with oscillations, kink wave with breather-type solitons, and single lump-type solitons are obtained. The proposed mathematical techniques are effective, trustworthy, and reliable mathematical tools to work out new exact closed-form solutions of various types of nonlinear evolution equations in mathematical physics and engineering sciences.

Symmetry analysis and conservation laws of a further modified 3D Zakharov-Kuznetsov equation

We study a further modified (3 + 1)-dimensional(3D) Zakharov-Kuznetsov equation. The classical Lie symmetry method will be employed to obtain solutions of a further modified 3D Zakharov-Kuznetsov equation. We will also establish the multiplier method to derive conservation laws of the underlying equation. Moreover, a brief physical interpretation of the derived conserved quantities is conferred.

A complete Lie symmetry classification of a class of (1+2)-dimensional reaction-diffusion-convection equations

A class of nonlinear reaction-diffusion-convection equations describing various processes in physics, biology, chemistry etc. is under study in the case of time and two space variables. The group of equivalence transformations is constructed, which is applied for deriving a Lie symmetry classification for the class of such equations by the well-known algorithm. It is proved that the algorithm leads to 32 reaction-diffusion-convection equations admitting nontrivial Lie symmetries. Furthermore a set of form-preserving transformations for this class is constructed in order to reduce this number of the equations and obtain a complete Lie symmetry classification. As a result, the so called canonical list of all inequivalent equations admitting nontrivial Lie symmetry (up to any point transformations) and their Lie symmetries are derived. The list consists of 22 equations and it is shown that any other reaction-diffusion-convection equation admitting a nontrivial Lie symmetry is reducible to one of these 22 equations. As a nontrivial example, the symmetries derived are applied for the reduction and finding exact solutions in the case of the porous-Fisher type equation with the Burgers term.

Classical Lie symmetries and similarity reductions of the (2 + 1)-dimensional dispersive long wave system

In the present work, classical Lie symmetry method is adopted to obtain the Lie symmetries and similarity reductions of the [Formula: see text]-dimensional dispersive long wave equation. We also demonstrate that the symmetry algebra of this equation is an infinte dimensional, together with Kac–Moody–Virasoro type subalgebras.

Group-invariant solutions for time-fractional Fornberg-Whitham equation by Lie symmetry analysis

This paper is concerned with the time-fractional Fornberg-Whitham equation using Lie symmetry analysis. This equation is used to describe the physical processes of models possessing memory. By employing the classical and nonclassical Lie symmetry analysis, the invariance properties of this equation are investigated. The similarity reductions and new exact solutions are obtained.

Some New Nonlinear Wave Solutions for a Higher-Dimensional Shallow Water Wave Equation

In this manuscript, we first perform a complete Lie symmetry classification for a higher-dimensional shallow water wave equation and then construct the corresponding reduced equations with the obtained Lie symmetries. Moreover, with the extended F-expansion method, we obtain several new nonlinear wave solutions involving differentiable arbitrary functions, expressed by Jacobi elliptic function, Weierstrass elliptic function, hyperbolic function and trigonometric function.

Optical solitons with Chen–Lee–Liu equation by Lie symmetry

This paper avails of classical Lie symmetry analysis to exhibit optical solitons to Chen–Lee–Liu model. By the aid of the proposed method, we secure symmetries that transform the model to a system of ordinary differential equations which are subsequently investigated by a number of methods to recover bright, dark and singular solitons.

The generalized convective Cahn–Hilliard equation: Symmetry classification, power series solutions and dynamical behavior

We first perform a complete Lie symmetry classification of the generalized convective Cahn–Hilliard equation. Then using the obtained symmetries, we mainly study the convective Cahn–Hilliard equation, of which a new power series solution is constructed. In particular for the crystal surface growth processes, the truncated series solution shows that the surface structures include peaks and valleys, and can exhibit different evolution trends with the driving force varying from compressive force to tensile force. Moreover, there exist several critical points for the driving force, where the surface configurations take the jump changes and show different features on the both sides of such critical points. According to the effects of driving forces, we analyze the dynamical features of crystal growth.

Invariant solutions of the normal hyperbolic mean curvature flow with dissipation

In this paper, based on the classical Lie symmetry method, the group invariant solutions of the normal hyperbolic mean curvature flow with dissipation are discussed. The optimal system of the obtained symmetries is found, the reduced equations and exact solutions are investigated. Then explicit solutions are obtained by the power series method. In addition, the convergence of the power series solutions is proved. The objective shapes of the solutions of the normal hyperbolic mean curvature flow with dissipation are performed.

Lie symmetry analysis and exact solutions of the time-fractional biological population model

We first perform a complete Lie symmetry classification for the time-fractional biological population model with Riemann–Liouville fractional derivative and then construct the corresponding reduced equations with the obtained Lie symmetries. Moreover, with the F-expansion method and the reduced equations, we obtain several new exact solutions for the equation and show the propagation pattern via the evolutional figures. By means of the power series theory, an exact power series solution of the equation is also constructed.

On invariant analysis and conservation laws for degenerate coupled multi-KdV equations for multiplicity $$l = 3$$ l = 3

The degenerate coupled multi-KdV equations for coupled multiplicity l=3 are studied. The equations also known as three fields Kaup-Boussinesq equations are considered for invariant analysis and conservation laws. The classical Lie's symmetry method is used to analyze the symmetries of equations. Based on Killing's form which is invariant of adjoint action, the full classification for Lie algebra is presented. Further, one-dimensional optimal group classification is used to obtain invariant solutions. Besides this, using general theorem proved by Ibragimov we find several nonlocal conservation laws for these equations. The conserved currents obtained in this work can be useful for the better understanding of some physical phenomena modeled by the underlying equations.

Symmetry analysis, explicit power series solutions and conservation laws of the space-time fractional variant Boussinesq system

In this study, the classical Lie symmetry method is successfully applied to investigate the symmetries of the space-time fractional variant Boussinesq system which was introduced as a model of water waves. With the help of the obtained symmetries, the governing system is reduced into the system of nonlinear fractional ordinary differential equations (NLFODEs) which contains Erdelyi-Kober fractional differential operators via Riemann-Liouville fractional derivative. The system is also studied for the explicit power series solution. The obtained power series solution is further examined for the convergence. The conservation laws of the governing system are constructed by using the new conservation theorem and generalization of the Noether operators. The numerical approximation for the fractional system is also found by using the residual power series method (RSPM). Some figures are also presented to explain the physical understanding for both explicit and approximate solutions.

Group analysis of variable coefficients heat and mass transfer equations with power nonlinearity of thermal diffusivity

The paper presents symmetry analysis of three-dimensional equations of heat and mass transfer in a binary liquid. The system contains three unknown functions related to physical properties of liquid. Supposing thermal diffusivity to be depended on temperature with respect to power law, diffusion and thermal diffusion coefficients are found using of classical Lie symmetry approach. It is shown that the solution of the group classification problem consists of two parts. We obtain different results if we take into account that diffusion coefficient either has the same form as the thermal diffusivity coefficient or it depends on temperature and concentration essentially. Some reductions of the governing equations are constructed with the help of the obtained transformations of dependent and independent variables. New exact solutions of the reduced equations have been found in several cases.

Exact solutions of nonlinear diffusion-convection-reaction equation: A Lie symmetry analysis approach

We derive some exact solutions of a nonlinear diffusion-convection-reaction equation which models biological, chemical and physical phenomena. The Lie symmetry classification approach is employed to specify the model parameters and then the symmetries of resulting submodels are utilized for construction of exact solutions.

ТОЧНІ РОЗВ’ЯЗКИ НЕЛІНІЙНОГО (1+2)-ВИМІРНОГО РІВНЯННЯ РЕАКЦІЇ-КОНВЕКЦІЇ-ДИФУЗІЇ

Предметом вивчення в статті є застосування ліївського методу до побудови інваріантних анзаців, редукції та знаходження точних розв’язків (1+2)-вимірного рівняння реакції-конвекції-дифузії. Мета - здійснити побудову точних розв’язків (1+2)-вимірного рівняння реакції-конвекції-дифузії на основі використання симетричних властивостей цього рівняння. Задача − використати ліївську симетрію рівняння (1+2)-вимірного рівняння реакції-конвекціїдифузії для побудови інваріантних анзаців, редукції та знаходження його точних розв’язків. Для реалізації цієї задачі використано метод Софуса Лі, в основі його лежить принцип симетрії. Згідно з методом С. Лі диференціальні рівняння з частинними похідними, які володіють класичною лііївською симетрією, можна редукувати до звичайних диференціальних рівнянь за допомогою спеціальних підстановок(анзаців). Розв’язавши редуковані рівняння, можна побудувати точні розв’язки вихідного диференціального рівняння з частинними похідними. Висновки: використано симетрійні властивості (1+2)-вимірного рівняння реакції-конвекції-дифузії для побудови інваріантних анзаців, редукції та знаходження його точних розв’язків.

Group classification of a class of generalized nonlinear Kolmogorov equations and exact solutions

A class of generalized nonlinear Kolmogorov equations is investigated. We present the group classification of Lie symmetries of the class with respect to the group of equivalence transformations. We find a number of exact solutions of nonlinear Kolmogorov equations which have the maximal symmetry properties.

Lie Symmetries of Nonlinear Parabolic-Elliptic Systems and Their Application to a Tumour Growth Model

A generalisation of the Lie symmetry method is applied to classify a coupled system of reaction-diffusion equations wherein the nonlinearities involve arbitrary functions in the limit case in which one equation of the pair is quasi-steady but the other is not. A complete Lie symmetry classification, including a number of the cases characterised as being unlikely to be identified purely by intuition, is obtained. Notably, in addition to the symmetry analysis of the PDEs themselves, the approach is extended to allow the derivation of exact solutions to specific moving-boundary problems motivated by biological applications (tumour growth). Graphical representations of the solutions are provided and a biological interpretation is briefly addressed. The results are generalised on multi-dimensional case under the assumption of the radially symmetrical shape of the tumour.