Searcharxiv⌕ Search

arXiv subjects

Mehdi Nadjafikhah

Publications and source records attributed to Mehdi Nadjafikhah.

At least 19 recordsLinked to original sources
arXiv2024

Cartan equivalence method on fifth-order differential operator

In this paper, we carry out the equivalence problem for fifth-order differential operators on the line under general fiber-preserving transformation using the Cartan method of equivalence. Two versions of equivalence problems have been solved. We consider the direct equivalence problem and an equivalence problem to determine the sufficient and necessary conditions on fifth-order differential operators such that there exists a fiber--preserving transformation mapping one to the other according to gauge equivalence.

math.DG↗
arXiv2021

On the invariance properties of Vaidya-Bonner geodesics via symmetry operators

In the present paper, we try to investigate the Noether symmetries and Lie point symmetries of the Vaidya-Bonner geodesics. Classification of one-dimensional subalgebras of Lie point symmetries are considered. In fact, the collection of pairwise non-conjugate one-dimensional subalgebras that are called the optimal system of subalgebras is determined. Moreover, as illustrative examples, the symmetry analysis is implemented on two special cases of the system.

math.DG↗
arXiv2019

Preliminary Group Classification and some exact solutions of 2Hessian equation

We study the class of 3-dimensional nonlinear 2-hessian equations mentioned in the text. We perform preliminary group classification on 2-hessian equation. In fact, we find additional equivalence transformation on the space (x,y,z,u,f), with the aid of a method, then we take their projections on the space (x,y,z,f), so we prove an optimal system of one-dimensional Lie sub algebras of this equation is generated by A1 to A12, which introduced in theorem 2, ultimately, A number of new interesting nonlinear invariant models are obtained which have non-trivial in variance algebras. The result of these works is a wide class of equations which summarized in table. So at the end of this work, some exact solutions of 2-hessian equation are presented. The paper is one of the few applications of an algebraic approach to the group classification using Lie method.

math.DG↗
arXiv2017

Geometric study of Gardner equation

In this paper, we apply the method of approximate transformation groups proposed by Baikov, Gaziziv and Ibragimov, to compute the first-order approximate symmetry for the Gardner equations with the small parameters. We compute the optimal system and analyze some invariant solutions of These types of equations. Particularly, general forms of approximately Galilean-invariant solutions have been computed.

math.AP↗
arXiv2017

G-set Theory and Applications in Lie Theory

This paper is devoted to the development and applications of some (new) basic concepts in Lie theory, both from `computational" and "observability" viewpoint. We specify set of all "G-equivariant" maps from a given Lie group G to the underlying manifold M, namely $G$-set, and also we introduce "conjugacy" in Lie group theory. The next goal of this paper is detailed analysis of the G-sets in connection with underlying transformation groups and providing a rigorous theoretical justification of "G-sets", when a group of transformations G acts on manifold M.

math.DG↗
arXiv2014

Contact equivalence problem for KDV-type equations

The Cartan's method of equivalence and moving coframe method has been applied to solve the local equivalence problem for KDV-type equations under the action of a pseudo-group of contact transformations. The structure equations, the sets of differential invariants for symmetry groups and equivalent conditions of these equations are found.

math.DG↗
arXiv2014

Computation of Partially Invariant Solutions for the Einstein Walker Manifolds' Identifying Equations

In this paper, partially invariant solutions (PISs) method is applied in order to obtain new four-dimensional Einstein Walker manifolds. This method is based on subgroup classification for the symmetry group of partial differential equations (PDEs) and can be regarded as the generalization of the similarity reduction method. For this purpose, those cases of PISs which have the defect structure delta=1 and are resulted from two-dimensional subalgebras are considered in the present paper. Also it is shown that the obtained PISs are distinct from the invariant solutions that obtained by similarity reduction method.

math.DG↗
arXiv2014

Symmetry Reduction of the Two-Dimensional Ricci Flow Equation

This paper is devoted to obtain the one-dimensional group invariant solutions of the two-dimensional Ricci flow ((2D) Rf) equation. By classifying the orbits of the adjoint representation of the symmetry group on its Lie algebra, the optimal system of one-dimensional subalgebras of the ((2D) Rf) equation is obtained. For each class, we will find the reduced equation by the method of similarity reduction. By solving these reduced equations, we will obtain new sets of group invariant solutions for the ((2D) Rf) equation.

math.DG↗
arXiv2014

Approximate symmetries of the Harry Dym equation

In this paper, we derive the first order approximate symmetries for the Harry Dym equation by the method of approximate transformation groups proposed by Baikov, Gaszizov and Ibragimov. Moreover, we investigate the structure of the Lie algebra of symmetries of the perturbed Harry Dym equation. We compute the one-dimensional optimal system of subalgebras as well as point out some approximately differential invariants with respect to the generators of Lie algebra and optimal system.

math-ph↗
arXiv2014

Approximate Symmetry Analysis of a Class of Perturbed Nonlinear Reaction-Diffusion Equations

In this paper, the problem of approximate symmetries of a class of non-linear reaction-diffusion equations called Kolmogorov-Petrovsky-Piskounov (KPP) equation is comprehensively analyzed. In order to compute the approximate symmetries, we have applied the method which was proposed by Fushchich and Shtelen [8] and fundamentally based on the expansion of the dependent variables in a perturbation series. Particularly, an optimal system of one dimensional subalgebras is constructed and some invariant solutions corresponding to the resulted symmetries are obtained.

math-ph↗
arXiv2012

Approximate Hamiltonian Symmetry Groups and Recursion Operators for Perturbed Evolution Equations

In this paper, the method of approximate transformation groups which was proposed by Baikov, Gazizov and Ibragimov, is extended on Hamiltonian and bi-Hamiltonian systems of evolution equations. Indeed, as a main consequence, this extended procedure is applied in order to compute the approximate conservation laws and approximate recursion operators corresponding to these types of equations. In particular, as an application, a comprehensive analysis of the problem of approximate conservation laws and approximate recursion operators associated to the Gardner equation with the small parameters is presented.

math.AP↗
arXiv2012

Some general new Einstein Walker manifolds

In this paper, Lie symmetry group method is applied to find the lie point symmetries group of a PDE system that is determined general form of four-dimensional Einstein Walker manifold. Also we will construct the optimal system of one-dimensional Lie subalgebras and investigate some of its group invariant solutions.

math.DG↗
arXiv2012

Symmetry Group of Surfaces PDE

Using the theory of the symmetry group for PDEs [15, 17], we derive the symmetry group G associated to surfaces PDE. Several group invariant solutions of the surfaces PDE are given by solving a reduced system of partial differential equations.

math.DG↗
arXiv2012

Lie group analysis for short pulse equation

In this paper, the classical Lie symmetry analysis and the generalized form of Lie symmetry method are performed for a general short pulse equation. The point, contact and local symmetries for this equation are given. In this paper, we generalize the results of H. Liu and J. Li [1], and add some further facts, such as optimal system of Lie symmetry subalgebras and two local symmetries.

math.AP↗
arXiv2011

Symmetry classification and conservation laws for higher order Camassa-Holm equation

Lie symmetry group method is applied to study for the higher order Camassa-Holm equation. The symmetry group and its optimal system are given. Furthermore, preliminary classification of its group invariant solutions, symmetry reduction and nonclassical symmetries are investigated. Finally conservation laws for the higher order Camassa-Holm equation are presented.

math.AP↗
arXiv2011

Lie symmetries and conservation laws of the Hirota-Ramani equation

In this paper, Lie symmetry method is performed for the Hirota-Ramani (H-R) equation. We will find The symmetry group and optimal systems of Lie subalgebras. Furthermore, preliminary classification of its group invariant solutions, symmetry reduction and nonclassical symmeries are investigated. Finally the conservation laws of the H-R equation are presented.

math.AP↗
arXiv2011

Cartan equivalence problem for third order differential operators

This article is dedicated to solve the equivalence problem for two third order differential operators on the line under general fiber--preserving transformation using the Cartan method of equivalence. We will do three versions of the equivalence problems: first via the direct equivalence problem, second equivalence problem is to determine conditions on two differential operators such that there exists a fiber-preserving transformations mapping one to the other according to gauge equivalence.

math.DG↗