Comment on: "New exact solutions for the Kawahara equation using Exp-function method"

Exact solutions of the Kawahara equation by Assas [L.M.B. Assas, J. Com. Appl. Math. 233 (2009) 97--102] are analyzed. It is shown that all solutions do not satisfy the Kawahara equation and consequently all nontrivial solutions by Assas are wrong.Comment: 4 pages, This comment was sent in september 2009 to the Journal of Computational and Applied Mathematics. It was the long story with this comment. However recently I received the decision from the journal that the paper being commented on will be retracted

Special polynomials associated with the K2 hierarchy

New special polynomials associated with the rational solutions of analogue to the Painleve hierarchies are introduced. The Hirota relations for these special polynomials are found. Differential - difference hierarchies for finding special polynomials are presented. These formulae allow us to search the special polynomials associated with the hierarchy studied. The ordinary differential hierarchy for the Yablonskii - Vorob'ev polynomials is given.Comment: 24 pages, 5 figure

Self-similar solutions of the Burgers hierarchy

Self-similar solutions of the equations for the Burgers hierarchy are presented

Remarks on rational solutions for the Korteveg - de Vries hierarchy

Differential equations for the special polynomials associated with the rational solutions of the second Painleve hierarchy are introduced. It is shown rational solutions of the Korteveg - de Vries hierarchy can be found taking the Yablonskii - Vorob'ev polynomials into account. Special polynomials associated with rational solutions of the Korteveg - de Vries hierarchy are presented.Comment: 8 page

Logistic function as solution of many nonlinear differential equations

The logistic function is shown to be solution of the Riccati equation, some second-order nonlinear ordinary differential equations and many third-order nonlinear ordinary differential equations. The list of the differential equations having solution in the form of the logistic function is presented. The simple method of finding exact solutions of nonlinear partial differential equations (PDEs) is introduced. The essence of the method is based on comparison of nonlinear differential equations obtained from PDEs with standard differential equations having solution in the form of the logistic function. The wide application of the logistic function for finding exact solutions of nonlinear differential equations is demonstrated.Comment: 19 page

Approximate Solutions of Nonlinear Heat Equation for Given Flow

The one-dimensional problem of the nonlinear heat equation is considered. We assume that the heat flow in the origin of coordinates is the power function of time and the initial temperature is zero. Approximate solutions of the problem are given. Convergence of approximate solutions is discussed.Comment: 7 pages, 1 figur

Explicit form of the Yablonskii - Vorob'ev polynomials

Special polynomials associated with rational solutions of the second Painlev\'{e} equation and other members of its hierarchy are discussed. New approach, which allows one to construct each polynomial is presented. The structure of the polynomials is established. Formulas of their coefficients are found. Correlations between the roots of every polynomial are obtained.Comment: 21 page

Newton polygons for finding exact solutions

A method for finding exact solutions of nonlinear differential equations is presented. Our method is based on the application of the Newton polygons corresponding to nonlinear differential equations. It allows one to express exact solutions of the equation studied through solutions of another equation using properties of the basic equation itself. The ideas of power geometry are used and developed. Our approach has a pictorial rendition, which is is illustrative and effective. The method can be also applied for finding transformations between solutions of the differential equations. To demonstrate the method application exact solutions of several equations are found. These equations are: the Korteveg - de Vries - Burgers equation, the generalized Kuramoto - Sivashinsky equation, the fourth - order nonlinear evolution equation, the fifth - order Korteveg - de Vries equation, the modified Korteveg - de Vries equation of the fifth order and nonlinear evolution equation of the sixth order for the turbulence description. Some new exact solutions of nonlinear evolution equations are given.Comment: 24 pages, 10 figure

Power expansions for the self-similar solutions of the modified Savada-Kotera equation

The fourth-order ordinary differential equation, defining new transcendents, is studied. The self-similar solutions of the Kaup-Kupershmidt and Savada-Kotera equations are shown to be found taking its solutions into account. Equation studied belongs to the class of fourth-order analogues of the Painlev\'{e} equations. All the power and non-power asymptotic forms and expansions near points $z=0$, $z=\infty$ and near arbitrary point $z=z_0$ are found by means of power geometry methods. The exponential additions to the solutions of studied equation are also determined.Comment: 31 pages, 9 figure

Power and non-power expansions of the solutions for the fourth-order analogue to the second Painlev\'{e} equation

Fourth - order analogue to the second Painlev\'{e} equation is studied. This equation has its origin in the modified Korteveg - de Vries equation of the fifth order when we look for its self - similar solution. All power and non - power expansions of the solutions for the fouth - order analogue to the second Painlev\'{e} equation near points $z=0$ and $z=\infty$ are found by means of the power geometry method. The exponential additions to solutions of the equation studied are determined. Comparison of the expansions found with those of the six Painlev\'{e} equations confirm the conjecture that the fourth - order analogue to the second Painlev\'{e} equation defines new transcendental functions.Comment: 34 pages, 8 figures; submitted to Chaos,Solitons & Fractal