Computational applications by ITEM and the variational method for solving the Hamiltonian amplitude equation

The paper presents a significant improvement to the implementation of the improved \tan(\phi(\xi)/۲)-expansion method (ITEM) for solving the Hamiltonian amplitude equation (HAE). We seek to improve the exact solutions by applying the ITEM. Computed solutions are compared with previously published results obtained using the simplest equation method \cite{Eslami} and the (G'/G,۱/G)-expansion method \cite{Demiray}. There is clear evidence that the new approach produces results that are as good as, if not better than, published results determined using the other methods. The main advantage of the method is that it offers further solutions.  By using this method, exact solutions, including the hyperbolic function solution, traveling wave solution, soliton solution, rational function solution,  and periodic wave solution of this equation, have been obtained. Moreover, variational principles for the HAE are formulated. The invariance identities of the HAE involving the Lagrangian L and the generators of the infinitesimal Lie group of transformations have been utilized for writing down their first integrals via Noether's theorem, Logan. We demonstrate the simplest example of the application of this technique, taking the box-shaped initial pulse and an ansatz based on linear Jost functions. We consider a combination of two boxes of opposite signs, the total area of the initial pulse being thus zero. Therewith, we develop a variational approximation for finding the eigenvalues of this pulse, by a piece-wise linear ansatz and tanh functions of the piece-wise linear function.  Moreover, by using MATLAB, some graphical simulations were done to see the behavior of these solutions.

کلیدواژه ها:

Improved tan(ϕ(ξ)/۲)-expansion method ، Hamiltonian amplitude equation ، Soliton wave solutions ، Variational principles