Direct Approach for Kink Solution of Ф - 4 Equation Under Perturbation

Perturbations about kink solution of Ф- 4 equation are investigated by a direct approach which was recently developed in a study of soliton perturbation theory. In this scheme, the derivative expansion method from classical perturbation theory is employed to linearize the perturbed equation. The solution of the linearized equation for first-order correction is derived by the method of Laplace transformation. At the same time, the parameters variation is obtained directly from the secularity conditions.