Extended Particle and Renormalization of Fluctuation

The perturbation theory around the classical solution of two dimensional non-linear field equation is developed by using the collective coordinate method of Gervais, Jevicki and Sakita (GJS). In contrast to GJS, the separation of the soliton degree of freedom is made Lorentz invariant. As an example of such calculation the soliton energy for a fixed momen tum is computed explicitly up to one loop in the ¢'-field theory. It is shown that the fluctuation around the kink solution makes a finite contribution to the quantum correction for the mass of soliton since all ultraviolet divergences can be removed by renormalization. Discussions about the formulation and its results are given, compared with those of GJS.