EQUIVALENT HAMILTONIAN METHOD IN COHERENT SOLITONS THEORY

Using Frohlich transformations, a system of interacting excitons and p honons, is substituted by an equivalent system of interacting excitons . It was concluded, by this approach that solitons can be formed only by coherent excitons. It was also shown, that restrictions on the boun dary wave vector of excitons, which can form the solitons, are more st rict than in the standard approach. Due to this restriction we elimina te the difficulty appearing in the standard approach manifesting itsel f in the enormously high nonlinear corrections of spectrum in the rang e in which phase velocity of excitons and velocity of sound are very c lose. The equivalent Hamiltonian method also corrects the standard pha se factor of soliton wave packets for the rate which is proportional t o the square of the ratio of the exciton-phonon coupling constant to t he bandwidth. This correction could be important for analysis of solit on scattering processes.