Defective degenerate mode and dynamics of perturbed sine-Gordon soliton plus phonon

Two new idea are introduced in the case of the sine-Gordon 2 pi kink. The first refers to non-interacting phonon plus soliton which is found to be the correct picture in first-order theory. This justifies the additive paradigm of soliton plus oscillation plus translation and hence the Newtonian dynamics. The non-Newtonian behaviour is due to an inappropriate consideration of the soliton-phonon wavepacket interaction. The significance of the defective degenerate mode to the sG 2 pi kink in the presence of perturbing force fields and/or damping is discussed and a surprising result (the absence of the mode) is reported.