Resonance structures in coupled two-component φ4 model

We present a numerical study of the process of the kink-antikink collisions in the coupled one-dimensional two-component phi(4) model. Our results reveal two different soliton solutions which represent double kink configuration and a kink-nontopological soliton (lump) bound state. Collision of these solitons leads to reveal very rich structure which is related to the reversible energy exchange between the kinks, nontopological solitons and the internal vibrational modes. Various channels of the collisions are discussed; it is shown there is a new type of self-similar fractal structure which appears in the collisions of the relativistic kinks. There the width of the resonance windows increases with the increase of the impact velocity. An analytical approximation scheme is discussed in the limit of the perturbative coupling between the sectors. Considering the spectrum of linear fluctuations around the solitons we found that the double kink configuration is unstable if the coupling constant between the sectors is negative.