Solitary oscillations and multiple antikink-kink pairs in the double sine-Gordon model

We study kink-antikink collisions in a particular case of the double sine-Gordon model depending on only one parameter $r$. The scattering process of large kink-antikink shows the changing of topological sector. For some parameter intervals we observed two connected effects: the production of up to five antikink-kink pairs and up to three solitary oscillations with significant radiation rate. For each time, the produced antikink-kink pairs more distant from the collision point have the smaller thickness, do not emit detected radiation and oscillates around the vacuum, with frequencies bellow the continuum. The scattering process for small kink-antikink shows, for small values of $r$, the formation of false two-bounce windows and the suppression of true two-bounce windows, despite the presence of an internal shape mode. The increasing of $r$ from moderate values shows the gradual recovering of the structure of two-bounce windows.