Multi-kinks and composite oscillons in a commensurable and non degenerate double sine-Gordon model

A bstract In this paper, we introduce a commensurable and non-degenerate double sine-Gordon model, in which a partial breaking of vacuum degeneracy provides a mechanism for the emergence of static multi-kinks. These multi-kinks K n are stable field configurations with internal structure, consisting of n localized energy packets with well-defined separations. The properties of the multi-kinks are thoroughly analyzed, including the novel phenomenology that arises during their collisions. In particular, we observe the emergence of long-lived composite oscillons that reflect the original structure of the multi-kinks. The sub-kink’s positions and their vibration modes provide collective coordinates that are used to construct a phenomenological model, which offers a good qualitative explanation of the observed oscillon properties. Linear radiation effects are consistently incorporated into the model, revealing their important role in the synchronization of the oscillon’s vibrational components. In contrast, oscillon decay and the sudden annihilations observed in some collisions are driven by a novel staccato-like mechanism, whereby repeated crossings of the mass threshold by the dominant frequency generate a sequence of radiation bursts.