We investigate the role that quasinormal modes can play in kink-antikink collisions, via an example based on a perturbation of the $phi^4$ model. We find that narrow quasinormal modes can store energy during collision processes and return it back to the translational degrees of freedom. Quasinormal modes also decay, which leads to energy leakage, causing a closing of resonance windows and an increase of the critical velocity. We observe similar phenomena in an effective model, a small modification of the collective-coordinate approach to the $phi^4$ model.
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