We study kink-antikink collisions in the one-dimensional nonintegrable scalar ${\varphi }^6$ model. Although the single-kink solutions for this model do not possess an internal vibrational mode, our simulations reveal a resonant scattering structure, thereby providing a counterexample to the standard belief that the existence of such a mode is a necessary condition for multibounce resonances in general kink-antikink collisions. We investigate the two-bounce windows in detail, and present evidence that this structure is caused by the existence of bound states in the spectrum of small oscillations about a combined kink-antikink configuration.

• Received 17 February 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.091602