Spectral walls in antikink-kink scattering in the $\phi^6$ model

We show that thick spectral walls exist in antikink-kink collisions in the $\phi^6$ model. In this model, they are triggered by the so-called delocalized modes that do not exist in the single-soliton sector but emerge in antikink-kink collisions. Therefore, spectral walls are a rather common phenomenon that should occur in many solitonic collisions involving nonsymmetric kinks as, e.g., in the $\phi^8$ or higher power models.