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 $delocalized$ $modes$ which do not exist in the single-soliton sector but emerge in antikink-kink ($\bar{K}K$) collisions. Therefore, spectral walls are a rather common phenomenon that should occur in many solitonic collisions involving non-symmetric kinks as, e.g., in the ${\phi }^8$ or higher power models.