Dual fronts in a phase field model

We study a dual front behavior observed in a reaction–diffusion system arising initially in the context of phase field models. A precursor front propagates into a stable phase, generating a metastable “intermediate phase”. This intermediate phase then decays via an oscillating front, producing a periodic structure which later coarsens. Unlike previously studied models in which dual fronts appear, the appearance of the split front is controlled not by an interchange of wave speeds, but by the existence of the precursor wave. By means of an expansion in small thermal diffusivity, we argue that this behavior is generic.