Towards a strong coupling theory for the KPZ equation

After a brief introduction we review the nonperturbative weak noise approach to the Kardar–Parisi–Zhang (KPZ) equation in one dimension. We argue that the strong coupling aspects of the KPZ equation are related to the existence of localized propagating domain walls or solitons representing the growth modes; the statistical weight of the excitations is governed by a dynamical action representing the generalization of the Boltzmann factor to kinetics. This picture is not limited to one dimension. We thus attempt a generalization to higher dimensions where the strong coupling aspects presumably are associated with a cellular network of domain walls. Based on this picture we present arguments for the Wolf–Kertez expression z=(2d+1)/(d+1) for the dynamical exponent.