Modulational instabilities and domain walls in coupled discrete nonlinear Schrodinger equations

We consider a system of two discrete nonlinear Schrodinger equations, coupled by nonlinear and linear terms. For various physically relevant cases, we derive a modulational instability criterion for plane-wave solutions. We also find and examine domain-wall solutions in the model with the linear coupling. (C) 2004 Published by Elsevier B.V.