New integrable extensions of N=2 KdV and boussinesq hierarchies

We construct a new variety of N = 2 supersymmetric integrable systems by the junction of pseudo-differential superspace Lax operators for a = 4, N = 2 KdV and multi-component N = 2 NLS hierarchies. As an important special case, we obtain the Lax operator for the N = 4 super KdV system. A similar extension of one of the N = 2 super Boussinesq hierarchies is given. We also present a minimal N = 4 supersymmetric extension of the second flow of the N = 4 KdV hierarchy, and comment on its possible integrability. (C) 1997 Published by Elsevier Science B.V.