The fully supersymmetric AKNS problem: Darboux transformations and discrete systems

Abstract

The fully supersymmetric AKNS spectral problem with four superfields proposed by Morosi and Pizzocchero is considered. This is a hybrid problem of the classical AKNS and supersymmetric AKNS spectral problems. Under the assumption that Darboux matrices are linear with respect to the spectral parameter, three Darboux transformations and the corresponding Bäcklund transformations are constructed. Through proper reductions, we obtain Darboux transformations for the coupled supersymmetric nonlinear Schrödinger and coupled supersymmetric modified Korteweg–de Vries equations, and recover the Darboux transformations for Manin-Radul supersymmetric Korteweg–de Vries equation and supersymmetric AKNS hierarchy, respectively. The first Darboux-Bäcklund transformation is further applied to construct integrable discrete super systems, and both semi-discrete and fully discrete systems are obtained. The associated continuum limits are studied as well.