Generalised reversible transformations and the inhomogeneous nonlinear Schr\"odinger equation hierarchy

Abstract

Under investigation is the nonlinear Schr\"odinger equation hierarchies and the reversible transformations. We propose a generalized reversible transformation between the the generalized NLSE hierarchy with focussing and defocussing nonlinearity and the NLSE hierarchy forced with a linear potential term. The corresponding extended concept of classical dark and bright solitons of the forced hierarchy, accelerating due to linear potential as well as due to the dispersion are obtained directly without resolving the nonisospectral inverse scattering problem. We have identified a set of new constraints among the dispersion and the nonlinear coefficients in the inhomogeneous NLSE hierarchy, which are preserved after the transformations. The reversible transformations allow us to encompass inhomogeneous NLS, HNLS and higher order equations belonging to the class of nonisospectral family of inverse scattering problems to the isospectral NLS class of equations and study them under a general mathematical framework. We hope that our analysis provides a mathematical platform to study inhomogeneous NLSEs as well as open up the possibility of new applications in physics.