School of Mathematics, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
Copyright © 2011 Sonja Currie and Anne D. Love. This is an open access article distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This paper generalises the work done in Currie and Love (2010), where we studied the effect of applying
two Crum-type transformations to a weighted second-order difference equation with various
combinations of Dirichlet, non-Dirichlet, and affine -dependent boundary conditions at the end points, where is the eigenparameter. We now consider general -dependent boundary conditions. In particular we show, using one of the Crum-type transformations, that it is
possible to go up and down a hierarchy of boundary value problems keeping the form of the second-order difference equation constant but possibly increasing or decreasing the dependence on of the boundary conditions at each step. In addition, we show that the transformed
boundary value problem either gains or loses an eigenvalue, or the number of eigenvalues
remains the same as we step up or down the hierarchy.