Curvature collineations of non-expanding and twist-free vacuum type-N metrics in general relativity

Abstract
The curvature collineation equations have been solved for the two families of Petrov type-N plane-fronted gravitational wave solutions of Einstein's vacuum field equations in general relativity. Both of these solutions always have non-trivial curvature collineations, i.e. vector fields xi with respect to which the components Rmu nu alpha beta of the Riemann tensor for those solutions are Lie derivable.