Lie theory and the wave equation in space–time. 5. R‐separable solutions of the wave equation ψtt−Δ3ψ=0

Abstract

A detailed classification is made of all orthogonal coordinate systems for which the wave equation ψtt−Δ3ψ=0 admits an R‐separable solution. Only those coordinate systems are given which are not conformally equivalent to coordinate systems that have already been found in previous articles. We find 106 coordinates to given a total of 368 conformally inequivalent orthogonal coordinates for which the wave equation admits an R separation of variables.