A complete classification of separable non-orthogonal systems for the flat space Helmholtz equation is given. The relation between separability conditions for the various systems and the classification of abelian sub-algebras of the Euclidean symmetry algebra epsilon (4) is explicitly indicated.
No takes yet. Share an insight, caveat, or question.
E. G. Kalnins (1979) studied this question.
Synapse has enriched 5 related papers. Consider them for comparative context: