Kalnins, Ernie G.Miller, W., Jr.2008-10-312008-10-311985-07Kalnins, E.G. & Miller, W., Jr. (1985). Differential-Stäckel matrices. Journal of Mathematical Physics, 26, 1560.0022-2488https://hdl.handle.net/10289/1224We show that additive separation of variables for linear homogeneous equations of all orders is characterized by differential-Stäckel matrices, generalizations of the classical Stäckel matrices used for multiplicative separation of (second-order) Schrödinger equations and additive separation of Hamilton–Jacobi equations. We work out the principal properties of these matrices and demonstrate that even for second-order Laplace equations additive separation may occur when multiplicative separation does not.application/pdfenCopyright 1985 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in the Journal of Mathematical Physics and may be found at http://jmp.aip.org/jmp/top.jspMathematicsmatricesdifferential equationspartial differential equationsHamilton&minusJacobi equationslaplace equationanalytical solutionnonlinear problemscouplingcoordinatesRiemann spacepolynomialsmathematical operatorsJournal Article10.1063/1.526917