Generalized anharmonic oscillator: A simple variational approach. II. TheD-dimensional anisotropic case

An approximate, variational method for the study of the generalized anharmonic oscillator in $D$ dimensions is given, where the anharmonicity is represented by a broad class of even functions of the $D$ coordinates. The idea of the method is to introduce into the unperturbed oscillator states the correlations due to the presence of the anharmonicity via a unitary operator which is determined by the variational principle.