A variational solution of the time-dependent Schrodinger equation

A variational method is described for finding approximate solutions of the time-dependent Schrodinger equation. It is closely related to Frenkel's, but better in some respects because it always leads to a true minimum of the error. For several interacting systems it leads to the time-dependent Hartree equations; for a system in an oscillating electric or magnetic field it gives a variational principle for calculating the susceptibility at any frequency.