In each mode a number of active modals (indexed u m , v m , ...) are used and all possible Hartree products using combinations of active modals of different modes are used in the wave function. The index vector u, indexes the specific Hartree product Φu (t) and the corresponding coefficient C u (t) in the wave function. When the time-evolution is carried out, both the Hartree products and their coefficients change opening for using a much more compact wave function than if it was simply expanded in time-independent modal functions.