“…Since this system is numerically intractable, usually effective "one particle" models are used, by using approximations like the Hartree(-Fock) ansatz and mean field theory [2,13,14,15,28,29,30,32,41,45]. Thus, the original 3N -or 3N + 1-dimensional problem (stationary or time-dependent) can be reduced to one or a coupled system of nonlinear Schrödinger (NLS) equation(s) in 3D [13,14,15,28,29,36]. In some situations, the 3D "one particle" NLS equation can be further reduced to lower-dimensional NLS equations in one or two space dimensions (1D or 2D), which decreases the numerical effort once more.…”