 A free quantum particle is described by a single-particle Schrödinger equation.Interaction between particles in a real gas is taken into account by a pertinent many-body Schrödinger equation.In the Hartree–Fock approximation, the total wave-function formula_1 of the system of formula_2 bosons is taken as a product of single-particle functions formula_3,

where formula_5 is the coordinate of the formula_6-th boson.