Bose-Einstein condensation of a non-ideal Bose gas of atoms with large spin

A non-ideal diluted quantum Bose gas of atoms with spin-spin interaction of dipole type is described in the spin coherent states representation. Large values of spin can be treated quasi-classically up to exponentially small corrections, that allows to derive effective interaction between particles of the gas. A preferable ground state configuration of the system is determined by this effective interaction, the spin-spin coupling constant regulates whether the system takes ferromagnetic or antiferromagnetic ground state. The coupling constants of long-ranged spin-spin interaction and short-ranged scattering also define a condition when the system collapses, causing formation of molecules.