Bound states in nonrelativistic four-fermion interaction model
  The bound states of two particles are studied in frames of non-relativistic quantum field model with current $\times$ current type interaction by analyzing the Bethe-Salpeter amplitudes. The Bethe-Salpeter equations are obtained in closed form. The existence of Goldstone mode corresponding to the spontaneous breaking of additional SU(2) symmetry of the model is revealed. 
A.V.Sinitskaya, E.V.Pavlova