Mass Hierarchy from SU(1,1) Horizontal Symmetry
  The new mechanism for the generation of the chiral generations is proposed based on the SU(1,1) horizontal gauge symmetry. The appearance of the chiral generations is controlled by the coupling constant s of the model. This is crucial in the grand unification scheme. The resulting chiral generations naturally acquire the hierarchal Yukawa coupli ng matrices. Propriety of the model to the observed hierarchical structure is discussed nume rically under the minimal parameter set. 
Kenzo Inoue and Nao-aki Yamashita