Chiral grand unification in SU(N>5)

Abstract

Discusses a general scheme for anomaly-free SU(N>5) chiral unification models which can accommodate several conventional generations of quarks and leptons. This scheme predicts at least one (V+A) generation and admits superweak flavour-changing transitions. Multistage breaking hierarchies, compatible with the observed values of the strong and the weak couplings as well as the weak mixing angle, with a grand unification mass of about 1012 MW, are proposed. Illustrative models based on SU(6), SU(7), SU(8) and SU(9) are presented. Possibilities of suppressing proton decay in these SU(N>5) chiral models are demonstrated.