From the Standard Model to Grand Unification

This paper reviews the limitations of the standard SU(3) × SU(2) × U(1) model and develops the philosophy of grand unification. Some simple grand unified theories are presented, and calculations made of the order of magnitude of the fine-structure constant α , as well as of sin²\ θ _W and some quark masses. Predictions for nucleon decay and neutrino masses are then discussed; they may be observable in the near future. It is suggested that grand unified theories complex enough for the understanding of the baryon asymmetry of the Universe may also predict a neutron electric dipole moment large enough to be measured. Finally, some inadequacies of GUTs are mentioned.