The Quark Lepton Mass Problem and the Anti-Grand Unification Model

Abstract

The fermion mass problem and the ideas of mass protection are briefly reviewed. The Fritzsch ansatz for the quark mass matrices and a recent variant, based on a lightest flavour mixing mechanism in which all the CKM mixing angles disappear in the chiral symmetry limit of vanishing up and down quark masses, are discussed. The Anti-Grand Unification Model (AGUT) and the Multiple Point Principle (MPP) used to calculate the values of the Standard Model gauge coupling constants in the theory are described. The application of the MPP to the pure Standard Model predicts the top quark mass to be $173 \pm 5$ GeV and the Higgs particle mass to be $135 \pm 9$ GeV. Mass protection by the chiral quantum numbers of the maximal AGUT gauge group $SMG \times U(1)_f$ provides a successful fit to the charged fermion mass spectrum, with an appropriate choice of Higgs fields to break the AGUT gauge group down to the Standard Model gauge group (SMG) close to the Planck scale. The puzzle of the neutrino masses and mixing angles presents a challenge to the AGUT model and approaches to this problem are briefly discussed.