Democratic mass matrices induced by strong gauge dynamics and large mixing angles for leptons

Abstract

We consider dynamical realization of the democratic type Yukawa coupling matrices as the Pendelton-Ross infrared fixed points.?Such fixed points of the Yukawa couplings become possible by introducing many Higgs fields, which are made superheavy but one massless mode. Explicitly, we consider a strongly coupled GUT based on $SU(5) \times SU(5)$, where rapid convergence to the infrared fixed point generates sufficiently large mass hierarchy for quarks and leptons. Especially, it is found that the remarkable difference between mixing angles in the quark and lepton sectors may be explained as a simple dynamical consequence. We also discuss a possible scenario leading to the realistic mass spectra and mixing angles for quarks and leptons. In this scheme, the Yukawa couplings not only for top but also for bottom appear close to their quasi-fixed points at low energy and, therefore, $\tan β$ should be large.