Acceptable axion in SUSY SO10 GUT and E8×E8 superstring theories

Abstract

We present an SUSY GUT model, in which the strong CP violation can be eliminated via the invisible axion mechanism. We show that any b1, 1=0 model cannot use the entropy production mechanism, however, A2, A3, A4, A5, B2, B4, B5 and C2 in b1, 1 ⩾ 1 case can do. As an example, we present an A4 model in which axion are diluted efficiently by the entropy production and the fast proton decay is forbidden without requirement of discrete symmetry.