ACCEPTABLE AXION IN SUSY SO₁₀ GUT AND E₈ x E₈ SUPERSTRING THEORIES

We present an SUSY GUT model, in which the strong CP violation can be eliminated via the invisible axion mechanism. We show that any b_1,1 = 0 model cannot use the entropy production mechanism, however, A2 ,A3 , A4 , A5, B2, B4,B5 and C2 in b_1,1 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.