Weak mixing angle and proton stability in F-theory GUT

It is pointed out that a class of flipped SU(5)SU(5) models based on F-theory naturally explains the gauge coupling unification. It is because the gauge group SU(5)×U(1)XSU(5)×U(1)X is embedded in SO(10)SO(10) and E8E8. To prohibit the dimension 4 and 5 proton decay processes, the structure group associated with monodromy should be SU(3)⊥SU(3)⊥ or smaller. Extra heavy vector-like pairs of {5−2,5¯2} except only one pair of Higgs should be disallowed, because they could induce the unwanted dimension 5 proton decays. We construct a simple global F-theory model considering these points. To maintain sin2θW0=38 at the GUT scale, the fluxes are turned on only on the flavor branes.