Abstract

We investigate a string-inspired axion extension of the standard model obtained from Type II superstrings using quiver method. In the first part, we discuss intersecting Type IIA D6-branes wrapping non trivial 3-cycles in the presence of the Peccei-Quinn symmetry U(1)PQ. Concretely, a complex scalar field phi=rho exp(i sigma f sigma), where sigma is a stringy axion generates a general fermion Yukawa coupling weighted by a flavor-dependent power nf taking specific values. Using string theory and standard model data with adequate scales, we show that the corresponding axion window could lie in the allowed range 109GeV <= f sigma <= 1012GeV matching with the recent cosmological results.