On two string axions as inflaton
  We study an inflationary model where two decoupled string axions drive inflation. The number of e-folds is dependent on the energy scale and the decay constant, but is almost independent of the angular component in spite of the rich geometry of the moduli space. This suppresses the nearly scale-invariant spectrum of the isocurvature perturbations, making the power spectrum of the primordial density perturbations dominated by the adiabatic component. We also briefly discuss some amendments to improve the situation. 
Jinn-Ouk Gong