Fermion masses and mixings from heterotic orbifold models
  We search for a possibility of getting realistic fermion mass ratios and mixing angles from renormalizable couplings on the Z_6-I heterotic orbifold with one pair of Higgs doublets. In the quark sector, we find cases with reasonable m_c/m_t, m_s/m_b, and V_{cb}, if we ignore the first family. In the lepton sector, we can fit the charged lepton mass ratios, the neutrino mass squared difference ratio, and the lepton mixing angles, considering all three families. 
Jae-hyeon Park (KIAS)