Large neutrino mixing angles for type-I see-saw mechanism in SO(10) GUT
  We consider the neutrino mixing angles in an SO(10) GUT with the usual Higgs structure in which neutrino masses are explained by the type-I see-saw mechanism. The Dirac-neutrino Yukawa matrix then has a structure similar to that of the $u$-quark. We determine the light neutrino mass matrix through type-I see-saw mechanism using the experimentally consistent $u$-quark Yukawa matrix. We find that large neutrino mixing-angles emerge naturally in this model. 
Bipin R. Desai, G. Rajasekaran and U. Sarkar