Fermion masses and mixing in models with SO(10) x A_4 symmetry
  We study the flavour sector in models where the three families of matter are unified in a $(16,3)$ representation of the $SO(10)\times A_4$ group. The necessary ingredients to realize tri-bi-maximal mixing in the lepton sector are identified systematically. The non-renormalizable operators contributing to the fermion mass matrices play an important role. We also present a mechanism to explain the inter-family mass hierarchy of quarks and charged leptons, which relies on a `universal seesaw' mechanism and is compatible with tri-bi-maximal mixing. 
Federica Bazzocchi (Valencia U., IFIC), Michele Frigerio (IPhT,   Saclay), Stefano Morisi (Valencia U., IFIC)