Democratic Approach To Atmospheric And Solar Neutrino Oscillations
  Working with a ${\cal U}(1)$ flavor symmetry, we show how the hierarchical structure in the charged fermion sector and a democratic approach for neutrinos that yields large solar and atmospheric neutrino mixings can be simultaneously realized in the MSSM framework. However, in SU(5) due to the unified multiplets we encounter difficulties. Namely, democracy for the neutrinos leads to a wrong hierarchical pattern for charged fermion masses and mixings. We discuss how this is overcome in flipped SU(5). 
Qaisar Shafi, Zurab Tavartkiladze