Large Lepton-flavor Mixings from E8 Kodaira Singularity: Lopsided   Texture via F-theory Family Unification
  We show that a special type of colliding 7-brane configuration of a codimension-two singularity realizes not only a six-dimensional spectrum with exactly the same quantum numbers as that of the three-generation E7/(SU(5) x U(1)^3) coset family unification model, but also the three sets of nonchiral singlet pairs with precisely the correct U(1) charges needed for explaining the Yukawa hierarchies and large lepton-flavor mixings in a well-known seesaw scenario. 
Shun'ya Mizoguchi
hep-th hep-ph