A Solvable Model for Fermion Masses on a Warped 6D World with the Extra   2D Sphere
  In a warped 6D world with an extra 2-dimensional sphere, we propose an exactly solvable model for fermion masses with zero mode. The warp factor is given by $\phi (\theta ,\varphi )=\sin{\theta }\cos{\varphi }$, which is a solution to the 6D Einstein equation with the bulk cosmological constant $\Lambda $ and the energy-momentum tensor of the bulk matter fields. Our model provides another possibility of obtaining fermion zero mode, rather than traditional model based on Dirac's monopole. 
Akira Kokado, Takesi Saito
hep-th