Mass hierarchies from two extra dimensions
  The string, MSSM GUT, weak and QCD scales, and the Rydberg constant, correspond to the positions of AdS domain wall intersections in a two-dimensional extra space of infinite extent. The domain walls lie along and parallel to the sides of cells which tile the extra space. The cells are four-sided with parallel opposite sides of lengths Rln(pi/2) and Rln(pi), where R is the AdS radius of curvature. Particle masses correspond to the positions of domain walls. We represent the extra space graphically. 
B. F. Riley