Developments In 5D Quark-Lepton Symmetric Models
  We outline some recent developments in higher dimensional Quark-Lepton (QL) symmetric models. The QL symmetric model in five dimensions is discussed, with particular emphasis on the use of split fermions. An interesting fermionic geography which utilises the QL symmetry to suppress the proton decay rate and to motivate the flavor differences in the quark and leptonic sectors is considered. The 5D quartification model is outlined and contrasted with 4D constructs. 
A. Coulthurst, A. Demaria, K. L. McDonald and B. H. J. McKellar