On fixed points and fermion mass structure from large extra dimensions

Abstract

We examine the fixed point behaviour of Yukawa couplings in supersymmetric theories with varying numbers of dimensions. We show that Pendleton-Ross fixed point behaviour is greatly amplified in the MSSM with no extra dimensions and 4 extra $5+\bar{5}$ multiplets or the MSSM with one extra large dimension and 3 extra $5+\bar{5}$ multiplets. We also show that power law running in models with large extra dimensions can give a hierarchical set of quasi-fixed points for the Yukawa couplings in a manner which is similar to the Froggatt-Nielsen mechanism. However, we also point out the limited perturbative domain in models with power law running

Comments: 17 Pages plain latex; includes 3 postscript figures