Families as Neighbors in Extra Dimension

Abstract

We propose a new mechanism for explanation of the fermion hierarchy without introducing any family symmetries. Instead, we postulate that different generations live on different branes embedded in a relatively large extra dimension, where the gauge fields can propagate. The electroweak symmetry is broken on a separate brane, which is a source of exponentially decaying Higgs profile in the bulk. The resulting fermion masses and mixings are determined by an exponentially suppressed overlap of the fermion and Higgs wave functions and are automatically hierarchical even if all copies are identical and there is no hierarchy of distances. In this framework the well known pattern of the "nearest neighbor mixing" is predicted due to the fact that the families are literally neighbors in the extra space. This picture may also provide a new way of a hierarchically weak supersymmetry breaking, provided that the combination of three family branes is a non-BPS configuration, although each of them, individually taken, is. This results in exponentially weak supersymmetry breaking. We also discuss the issue of embedding identical branes in the compact spaces and localization of the fermionic zero modes.