Spontaneous Symmetry Breaking on non-Abelian Kaluza-Klein and   Randall-Sundrum Theories
  The fibre bundle formalism inherent to the construction of non-abelian Kaluza-Klein theories is presented and its associated dimensional reduction process analysed: is performed the dimensional reduction of G-invariant matter and gauge fields over a multidimensional universe; the harmonic decomposition of non-symmetric fields over its internal space established and their dimensional reduction done. The spontaneous compactification process is presented. It is shown that during the dimensional reduction process two types of symmetry breaking can occur: a geometric followed by a spontaneous symmetry breaking. This last is connected to a scalar field resulting from the dimensional reduction process itself. We determine explicitly the scalar potential form leading to that symmetry breaking for the case in which the internal space is symmetric and an analysis for the general case is performed. The principal problems found in the construction of realistic Kaluza-Klein models are discussed and some solutions reviewed. The hierarchy problem is examined and its solution within Kaluza-Klein models with a large volume internal space considered. As an alternative solution, the Randall-Sundrum model is presented and its principal properties analysed. In special, the stability of the hierarchy is studied. 
Rui F. L. Matos