== Two Universal Extra Dimensions ==

=== Author ===

Peter Manning Jr[[BR]]
University of California Santa Cruz[[BR]]
pmmannin at ucsc dot edu[[BR]]

=== Description of the model and references ===

In the Two Universal Extra Dimensions (2UED) model, all of the Standard Model fields are permitted to propagate in the six dimensional space-time. This model is similar to its predecessor, the Universal Extra Dimensions (MUED) model in that the extra dimensions are compactified on some manifold. There are several schema for compactifying two extra dimensions (reference), but in the case of this model, the two extra dimensions are compactified on a square. This scheme allows for the existence of chiral fermions, as there are in the Standard Model. There are several very phenomenologically attractive features of this model. These include the existence of a heavy, weakly interacting, stable particle (dark matter candidate), allowance of only integer multiples of 3 fermion generations, as well as the production of a completely new set of heavy scalar particles. The particle spectra of this model includes all of the Standard Model particles as well as their Kaluza-Klein excitations in either one or both of the compactified extra dimensions. Upon compactification one recovers the four dimensional gauge fields, but are left with 2 extra components. One of these components, the spinless adjoint to the gauge field, is invariant under a 6D gauge transformation. The other, orthogonal excitation, corresponds to the Nambu-Goldstone boson eaten by the massive vector gauge field level by level.