Radiative effects on the chiral square

We consider general field theories in six dimensions, with two of thedimensions compactified on a T_{2}/Z_{4} orbifold. Six-dimensional Weylfermions propagating on this background give rise to a chiral zero-mode, whichmakes them interesting for phenomenological applications. The compacttwo-dimensional space is flat and has three conical singularities. We considerthe one-loop structure of these theories, and show that the presence oflogarithmic divergences requires the introduction of counterterms precisely atthese three singular points. We also show that the corresponding localizedoperators are rotationally symmetric in the plane of the two extra dimensions,as expected from the geometry about the singularities. We derive thepropagators for spin-0, spin-1/2 and spin-1 fields in momentum space, in such away that the appropriate boundary conditions are satisfied. This allows us toefficiently calculate loop diagrams in any given model. We give generalexpressions for the mass splittings among Kaluza-Klein modes within a givenlevel. Our results can also be used to obtain interesting KK-parity preservinginteractions among Kaluza-Klein modes. We pay special attention to thecomponents of six-dimensional gauge fields that transform as scalars under thefour-dimensional Lorentz group. These states provide a characteristic signaturefor these scenarios. In particular, we find that they can easily be thelightest particles in the Kaluza-Klein spectrum.Comment: 70 pages, 15 figure