2005/01/27 by Erik Kramer, Kramer, Erik
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Theory (hep-th) #hep-th
paper · pdf · doi:10.48550/arxiv.hep-th/0501224
arxiv created 2005/01/27 · arxiv updated 2009/12/01
Various ideas support the notion that the GUT gauge group might be a semi-simple direct-product group such as SU(5) × SU(5). The doublet-triplet splitting problem can be solved with a direct product group. String theory suggests that the GUT scale is a modulus. Requiring this rules out a single SU(5) gauge group. A model with SU(5) × SU(5) gauge symmetry and the GUT scale as a modulus has been shown to exist. It is shown that extending these ideas to SO(10) × SO(10) cannot be done with the above requirement without unwanted massless modes at lower energy scales that spoil the unification of couplings. Therefore these two conditions highly constrain the class of possible GUT models.