New Constraints on SO(10) Model-Building from String Theory

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  • 28 June 1996
Abstract
A recent analysis of the methods by which higher-level gauge symmetries are realized in string theory has made it possible to systematically obtain new constraints on string GUT model-building. In this paper, we perform such a study for the case of SO(10) string GUT models, and find a number of significant new results. We find, for example, that free-field heterotic string models can never give rise to massless SO(10) representations with dimensions exceeding 54, regardless of the affine level at which SO(10) is realized. This rules out the useful 120, 126, 144, and 210 representions. We also find that the possibilities for massless adjoint scalars are highly constrained, and prove that for conventional free-field embeddings these states must always be singlets under all gauge symmetries beyond SO(10). These results thus severely limit the types of phenomenologically realistic SO(10) models that can be derived from string theory, and suggest new embeddings which may be of phenomenological interest for string GUT model construction.

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