RADIATIVE GUT SYMMETRY-BREAKING IN AN R-SYMMETRICAL FLIPPED SU(5) MODEL

We study the generation of the grand unified theory (GUT) scale throug h radiative corrections in the context of an R-symmetric ''flipped'' S U(5)x U(1)(X) model. A negative mass squared term for the GUT Higgs fi elds develops due to radiative effects along a flat direction at a sup erheavy energy scale. The R symmetry is essential in maintaining tripl et-doublet splitting and F flatness in the presence of nonrenormalizab le terms. The model displays radiative electroweak symmetry breaking a nd satisfies all relevant phenomenological constraints.