Flipped SU ( 5 ) : a Grand Unified Superstring Theory ( GUST ) Prototype

In this Lecture we first review the basic properties that make flipped SU(5) a very economical and well motivated unified model, including some recent developments regarding the prediction for αs and new implications for proton decay. Then we sketch the derivation of flipped SU(5) from strings, stressing some new results concerning the cosmological constant, the stability of the no-scale mechanism, and a new mechanism for generating the “LEP” scale MLEP ∼ 1016 GeV in string models. Finally we present a sample supersymmetry breaking scenario, where all sparticle masses depend on a single parameter, and discuss the experimental signatures at LEP and the Tevatron. This scenario also predicts the top-quark mass to be close to 175 GeV. CTP-TAMU-41/95 DOE/ER/40717–19 ACT-15/95 November 1995 Lecture presented by D. V. Nanopoulos at the 33rd International School of Subnuclear Physics “Vacuum and vacua: the physics of nothing”, Erice, July 2-10, 1995.