COUPLINGS IN ASYMMETRIC ORBIFOLDS AND GRAND UNIFIED STRING MODELS

Using the bosonic supercurrent (or covariant lattice) formalism, we re view how to compute scattering amplitudes in asymmetric orbifold strin g models. This method is particularly useful for calculating scatterin g of multiple asymmetrically twisted string states, where the twisted states are rewritten as ordinary momentum states. We show how to recon struct some of the three family grand unified string models in this fo rmalism, and identify the quantum numbers of the massless states in th eir spectra. The discrete symmetries of these models are rather intric ate. The superpotentials for the three-family E-6 model and a closely related SO(10) model are discussed in some detail, The forms of the su perpotentials of the two three-family SU(6) models (with asymptoticall y free hidden sectors SU(3) and SU(2) x SU(2)) are also presented. (C) 1997 Elsevier Science B.V.