ASYMMETRIC ORBIFOLDS AND HIGHER-LEVEL MODELS

I introduce a class of string constructions based on asymmetric orbifo lds leading to level two models. In particular, I derive in detail var ious models with gauge groups E(6) and SO(10), including a four genera tion E(6) model with two adjoint representations. The occurrence of mu ltiple adjoint representations is a generic feature of the constructio n. In the course of describing this approach, I will address the probl em of twist phases in higher twisted sectors of asymmetric orbifolds.