Space-time supersymmetry in compactified string theory and superconformal models

Space-time supersymmetric compactified string theories which obey spin and statistics, tachyon free, and modular invariant, are constructed by compactifying on arbitrary sums of N = 2 minimal superconformal models. Heterotic-type compactifications with realistic phemomenology are described. The theories offer a considerably simpler structure than standard supersymmetric compactifications, gauge groups which contain E ₆ with chiral fermions in realistic grand unification representations, and no free parameters. Also given are the partition functions and the classification of modular invariants for the N = 2 minimal superconformal models.