The (0,2) exactly solvable structure of chiral rings, Landau-Ginzburg theories and Calabi-Yau manifolds

We identify the exactly solvable theory of the conformal fixed point of (0,2) Calabi-Yau σ-models and their Landau-Ginzburg phases. To this end we consider a number of (0,2) models constructed from a particular (2,2) exactly solvable theory via the method of simple currents. In order to establish the relation between exactly solvable (0,2) vacua of the heterotic string, (0,2) Landau-Ginzburg orbifolds and (0,2) Calabi-Yau manifolds, we compute the Yukawa couplings of the exactly solvable model and compare the results with the product structure of the chiral ring which we extract from the structure of the massless spectrum of the exact theory. We find complete agreement between the two up to a finite number of renormalizations. For a particularly simple example we furthermore derive the generating ideal of the chiral ring from a (0,2) linear σ-model which has both a Landau-Ginzburg and a (0,2) Calabi-Yau phase. (orig.)