Exactly Solvable Points in the Moduli Space of Heterotic N=2 Strings
  We investigate the subset of exactly solvable (0,4) world sheet supersymmetric string vacua contained in a recent class of Gepner-like (0,2) superconformal models. The identification of these models with certain points of enhanced gauge symmetry on K_3 x T_2 can be achieved completely. Furthermore, we extend the construction of in general (0,2) supersymmetric exactly solvable models to the case where also a nontrivial part of the vector bundle is embedded into the hidden E_8 gauge group. For some examples we explicitly calculate the enhanced gauge symmetries and show that they open up the way to interesting branches of the N=2 moduli space. For some of these models candidates of typeII dual descriptions exist. 
Ralph Blumenhagen and Andreas Wisskirchen