SOME FEATURES OF (0,2)MODULI SPACES

We discuss some aspects of perturbative (0, 2) Calabi-Yau moduli space . In particular, we show how models with different (0, 2) data can mee t along various sub-loci in their moduli space. In the simplest exampl es, the models differ by the choice of desingularization of a holomorp hic V-bundle over the same resolved Calabi-Yau base while in more comp licated examples, even the smooth Calabi-Yau base manifolds can be top ologically distinct. These latter examples extend and clarify a previo us observation which was limited to singular Calabi-Yau spaces and see m to indicate a multicritical structure in moduli space. This should h ave a natural F-theory counterpart in terms of the moduli space of Cal abi-Yau four-folds. (C) 1997 Elsevier Science B.V.