COMPLEX WORLD-SHEETS FROM N=2 STRINGS

We study some properties of target space strings constructed from (2,1 ) heterotic strings. We argue that world-sheet complexification is a g eneral property of the bosonic sector of such target world-sheets. We give a target space interpretation of this fact and relate it to the n on-gaussian nature of free String Field Theory. We provide several one -loop calculations supporting the stringy construction of critical wor ld-sheets in terms of (2,1) models. Using finite-temperature boundary conditions in the underlying (2,1) string we obtain non-chiral target space spin structures, and point out some of the problems arising for chiral spin structures, such as the heterotic world-sheet. To this end , we study the torus partition function of the corresponding asymmetri c orbifold of the (2,1) string.