COVARIANT CALCULATION OF THE HETEROTIC STRING EFFECTIVE ACTION IN A CURVED (1,0) SUPERSPACE

Covariant methods for studying the non-local structure of the effective action for the two-dimensional non-linear heterotic sigma -model are developed in a curved (1,0) superspace. The calculational techniques are based on the suitably generalised (to the case of a curved (1,0) superspace) Schwinger-De Witt-Seely representation for the superpropagator heat kernels (Green functions). The results obtained for the low-energy heterotic string effective action are in agreement with the known ones.