STRING FIELD-EQUATIONS FROM THE GENERALIZED SIGMA-MODEL-II

We improve and extend a method introduced in an earlier paper for deri ving string field equations. The idea is to impose conformal invarianc e on a generalized sigma model, using a background field method that e nsures covariance under very general non-local coordinate transformati ons. The method is used to derive the free string equations, as well a s the interacting equations for the graviton-dilaton system. The full interacting string field equations derived by this method should be ma nifestly background independent. (C) 1998 Elsevier Science B.V.