2D GRAVITY COUPLED TO TOPOLOGICAL MINIMAL MODELS

We discuss the properties of genus 0 correlation functions of a topological minimal model (the model A(k+1)) coupled to 2D topological gravity. The action of the twisted minimal model is perturbed by nontrivial couplings to gravitational descendants, which, in turn, are constructed entirely from the fields in the matter sector of the theory. We develop an explicit formulation, in terms of orthogonal polynomials, for investigating the large phase space of the theory. Some useful identities for correlation functions (valid on the large phase space) of the theory are established and the puncture and dilaton equations of topological gravity are obtained as special cases of these general relations. Finally, we obtain an important relation expressing the gravitational couplings in terms of the couplings in the small phase space (i.e. the couplings to the chiral primaries). Thus eventually we are able to solve for the coordinates (couplings) of the large phase space in terms of the Landau-Ginzburg superpotential characterizing the matter sector of the model.