On topological 2D string and intersection theory

The topological description of 2D string theory at the self-dual radius is studied in the algebro-geometrical formulation of the Ak+1 topological models at k = −3. Genus-zero correlators of tachyons and their gravitational descendants are computed as intersection numbers on moduli space and compared to 2D string results. The interpretation of negative momentum tachyons as gravitational descendants of the cosmological constant, as well as modifications of this, is shown to imply a disagreement between 2D string correlators and the associated intersection numbers.