(1,q=-1) model as a topological description of 2D string theory

We study the (1,q=-1) model coupled to topological gravity as a candidate to describing 2D string theory at the self-dual radius. We define the model by analytical continuation of q>1 topological recursion relations to q=-1. We show that at genus zero the q=-1 recursion relations yield the W1+∞ Ward identities for tachyon correlators on the sphere. A scheme for computing correlation functions of q=-1 gravitational descendants is proposed and applied for the computation of several correlators. It is suggested that the latter correspond to correlators of discrete states of the c=1 string. In a similar manner to the q>1 models, we show that there exist topological recursion relations for the correlators in the q=-1 theory that consist of only one and two splittings of the Riemann surface. Using a postulated regularized contact, we prove that the genus one q=-1 recursion relations for tachyon correlators coincide with the W1+∞ Ward identities on the torus. We argue that the structure of these recursion relations coincides with that of the W1+∞ Ward identities for any genus. ((orig.))