Uniformization theory and 2D gravity I. Liouville action and intersection numbers

Abstract

This is the first part of an investigation concerning the formulation of 2D gravity in the framework of the uniformization theory of Riemann surfaces. As a first step in this direction we show that the classical Liouville action appears in the expression of the correlators of topological gravity. Next we derive an inequality involving the cutoff of 2D gravity and the background geometry. Another result, always related to uniformization theory, concerns a relation between the higher genus normal ordering and the Liouville action. Furthermore, we show that the chirally split anomaly of CFT is equivalent to the Krichever-Novikov cocycle. By means of the inverse map of uniformization we give a realization of the Virasoro algebra on arbitrary Riemann surfaces and find the eigenfunctions for {\it holomorphic} covariant operators defining higher order cocycles and anomalies which are related to $W$-algebras. Finally we attack the problem of considering the positivity of $e^\sigma$, with $\sigma$ the Liouville field, by proposing an explicit construction for the Fourier modes on compact Riemann surfaces.Comment: 53 pages. '95 publ. version, contains Eq.(5.23), independently derived in hep-th/0004194 studying the null compactification of type-IIA-strin