Finite in All Directions

Abstract

We study toroidal compactifications of string theories which include compactification of a timelike coordinate. Some new features in the theory of toroidal compactifications arise. Most notably, Narain moduli space does not exist as a manifold since the action of duality on background data is ergodic. For special compactifications certain infinite dimensional symmetries, analogous to the infinite dimensional symmetries of the $2D$ string are unbroken. We investigate the consequences of these symmetries and search for a universal symmetry which contains all unbroken gauge groups. We define a flat connection on the moduli space of toroidally compactified theories. Parallel transport by this connection leads to a formulation of broken symmetry Ward identities. In an appendix this parallel transport is related to a definition of conformal perturbation theory.