Liouville D-branes in two-dimensional strings and open string field theory

Abstract

We study open strings in the noncritical c = 1 bosonic string theory compactified on a circle at self-dual radius. These strings live on D-branes that are extended along the Liouville direction (FZZT branes). We present explicit expressions for the disc two- and three-point functions of boundary operators in this theory, as well as the bulk-boundary two-point function. The expressions obtained are divergent because of resonant behaviour at self-dual radius. However, these can be regularised and renormalized in a precise way to get finite results. The boundary correlators are found to depend only on the differences of boundary cosmological constants, suggesting a fermionic behaviour. We initiate a study of the open-string field theory localised to the physical states, which leads to an interesting matrix model.