The closed strings in Witten's open string field theory

Abstract

We construct the open string states that describe closed strings in Witten's string field theory, enabling amplitudes involving asymptotic closed string states to be computed. We also describe the LSZ formalism for strings and give an heuristic demonstration of the equivalence of Witten's field theory to the Polyakov functional integral. Finally, we construct a field theory which reproduces the usual topological expansion for closed strings only, covering moduli space once and having a large non-abelian symmetry.