Towards open-closed string duality: Closed Strings as Open String Fields

TL;DR

This paper develops a framework linking open and closed string theories by representing closed string states as projectors in open string field theory, revealing a new perspective on D-branes and string duality.

Contribution

It introduces a translation dictionary between open and closed strings, showing how closed string states correspond to star algebra projectors in open string field theory, especially emphasizing the zero mode sector.

Findings

Boundary states correspond to the identity string field in open string theory.

Closed string D-branes are represented as superpositions of star algebra projectors.

The approach provides a new perspective on open-closed string duality.

Abstract

We establish a translation dictionary between open and closed strings, starting from open string field theory. Under this correspondence, (off-shell) level-matched closed string states are represented by star algebra projectors in open string field theory. Particular attention is paid to the zero mode sector, which is indispensable in order to generate closed string states with momentum. As an outcome of our identification, we show that boundary states, which in closed string theory represent D-branes, correspond to the identity string field in the open string side. It is to be remarked that closed string theory D-branes are thus given by an infinite superposition of star algebra projectors.