Gauge Invariant Operators and Closed String Scattering in Open String Field Theory

TL;DR

This paper computes gauge-invariant operators in open string field theory and demonstrates that their tree-level scattering amplitudes for closed string states match known bosonic string theory results, confirming the validity of the proposed observables.

Contribution

It explicitly calculates couplings of closed string states with open string states and verifies that the resulting scattering amplitudes align with established bosonic string theory amplitudes.

Findings

Tree-level amplitudes match bosonic string theory results

Explicit couplings of closed and open string states are derived

Supports the validity of recent observables proposal in open string field theory

Abstract

Using the recent proposal for the observables in open string field theory, we explicitly compute the coupling of closed string tachyon and massless states with the open string states up to level two. Using these couplings, we then calculate the tree level S-matrix elements of two closed string tachyons or two massless states in the open string field theory. Up to some contact terms, the results reproduce exactly the corresponding amplitudes in the bosonic string theory.