Open string field theory in lightcone gauge

TL;DR

This paper analyzes covariant open bosonic string field theory in lightcone gauge, revealing how gauge fixing alters the moduli space coverage of interaction vertices and involves longitudinal degrees of freedom in scattering.

Contribution

It demonstrates that gauge-fixed vertices correspond to Mandelstam diagrams covering specific moduli space regions, differing from covariant vertices, with longitudinal degrees facilitating additional moduli space coverage.

Findings

Vertices correspond to Mandelstam diagrams with stubs covering specific moduli space regions

Gauge fixing changes the moduli space coverage of interaction vertices

Longitudinal degrees of freedom facilitate additional moduli space coverage in scattering

Abstract

We study covariant open bosonic string field theory in lightcone gauge. When lightcone gauge is well-defined, we find two results. First, the vertices of the gauge-fixed action consist of Mandelstam diagrams with stubs covering specific portions of the moduli spaces of Riemann surfaces. This is true regardless of how the vertices of the original covariant string field theory are constructed (e.g. through minimal area metrics, hyperbolic geometry, and so on). Second, the portions of moduli space covered by gauge-fixed vertices are changed relative to those covered by the original covariant vertices. The extra portions are supplied through the exchange of longitudinal degrees of freedom in scattering processes.