D-brane and Gauge Invariance in Closed String Field Theory

TL;DR

This paper develops a bosonic closed string field theory coupled to a D-brane, analyzing gauge invariance and boundary state interactions with constant field strength and tilt, connecting to low-energy effective actions.

Contribution

It introduces a gauge-invariant formalism for closed string field theory coupled to D-branes using boundary states with constant field strength and tilt.

Findings

Gauge invariance determines boundary state normalization.

The formalism reproduces low-energy effective actions.

The dependence on field strength and tilt is explicitly derived.

Abstract

We construct a system of bosonic closed string field theory coupled to a D-brane. The interaction between the D-brane and closed string field is introduced using the boundary state which is a function of constant field strength $F_{\mu\nu}$ and the tilt $\theta_\mu^i$ of the D-brane. We find that the gauge invariance requirement on the system determines the $(F_{\mu\nu},\theta_\mu^i)$-dependence of the normalization factor of the boundary state as well as the form of the purely $(F_{\mu\nu},\theta_\mu^i)$ term of the action. Correspondence between the action in the present formalism and the low energy effective action (bulk + D-brane actions) in the $\sigma$-model approach is studied.