Boundary String Field Theory as a Field Theory -- Mass Spectrum and Interaction

TL;DR

This paper analyzes Boundary String Field Theory (BSFT) actions using analytic continuation, computing low-lying excitation functions, confirming known mass-shell conditions, and matching previous tachyon action results, thus advancing the understanding of string interactions.

Contribution

It introduces an analytic continuation method in momentum space to compute BSFT actions, including massive states, and confirms their consistency with known string theory results.

Findings

Reproduces string mass-shell conditions for various fields.

Matches previous tachyon action results from derivative expansion.

Successfully computes three-point functions on brane-anti-brane systems.

Abstract

We study the BSFT actions by using an analytic continuation in momentum space. We compute various two- and three- point functions for some low-lying excitations including massive states on BPS/non-BPS D-branes. The off-shell two-point functions for the tachyon, the gauge field and the massive fields are found to reproduce the well-known string mass-shell conditions. We compare our action with the tachyon actions previously obtained by the derivative expansion (or the linear tachyon profiles), and find complete agreement. Furthermore, we reproduce the correct on-shell value of the tachyon-tachyon-gauge three-point function on brane-anti-brane systems. Though inclusion of the massive modes has been thought difficult because of the non-renormalizability in string sigma models, we overcome this by adopting general off-shell momenta and the analytic continuation.