BCFW Recursion Relations and String Theory

TL;DR

This paper shows that all tree-level string amplitudes can be derived using BCFW recursion, revealing deep connections with field theory and proposing a new recursion relation for tachyon amplitudes.

Contribution

It introduces a novel proof that employs the pomeron vertex operator and uncovers a large momentum limit where string and field theory amplitudes coincide.

Findings

Tree-level string amplitudes are computable via BCFW recursion.

Massless string amplitudes asymptotically match field theory amplitudes in a large momentum limit.

A new recursion relation links tachyon amplitudes to lower-point tachyon amplitudes.

Abstract

We demonstrate that all tree-level string theory amplitudes can be computed using the BCFW recursion relations. Our proof utilizes the pomeron vertex operator introduced by Brower, Polchinski, Strassler, and Tan. Surprisingly, we find that in a particular large complex momentum limit, the asymptotic expansion of massless string amplitudes is identical in form to that of the corresponding field theory amplitudes. This observation makes manifest the fact that field-theoretic Yang-Mills and graviton amplitudes obey KLT-like relations. Moreover, we conjecture that in this large momentum limit certain string theory and field theory amplitudes are identical, and provide evidence for this conjecture. Additionally, we find a new recursion relation which relates tachyon amplitudes to lower-point tachyon amplitudes.