Classical string profile for a class of DDF amplitudes

TL;DR

This paper explicitly computes three-point scattering amplitudes involving photons and massive higher spins in bosonic string theory, then explores the classical limit revealing a rotating string with a kink.

Contribution

It provides explicit calculations of DDF-based scattering amplitudes and derives the classical string profile in the infinite spin limit.

Findings

Explicit three-point amplitude calculations for massive higher spins.

Identification of a classical rotating string with a transverse kink.

Connection between quantum amplitudes and classical string dynamics.

Abstract

In the critical bosonic string theory, we explicitly evaluate the three point scattering amplitude at tree level, of a photon with two massive higher spins. The massive excitations belong to states of the form $A_{-r_1}^{s_1} A_{-r_2}^{s_2}$ where $A_{-n}$ is a DDF creation operator. Next, we take the infinite ``spin'' limit to arrive at the classical string dynamics. We find a rotating ``floppy'' string lying mostly on a plane which develops a transverse kink.