Four-Point Amplitude from Open Superstring Field Theory

TL;DR

The paper presents a Wess-Zumino-Witten-like open superstring field theory action that avoids contact-term divergences and computes the on-shell four-point tree amplitude using the Giddings map. It demonstrates that, after including the quartic vertex, the second-quantized amplitude exactly reproduces the first-quantized result, with contour deformations and the Giddings map ensuring correct moduli dependence. The key finding is that the quartic interaction cancels a finite contact-term from cubic interactions, preserving gauge invariance and yielding a consistent, divergence-free description of four-point amplitudes. This work reinforces the viability of the open superstring field theory framework for perturbative amplitudes and provides a concrete check against the standard first-quantized prescription.

Abstract

An open superstring field theory action has been proposed which does not suffer from contact term divergences. In this paper, we compute the on-shell four-point tree amplitude from this action using the Giddings map. After including contributions from the quartic term in the action, the resulting amplitude agrees with the first-quantized prescription.