Gauge-covariant S-matrices for field theory and strings

TL;DR

This paper presents a Lorentz covariant formulation of S-matrices using free field strengths, applicable to both field theory and string theory, with explicit examples of superstring amplitudes and related actions.

Contribution

It introduces a gauge-covariant approach to S-matrices in field and string theory, simplifying calculations and ensuring gauge invariance.

Findings

Explicit four-vector superstring tree amplitudes in covariant form

Field theory actions derived for first three orders in the slope

Demonstration of automatic gauge invariance in string vertex operators

Abstract

S-matrices can be written Lorentz covariantly in terms of free field strengths for vector states, allowing arbitrary gauge choices. In string theory the vertex operators can be chosen so this gauge invariance is automatic. As examples we give four-vector (super)string tree amplitudes in this form, and find the field theory actions that give the first three orders in the slope.