# On the gauge chosen by the bosonic open string

## TL;DR

This paper investigates the gauge choice in bosonic open string theory, revealing that string theory naturally selects a simplified gauge (Gervais-Neveu gauge) that leads to more efficient color-ordered vertices and clarifies the connection to effective field theories.

## Contribution

It demonstrates that string theory's natural gauge choice simplifies the color-ordered vertices and relates to the Gervais-Neveu gauge, providing insights into the gauge structure of string-derived effective field theories.

## Key findings

- Color-ordered vertices from string theory are more efficient than traditional ones.
- String theory naturally adopts the Gervais-Neveu gauge for these vertices.
- A field redefinition aligns string theory vertices with effective field theory.

## Abstract

String theory gives S matrix elements om which is not possible to read any gauge information. Using factorization we go off shell in the simplest and most naive way and we read which are the vertices suggested by string. To compare with the associated Effective Field Theory it is natural to use color ordered vertices. The alpha'=0 color ordered vertices suggested by string theory are more efficient than the usual ones since the three gluon color ordered vertex has three terms instead of six and the four gluon one has one term instead of three. They are written in the so called Gervais-Neveu gauge. The full Effective Field Theory is in a generalization of the Gervais-Neveu gauge with alpha') corrections. Moreover a field redefinition is required to be mapped to the field used by string theory. We also give an intuitive way of understanding why string choose this gauge in terms of the minimal number of couplings necessary to reproduce the non abelian amplitudes starting from color ordered ones.