Celestial IR divergences in general most-subleading-color gluon and gravity amplitudes

TL;DR

This paper investigates the infrared divergence structure of celestial most-subleading-color gluon amplitudes, revealing similarities with gravity amplitudes, and proposes a celestial exponentiation formula, with implications for effective models in the Regge limit.

Contribution

It introduces a simple celestial exponentiation formula for IR divergences in most-subleading-color gluon amplitudes and explores their relation to gravity amplitudes and effective Wess-Zumino-Witten models.

Findings

Celestial IR divergences in gluon and gravity amplitudes share structural similarities.

A simple exponentiation formula for dipole IR divergences is proposed.

In the Regge limit, the soft factor obeys the Knizhnik-Zamolodchikov equation.

Abstract

Gluon amplitudes at most-subleading order in the $1/N$ expansion share a remarkable simplicity with graviton amplitudes: collinear divergences are completely absent in both and, as a consequence, their full IR behavior arises from soft gluon/graviton exchange among the external states. In this paper we study the effect of all-loop IR divergences of celestial most-subleading color gluon amplitudes and their similarities with the celestial gravity case. In particular, a simple celestial exponentiation formula for the dipole part can be written. We also analize how this exponentiation is modified by non-dipole contributions. Finally we also show that, in the Regge limit, the soft factor satisfies the Knizhnik-Zamolodchikov equation hinting at the possibility that, in this limit, an effective Wess-Zumino-Witten model would describe the dynamics of the infrared sector.