Progress on the infrared structure of multi-particle gauge theory amplitudes

TL;DR

This paper reviews recent progress in understanding infrared divergences in gauge theory amplitudes, focusing on the soft anomalous dimension matrix and its implications for high-energy behavior and perturbative calculations.

Contribution

It highlights the known two-loop structure of the soft anomalous dimension matrix and discusses new techniques and results extending to higher loops and all orders for specific cases.

Findings

The soft anomalous dimension matrix is fully known at two loops for massless and massive particles.

The dipole-like structure simplifies analysis in the high-energy limit.

A new all-orders result for a class of diagrams is presented.

Abstract

I will review some of the recent intense activity concerning infrared and collinear divergences in gauge theory amplitudes. The central quantity in these studies is the multi-particle soft anomalous dimension matrix, which is completely known at two loops for both massless and massive particles, and whose properties are currently being studied at three-loops and beyond. I will describe how, in the massless case, the simple dipole-like structure of the anomalous dimension up to two loops can be exploited in the high-energy limit to study effects that go beyond the standard form of Regge factorization. Furthermore, I will briefly review some of the techniques that have recently been developed to compute the soft anomalous dimension at high orders in perturbation theory, and I will give some examples of applications, including a result valid to all orders in perturbation theory for a specific class of diagrams.