La dimensione anomala soffice per ampiezze di scattering in teorie di gauge

Understanding the infrared behaviour of gauge theories is a fundamental step in making accurate Standard Model predictions. Infrared divergences are known to exponentiate, and in this thesis we focus our attention on the soft anomalous dimension, which is the fundamental object governing the infrared behaviour of a theory. The soft anomalous dimension can be computed diagrammatically using special types of Feynman diagrams known as multiparton webs. The first part of this thesis is devoted to a review of infrared divergences and how to calculate the anomalous dimension. I provide examples of up to a three-loop order. Webs without three or four-gluon vertices are shown to be rather well understood, even at high-loop order, while webs with gluon-gluon interactions are strikingly more difficult to handle, even in the simplest cases; in this dissertation, I explore the approach relying on multifold Mellin-Barnes representations. The core of my work is to explore the factorisation properties of some classes of webs, first by carrying out explicit calculations for the simplest examples, and then providing the formal proof of a factorisation theorem for webs composed of two connected subdiagrams spanning a maximum number of external legs. This kind of webs contributes to the anomalous dimension in a factorised manner, as a sum of pairs of transcendental functions, each function pertaining to one of the two subdiagrams and depending only on the cusp angles spanned by the relevant subdiagram. Understanding the factorisation properties of webs potentially allows to constrain the anomalous dimension, making some steps towards the boostrap of the soft anomalous dimension at four loops.