Analytical methods in Quantum Field Theories: from loop integrals to defect correlators

TL;DR

This thesis develops new analytical techniques for Feynman integrals and applies them to defect conformal field theories, specifically analyzing correlation functions in N=4 super Yang-Mills with line defects at weak coupling.

Contribution

It introduces a novel approach to derive linear relations among Feynman integrals and applies these methods to study defect CFTs, identifying classes of integrals essential for perturbative calculations.

Findings

Derived linear relations among Feynman integrals from projective form properties.

Analyzed defect CFT correlators in N=4 super Yang-Mills with Wilson lines.

Identified integral classes involving rational functions and Goncharov polylogarithms.

Abstract

This thesis expands the available techniques at weak coupling by investigating the linear space of Feynman integrals and the role that (super)symmetry plays in reducing the number of integrals necessary to calculate correlators in the presence of a one-dimensional extended operator - the line defect. In the first part, linear relations among Feynman parametrized integrals are derived from their properties as projective forms; these relations are then tested on one- and multi-loop examples, and their connection to the algebra of polynomial ideals is uncovered. In the second part, made of two chapters, the defect CFT formed by the N = 4 super Yang-Mills theory in the presence of a Maldacena-Wilson line is studied through bulk-defect-defect and multipoint correlation functions up to next-to-next-to-leading order in the perturbative expansion at weak coupling. The investigations into this defect CFT lead to the identification of classes of integrals containing all the perturbative information necessary to compute the correlators, which turn out to be either rational functions or Goncharov polylogarithms.