Correlation functions of local composite operators from generalized unitarity

TL;DR

This paper introduces a generalized unitarity method to compute correlation functions of local gauge-invariant operators in quantum field theories, demonstrated through examples in N=4 super-Yang-Mills theory involving BPS and non-BPS operators.

Contribution

It develops a novel approach using generalized unitarity for constructing correlation functions, including form factors and multi-operator correlators, with applications to symmetries and energy flow calculations.

Findings

Successful calculation of correlation functions involving BPS and non-BPS operators.

Identification of symmetry properties in momentum space representations.

Application to energy flow and background gravitational field correlators.

Abstract

We describe the use of generalized unitarity for the construction of correlation functions of local gauge-invariant operators in general quantum field theories and illustrate this method with several calculations in N=4 super-Yang-Mills theory involving BPS and non-BPS operators. Form factors of gauge-invariant operators and their multi-operator generalization play an important role in our construction. We discuss various symmetries of the momentum space presentation of correlation functions, which is natural in this framework and give examples involving non-BPS and any number of BPS operators. We also discuss the calculation of correlators describing the energy flow in scattering processes as well as the construction of the effective action of a background gravitational field.