A Mellin space approach to cosmological correlators
Charlotte Sleight
Abstract
A bstract We propose a Mellin space approach to the evaluation of late-time momentum-space correlation functions of quantum fields in ( d + 1)-dimensional de Sitter space. The Mellin-Barnes representation makes manifest the analytic structure of late-time correlators and, more generally, provides a convenient general d framework for the study of conformal correlators in momentum space. In this work we focus on tree-level correlation functions of general scalars as a prototype, including n -point contact diagrams and 4-point exchanges. For generic scalars, both the contact and exchange diagrams are given by (generalised) Hypergeometric functions, which reduce to existing expressions available in the literature for d = 3 and external scalars which are either simultaneously conformally coupled or massless. This approach can also be used for the perturbative bulk evaluation of momentum space boundary correlators in ( d + 1)-dimensional anti-de Sitter space (Witten diagrams).