The Cosmological Flow

by Denis Werth (IAP, Sorbonne Université)

Tuesday Mar 5, 2024, 11:00 AM → 12:00 PM Europe/Paris

Salle des séminaires (IAP)

Cosmological correlators hold the key to high-energy physics as they probe the earliest moments of our Universe. However, even at tree-level, perturbative calculations are limited by technical difficulties absent in flat-space Feynman diagrammatic. As a result, a complete dictionary mapping the landscape of inflationary theories and the corresponding observable signatures is not yet available.

In this talk, I will start with a pedagogical introduction to observational, phenomenological and theoretical aspects of cosmological correlators meant for the broad audience, at the same time also reviewing the physics of inflation. Then, I will present the cosmological flow: a complete formalism to systematically compute tree-level primordial correlators in any theory, bypassing the intricacies of Feynman diagram computations. This framework relies on following the time evolution of these correlators from the initial quantum vacuum state to the end of inflation. From first principles, the structure of the bulk time evolution imposes a set of universal differential equations in time satisfied by equal-time correlators. These equations can be systematically solved in an automatic manner.

I will then demonstrate the power of this approach by exposing new results in various classes of inflationary models that are difficult to track analytically, such as the strongly mixed regime of the cosmological collider—a robust probe of the field content of inflation—that requires a non-perturbative treatment of quadratic mixings, or in the presence of primordial features. These results might be of interest to you as we provide new templates to be constrained by LSS and/or CMB maps.

Eventually, I will introduce CosmoFlow: a new accurate open source Python code that is specifically designed to offer a simple, intuitive and flexible coding environment to theorists, primordial and late-time cosmologists. Our numerical implementation of the cosmological flow allows any new user to quickly become familiar with this approach and obtain immediate high-resolution results for correlators that were previously out of reach.

This talk is based on arXiv:2302.00655, arXiv:2312.06559, arXiv:2402.03693.