# Loops in the separate universe framework

- Institution: CERN
- Department: TH institutes
- Speaker: David Seery
- Year: 2024
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3019552)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

In this talk I will review the separate universe framework as a tool to perform loop calculations during and after inflation. I will describe recent work (with L. Iacconi and D. Mulryne) in which we use this framework to calculate loops representing a cascade of power from short scales to much longer, infrared scales. The backreaction associated with this cascade can destroy our ability to uniquely predict the subsequent evolution of a superhorizon volume based on the smoothed field values at its location, which is an essential condition for use of the separate universe method. I will discuss a personal selection of open issues in relating separate-universe type calculations to in-in type calculations using the full formulation of out-of-equilibrium field theory..

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## Lectures

1. [Loops in the separate universe framework](https://invisiblenetwork.ai/learn/cern/3019552/8d2c4d5dcffc), 55 min (CERN's player)