Theory HEP Seminar

Open EFTs and Decoherence of Primordial Fluctuations

Cliff Burgess

Perimeter Institute & McMaster University

Inflationary models famously provide a quantum origin for the primordial fluctuations that are observed in structure formation and the cosmic microwave background, and efforts are being made to see whether having a quantum origin can be tested observationally. This talk reports on a calculation of the decoherence rate of primordial fluctuations within the most widely used single-field inflationary models using only the minimal interactions required by General Relativity and show that decoherence proceeds very efficiently for super-Hubble modes during inflation despite the weak strength of gravitational interactions. Besides having implications for testing the quantum nature of primordial fluctuations, the calculation also provides a testing ground for ‘Open EFT’ techniques. These are theoretical tools (borrowed from optics and atomic systems) that allow perturbative methods to be extended reliably to very late times in gravitating systems, as seems necessary for understanding phenomena like eternal inflation or black-hole information loss.