Stochastic inflation from a non-equilibrium renormalization group

by Sebastian Cespedes (Imperial College Londan)

Wednesday 13 May 2026, 11:30 → 12:30 Europe/Zurich

4/2-011 - TH common room (CERN)

Understanding stochastic inflation, and in particular how to compute controlled corrections, remains an important open problem. In this talk, we study this problem using an effective field theory description of light fields in de Sitter space. Starting from a coarse-grained description, we derive an effective theory for the infrared dynamics of long-wavelength modes. As the coarse-graining scale is pushed below the Hubble scale, the dynamics becomes dominated by stochastic fluctuations and diffusion, reproducing stochastic inflation at leading order while allowing systematic corrections to be computed. We then analyse the renormalisation-group flow of the reduced density matrix under changes of the coarse-graining scale. In the infrared limit, the flow approaches a local stochastic regime described by a generalised Fokker–Planck equation. These results provide a unified framework for understanding stochastic inflation as the infrared limit of an effective field theory in de Sitter space.

This seminar will be a blackboard talk.