“Soft de Sitter Effective Theory” by Timothy Cohen

In this talk, I will introduce the Soft de Sitter Effective Theory (SdSET), whose purpose is to model the long wavelength dynamics of quantum fluctuations beyond the horizon.  After providing some conceptual and technical issues that motivate the need for a new EFT approach, I will explain how we identify the propagating low energy degrees of freedom, along with their scaling under a power counting scheme and their transformation properties under the symmetries that persist to the IR.  I will sketch how to derive  the SdSET action, and will argue that it can be expressed as an expansion in local operators, augmented by stochastic initial conditions.  Finally, I will show how this framework can be applied to a number of physically interesting problems: massive scalar fields in dS, light scalar fields and stochastic inflation, and the conservation of the inflationary adiabatic modes.