Large Deviations in the Early Universe

by Prof. Cohen Tim (CERN)

Thursday 22 Feb 2024, 15:00 → 16:30 Europe/Madrid

IFAE Seminar Room (Face-to-face Only)

Fluctuations play a critical role in cosmology. They are relevant across a range of phenomena from the dynamics of inflation to the formation of structure. In many cases, these it is a good approximation to coarse grain these fluctuations (in the sense of a Renormalization Group flow), and they follow a Gaussian distribution as a consequence of the Central Limit Theorem. Yet, some classes of observables are dominated by rare fluctuations and are sensitive to the details of the underlying microphysics. In this talk, I will introduce the Large Deviation Principle, and will explain how it can be used to diagnose when effective approaches fail and one must instead to appeal to the microscopic description.  I will illustrate this phenomenon in the context of determining the validity of the determination of parameter space for the EFT of inflation that leads to an eternally inflating universe.