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SUMMARY:Stochastic effective theory for scalar fields in de Sitter space -
  Arttu Rajantie - Imperial College London
DTSTART:20221017T120000Z
DTEND:20221017T130000Z
UID:TALK183227@talks.cam.ac.uk
CONTACT:Francesco
DESCRIPTION:The stochastic Starobinsky-Yokoyama approach is a powerful non
 -perturbative effective description of long-wavelength dynamics of a scala
 r field in de Sitter spacetime. It is based on the observation that on sup
 erhorizon distances the field behaves classically\, with a noise term prod
 uced by subhorizon quantum modes. The approach has been mostly used to cal
 culate the one-point probability distribution of the field\, but its real 
 power lies in describing the asymptotic long-distance behaviour of correla
 tion functions through a spectral expansion. I demonstrate this by calcula
 ting isocurvature constraints for scalar dark matter models and decay rate
 s of metastable vacua. I also show how to extend the stochastic theory bey
 ond the overdamped approximation used by Starobinsky and Yokoyama. The par
 ameters of this effective theory are determined at one-loop order in pertu
 rbation theory\, and do not suffer from the same infrared problems as a di
 rect perturbative computation of observables. Therefore the stochastic the
 ory provides a powerful and accurate way of computing cosmological observa
 bles.
LOCATION:CMS\, Pav. B\, CTC Common Room (B1.19) [Potter Room]
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