Résumé / Abstract Seminaire_GReCO

"Free scalar correlators in de Sitter spacetime via the stochastic approach beyond slow roll"

Archie Cable
Department of Physics, Imperial College (Londres, Royaume-Uni)

There are many areas of cosmology where the calculation of spectator scalar field correlators in de Sitter spacetime is necessary, most notably during the inflationary epoch. The mode expansion of the QFT in a de Sitter background can be used to evaluate them in free field theory; however, perturbative techniques break down due to IR divergences when scalar self-interactions are considered. The stochastic method, pioneered by Starobinsky and Yokoyama, is an alternative approach to calculating these correlators but thus far most of the work in this area has been applied to the case where the field is in “slow roll”. In this talk, I will discuss our recent work (https://arxiv.org/abs/2011.00907) where we extend the method beyond this approximation. We find that the stochastic noise evaluated by the Starobinsky-Yokoyama approach, extended to beyond the overdamped limit, does not reproduce the exact asymptotic long-distance behaviour of field correlators in free field theory. Therefore we propose a new method whereby the stochastic 2-point function is matched to its QFT counterpart in order to calculate the correct noise. Using this matched noise, we proceed to show that the stochastic approach correctly reproduces all higher-order correlators for free fields.

lundi 7 décembre 2020 - 11:00
Institut d'Astrophysique de Paris

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