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Article Dans Une Revue Physical Review D Année : 2010

Stochastic growth of quantum fluctuations during slow-roll inflation

F. Finelli
A. A. Starobinsky
  • Fonction : Auteur
G. P. Vacca
  • Fonction : Auteur
G. Venturi
  • Fonction : Auteur

Résumé

We compute the growth of the mean square of quantum fluctuations of test fields with small effective mass during a slowly changing, nearly de Sitter stage which takes place in different inflationary models. We consider a minimally coupled scalar with a small mass, a modulus with an effective mass ∝H2 (with H the Hubble parameter), and a massless nonminimally coupled scalar in the test field approximation and compare the growth of their relative mean square with the one of gauge-invariant inflaton fluctuations. We find that in most of the single field inflationary models the mean square gauge-invariant inflaton fluctuation grows faster than any test field with a non-negative effective mass. Hybrid inflationary models can be an exception: the mean square of a test field can dominate over the gauge-invariant inflaton fluctuation one on suitably chosen parameters. We also compute the stochastic growth of quantum fluctuations of a second field, relaxing the assumption of its zero homogeneous value, in a generic inflationary model; as a main result, we obtain that the equation of motion of a gauge-invariant variable associated, order by order, with a generic quantum scalar fluctuation during inflation can be obtained only if we use the number of e-folds as the time variable in the corresponding Langevin and Fokker-Planck equations for the stochastic approach. We employ this approach to derive some bounds for the case of a model with two massive fields.
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Dates et versions

hal-03646062 , version 1 (27-08-2022)

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F. Finelli, G. Marozzi, A. A. Starobinsky, G. P. Vacca, G. Venturi. Stochastic growth of quantum fluctuations during slow-roll inflation. Physical Review D, 2010, 82, ⟨10.1103/PhysRevD.82.064020⟩. ⟨hal-03646062⟩
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