Backreaction of super-Hubble cosmological perturbations beyond perturbation theory

We discuss the effect of super-Hubble cosmological fluctuations on the locally measured Hubble expansion rate. We consider a large bare cosmological constant in the early Universe in the presence of scalar field matter (the dominant matter component), which would lead to a scale-invariant primordial...

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Bibliographic Details
Published in:Physical review. D 2018-11, Vol.98 (10), p.103523, Article 103523
Main Authors: Brandenberger, Robert, Graef, Leila L., Marozzi, Giovanni, Vacca, Gian Paolo
Format: Article
Language:English
Subjects:
Cosmological constant
Perturbation theory
Universe
Variations
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Summary:We discuss the effect of super-Hubble cosmological fluctuations on the locally measured Hubble expansion rate. We consider a large bare cosmological constant in the early Universe in the presence of scalar field matter (the dominant matter component), which would lead to a scale-invariant primordial spectrum of cosmological fluctuations. Using the leading-order gradient expansion, we show that the expansion rate measured by a (secondary) clock field which is not comoving with the dominant matter component obtains a negative contribution from infrared fluctuations, a contribution whose absolute value increases in time. This is the same effect that a decreasing cosmological constant would produce. This supports the conclusion that infrared fluctuations lead to a dynamical relaxation of the cosmological constant. Our analysis does not make use of any perturbative expansion in the amplitude of the inhomogeneities.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.98.103523