2012/12/31 by Giovanni Marozzi, Gian Paolo Vacca, Robert H. Brandenberger +1 · 38 citations
Economics, Econometrics and Finance · Physics and Astronomy · #Black Holes and Theoretical Physics #Chaotic #Context (archaeology) #Cosmological perturbation theory #Cosmology and Gravitation Theories #Eternal inflation #Invariant (physics) #Isotropy #Observer (physics) #Perturbation (astronomy) #Perturbation theory (quantum mechanics) #Stochastic processes and financial applications #astro-ph.CO #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1088/1475-7516/2013/02/027
published in Journal of Cosmology and Astroparticle Physics 2013(02), 027 (Institute of Physics) · 15 pages, 4 figures. A comment added, typos corrected, version accepted for publication in JCAP
arxiv created 2013/01/30 · openalex publication_date 2013/02/19 · arxiv updated 2015/06/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
In an inhomogeneous universe, an observer associated with a particular matter field does not necessarily measure the same cosmological evolution as an observer in a homogeneous and isotropic universe. Here we consider, in the context of a chaotic inflationary background model, a class of observers associated with a ``clock field" for which we use a light test field. We compute the effective expansion rate and fluid equation of state in a gauge invariant way, taking into account the quantum fluctuations of the long wavelength modes, and working up to second order in perturbation theory and in the slow-roll approximation. We find that the effective expansion rate is smaller than what would be measured in the absence of fluctuations. Within the stochastic approach we study the bounds for which the approximations we make are consistent.