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Title: On the non-linear scale of cosmological perturbation theory

We discuss the convergence of cosmological perturbation theory. We prove that the polynomial enhancement of the non-linear corrections expected from the effects of soft modes is absent in equal-time correlators like the power or bispectrum. We first show this at leading order by resumming the most important corrections of soft modes to an arbitrary skeleton of hard fluctuations. We derive the same result in the eikonal approximation, which also allows us to show the absence of enhancement at any order. We complement the proof by an explicit calculation of the power spectrum at two-loop order, and by further numerical checks at higher orders. Using these insights, we argue that the modification of the power spectrum from soft modes corresponds at most to logarithmic corrections at any order in perturbation theory. Finally, we discuss the asymptotic behavior in the large and small momentum regimes and identify the expansion parameter pertinent to non-linear corrections.
Authors:
 [1] ; ;  [2]
  1. Theory Division, CERN, 1211 Geneva (Switzerland)
  2. DESY, Notkestr. 85, 22607 Hamburg (Germany)
Publication Date:
OSTI Identifier:
22282680
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2013; Journal Issue: 09; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMPTOTIC SOLUTIONS; CORRECTIONS; EIKONAL APPROXIMATION; ENERGY SPECTRA; EXPANSION; FLUCTUATIONS; NONLINEAR PROBLEMS; PERTURBATION THEORY; POLYNOMIALS