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Nonlinear perturbations of cosmological scalar fields

David Langlois 1 F. Vernizzi
1 APC - THEORIE
APC (UMR_7164) - AstroParticule et Cosmologie, Institut für theoretische Physik
Abstract : We present a covariant formalism to study nonlinear perturbations of scalar fields. In particular, we consider the case of two scalar fields and introduce the notion of adiabatic and isocurvature covectors. We obtain differential equations governing the evolution of these two covectors, as well as the evolution equation for the covector associated to the curvature perturbation. The form of these equations is very close to the analogous equations obtained in the linear theory but our equations are fully nonlinear and exact. As an application of our formalism, we expand these equations at second order in the perturbations. On large scales, we obtain a closed system of coupled scalar equations giving the evolution of the second-order adiabatic and entropy perturbations in terms of the first-order perturbations. These equations in general contain a nonlocal term which, however, rapidly decays in an expanding universe.
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http://hal.in2p3.fr/in2p3-00126653
Contributor : Simone Lantz <>
Submitted on : Thursday, January 25, 2007 - 3:25:18 PM
Last modification on : Saturday, September 19, 2020 - 4:51:30 AM

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David Langlois, F. Vernizzi. Nonlinear perturbations of cosmological scalar fields. Journal of Cosmology and Astroparticle Physics, Institute of Physics (IOP), 2007, 02, pp.017. ⟨10.1088/1475-7516/2007/02/017⟩. ⟨in2p3-00126653⟩

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