title: Evolution of nonlinear cosmological perturbations.
abstract: We define fully nonperturbative generalizations of the uniform density and comoving curvature perturbations, which are known, in the linear theory, to be conserved on sufficiently large scales for adiabatic perturbations. Our nonlinear generalizations are defined geometrically, independently of any coordinate system. We give the equations governing their evolution on all scales. Also, in order to make contact with previous works on first- and second-order perturbations, we introduce a coordinate system and show that previous results can be recovered, on large scales, in a remarkably simple way, after restricting our definitions to first and second orders in a perturbative expansion.
authors.affiliation: APC (Astroparticules et Cosmologie), UMR 7164 (CNRS, Université Paris 7, CEA, Observatoire de Paris), 11 Place Marcelin Berthelot, F-75005 Paris, France.
authors.forename: David
authors.initials: D
authors.lastname: Langlois
authors.forename: Filippo
authors.initials: F
authors.lastname: Vernizzi