Aspects of Nonlinear Perturbations in Cosmological Models

          @misc{ pirsa_PIRSA:06120013,
            doi = {10.48660/06120013},
            url = {https://pirsa.org/06120013},
            author = {Losic, Bojan},
            keywords = {Cosmology},
            language = {en},
            title = {Aspects of Nonlinear Perturbations in Cosmological Models},
            publisher = {Perimeter Institute},
            year = {2006},
            month = {dec},
            note = {PIRSA:06120013 see, \url{https://pirsa.org}}
          }
          

Abstract

I discuss two instances in which nonlinear perturbations in cosmological models are important. First, in de Sitter space-time, the bare necessity that the perturbations should be part of a consistent Taylor expansion of the field equations leads to the requirement, using the 'linearization stability' arguments of the '70's, that the quantum field theory of a scalar field on de Sitter space-time is manifestly de Sitter invariant (not covariant). Second, the concern that in slow-roll inflation the effect of second order perturbations on the long wavelength (super Hubble) perturbations could be much stronger than that of the first order perturbations, for a wide range of slow-roll conditions, is explored in the context of a linear inflation potential and chaotic inflation.