2014/05/31 by Sébastien Renaux-Petel, Krzysztof Turzyński, Krzysztof Turzynski · 4 citations
Physics and Astronomy · #A priori and a posteriori #Adiabatic process #Black Holes and Theoretical Physics #Cosmological perturbation theory #Cosmology and Gravitation Theories #Curvature #Galaxies: Formation, Evolution, Phenomena #Inflation (cosmology) #Limit (mathematics) #Non-Gaussianity #Perturbation (astronomy) #Scalar (mathematics) #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1088/1475-7516/2015/06/010
26 pages. 13 figures. One additional author. Substantially reworked and extended
arxiv created 2014/12/29 · openalex publication_date 2015/06/05 · arxiv updated 2015/06/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We calculate the scalar spectral index n s and the tensor-to-scalar ratio r in a class of recently proposed two-field no-scale inflationary models in supergravity. We show that, in order to obtain correct predictions, it is crucial to take into account the coupling between the curvature and the isocurvature perturbations induced by the noncanonical form of the kinetic terms. This coupling enhances the curvature perturbation and suppresses the resulting tensor-to-scalar ratio to the per mille level even for values of the slow-roll parameter ∼ 0.01. Beyond these particular models, we emphasise that multifield models of inflation are a priori not predictive, unless one supplies a prescription for the post-inflationary era, or an adiabatic limit is reached before the end of inflation. We examine the conditions that enabled us to actually derive predictions in the models under study, by analysing the various contributions to the effective isocurvature mass in general two-field inflationary models. In particular, we point out a universal geometrical contribution that is important at the end of inflation, and which can be directly extracted from the inflationary Lagrangian, independently of a specific trajectory. Eventually, we point out that spectator fields can lead to oscillatory features in the time-dependent power spectra at the end of inflation. We demonstrate how these features can be model semi-analytically as well as the theoretical uncertainties they can entail.