2017/12/31 by Yi-Fu Cai, Xingang Chen, Mohammad Hossein Namjoo +3 · 125 citations
Physics and Astronomy · #Attractor #Black Holes and Theoretical Physics #Consistency (knowledge bases) #Cosmology #Cosmology and Gravitation Theories #Curvature #Inflation (cosmology) #Particle physics theoretical and experimental studies #Phase transition #Transition (genetics) #Vacuum state #astro-ph.CO #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1088/1475-7516/2018/05/012
published in Journal of Cosmology and Astroparticle Physics 2018(05), 012 (Institute of Physics) · 26 pages, 10 figures; v2, discussion extended and references added
arxiv created 2018/01/04 · openalex created_date 2018/01/05 · openalex publication_date 2018/05/03 · arxiv updated 2018/05/08 · openalex updated_date 2026/08/06
Non-attractor inflation is known as the only single field inflationary scenario that can violate non-Gaussianity consistency relation with the Bunch-Davies vacuum state and generate large local non-Gaussianity. However, it is also known that the non-attractor inflation by itself is incomplete and should be followed by a phase of slow-roll attractor. Moreover, there is a transition process between these two phases. In the past literature, this transition was approximated as instant and the evolution of non-Gaussianity in this phase was not fully studied. In this paper, we follow the detailed evolution of the non-Gaussianity through the transition phase into the slow-roll attractor phase, considering different types of transition. We find that the transition process has important effect on the size of the local non-Gaussianity. We first compute the net contribution of the non-Gaussianities at the end of inflation in canonical non-attractor models. If the curvature perturbations keep evolving during the transition—such as in the case of smooth transition or some sharp transition scenarios—the (1) local non-Gaussianity generated in the non-attractor phase can be completely erased by the subsequent evolution, although the consistency relation remains violated. In extremal cases of sharp transition where the super-horizon modes freeze immediately right after the end of the non-attractor phase, the original non-attractor result can be recovered. We also study models with non-canonical kinetic terms, and find that the transition can typically contribute a suppression factor in the squeezed bispectrum, but the final local non-Gaussianity can still be made parametrically large.