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Article overview
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Revisiting non-Gaussianity from non-attractor inflation models | | Yi-Fu Cai
; Xingang Chen
; Mohammad Hossein Namjoo
; Misao Sasaki
; Dong-Gang Wang
; Ziwei Wang
; | | Date: |
28 Dec 2017 | | Abstract: | 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 $mathcal{O}(1)$
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. | | Source: | arXiv, 1712.9998 | | Services: | Forum | Review | PDF | Favorites | |
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