Revisiting non-Gaussianity from non-attractor inflation models
By Yi-Fu Cai, Xingang Chen, M. H. Namjoo, Misao Sasaki, Dong-Gang Wang, Ziwei Wang. 2017
154 citations recorded by the source corpus.
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 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.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/9db11b46d56169df1be3b5343682c3346f715f7d
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Citations in the corpus
- Primordial black holes from inflation and quantum diffusion (2018, background): “J C A P 0 7 ( 2 0 1 8 ) 0 3 2 and the second slow-roll phase [39].”
- Steepest growth of the power spectrum and primordial black holes (2018, background): “This was investigated for the bispectrum in [74], where it was found that local non-Gaussianity is erased during a smooth exit from ultra slow roll, but that it can survive a sharp transition.”