Revisiting non-Gaussianity from non-attractor inflation models
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 sh...
| Main Authors: | , , , , , |
|---|---|
| Other Authors: | |
| Format: | Article |
| Published: |
IOP Publishing
2019
|
| Online Access: | http://hdl.handle.net/1721.1/120173 https://orcid.org/0000-0002-3093-4766 |
| _version_ | 1826208817718755328 |
|---|---|
| author | Cai, Yi-Fu Chen, Xingang Namjoo, Mohammad Hossein Sasaki, Misao Wang, Dong-Gang Wang, Ziwei |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Cai, Yi-Fu Chen, Xingang Namjoo, Mohammad Hossein Sasaki, Misao Wang, Dong-Gang Wang, Ziwei |
| author_sort | Cai, Yi-Fu |
| collection | MIT |
| description | 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. |
| first_indexed | 2024-09-23T14:13:06Z |
| format | Article |
| id | mit-1721.1/120173 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T14:13:06Z |
| publishDate | 2019 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/1201732022-10-01T19:51:19Z Revisiting non-Gaussianity from non-attractor inflation models Cai, Yi-Fu Chen, Xingang Namjoo, Mohammad Hossein Sasaki, Misao Wang, Dong-Gang Wang, Ziwei Massachusetts Institute of Technology. Department of Physics Namjoo, Mohammad Hossein 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. United States. Department of Energy (Contract de-sc0012567) 2019-02-04T18:05:08Z 2019-02-04T18:05:08Z 2018-05 2018-01 2019-01-29T12:51:06Z Article http://purl.org/eprint/type/JournalArticle 1475-7516 1475-7508 http://hdl.handle.net/1721.1/120173 Cai, Yi-Fu, Xingang Chen, Mohammad Hossein Namjoo, Misao Sasaki, Dong-Gang Wang, and Ziwei Wang. “Revisiting Non-Gaussianity from Non-Attractor Inflation Models.” Journal of Cosmology and Astroparticle Physics 2018, no. 05 (May 3, 2018): 012–012. © 2018 IOP Publishing Ltd and Sissa Medialab https://orcid.org/0000-0002-3093-4766 http://dx.doi.org/10.1088/1475-7516/2018/05/012 Journal of Cosmology and Astroparticle Physics Creative Commons Attribution 4.0 International license https://creativecommons.org/licenses/by/4.0/ application/pdf IOP Publishing IOP Publishing |
| spellingShingle | Cai, Yi-Fu Chen, Xingang Namjoo, Mohammad Hossein Sasaki, Misao Wang, Dong-Gang Wang, Ziwei Revisiting non-Gaussianity from non-attractor inflation models |
| title | Revisiting non-Gaussianity from non-attractor inflation models |
| title_full | Revisiting non-Gaussianity from non-attractor inflation models |
| title_fullStr | Revisiting non-Gaussianity from non-attractor inflation models |
| title_full_unstemmed | Revisiting non-Gaussianity from non-attractor inflation models |
| title_short | Revisiting non-Gaussianity from non-attractor inflation models |
| title_sort | revisiting non gaussianity from non attractor inflation models |
| url | http://hdl.handle.net/1721.1/120173 https://orcid.org/0000-0002-3093-4766 |
| work_keys_str_mv | AT caiyifu revisitingnongaussianityfromnonattractorinflationmodels AT chenxingang revisitingnongaussianityfromnonattractorinflationmodels AT namjoomohammadhossein revisitingnongaussianityfromnonattractorinflationmodels AT sasakimisao revisitingnongaussianityfromnonattractorinflationmodels AT wangdonggang revisitingnongaussianityfromnonattractorinflationmodels AT wangziwei revisitingnongaussianityfromnonattractorinflationmodels |