Non-gaussian signatures of a thermal big bang
File(s)
Accepted version
Author(s)
Mylova, Maria
Moschou, Marianthi
Afshordi, Niayesh
Magueijo, Joao
Type
Journal Article
Abstract
What if Big Bang was hot from its very inception? This is possible in a bimetric theory where the source of fluctuations is thermal, requiring the model to live on a critical boundary in the space of parameters and can be realized when an anti-DBI brane moves within an EAdS2 ×E3 geometry. This setup renders the model unique, with sharp predictions for the scalar spectral index and its running. We investigate the non-Gaussian signatures of this thermal bimetric model, or "bi-thermal" for short. We adapt the standard calculation of non-Gaussianities for P(X,ϕ) models to the thermal nature of the model, emphasising how the bi-thermal peculiarities affect the calculation and alter results. This leads to precise predictions for the shape and amplitude of the three-point function of the bi-thermal model (at tree-level): flocalNL = -3/2 and fequilNL = -2 + 4 √(3)π/9 ≃ 0.4. We also discover a new shape of flattened non-gaussianity ∝ (k1 + k2 - k3)-3/2 + permutations, which is expected due to the excited thermal initial conditions. These results, along with our earlier predictions for the scalar power spectrum, provide sharp targets for the future generation of cosmological surveys.
Date Issued
2022-07-01
Date Acceptance
2022-05-22
Citation
Journal of Cosmology and Astroparticle Physics, 2022, 2022 (7), pp.1-25
ISSN
1475-7516
Publisher
IOP Publishing
Start Page
1
End Page
25
Journal / Book Title
Journal of Cosmology and Astroparticle Physics
Volume
2022
Issue
7
Copyright Statement
© 2022 IOP Publishing Ltd and Sissa Medialab
Sponsor
Science and Technology Facilities Council (STFC)
Identifier
https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000831140900001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
ST/T000791/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Physics, Particles & Fields
Physics
alternatives to inflation
non-gaussianity
Publication Status
Published
Date Publish Online
2022-07-04