Non-Gaussianities in generalized non-local R2-like inflation
Abstract
In [1], a most general higher curvature non-local gravity action was derived that admits a particular R2-like inflationary solution predicting the spectral index of primordial scalar perturbations ns(N )≈1 −1/2 , where N is the number of e-folds before the end of inflation, N ≫ 1, any value of the tensor-to-scalar ratio r(N) < 0.036 and the tensor tilt nt(N) violating the r = -8nt condition. In this paper, we compute scalar primordial non-Gaussianities (PNGs) in this theory and effectively demonstrate that higher curvature non-local terms lead to reduced bispectrum fNL (k1, k2, k3) mimicking several classes of scalar field models of inflation known in the literature. We obtain |fNL| ~ O(1 - 10) in the equilateral, orthogonal, and squeezed limits and the running of these PNGs measured by the quantity |d/lnfNL d lnk |≲1 . Such PNGs are sufficiently large to be measurable by future CMB and Large Scale Structure observations, thus providing a possibility to probe the nature of quantum gravity. Furthermore, we demonstrate that the R2-like inflation in non-local modification of gravity brings non-trivial predictions which go beyond the current status of effective field theories (EFTs) of single field, quasi-single field and multiple field inflation. A distinguishable feature of non-local R2-like inflation compared to local EFTs is that we can have running of PNGs at least an order of magnitude higher. In summary, through our generalized non-local R2-like inflation, we obtain a robust geometric framework of inflation that can explain any detection of observable quantities related to scalar PNGs.
- Publication:
-
Journal of High Energy Physics
- Pub Date:
- July 2023
- DOI:
- 10.1007/JHEP07(2023)094
- arXiv:
- arXiv:2210.16459
- Bibcode:
- 2023JHEP...07..094K
- Keywords:
-
- Cosmology of Theories BSM;
- Models of Quantum Gravity;
- Early Universe Particle Physics;
- String Models;
- High Energy Physics - Theory;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- General Relativity and Quantum Cosmology
- E-Print:
- 31 pages, 7 figures, discussions are improved, the abstract is slightly extended, matches with the version published in JHEP