NonGaussianities and tensortoscalar ratio in nonlocal R^{2}like inflation
Abstract
In this paper we will study R^{2}like inflation in a nonlocal modification of gravity which contains quadratic in Ricci scalar and Weyl tensor terms with analytic infinite derivative formfactors in the action. It is known that the inflationary solution of the local R + R^{2} gravity remains a particular exact solution in this model. It was shown earlier that the power spectrum of scalar perturbations generated during inflation in the nonlocal setup remains the same as in the local R + R^{2} inflation, whereas the power spectrum of tensor perturbations gets modified due to the nonlocal Weyl tensor squared term. In the present paper we go beyond 2point correlators and compute the nonGaussian parameter f_{NL} related to 3point correlations generated during inflation, which we found to be different from those in the original local inflationary model and scenarios alike based on a local gravity. We evaluate nonlocal corrections to the scalar bispectrum which give nonzero contributions to squeezed, equilateral and orthogonal configurations. We show that f_{NL}∼ O(1) with an arbitrary sign is achievable in this model based on the choice of formfactors and the scale of nonlocality. We present the predictions for the tensortoscalar ratio, r, and the tensor tilt, n_{t}. In contrast to standard inflation in a local gravity, here the possibility n_{t}> 0 is not excluded. Thus, future CMB data can probe nonlocal behaviour of gravity at high spacetime curvatures.
 Publication:

Journal of High Energy Physics
 Pub Date:
 June 2020
 DOI:
 10.1007/JHEP06(2020)152
 arXiv:
 arXiv:2003.00629
 Bibcode:
 2020JHEP...06..152K
 Keywords:

 Cosmology of Theories beyond the SM;
 Models of Quantum Gravity;
 High Energy Physics  Theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 40 pages, 6 figures