Non-Gaussianities and tensor-to-scalar ratio in non-local $R^2$-like inflation

Abstract

In this paper we will study $R^2$-like inflation in a non-local modification of gravity which contains quadratic in Ricci scalar and Weyl tensor terms with analytic infinite derivative form-factors 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 non-local setup remains the same as in the local $R+R^2$ inflation, whereas the power spectrum of tensor perturbations gets modified due to the non-local Weyl tensor squared term. In the present paper we go beyond 2-point correlators and compute the non-Gaussian parameter $f_{NL}$ related to 3-point 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 non-local corrections to the scalar bi-spectrum which give non-zero contributions to squeezed, equilateral and orthogonal configurations. We show that $f_{NL}\sim O(1)$ with an arbitrary sign is achievable in this model based on the choice of form-factors and the scale of non-locality. We present the predictions for the tensor-to-scalar 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 non-local behaviour of gravity at high space-time curvatures.

40 pages, 6 figures; v2 matching the one published in JHEP, further discussion on the single field consistency relation is added

References in corpus (13)

• The Standard Model Higgs boson as the inflaton
• Observational Signatures and Non-Gaussianities of General Single Field Inflation
• Primordial Non-Gaussianities from Inflation Models
• On the consistency relation of the 3-point function in single field inflation
• Towards a Resolution of the Cosmological Singularity in Non-local Higher Derivative Theories of Gravity
• Primordial non-Gaussianities in general modified gravitational models of inflation
• Embedding (R+R^2)-Inflation into Supergravity
• Primordial Non-Gaussianities of General Multiple Field Inflation
• Large Nongaussianity from Nonlocal Inflation
• A new method for calculating the primordial bispectrum in the squeezed limit
• Aspects of Nonlocality in Quantum Field Theory, Quantum Gravity and Cosmology
• Gravitational wave consistency relations for multifield inflation
• Cosmological perturbations in non-local higher-derivative gravity

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