Abstract
In this paper we report on a major theoretical observation in cosmology. We present a concrete cosmological model for which inflation has a natural beginning and natural ending. Inflation is driven by a cosine-form potential, , which begins at and ends at . The distance traversed by the inflaton field is sub-Planckian. The Gauss-Bonnet term arising as leading curvature corrections in the action (where and are constants and is the five-dimensional Planck mass) plays a key role to terminate inflation. The model generates appropriate tensor-to-scalar ratio and inflationary perturbations that are consistent with Planck and BICEP2 data. For example, for and , the model predicts that and [ is the number of -folds of inflation and () is the scalar (tensor) spectrum spectral index]. The ratio is (13%–24%) less than its value in 4D Einstein gravity, . The upper bound on the energy scale of inflation () implies that and , which thereby rule out the case (Randall-Sundrum model). The true nature of gravity is holographic as implied by the braneworld realization of string and M theory. The model correctly predicts a late-epoch cosmic acceleration with the dark energy equation of state .
2 More- Received 30 September 2014
DOI:https://doi.org/10.1103/PhysRevD.90.123502
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