1/R Correction to Gravity in the Early Universe

Abstract

To explain the accelerated expansion of late universe, the 1/R correction to Einstein gravity is usually considered, where R is the Ricci scalar. This correction term is generally believed to be negligible in the early universe. However, if the 1/R term is inflaton-dependent, it will dramatically change the story of inflation. The entropy perturbation will naturally appear and drive the evolution of curvature perturbation outside the Hubble horizon. In a large class of models, the entropy perturbation can be made nearly scale-invariant. In Einstein gravity the single-field inflation with a quartic potential has been ruled out by recent observations, but it revives when the 1/R term is turned on. The evolution of non-Gaussianities on large scale are also studied and applied to inflation with 1/R correction. In some specific models, a large non-Gaussianity can be naturally generated outside the horizon.

27 pages, 7 figures, even more references added

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Cited by in corpus (7)

• Static Solutions with Spherical Symmetry in f(T) Theories
• Primordial Non-Gaussianities from the Trispectra in Multiple Field Inflationary Models
• Non-Gaussianities of Single Field Inflation with Non-minimal Coupling
• Evolution of curvature perturbation in generalized gravity theories
• On primordial trispectrum from exchanging scalar modes in general multiple field inflationary models
• Singularity problem in f(R) model with non-minimal coupling
• A New Exponential Gravity