A Unified Evolution of the Universe

Preprint number: CP3-Origins-2016-9 DNRF90 and DIAS-2016-9
Authors: Alessandro Codello (CP3-Origins & DIAS) and Rajeev Kumar Jain (CP3-Origins & DIAS)
External link: arXiv.org

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We present a unified evolution of the universe from very early times until the present epoch by including both the leading local correction $R^2$ and the leading non-local term $Rfrac{1}{square^2}R$ to the classical gravitational action.
We find that the inflationary phase driven by $R^2$ term gracefully exits in a transitory regime characterized by coherent oscillations of the Hubble parameter. The universe then naturally enters into a radiation dominated epoch followed by a matter dominated era. At sufficiently late times after radiation-matter equality, the non-local term starts to dominate inducing an accelerated expansion of the universe at the present epoch. We further exhibit the fact that both the leading local and non-local terms can be obtained within the covariant effective field theory of gravity. Our scenario thus provides a unified picture of inflation and dark energy in a single framework by means of a purely gravitational action without the usual need of a scalar field.