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arXiv · 1308.1413

Super-renormalizable or finite completion of the Starobinsky theory

Fabio Briscese·Leonardo Modesto·Shinji Tsujikawa
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Abstract

The recent Planck data of Cosmic Microwave Background (CMB) temperature anisotropies support the Starobinsky theory in which the quadratic Ricci scalar drives cosmic inflation. We build up a multi-dimensional quantum consisted ultraviolet completion of the model in a phenomenological "bottom-up approach". We present the maximal class of theories compatible with unitarity and (super-)renormalizability or finiteness which reduces to the Starobinsky theory in the low-energy limit. The outcome is a maximal extension of the Krasnikov-Tomboulis-Modesto theory including an extra scalar degree of freedom besides the graviton field. The original theory was afterwards independently discovered by Biswas-Gerwick-Koivisto-Mazumdar starting from first principles. We explicitly show power counting super-renormalizability or finiteness (in odd dimensions) and unitarity (no ghosts) of the theory. Any further extension of the theory is non-unitary confirming the existence of at most one single extra degree of freedom, the scalaron. A mechanism to achieve the Starobinsky theory in string (field) theory is also investigated at the end of the paper.

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Fabio Briscese, Leonardo Modesto, Shinji Tsujikawa. 2014-01-29. Super-renormalizable or finite completion of the Starobinsky theory. https://doi.org/10.1103/physrevd.89.024029

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