On higher derivative corrections to the R+R^{2} inflationary model
Abstract
The R+R^{2} model is successful in describing inflation, as it provides an excellent fit to the full set of available observational data. On the other hand, the same model is the simplest extension of general relativity which does not produce higher derivative ghosts and related instabilities. Long ago, it was proposed to treat all terms which cause higher derivative instabilities as small perturbations that could avoid the presence of ghosts in the spectrum. We put this proposal into practice and consider an explicit example of treating more complicated higher derivative terms as small perturbations over the R+R^{2} model by introducing the Rsquare R term into the action. Within the described scheme, it is possible to obtain an upper bound on the coefficient of this nonscalefree sixthderivative term by mapping the theory into a onescalar field potential. It is shown that the result differs from treating this term on equal footing with other terms that requires mapping to a twoscalar field model, and in general leads to different observational consequences.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 December 2018
 DOI:
 10.1088/14757516/2018/12/007
 arXiv:
 arXiv:1810.07787
 Bibcode:
 2018JCAP...12..007R
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 19 pages, 6 figures. Comment: One typo fixed