Constant-roll inflation in F(R) gravity
Abstract
In this paper, we study constant-roll inflation in F(R) gravity. We take two different approaches, one that relates F(R) gravity to well-known scalar models of constant-roll and a second that examines the constant-roll condition in F(R) gravity directly. With regard to the first approach, by using well-known techniques, we find the F(R) gravity that realizes a given constant-roll evolution in the scalar-tensor theory. We also perform a conformal transformation in the resulting F(R) gravity and find the Einstein frame counterpart theory. As we demonstrate, the resulting scalar potential is different in comparison to the original scalar constant-roll case, and the same applies for the corresponding observational indices. Moreover, we discuss how cosmological evolutions that can realize constant-roll to constant-roll era transitions in the scalar-tensor description can be realized by vacuum F(R) gravity. With regard to the second approach, we examine the effects of the constant-roll condition on the inflationary dynamics of vacuum F(R) gravity directly. We present in detail the formalism of constant-roll F(R) gravity inflationary dynamics and we discuss the inflationary indices for this case. We use two well-known F(R) gravities in order to illustrate our findings: the R 2 model and a power-law F(R) gravity in vacuum. As we demonstrate, in both cases the parameter space is enlarged in comparison to the slow-roll counterparts of the models and, in effect, the models can also be compatible with the observational data. Finally, we briefly address the graceful exit issue.
- Publication:
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Classical and Quantum Gravity
- Pub Date:
- December 2017
- DOI:
- 10.1088/1361-6382/aa92a4
- arXiv:
- arXiv:1704.05945
- Bibcode:
- 2017CQGra..34x5012N
- Keywords:
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- General Relativity and Quantum Cosmology;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- High Energy Physics - Theory
- E-Print:
- CQG accepted