We single out the Starobinsky model and its extensions among generic f(R) gravity as attractors at large field values for chaotic inflation. Treating a R3 curvature term as a perturbation of the Starobinsky model, we impose the phenomenological bounds on the additional term satisfying the successful inflationary predictions. We find that the scalar spectral index can vary in both the red or blue tilted direction, depending on the sign of the coefficient of the R3 term, whereas the tensor-to-scalar ratio is less affected in the Planck-compatible region. We also discuss the role of higher order curvature term for stability and the reheating dynamics for the unambiguous prediction for the number of efoldings up to the R3 term.
|Journal||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|Publication status||Published - 2020 Jun 10|
Bibliographical noteFunding Information:
We thank Shi Pi, Misao Sasaki and Qing-Guo Huang for helpful discussions and comments. The work was initiated during the CERN-CKC Theory Institute on New Physics in Low-Energy Precision Frontier in 2020. The work is supported in part by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology ( NRF-2018R1A4A1025334 , NRF-2019R1A2C2003738 (HML), NRF-2019R1A2C1089334 (SCP)).
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics