TY - JOUR

T1 - Analytic extensions of Starobinsky model of inflation

AU - Ivanov, Vsevolod R.

AU - Ketov, Sergei V.

AU - Pozdeeva, Ekaterina O.

AU - Vernov, Sergey Yu

N1 - Acknowledgments: The authors are grateful to Gia Dvali, Olaf Lechtenfeld, Kei-ichi Maeda and Alexei Starobinsky for discussions and correspondence. V.R.I. was supported by the Theoretical Physics and Mathematics Advancement Foundation “BASIS”. S.V.K. was supported by Tokyo Metropolitan University, the World Premier International Research Center Initiative (MEXT) and Yamada Foundation in Japan. S.V.K. is grateful to Leibniz Universit ̈at Hannover in Germany for pleasant hospitality during this investigation. E.O.P. and S.Yu.V. were partially supported by the Russian Foundation for Basic Research grant No. 20-02-00411.

PY - 2022/3

Y1 - 2022/3

N2 - We study several extensions of the Starobinsky model of inflation, which obey all observational constraints on the inflationary parameters, by demanding that both the inflaton scalar potential in the Einstein frame and the F(R) gravity function in the Jordan frame have the explicit dependence upon fields and parameters in terms of elementary functions. Our models are continuously connected to the original Starobinsky model via changing the parameters. We modify the Starobinsky (R + R 2) model by adding an R 3-term, an R 4-term, and an R 3/2-term, respectively, and calculate the scalar potentials, the inflationary observables and the allowed limits on the deformation parameters by using the latest observational bounds. We find that the tensor-to-scalar ratio in the Starobinsky model modified by the R 3/2-term significantly increases with raising the parameter in front of that term. On the other side, we deform the scalar potential of the Starobinsky model in the Einstein frame in powers of y = exp(-(2/3)φ/M Pl), where φ is the canonical inflaton (scalaron) field, calculate the corresponding F(R) gravity functions in the two new cases, and find the restrictions on the deformation parameters in the lowest orders with respect to the variable y that is physically small during slow-roll inflation.

AB - We study several extensions of the Starobinsky model of inflation, which obey all observational constraints on the inflationary parameters, by demanding that both the inflaton scalar potential in the Einstein frame and the F(R) gravity function in the Jordan frame have the explicit dependence upon fields and parameters in terms of elementary functions. Our models are continuously connected to the original Starobinsky model via changing the parameters. We modify the Starobinsky (R + R 2) model by adding an R 3-term, an R 4-term, and an R 3/2-term, respectively, and calculate the scalar potentials, the inflationary observables and the allowed limits on the deformation parameters by using the latest observational bounds. We find that the tensor-to-scalar ratio in the Starobinsky model modified by the R 3/2-term significantly increases with raising the parameter in front of that term. On the other side, we deform the scalar potential of the Starobinsky model in the Einstein frame in powers of y = exp(-(2/3)φ/M Pl), where φ is the canonical inflaton (scalaron) field, calculate the corresponding F(R) gravity functions in the two new cases, and find the restrictions on the deformation parameters in the lowest orders with respect to the variable y that is physically small during slow-roll inflation.

KW - inflation

KW - modified gravity

UR - http://www.scopus.com/inward/record.url?scp=85128157023&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2111.09058

DO - 10.48550/arXiv.2111.09058

M3 - Article

AN - SCOPUS:85128157023

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 3

M1 - 058

ER -