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On extensions of Starobinsky model of inflation
* 1 , 2, 3 , 4 , 4
1  Physics Department, Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow, Russia
2  Department of Physics, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji-shi, Tokyo 192-0397, Japan
3  Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, Kashiwa 277-8583, Japan
4  Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Leninskiye Gory 1, 119991 Moscow, Russia
Academic Editor: Lorenzo Iorio

Published: 16 February 2023 by MDPI in 2nd Electronic Conference on Universe session Gravitation and Cosmology

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 + R2) model by adding an R3-term, an R4-term, and an R3/2-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 R3/2-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/MPl), 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.

This talk is based on the paper [1].

[1] Vsevolod R. Ivanov, Sergei V. Ketov, Ekaterina O. Pozdeeva, and Sergey Yu Vernov. Analytic extensions of starobinsky model of inflation. Journal of Cosmology and Astroparticle Physics, 2022(03):058, 2022.

Keywords: inflation; modified gravity