https://doi.org/10.1140/epjc/s10052-019-7080-1
Regular Article - Theoretical Physics
Viable inflationary models in a ghost-free Gauss–Bonnet theory of gravity
1
Department of Physics, Nagoya University, Nagoya, 464-8602, Japan
2
Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya, 464-8602, Japan
3
ICREA, Passeig Luis Companys, 23, 08010, Barcelona, Spain
4
Institute of Space Sciences (IEEC-CSIC) C. Can Magrans s/n, 08193, Barcelona, Spain
5
Department of Physics, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece
6
International Laboratory for Theoretical Cosmology, Tomsk State University of Control Systems and Radioelectronics (TUSUR), Tomsk, 634050, Russia
7
Tomsk State Pedagogical University, Tomsk, 634061, Russia
8
Department of Theoretical Physics, Indian Association for the Cultivation of Science, 2A & 2B Raja S.C. Mullick Road, Kolkata, 700 032, India
* e-mail: v.k.oikonomou1979@gmail.com
Received:
21
May
2019
Accepted:
26
June
2019
Published online:
4
July
2019
In this work we investigate the inflationary phenomenological implications of a recently developed ghost-free Gauss–Bonnet theory of gravity. The resulting theory can be viewed as a scalar Einstein–Gauss–Bonnet theory of gravity, so by employing the formalism for cosmological perturbations for the latter theory, we calculate the slow-roll indices and the observational indices, and we compare these with the latest observational data. Due to the presence of a freely chosen function in the model, in principle any cosmological evolution can be realized, so we specify the Hubble rate and the freely chosen function and we examine the phenomenology of the model. Specifically we focus on de Sitter, quasi-de Sitter and a cosmological evolution in which the Hubble rate evolves exponentially, with the last two being more realistic choices for describing inflation. As we demonstrate, the ghost-free model can produce inflationary phenomenology compatible with the observational data. We also briefly address the stability of first order scalar and tensor cosmological perturbations, for the exponential Hubble rate, and as we demonstrate, stability is achieved for the same range of values of the free parameters that guarantee the phenomenological viability of the models.
© The Author(s), 2019
