Viable Inflationary Models in a Ghost-free Gauss-Bonnet Theory of Gravity

Abstract

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.

EPJC Accepted

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• Study of Goldstone Inflation in the domain of Einstein-Gauss-Bonnet gravity
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• Primordial blackholes from Gauss-Bonnet-corrected single field inflation
• Viable Anisotropic Inflation and Reheating in the Tachyon Model
• Primordial perturbations and inflation in a holography inspired Gauss-Bonnet cosmology
• String-inspired Gauss-Bonnet Gravity Inflation and ACT
• Echoes of $R^3$ modification and Goldstone preheating in the CMB-BAO landscape