Abstract
In this paper we study a class of quintessential Einstein Gauss-Bonnet models, focusing on their early and late-time phenomenology. With regard to the early-time phenomenology, we formalize the slow-roll evolution of these models and we calculate in detail the spectral index of the primordial curvature perturbations and the tensor-to-scalar ratio. As we demonstrate, the resulting observational indices can be compatible with both the Planck and the BICEP2/Keck-Array observational constraints on inflation. With regard to the late-time behavior, by performing a numerical analysis we demonstrate that the class of models for which the coupling function ξ(ϕ) to the Gauss-Bonnet scalar satisfies ξ(ϕ)∼1V(ϕ), produce a similar pattern of evolution, which at late-times is characterized by a decelerating era until some critical redshift, at which point the Universe super-decelerates and subsequently accelerates until present time, with a decreasing rate though. The critical redshift crucially depends on the initial conditions chosen for the scalar field and for all the quintessential Einstein Gauss-Bonnet models studied, the late-time era is realized for large values of the scalar field.
Highlights
The early-time acceleration era of our Universe is the last resort of the classical physics to our Universe’s description
As we will show, it is possible to obtain a late-time accelerating era, with the transition from deceleration to acceleration depending strongly on the initial conditions chosen for the scalar field
With regard to the early-time behavior, we presented the slow-roll formalism of the theory and we investigated if a viable inflationary era can be achieved
Summary
In this paper we study a class of quintessential Einstein Gauss-Bonnet models, focusing on their early and late-time phenomenology. With regard to the early-time phenomenology, we formalize the slow-roll evolution of these models and we calculate in detail the spectral index of the primordial curvature perturbations and the tensor-to-scalar ratio. With regard to the late-time behavior, by performing a numerical analysis we demonstrate that the class of models for which the coupling function ξ(φ) to the Gauss-Bonnet scalar satisfies ξ(φ). Produce a similar pattern of evolution, which at late-times is characterized by a decelerating era until some critical redshift, at which point the Universe super-decelerates and subsequently accelerates until present time, with a decreasing rate though. Einstein Gauss-Bonnet models studied, the late-time era is realized for large values of the scalar field. PACS numbers: 04.50.Kd, 95.36.+x, 98.80.-k, 98.80.Cq,11.25.-w arXiv:1909.05318v1 [gr-qc] 11 Sep 2019
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