Emergent cosmology in 4D Einstein Gauss Bonnet theory of gravity

• Published in: Physica scripta Vol. 99; no. 7
• Main Authors: Gohain, Mrinnoy M, Bhuyan, Kalyan
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.07.2024
• Subjects: 4D-Einstein-Gauss-Bonnet gravity; cosmology; einstein static universe; emergent cosmology; modified gravity
• ISSN: 0031-8949; 1402-4896
• DOI: 10.1088/1402-4896/ad5238

Abstract In this paper, in an FLRW background and a perfect fluid equation of state, we explore the possibility of the realization of an emergent scenario in a 4D regularized extension of Einstein-Gauss-Bonnet gravity, with the field equations particularly expressed in terms of scalar-tensor degrees of freedom. By assuming non-zero spatial curvature ($k = \pm 1$), the stability of the Einstein static universe (ESU) and its subsequent exit into the standard inflationary system is tested through different approaches. In terms of dynamical systems, a spatially closed universe rather than an open universe shows appealing behaviour to exhibit a graceful transition from the ESU to standard cosmological history. We found that under linear homogeneous perturbations, for some constraints imposed on the model parameters, the ESU is stable under those perturbations. Moreover, it is noted that for a successful graceful transition, the equation of state $\omega$ must satisfy the conditions $-1 < \omega <0$ and $\omega < -1$ for closed and open universes, respectively. Furthermore, the ESU is seen to be neutrally stable under matter perturbation in the Newtonian gauge.