Early Universe with modified scalar-tensor theory of gravity

Abstract

Scalar-tensor theory of gravity with non-minimal coupling is a fairly good candidate for dark energy, required to explain late-time cosmic evolution. Here we study the very early stage of evolution of the universe with a modified version of the theory, which includes scalar curvature squared term. One of the key aspects of the present study is that, the quantum dynamics of the action under consideration ends up generically with de-Sitter expansion under semiclassical approximation, rather than power-law. This justifies the analysis of inflationary regime with de-Sitter expansion. The other key aspect is that, while studying gravitational perturbation, the perturbed generalized scalar field equation obtained from the perturbed action, when matched with the perturbed form of the background scalar field equation, relates the coupling parameter and the potential exactly in the same manner as the solution of classical field equations does, assuming de-Sitter expansion. The study also reveals that the quantum theory is well behaved, inflationary parameters fall well within the observational limit and quantum perturbation analysis shows that the power-spectrum does not deviate considerably from the standard one obtained from minimally coupled theory.

28 pages, 0 figures, JHEP, 2018

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• Black hole entropy in modified gravity models
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• Inflation and cosmological evolution with $F(R,G)$ gravity theory
• Raychaudhuri-based reconstruction of anisotropic Einstein-Maxwell equation in 1+3 covariant formalism of $f(R)$-gravity
• Probing symmetric teleparallel gravity in the early universe
• Vulnerability of f(Q) gravity theory and a possible resolution
• Canonical equivalence in anisotropic models for higher order theory of gravity
• Perusing Buchbinder--Lyakhovich canonical formalism for Higher-Order Theories of Gravity
• Conflict between some higher-order curvature invariant terms