Cosmological models with arbitrary spatial curvature in the theory of gravity with non-minimal derivative coupling
Abstract
We investigate isotropic and homogeneous cosmological scenarios in the scalar-tensor theory of gravity with non-minimal derivative coupling of a scalar field to the curvature given by the term in the Lagrangian. In general, a cosmological model is determined by six dimensionless parameters: the coupling parameter , and density parameters (cosmological constant), (spatial curvature term), (non-relativistic matter), (radiation), (scalar field term), and the universe evolution is described by the modified Friedmann equation. In the case (no non-minimal derivative coupling) and (no scalar field) one has the standard CDM-model, while if -- the CDM-model with an ordinary scalar field. The situation is crucially changed when the scalar field possesses non-minimal derivative coupling to the curvature, i.e. when . Now, depending on model parameters, (i) There are three qualitatively different initial state of the universe: an eternal kinetic inflation, an initial singularity, and a bounce. The bounce is possible for all types of spatial geometry of the homogeneous universe; (ii) For all types of spatial geometry, the universe goes inevitably through the primary quasi-de Sitter (inflationary) epoch when with the de Sitter parameter . The mechanism of primary or kinetic inflation is provided by non-minimal derivative coupling and needs no fine-tuned potential; (iii) There are cyclic scenarios of the universe evolution with the non-singular bounce at a minimal value of the scale factor, and a turning point at the maximal one; (iv) There is a natural mechanism providing a change of cosmological epochs.
Keywords
Cite
@article{arxiv.2306.00611,
title = {Cosmological models with arbitrary spatial curvature in the theory of gravity with non-minimal derivative coupling},
author = {Sergey V. Sushkov and Rafkat Galeev},
journal= {arXiv preprint arXiv:2306.00611},
year = {2023}
}