Bouncing cosmological isotropic solutions in scalartensor gravity
Abstract
Bouncing nonsingular isotropic cosmological solutions are investigated in a simple model of scalartensor gravity. New families of such solutions are found and their properties are presented and analyzed using an effective potential as the main tool. Bouncing solutions are shown to exist for a Higgslike selfinteraction potential which is bounded from below, in contrast to previous solutions that appeared in the literature based on potentials which were unbounded from below. In the simplest version of a scalar field with the quartic potential and conformal coupling to gravity, bouncing spatially flat solutions either have the Hubble function diverging in the past before the bounce, but with a wellbehaved future, or are globally regular but unstable with respect to anisotropic or inhomogeneous perturbations at some finite values of the scalar field and curvature. Regular solutions can only exist in the part of the parameter space where the maximum of the effective potential is larger than the first zero of the potential, and gravity becomes repulsive at the bounce.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 January 2022
 DOI:
 10.1088/14757516/2022/01/052
 arXiv:
 arXiv:2111.07319
 Bibcode:
 2022JCAP...01..052P
 Keywords:

 modified gravity;
 physics of the early universe;
 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Theory
 EPrint:
 22 pages