F(R) gravity with an axionlike particle: Dynamics, gravity waves, late and earlytime phenomenology
Abstract
In this work we investigate several theoretical and phenomenological implications of a scalar  F(R) gravity containing a nonminimal coupling to the scalar curvature. This kind of model is a generalization of axion F(R) gravity models, so we shall examine several implications of the latter theory. Firstly we study in detail the Einstein frame picture of the model, and also we discuss the dynamics of the cosmological system. By appropriately using the equations of motion, we demonstrate that an arbitrary cosmological evolution can be realized. Also we study the gravitational waves of the theory, and we demonstrate that the speed of their propagation is the same as in F(R) gravity, but there is the possibility of enhancement or dissipation of the gravitational waves, an effect quite similar to the propagation of gravity waves in a viscous fluid. Finally, we examine the energymomentum tensor and we investigate which quantities related to it are conserved. We also present the constraints imposed by the radiation domination era on the nonminimal coupling of the axion scalar field to the scalar curvature.
 Publication:

Annals of Physics
 Pub Date:
 July 2020
 DOI:
 10.1016/j.aop.2020.168186
 arXiv:
 arXiv:1907.01625
 Bibcode:
 2020AnPhy.41868186N
 Keywords:

 Modified Gravity;
 F(R) gravity;
 Gravitational waves;
 Axion physics;
 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Theory
 EPrint:
 doi:10.1016/j.aop.2020.168186