Nonlinear phenomenology of disformally coupled quintessence
Abstract
The quintessence model is one of the simplest and better known alternatives to Einstein's theory for gravity. The properties of the solutions have been studied in great detail in the background, linear and nonlinear contexts in cosmology. Here we discuss new phenomenology that is induced by adding disformal terms to the interactions. Among other results, we show analytically and using cosmological simulations ran with the code ISIS that the model possesses a mechanism through which it is possible to obtain repulsive fifth forces, which are opposite to gravity. Although the equations are very complex, we also find that most of the new phenomenology can be explained by studying background quantities. We used our simulation data to test approximate relations that exist between the metric and scalar field perturbations as well as between the fifth force and gravity. Excellent agreement was found between exact and approximated solutions, which opens the way for running disformal gravity cosmological simulations using simply a Newtonian solver. These results could not only help us to find new ways of testing gravity, but also provide new motivations for building alternative models.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2020
 DOI:
 10.1093/mnras/stz2710
 arXiv:
 arXiv:1902.02125
 Bibcode:
 2020MNRAS.491.1868L
 Keywords:

 gravitation;
 methods: numerical;
 dark energy;
 dark matter;
 largescale structure of Universe;
 cosmology: theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 19 pages, 12 figures