Interacting Cosmological Fluids and the Coincidence Problem
Abstract
We examine the evolution of a universe comprising two interacting fluids, which interact via a term proportional to the product of their densities. In the case of two matter fluids it is shown that the ratio of the densities tends to a constant after an initial cooling-off period. We then obtain a complete solution for the cosmological constant (w = -1) scenario. Finally, we investigate the general case in which the dark energy equation of state is p = w*rho, where w is a constant, and show that periodic solutions can occur if w < -1. We further demonstrate that the ratio of the dark matter to dark energy densities is confined to a bounded interval, and that this ratio can be O(1) at infinitely many times in the history of the universe, thus solving the coincidence problem.
Cite
@article{arxiv.1009.4942,
title = {Interacting Cosmological Fluids and the Coincidence Problem},
author = {Sean Z. W. Lip},
journal= {arXiv preprint arXiv:1009.4942},
year = {2011}
}
Comments
20 pages, 8 figures. Added two new sections (VI and VII) constraining the parameters and examining the evolution of the periodic solution in more detail. Submitted to Phys. Rev. D