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.

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

References in corpus (35)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Likelihoods and Parameters from the WMAP data
• Cosmological Constraints from the SDSS Luminous Red Galaxies
• Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
• Measuring the Baryon Acoustic Oscillation scale using the SDSS and 2dFGRS
• Large-scale instability in interacting dark energy and dark matter fluids
• Dark Energy-Dark Matter Interaction and putative violation of the Equivalence Principle from the Abell Cluster A586
• Dynamics of dark energy with a coupling to dark matter
• Dynamics of interacting dark energy
• Cosmologies with Energy Exchange
• Effects of the interaction between dark energy and dark matter on cosmological parameters
• Le Chatelier-Braun principle in cosmological physics
• Coupled and Extended Quintessence: theoretical differences and structure formation
• Stability of the curvature perturbation in dark sectors' mutual interacting models
• Dark Interactions and Cosmological Fine-Tuning
• Challenges for scaling cosmologies
• Signature of the interaction between dark energy and dark matter in galaxy clusters
• Cosmological coincidence problem in interacting dark energy models
• Interacting models may be key to solve the cosmic coincidence problem
• Toward a solution of the coincidence problem
• Interacting holographic dark energy
• The oscillating dark energy: future singularity and coincidence problem
• Observational constraints on the dark energy and dark matter mutual coupling
• The Cosmological Dynamics of Interacting Holographic Dark Energy Model
• Adiabatic instability in coupled dark energy-dark matter models
• Interacting models of soft coincidence
• The imprint of the interaction between dark sectors in large scale cosmic microwave background anisotropies
• Effects of dark sectors' mutual interaction on the growth of structures
• Crossing the phantom divide in an interacting generalized Chaplygin gas
• The Coincidence Problem and Interacting Holographic Dark Energy
• Unified model of baryonic matter and dark components
• Dark Energy: A Unifying View
• Crossing the phantom divide line in the Holographic dark energy model in a closed universe
• Supernovae type Ia data favour coupled phantom energy
• Quintessence interacting dark energy from induced matter theory of gravity