Aspects of the cosmological "coincidence problem"

Abstract

The observational fact that the present values of the densities of dark energy and dark matter are of the same order of magnitude, ${\rho }_{de0}/{\rho }_{dm0}\sim \mathcal{O}(1)$, seems to indicate that we are currently living in a very special period of the cosmic history. Within the standard model, a density ratio of the order of one just at the present epoch can be seen as coincidental since it requires very special initial conditions in the early Universe. The corresponding "why now" question constitutes the cosmological "coincidence problem". According to the standard model the equality ${\rho }_{de}={\rho }_{dm}$ took place "recently" at a redshift $z\approx 0.55$. The meaning of "recently" is, however, parameter dependent. In terms of the cosmic time the situation looks different. We discuss several aspects of the "coincidence problem", also in its relation to the cosmological constant problem, to issues of structure formation and to cosmic age considerations.

arXiv comment8 pages, 7 figures

References in corpus (21)

• Planck 2013 results. XVI. Cosmological parameters
• Quintessence, Cosmic Coincidence, and the Cosmological Constant
• Coupled Quintessence
• Cosmological Tracking Solutions
• Interacting Quintessence
• Interacting quintessence solution to the coincidence problem
• Backreaction in late-time cosmology
• Likely Values of the Cosmological Constant
• Solving the Coincidence Problem: Tracking Oscillating Energy
• Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting
• Scaling Cosmology
• Interacting models may be key to solve the cosmic coincidence problem
• K-essence and the coincidence problem
• The cosmological constant and the time of its dominance
• Friedmann cosmology with decaying vacuum density
• What Fraction of Sun-like Stars have Planets?
• A tracker solution to the cold dark matter cosmic coincidence problem
• Cosmological dynamics with non-linear interactions
• On coincidence problem and attractor solutions in ELKO dark energy model
• Dark-Energy Dynamics Required to Solve the Cosmic Coincidence
• Anthropic versus cosmological solutions to the coincidence problem

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