Aspects of the cosmological "coincidence problem"

作者：Velten H E S^*; vom Marttens R F; Zimdahl W

来源：European Physical Journal C, 2014, 74(11): 3160.

DOI：10.1140/epjc/s10052-014-3160-4

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 similar to 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 approximate to 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.

• 出版日期2014-11-22