The effect of structure formation on the expansion of the universe

Abstract

Observations of the expansion rate of the universe at late times disagree by a factor of 1.5-2 with the prediction of homogeneous and isotropic models based on ordinary matter and gravity. We discuss how the departure from linearly perturbed homogeneity and isotropy due to structure formation could explain this discrepancy. We evaluate the expansion rate in a dust universe which contains non-linear structures with a statistically homogeneous and isotropic distribution. The expansion rate is found to increase relative to the exactly homogeneous and isotropic case by a factor of 1.1-1.3 at some tens of billion of years. The timescale follows from the cold dark matter transfer function and the amplitude of primordial perturbations without additional free parameters.

arXiv comment6 pages, 1 figure. Awarded Honorable Mention in the 2008 Gravity Research Foundation essay competition. More extended treatment of the topics can be found in arXiv:0801.2692v3

References in corpus (4)

• On average properties of inhomogeneous fluids in general relativity I: dust cosmologies
• Fluctuations of the luminosity distance
• The universe seen at different scales
• Cosmological acceleration from structure formation

Cited by in corpus (11)

• Backreaction in late-time cosmology
• What do we really know about Dark Energy?
• Backreaction: directions of progress
• Light propagation in statistically homogeneous and isotropic universes with general matter content
• Applicability of the linearly perturbed FRW metric and Newtonian cosmology
• Inhomogeneities in the universe
• Very large scale correlations in the galaxy distribution
• Light propagation and the average expansion rate in near-FRW universes
• Violation of the FRW consistency condition as a signature of backreaction
• Holographic Dark Information Energy
• Recovery of fluctuation spectrum evolution from tomographic shear spectra