Multiscale cosmology and structure-emerging Dark Energy: A plausibility analysis

Abstract

Cosmological backreaction suggests a link between structure formation and the expansion history of the Universe. In order to quantitatively examine this connection, we dynamically investigate a volume partition of the Universe into over-- and underdense regions. This allows us to trace structure formation using the volume fraction of the overdense regions $λ_{\CM}$ as its characterizing parameter. Employing results from cosmological perturbation theory and extrapolating the leading mode into the nonlinear regime, we construct a three--parameter model for the effective cosmic expansion history, involving $λ_{\CM_{0}}$, the matter density $Ω_{m}^{\CD_{0}}$, and the Hubble rate $H_{\CD_{0}}$ of today's Universe. Taking standard values for $Ω_{m}^{\CD_{0}}$ and $H_{\CD_{0}}$ as well as a reasonable value for $λ_{\CM_{0}}$, that we derive from $N$--body simulations, we determine the corresponding amounts of backreaction and spatial curvature. We find that the obtained values that are sufficient to generate today's structure also lead to a $\Lambda$CDM--like behavior of the scale factor, parametrized by the same parameters $Ω_{m}^{\CD_{0}}$ and $H_{\CD_{0}}$, but without a cosmological constant. However, the temporal behavior of $λ_{\CM}$ does not faithfully reproduce the structure formation history. Surprisingly, however, the model matches with structure formation with the assumption of a low matter content, $Ω_{m}^{\CD_{0}}\approx3\%$, a result that hints to a different interpretation of part of the backreaction effect as kinematical Dark Matter. (truncated)

25 pages, 10 figures, includes calculation of luminosity distances, matches published version in Phys. Rev. D

References in corpus (26)

• Dynamics of dark energy
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Improved Cosmological Constraints from New, Old and Combined Supernova Datasets
• Improved Dark Energy Constraints from ~100 New CfA Supernova Type Ia Light Curves
• A general test of the Copernican Principle
• Cosmic clocks, cosmic variance and cosmic averages
• The Aspen--Amsterdam Void Finder Comparison Project
• Exact solution to the averaging problem in cosmology
• Lemaitre-Tolman-Bondi model and accelerating expansion
• The universe seen at different scales
• Accelerated expansion from structure formation
• Correspondence between kinematical backreaction and scalar field cosmologies - the `morphon field'
• Scale dependence of cosmological backreaction
• On the onset of cosmological backreaction
• Evaluating backreaction with the peak model of structure formation
• On the curvature of the present-day Universe
• Applicability of the linearly perturbed FRW metric and Newtonian cosmology
• Gravitational energy as dark energy: Concordance of cosmological tests
• A cosmic equation of state for the inhomogeneous Universe: can a global far-from-equilibrium state explain Dark Energy?
• Spatially averaged cosmology in an arbitrary coordinate system
• Spectroscopy of High-Redshift Supernovae from the ESSENCE Project: The First Four Years
• Apparent and average acceleration of the Universe
• Description of our cosmological spacetime as a perturbed conformal Newtonian metric and implications for the backreaction proposal for the accelerating universe
• Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe
• Averaging Robertson-Walker Cosmologies
• Unification of cosmological scalar fields

Cited by in corpus (5)

• A new framework for analyzing the effects of small scale inhomogeneities in cosmology
• What is dust? - Physical foundations of the averaging problem in cosmology
• Effective inhomogeneous inflation: curvature inhomogeneities of the Einstein vacuum
• Towards physical cosmology: geometrical interpretation of Dark Energy, Dark Matter and Inflation without fundamental sources
• Multiscale approach to inhomogeneous cosmologies