Inhomogeneity-induced variance of cosmological parameters

Abstract

Modern cosmology relies on the assumption of large-scale isotropy and homogeneity of the Universe. However, locally the Universe is inhomogeneous and anisotropic. So, how can local measurements (at the 100 Mpc scale) be used to determine global cosmological parameters (defined at the 10 Gpc scale)? We use Buchert's averaging formalism and determine a set of locally averaged cosmological parameters in the context of the flat Lambda cold dark matter model. We calculate their ensemble means (i.e. their global values) and variances (i.e. their cosmic variances). We apply our results to typical survey geometries and focus on the study of the effects of local fluctuations of the curvature parameter. By this means we show, that in the linear regime cosmological backreaction and averaging can be reformulated as the issue of cosmic variance. The cosmic variance is found largest for the curvature parameter and discuss some of its consequences. We further propose to use the observed variance of cosmological parameters to measure the growth factor. [abbreviated]

12 pages, 10 figures, references added, estimate of lightcone effects added, matches version published in A&A

References in corpus (15)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• The Cosmic Evolution Survey (COSMOS) -- Overview
• Testing cosmological structure formation using redshift-space distortions
• On cosmological observables in a swiss-cheese universe
• Dynamical Dark Energy or Simply Cosmic Curvature?
• Correspondence between kinematical backreaction and scalar field cosmologies - the `morphon field'
• Scale dependence of cosmological backreaction
• Multiscale cosmology and structure-emerging Dark Energy: A plausibility analysis
• On the onset of cosmological backreaction
• Evaluating backreaction with the peak model of structure formation
• The influence of structure formation on the cosmic expansion
• Applicability of the linearly perturbed FRW metric and Newtonian cosmology
• Spatially averaged cosmology in an arbitrary coordinate system
• Geometrical order-of-magnitude estimates for spatial curvature in realistic models of the Universe
• Averaging Robertson-Walker Cosmologies

Cited by in corpus (20)

• Cosmic variance and the measurement of the local Hubble parameter
• The value of H_0 in the inhomogeneous Universe
• Constraints on anisotropic cosmic expansion from supernovae
• Einstein's Universe: Cosmological structure formation in numerical relativity
• Lagrangian theory of structure formation in relativistic cosmology II: average properties of a generic evolution model
• Backreaction on the luminosity-redshift relation from gauge invariant light-cone averaging
• Do we care about the distance to the CMB? Clarifying the impact of second-order lensing
• Ricci focusing, shearing, and the expansion rate in an almost homogeneous Universe
• Post-Newtonian Celestial Dynamics in Cosmology: Field Equations
• Constraining the local variance of $H_0$ from directional analyses
• The variance of the locally measured Hubble parameter explained with different estimators
• Intrinsic uncertainty on the nature of dark energy
• Relative information entropy and Weyl curvature of the inhomogeneous Universe
• Kinematic Bias in Cosmological Distance Measurement
• Backreaction: Gauge and Frame Dependences
• Angular distribution of cosmological parameters as a probe of inhomogeneities: a kinematic parametrisation
• On the physical effects of consistent cosmological averaging
• Lightcone Averaging and Precision Cosmology
• The Effect of $\alpha$-Vacua on the Scalar and Tensor Spectral Indices: Slow-Roll Approximation
• Cosmological model dependence of the galaxy luminosity function: far-infrared results in the Lemaitre-Tolman-Bondi model