Cosmic Complementarity: H_0 and Omega_m from Combining CMB Experiments and Redshift Surveys
Daniel J. Eisenstein, Wayne Hu, Max Tegmark
TL;DR
The paper tackles the degeneracy between $H_0$ and $\Omega_m$ in CMB data by proposing a joint analysis with large redshift surveys to detect baryon acoustic oscillations as a standard ruler. Using Fisher matrix forecasts for a 12-parameter adiabatic CDM model and combining MAP/Planck-like CMB data with SDSS BRG power spectra, it shows that the redshift survey information can reduce the uncertainties to below 5% for $H_0$ and about 10% for $\Omega_m$, with the improvement sensitive to the baryon fraction. The approach hinges on the sound horizon set by high-redshift physics, calibrated by the CMB, and measured in the galaxy power spectrum; non-linearities and bias are carefully considered. If successful, this method provides an independent, high-precision cross-check on cosmological parameters and a robust test of standard cosmology via baryonic acoustic oscillations.
Abstract
We show that upcoming CMB satellite experiments and large redshift surveys can be used together to yield 5% determinations of H_0 and Omega_m, an order of magnitude improvement over CMB data alone. CMB anisotropies provide the sound horizon at recombination as a standard ruler. For reasonable baryon fractions, this scale is imprinted on the galaxy power spectrum as a series of spectral features. Measuring these features in redshift space determines the Hubble constant, which in turn yields Omega_m once combined with CMB data. Since the oscillations in both power spectra are frozen in at recombination, this test is insensitive to low-redshift cosmology.