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Cosmic Complementarity: H_0 and Omega_m from Combining CMB Experiments and Redshift Surveys

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.