1303.3121 (Valerio Marra et al.)

Cosmic variance and the measurement of the local Hubble parameter    [PDF]

Valerio Marra, Luca Amendola, Ignacy Sawicki, Wessel Valkenburg

There is an approximately 7.5% discrepancy, corresponding to 2.0sigma, between two independent constraints on the expansion rate of the universe: one indirectly arising from the cosmic microwave background and baryon acoustic oscillations, and one more directly obtained from local measurements of the relation between redshifts and distances to sources. We argue that by taking into account the local gravitational potential at the position of the observer this tension is partially relieved and the concordance of the standard model of cosmology increased. We estimate that present measurements of the local Hubble constant are subject to a cosmic variance of about 2.4% (limiting the local sample to redshifts z>0.010) or 1.3% (limiting it to z>0.023), which should be added to the error budget of such measurements.

View original: http://arxiv.org/abs/1303.3121