The value of H_0 in the inhomogeneous Universe

Understand

Local measurements of the Hubble expansion rate are affected by structures like galaxy clusters or voids.

• Here we present a fully relativistic treatment of this effect, studying how clustering modifies the mean distance (modulus)-redshift relation and its dispersion in a standard $\Lambda$CDM universe.
• The best estimates of the local expansion rate stem from supernova observations at small redshifts (0.01<z<0.1).
• It is interesting to compare these local measurements with global fits to data from cosmic microwave background anisotropies.