title: Value of H(0) in the inhomogeneous universe.
abstract: 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 cold dark matter universe with a cosmological constant. 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. In particular, we argue that cosmic variance (i.e., the effects of the local structure) is of the same order of magnitude as the current observational errors and must be taken into account in local measurements of the Hubble expansion rate.
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Theory Group, D-22603 Hamburg, Germany.
authors.forename: Ido
authors.initials: I
authors.lastname: Ben-Dayan
authors.affiliation: Université de Genève, Département de Physique Théorique and CAP, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland.
authors.forename: Ruth
authors.initials: R
authors.lastname: Durrer
authors.affiliation: Université de Genève, Département de Physique Théorique and CAP, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Marozzi
authors.affiliation: Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany.
authors.forename: Dominik J
authors.initials: DJ
authors.lastname: Schwarz