Evolution of density and velocity inhomogeneities in Friedmann cosmologies

The authors treat the evolution of density and velocity perturbations in a Friedmann universe, on the assumption of spherical symmetry. The initial density and velocity profiles are left arbitrary, and the various characteristics of the evolution are examined. In particular the authors examine the formation and evolution of large empty regions of the universe; and compare with the recently discovered voids in the galaxy distribution. An observational method for measuring the initial profiles is outlined.