Spherical simulations of holes and honeycombs in Friedmann universes

We present extensive parameter studies of spherically symmetric models (without dissipation) of the formation of voids in the galaxy distribution, for cosmological density parameter Ω< or =1 in a standard cosmology. We find that deep holes can form only if Ω is near unity, and that an isolated deep hole is always accompanied by a dense, thin surrounding spherical ''ridge.'' If one starts with underdensities at the cell centers of a regular lattice array, similarly deep holes and similar surrounding dense ridges (mimicking a honeycomb structure) form even in the absence of dissipation. The converse does not occur, i.e., a lattice array with overdensities at the cell centers forms dense clusters but no deep holes between the cells. The density contracts at recombination required to form the observed holes and rich clusters are quite large, and smearing by radiative diffusion does not reduce the associated cosmic microwave background temperature fluctuations to the level required by the present observed upper limits to the small-scale anisotropy. The predicted anistropy is non-Gaussian, giving the appearance of discrete sources of size approx.10'. This discrepancy is particularly severe if Ω is small. Models with massive neutrinos and Ωroughly-equal1 are discussed, as are other possible resolutions to the dilemma