Is the universe filled with bubbles?

A phenomenological model is constructed in which galaxies populate surfaces of randomly placed shells, and rich clusters are placed at shell intersections. The distribution of shell sizes in varied. The spatial distribution of galaxies and clusters is determined and compared with observations. It is found that the model cluster correlation function is consistent with the observed cluster correlations, exhibiting the large observed increase in correlation strength over galaxies. The model galaxy correlations are consistent with observations on small scales. On large scales, a weak tail of positive galaxy correlations is seen in the simulations that is not observed in the data; this may suggest that galaxies are not distributed randomly on the shells. The results indicate that a simple geometry in which galaxies are located on cells, shells, or similar structures, with clusters located at their intersections, can explain the large-scale structure observed in the galaxy and cluster correlation functions. The main features of the observed agreement are essentially independent of the details of the model. 17 refs