Testing Cosmic Fluctuation Spectra

We show that the angular correlation function of galaxies, wgg(θ), may be used as a direct test of large scale power in cosmic density fluctuation spectra. Groth and Peebles (1986) found a break in w(θ) from a power-law at θ ∼ 3° in an analysis of the Shane-Wirtanen galaxy counts. Maddox and Efstathiou (1987) find evidence for a similar break in w(θ) in the Southern Sky Survey. Testing for a break is a powerful probe of the linear regime of fluctuation spectra. The CDM model has such a break; almost all candidate Gaussian theories with enough large scale power to explain the clustering of clusters do not.