Primordial density fluctuations and the structure of galactic haloes

N-body models used to study the formation of structure in Ω = 1 universes reveal that the mass profiles of the collapsed structures-galactic haloes-are intimately related to the power spectrum of initial, gaussian, density perturbations. In particular, flat rotation curves observed in disk galaxies are obtained only when the exponent of the power law P(k) ~ kⁿ is, on the megaparsec scale, less than -1, but not as small as -3. These results have important implications for various cosmological models.