Power spectra for cold dark matter and its variants

The bulk of recent cosmological research has focused on the adiabatic cold dark matter model and its simple extensions. Here we present an accurate fi tting formula that describes the matter transfer functions of all common va riants, including mixed dark matter models. The result is a function of wav enumber, time, and six cosmological parameters: the massive neutrino densit y, number of neutrino species degenerate in mass, baryon density, Hubble co nstant, cosmological constant, and spatial curvature. We show how observati onal constraints-e.g., the shape of the power spectrum, the abundance of cl usters and damped Ly alpha systems, and the properties of the Ly alpha fore st-can be extended to a wide range of cosmologies, which includes variation s in the neutrino and baryon fractions in both high-density and low-density universes.