Power Spectra for Cold Dark Matter and Its Variants

The bulk of recent cosmological research has focused on the adiabatic colddark matter model and its simple extensions. Here we present an accuratefitting formula that describes the matter transfer functions of all commonvariants, including mixed dark matter models. The result is a function ofwavenumber, time, and six cosmological parameters: the massive neutrinodensity, number of neutrino species degenerate in mass, baryon density, Hubbleconstant, cosmological constant, and spatial curvature. We show howobservational constraints---e.g. the shape of the power spectrum, the abundanceof clusters and damped Lyman-alpha systems, and the properties of theLyman-alpha forest--- can be extended to a wide range of cosmologies, includingvariations in the neutrino and baryon fractions in both high-density andlow-density universes.