Growth of adiabatic perturbations in self-interacting dark matter

The gauge-invariant formalism for uncoupled perfect fluids is used to investigate the evolution of scale-invariant (n=1) adiabatic density perturbations in a two-component, flat universe filled with radiation and self-interacting dark matter. The resulting spectra of density perturbations, evolved to the present and normalized to the Cosmic Background Explorer Satellite (COBE) DMR 10 deg data, are used to calculate filtered density and velocity dispersions as functions of scale. Self-interacting dark matter models supply more power on large scales compared to small scales than cold dark matter models, in better agreement with observations. The models, however, may have difficulty producing sufficient structure at high redshift with adiabatic perturbations alone.