COBE-DMR normalization for inflationary flat dark matter models

The two-year COBE-DMR 53- and 90-GHz sky maps, in both galactic and ecliptic coordinates, are used to determine the normalization of inflationary universe models with a flat global geometry and adiabatic density perturbations. The appropriately normalized cold dark matter (CDM) and mixed dark matter (MDM) models and cosmological-constant-dominated CDM models, computed for a range of values of Ωb and h, are then compared to various measures of structure in the universe. Critical density CDM models appear to be irreconcilable with observations on both large and small scales simultaneously, whereas MDM models provide a somewhat better fit to the data. Although the COBE-DMR data alone prefer a nearly critical value for the total density, low-density cosmological constant models with Ω0 ≥ 0.15 cannot be rejected at a confidence level exceeding 95 per cent. Such models may also provide a significantly better fit to the matter distribution data than critical density CDM.