COBE-DMR NORMALIZATION FOR INFLATIONARY FLAT DARK-MATTER MODELS

The two-year COBE-DMR 53- and 90-GHz sky maps, in both galactic and ec liptic coordinates, are used to determine the normalization of inflati onary universe models with a flat global geometry and adiabatic densit y perturbations. The appropriately normalized cold dark matter (CDM) a nd mixed dark matter (MDM) models and cosmological-constant-dominated CDM models, computed for a range of values of Omega(b) and h, are then compared to various measures of structure in the universe. Critical d ensity CDM models appear to be irreconcilable with observations on bot h large and small scales simultaneously, whereas MDM models provide a somewhat better fit to the data. Although the COBE-DMR data alone pref er a nearly critical value for the total density, low-density cosmolog ical constant models with Omega(0) greater than or equal to 0.15 canno t be rejected at a confidence level exceeding 95 per cent. Such models may also provide a significantly better fit to the matter distributio n data than critical density CDM.