Interpretation of the Cosmic Microwave Background Radiation Anisotropy Detected by the COBE Differential Microwave Radiometer

We compare the large-scale cosmic background anisotropy detected by the COBE Differential Microwave Radiometer (DMR) instrument to the sensitive previous measurements on various angular scales, and to the predictions of a wide variety of models of structure formation driven by gravitational instability. The observed anisotropy is consistent with all previously measured upper limits and with a number of dynamical models of structure formation. For example, the data agree with an unbiased cold dark matter (CDM) model with H0 = 50 Km s-1 Mpc-1 and ΔM/M = 1 in a 16 Mpc radius sphere. Other models, such as CDM plus massive neutrinos [hot dark matter (HDM)], or CDM with a nonzero cosmological constant are also consistent with the COBE detection and can provide the extra power seen on 5-10,000 Km s-1 scales.