Constraints on cosmological parameters from recent measurements of CMB anisotropy

A key prediction of cosmological theories for the origin and evolution of structure in the Universe is the existence of a Doppler peak' in the angular power spectrum of cosmic microwave background (CMB) fluctuations. We present new results from a study of recent CMB observations which provide the first strong evidence for the existence of a Doppler Peak’ localised in both angular scale and amplitude. This first estimate of the angular position of the peak is used to place a new direct limit on the curvature of the Universe, corresponding to a density of $\mathrm{\Omega }=0.7_{-0.5}^{+0.8}$, consistent with a flat Universe. Very low density `open’ Universe models are inconsistent with this limit unless there is a significant contribution from a cosmological constant. For a flat standard Cold Dark Matter dominated Universe we use our results in conjunction with Big Bang nucleosynthesis constraints to determine the value of the Hubble constant as $\text{ho}=30-70\text{kmspmpc}$ for baryon fractions ${\mathrm{\Omega }}_b=0.05$ to 0.2. For $\text{ho}=50\text{kmspmpc}$ we find the primordial spectral index of the fluctuations to be $n=1.1\pm 0.1$, in close agreement with the inflationary prediction of $n\simeq 1.0$