The BOOMERanG experiment and the curvature of the Universe

We. describe the BOOMERanG experiment and its main result, i.e. the measurement of the large scale curvature of the Universe. BOOMERanG is a balloon-borne microwave telescope with sensitive cryogenic detectors. BOOMERanG has measured the angular distribution of the Cosmic Microwave Background on similar to 3% of the sky, with a resolution of similar to 10 arcmin and a sensitivity of similar to 20muK per pixel. The resulting image is dominated by hot. and cold spots with rms fluctuations similar to 80muK and typical size of similar to 1degrees. The detailed angular power spectrum of the image features three peaks and two dips at l = (213(-13)(+10)) (541(-32)(+20)) (845(-25)(+12)) and l = (416(-12)(+22)), (750(-750)(+20)), respectively. Such very characteristic spectrum can be explained assurning that the detected structures are the result of acoustic oscillations in the primeval plasma. In this framework, the measured pattern constrains the, density parameter Omega to be 0.85 < Omega < 1.1 (95% confidence interval). Other cosmological parameters, like the spectral index of initial density fluctuations, the density parameter for baryons, dark matter and dark energy, are detected or constrained by the BOOMERanG measurements and by other recent, CMB anisotropy experiments. When combined with other cosmological observations, these results depict a new, consistent,, cosmological scenario.