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A flat Universe from high-resolution maps of the cosmic microwave background radiation


The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole lpeak = (197 ± 6), with an amplitude ΔT200 = (69 ± 8) µK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.

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Figure 1: Boomerang sky maps (equatorial coordinates).
Figure 2: Angular power spectrum measured by Boomerang at 150 GHz.
Figure 3: Observational constraints on Ωm and ΩΛ.


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The Boomerang experiment was supported by Programma Nazionale di Ricerche in Antartide, Universita' di Roma “La Sapienza”, and Agenzia Spaziale Italiana in Italy, by the NSF and NASA in the USA, and by PPARC in the UK. We thank the staff of the National Scientific Ballooning Facility, and the United States Antarctic Program personnel in McMurdo for their preflight support and an effective LDB flight. DOE/NERSC provided the supercomputing facilities.

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de Bernardis, P., Ade, P., Bock, J. et al. A flat Universe from high-resolution maps of the cosmic microwave background radiation. Nature 404, 955–959 (2000).

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