From anisotropy to omega

After the recent measurement of the acoustic peak in the CMB anisotropy ang ular power spectrum at l similar to 200, many analyses have found that the geometry of the Universe is nearly flat, while favoring slightly closed mod els. In this paper we will briefly remind how the CMB anisotropies depend o n the curvature, explaining any assumptions we could make and showing that this 'skewness' towards closed models can be easily explained by degeneraci es in the cosmological parameters. While it is difficult to give independen t constraints on the cosmological constant and/or different forms of dark e nergies, we will also show that combining CMB measurements with other obser vational data will put new and tighter constraints, like Omega (Lambda) > 0 at similar to7 sigma level. (C) 2001 Elsevier Science B.V. All rights rese rved.