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The WMAP results (Spergel et al. 2003) have given rather strict limits on the matter and energy content of the Universe, in agreement with the LambdaCDM model. Typically, for Omegatotal = 1, Omegadark energy = 0.73, and Omegamatter = 0.27, with Omegabaryon = 0.044, and Omeganon-baryonic = 0.23. Some of these results depend on data from the 2dF galaxy redshift survey. Initial results from the SDSS redshift survey are not much different (Tegmark et al. 2003). The ratio of baryonic to non-baryonic matter is thus 1 to ~ 5 - 6. The baryonic matter at z = 0 is mostly not in stars (Omegastars = 0.005), and the matter budget in e.g. the Local Group is still not well known : there could be hot gas in substantial amounts (Nicastro et al. 2003).

These results further support the LambdaCDM model for structure formation in the Universe, and underscore the need to understand galaxies in the framework of this theory. However, at the scale of galaxies, the "predictions" of the LambdaCDM model depend on numerical simulations, which, despite their sophistication, suffer from inadequate resolution, and may miss some of the physics. This meeting aims to see how well specific predictions from current cosmological simulations of dark matter halos fare on issues such as their central density profiles, the relation between dark to baryonic matter there, and their shape and extent.