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Unformatted text preview: 1/15/12 Gala[ieV and Whe UniYeuVe - CoVmolog\ in Whe Fuiedman UniYeuVe 1/2 ZZZ.aVWu.Xa.edX/keel/gala[ieV/fuiedman.hWml Cosmology in the Friedman Universe Before going on to galaxy formation and evolution, it is worthwhile to look at the connections between cosmological models and basic tenets of general relativity for the commonly-considered instance of an expanding Universe in the Friedman model . The connection between the world model and observables comes about from Weyl's postulate - that the wordlines of galaxies form a 3-bundle of non-intersecting geodisics orthogonal to a series of spacelike hypersurfaces. This is what is now generally meant by a comoving coordinate systems, since we appreciate that galaxies and clusters depart from this ideal through having nonzero peculiar motions. An excellent source for this material is Peebles' Ph\sical Cosmolog\ (Princeton 1971). Pedantically, using the relativistic coordinates [ , a spacelike hypersurface satisfies [ =constant, and a worldline which follows the...
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- Fall '09