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R. Lieu (Univ Alabama Huntsville)
The propagation of light through a Universe of (a) isothermal mass spheres amidst (b) a homogeneous matter component, is considered. We demonstrate by an analytical proof that as long as the light passes through a sufficient number of (a) at various impact parameters - a criterion of great importance - the average convergence of the beam will in the weak lensing limit exactly compensate the divergence within (b). The net effect on the light is statistically the same as if all the matter in (a) is `fully homogenized'. However, the above notion of a net convergence does not apply to the angular size of large emitters like the primary acoustic peaks of the microwave background. The reason is that most (by mass) of (a) are galaxies plus halos - their full mass profiles are not sampled by passing light - at least the inner 50 kpc regions of these systems are missed by the majority of rays. Thus a good fraction of the emission area of an acoustic peak is in fact demagnified, and even though there are embedded sightlines which intercept the galaxies at their inner radii, these only represent small spots of intense convergence - a large source will not be remagnified in this way. Conventional ideas of associating the WMAP observations of Euclidean geometry with a Universe at critical density cannot be deemed as robust, until the question raised here is addressed.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.