C. Marinoni, J. Bel, A. Buzzi
The most fundamental premise to the standard model of the universe, the Cosmological Principle (CP), states that the large-scale properties of the universe are the same in all directions and at all comoving positions. Demonstrating this theoretical hypothesis has proven to be a formidable challenge. The cross-over scale R_{iso} above which the galaxy distribution becomes statistically isotropic is vaguely defined and poorly (if not at all) quantified. Here we report on a formalism that allows us to provide an unambiguous operational definition and an estimate of R_{iso}. We apply the method to galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7, finding that R_{iso}\sim 150h^{-1} Mpc. Besides providing a consistency test of the Copernican principle, this result is in agreement with predictions based on numerical simulations of the spatial distribution of galaxies in cold dark matter dominated cosmological models.
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http://arxiv.org/abs/1205.3309
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