X iv : a st ro - p h / 98 04 06 2 v 1 6 A pr 1 99 8 HOW SMOOTH IS THE UNIVERSE ON LARGE SCALES ?
نویسندگان
چکیده
New measurements of galaxy clustering and background radiations can provide improved constraints on the isotropy and homogeneity of the Universe on scales larger than 100 h Mpc. In particular, the angular distribution of radio sources and the X-Ray Background probe density fluctuations on scales intermediate between those explored by galaxy surveys and Cosmic Microwave Background experiments. On scales larger than 300 h Mpc the distribution of both mass and luminous sources satisfies well the ‘Cosmological Principle’ of isotropy and homogeneity. Although the fractal dimension of the galaxy distribution on scales ∼< 20 h −1 Mpc is D2 ≈ 1.2− 2.2, the fluctuations in the X-ray Background and in the Cosmic Microwave Background are consistent with D2 = 3 to within 10 −4 on the very large scales. We also discuss limits on non-Gaussian fluctuations.
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