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On the detection of large-scale inhomogeneities in the Universe

Abstract

THE detection of large-scale inhomogeneities in the Universe has proceeded along a number of fronts. The observed spatial distribution of galaxies indicates clumping of matter on length scales up to 30 Mpc (ref. 1). Limits on fine-scale temperature fluctuations in the microwave background2 constrain mass concentrations at the epoch of recombination, and later3,4. Neither of these methods is particularly sensitive to large-scale low-density contrast (δρ/ρ 1), perturbations at the current epoch (that is, masses 1019 M on a scale 1,000 Mpc), although in principle the distribution of discrete radio sources on the sky may be investigated for such effects (see for example ref. 5). We show here that measurements of the isotropy of the X-ray background provide a sensitive means of detecting such large-scale inhomogeneities within Z 5.

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FABIAN, A., WARWICK, R. On the detection of large-scale inhomogeneities in the Universe. Nature 280, 39–40 (1979). https://doi.org/10.1038/280039a0

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