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arXiv · 2007.10472

The failure of testing for cosmic opacity via the distance-duality relation

Vaclav Vavrycuk·Pavel Kroupa
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Abstract

The distance-duality relation (DDR) between the luminosity distance $D_L$ and the angular diameter distance $D_A$ is viewed as a powerful tool for testing for the opacity of the Universe, being independent of any cosmological model. It was applied by many authors, who mostly confirm its validity and report a negligible opacity of the Universe. Nevertheless, a thorough analysis reveals that applying the DDR in cosmic opacity tests is tricky. Its applicability is strongly limited because of a non-unique interpretation of the $D_L$ data in terms of cosmic opacity and a rather low accuracy and deficient extent of currently available $D_A$ data. Moreover, authors usually assume that cosmic opacity is frequency independent and parametrize it in their tests by a prescribed phenomenological function. In this way, they only prove that cosmic opacity does not follow their assumptions. As a consequence, no convincing evidence of transparency of the universe using the DDR has so far been presented.

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Vaclav Vavrycuk, Pavel Kroupa. 2020-07-20. The failure of testing for cosmic opacity via the distance-duality relation. https://doi.org/10.1093/mnras%2Fstaa1936

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