### Abstract

Of all the distance and temporal measures in cosmology, the angular-diameter distance, d _{A}(z), uniquely reaches a maximum value at some finite redshift and then decreases to zero towards the Big Bang. This effect has been difficult to observe due to a lack of reliable, standard rulers, though refinements to the identification of the compact structure in radio quasars may have overcome this deficiency. In this letter, we assemble a catalog of 140 such sources with 0 ≲ z ≲ 3 for model selection and the measurement of z_{max}. In flat ΛCDM, we find that ω_{m} = 0.24_{-0.09} ^{+0.1}, fully consistent with the Planck optimized value, with z_{max} = 1.69. Both of these values are associated with a d _{A}(z) indistinguishable from that predicted by the zero active mass condition, p + 3p = 0, in terms of the total pressure p and total energy density ρ of the cosmic fluid. An expansion driven by this constraint, known as the R_{h} = ct universe, has z_{max} = 1.178, which differs from the ΛCDM optimized value by less than ∼ 1.6%. Indeed, the Bayes Information Criterion favours R_{h} = ct over flat ΛCDM with a likelihood of ∼ 81% vs. 19%, suggesting that the optimized parameters in Planck ΛCDM mimic the constraint p = -p^{/3}.

Original language | English (US) |
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Article number | 39001 |

Journal | EPL |

Volume | 123 |

Issue number | 3 |

DOIs | |

State | Published - Aug 2018 |

### ASJC Scopus subject areas

- Physics and Astronomy(all)