Revealing Intrinsic Flat $\Lambda$CDM Biases with Standardizable Candles

Abstract

Emerging high redshift cosmological probes, in particular quasars (QSOs), show a preference for larger matter densities, ${\Omega }_m\approx 1$, within the flat $\Lambda$CDM framework. Here, using the Risaliti-Lusso relation for standardizable QSOs, we demonstrate that the QSOs recover the \textit{same} Planck-$\Lambda$CDM Universe as Type Ia supernovae (SN), ${\Omega }_m\approx 0.3$ at lower redshifts $0<z\lesssim 0.7$, before transitioning to an Einstein-de Sitter Universe (${\Omega }_m=1$) at higher redshifts $z\gtrsim 1$. We illustrate the same trend, namely increasing ${\Omega }_m$ and decreasing $H_0$ with redshift, in SN but poor statistics prevent a definitive statement. We explain physically why the trend is expected in the flat $\Lambda$CDM cosmology, illustrate the intrinsic bias and non-Gaussian tails with mock Pantheon data, and identify a similar trend in BAO below $z=1$. Our results highlight an intrinsic bias in the flat $\Lambda$CDM Universe, whereby ${\Omega }_m$ increases, $H_0$ decreases and $S_8$ increases with effective redshift, thus providing a new perspective on $\Lambda$CDM tensions; even in a Planck-$\Lambda$CDM Universe the current tensions might have been expected.

Comments: 6 pages, 7 figures, comments welcome; v2 matches published version