Revealing intrinsic flat <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Λ</mml:mi><mml:mi>CDM</mml:mi></mml:mrow></mml:math> biases with standardizable candles

Emerging high-redshift cosmological probes, in particular quasars (QSOs), show a preference for larger matter densities, ${\mathrm{\ensuremath{\Omega}}}_{m}\ensuremath{\approx}1$, within the flat $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ framework. Here, using the Risaliti-Lusso relation for standardizable QSOs, we demonstrate that the QSOs recover the same Planck-$\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ universe as type Ia supernovae (SN), ${\mathrm{\ensuremath{\Omega}}}_{m}\ensuremath{\approx}0.3$ at lower redshifts $0&lt;z\ensuremath{\lesssim}0.7$, before transitioning to an Einstein--de Sitter universe (${\mathrm{\ensuremath{\Omega}}}_{m}=1$) at higher redshifts $z\ensuremath{\gtrsim}1$. We illustrate the same trend, namely increasing ${\mathrm{\ensuremath{\Omega}}}_{m}$ and decreasing ${H}_{0}$ with redshift, in SN but poor statistics prevent a definitive statement. We explain physically why the trend may be expected and show the intrinsic bias through non-Gaussian tails with mock SN data. Our results highlight an intrinsic bias in the flat $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ universe, whereby ${\mathrm{\ensuremath{\Omega}}}_{m}$ increases, ${H}_{0}$ decreases and ${S}_{8}$ increases with effective redshift, thus providing a new perspective on $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ tensions; even in a Planck-$\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ universe the current tensions may be expected.