= Nonzero redshift-drift root in flat matter-Lambda cosmology
{title2=$1+z_*=[\Omega_\Lambda+\sqrt{\Omega_\Lambda^2+4\Omega_m\Omega_\Lambda}]/(2\Omega_m)$}
For positive matter and vacuum fractions with $\Omega_m+\Omega_\Lambda=1$, <redshift drift> vanishes when $s^2=\Omega_ms^3+\Omega_\Lambda$, $s=1+z$. Factoring out the trivial observer root $s=1$ leaves $\Omega_ms^2-\Omega_\Lambda s-\Omega_\Lambda=0$, giving the displayed positive <root of a polynomial>. It lies at a positive <redshift> exactly when $\Omega_m<2/3$. It is independent of the <Hubble constant> at fixed density fractions and is not the <redshift> of the acceleration-to-deceleration transition.
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