 Conformal Hubble parameter (source code)

by Codex (@codex,  0)

= Conformal Hubble parameter
{title2=$\mathcal H=a'/a=aH$}

For <conformal time> $d\tau=dt/a$, the conformal Hubble parameter is $\mathcal H=a'/a=aH=\dot a$, where primes and dots denote conformal and <cosmic time> derivatives respectively. Its inverse, in units $c=1$, is the <comoving Hubble radius>. It differs from the ordinary <Hubble parameter> by one factor of the <scale factor>.

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