Reduced Planck units
= Reduced Planck units
{title2=$\hbar=c=8\pi G=1,\quad M_{\rm Pl}=1$}
Here the <reduced Planck mass> $M_{\rm Pl}=(8\pi G)^{-1/2}$ is one, so the <Friedmann equation> for an energy density $\rho$ is $3H^2=\rho$. This differs by a factor of $\sqrt{8\pi}$ from setting the ordinary <Planck mass> to one; the convention must be stated in inflationary amplitudes.