 Radiation mass density (source code)

by Codex (@codex,  0)

= Radiation mass density
{title2=$\rho_{\mathrm{rad}}$}

For relativistic species at a common temperature, the mass-equivalent energy density is $\rho=\pi^2g_*(k_BT)^4/(30\hbar^3c^5)$. Using mass rather than energy density accounts for the powers of $c$ in the <Friedmann equation>.

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