Beta function (physics)
= Beta function
{disambiguate=physics}
{title2=$\beta(g)=\mu\,dg/d\mu$}
{wiki}
The beta function of a coupling $g$ is
$$
\beta(g)=\mu\frac{dg}{d\mu}=\frac{dg}{d\log\mu}.
$$
It describes how the <running coupling> changes when the <renormalization scale> changes.