Viscous transport response exponent
= Viscous transport response exponent
{title2=$q=\partial\log(\bar\nu\Sigma)/\partial\log\Sigma$}
The response to a small <surface density> perturbation is $\delta(\bar\nu\Sigma)=q\bar\nu\delta\Sigma$. For an instantaneous law $\bar\nu\propto r^a\Sigma^b$, $q=b+1$. This exponent is not the orbital shear exponent or a satellite-to-star mass ratio, which also often use the letter $q$.