= Exponential-disk asymmetric drift
{title2=$V_c^2-\bar v_\phi^2=\sigma^2R(R_d^{-1}+R_\sigma^{-1})$}
For a stationary axisymmetric tracer with isotropic <velocity dispersion>, vanishing tilted stress, density $\nu\propto e^{-R/R_d}$, and $\sigma^2\propto e^{-R/R_\sigma}$, the radial <Jeans equation> gives the displayed expression. More generally its right side is $-\sigma^2 d\ln(\nu\sigma^2)/d\ln R$. It requires a nonnegative streaming-speed square; the density and dispersion laws must describe the same tracer and the chosen height or consistent vertical average.
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