= Kuzmin disk
{c}
{title2=$\Sigma(R)=mb/[2\pi(R^2+b^2)^{3/2}]$}
= Kuzmin disc
{c}
{synonym}
A Kuzmin disk is an infinitesimally thin axisymmetric <astrophysical disk> whose <relative potential> is $\psi=Gm/\sqrt{R^2+(|z|+b)^2}$, with $m,b>0$. Away from the disk this is a point-mass vacuum field. The jump of its vertical derivative is $-2Gmb/(R^2+b^2)^{3/2}$, so the <Poisson equation for Newtonian gravity>, written $\nabla^2\psi=-4\pi G\rho$, gives the displayed <surface density>. Integrating $2\pi R\Sigma$ gives total <mass> $m$.
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