Boundary virial term of a singular isothermal sphere
= Boundary virial term of a singular isothermal sphere
{title2=$4\pi R^3\rho(R)\sigma_r^2$}
A finite spherical subvolume has radial-pressure virial surface term $4\pi R^3\rho(R)\sigma_r^2$. The infinite <singular isothermal sphere> has divergent total mass and energies, so a finite isolated <virial theorem> cannot omit this term. Different orbital distributions with the same density can have different radial boundary pressures.