On an Extension of a Static Ball Solution
  A new exact static interior solution of the Einstein equations is obtained for a gravitating ball filled with a Pascal perfect fluid . The solution is an extension of the well-known interior solution with a parabolic distribution of mass density and describes more compact astrophysical objects such as neutron and hyperon stars. It is shown that a behaviour of the new mass density distribution near the stellar centre can be described as a cusp catastrophe. 
Alexandre M.Baranov
gr-qc math-ph math.MP