Adiabatic contraction of anisotropic spheres in general relativity

For specific equations of state, the paper studies the adiabatic contraction of a sphere with anisotropic stresses for different degrees of anisotropy. Attention is given to the equation of motion of particles which is integrated numerically for different initial conditions. The local pressure-density law for equilibrium is found to be different for different regions in the material. Finally, it is noted that in some examples the models are more stable than the isotropic model; in others they are less stable.