Critical rotation of general-relativistic polytropic models simulating   neutron stars: a post-Newtonian hybrid approximative scheme
  We develop a "hybrid approximative scheme" in the framework of the post-Newtonian approximation for computing general-relativistic polytropic models simulating neutron stars in critical rigid rotation. We treat the differential equations governing such a model as a "complex initial value problem", and we solve it by using the so-called "complex-plane strategy". We incorporate into the computations the complete solution for the relativistic effects, this issue representing a significant improvement with regard to the classical post-Newtonian approximation, as verified by extended comparisons of the numerical results. 
Vassilis S. Geroyannis, Vasileios G. Karageorgopoulos
gr-qc