The effective geometry of the $n=1$ uniformly rotating self-gravitating   polytrope
  The \lq\lq effective geometry" formalism is used to study the perturbations of a perfect barotropic Newtonian self-gravitating rotating and compressible fluid coupled with gravitational backreaction. The case of a uniformly rotating polytrope with index $n=1$ is investigated, due to its analytical tractability. Special attention is devoted to the geometrical properties of the underlying background acoustic metric, focusing in particular on null geodesics as well as on the analog light cone structure. 
Donato Bini, Christian Cherubini, Simonetta Filippi, Andrea Geralico
gr-qc