Kerr-Newman Solutions with Analytic Singularity and no Closed Timelike   Curves
  It is shown that the Kerr-Newman solution, representing charged and rotating stationary black holes, admits analytic extension at the singularity. This extension is obtained by using new coordinates, in which the metric tensor becomes smooth on the singularity ring. On the singularity, the metric is degenerale - its determinant cancels. The analytic extension can be naturally chosen so that the region with negative r no longer exists, eliminating by this the closed timelike curves normally present in the Kerr and Kerr-Newman solutions. On the extension proposed here the electromagnetic potential is smooth, being thus able to provide non-singular models of charged spinning particles. The maximal analytic extension of this solution can be restrained to a globally hyperbolic region containing the exterior universe, having the same topology as the Minkowski spacetime. This admits a spacelike foliation in Cauchy hypersurfaces, on which the information contained in the initial data is preserved. 
Ovidiu-Cristinel Stoica
gr-qc math-ph math.DG math.MP