Chaotic scattering around black holes
  It is shown that the scattering of a charged test particle by a system of four extreme Reissner-Nordtr\"om black holes is chaotic in some cases. The fractal structure of the scattering angle and time delay functions is another manifestation of the existence of a nonattracting chaotic set: fractal basin boundaries were previously known. 
Juan M. Aguirregabiria