Gravitational Waves from a Fissioning White Hole
  We present a fully nonlinear calculation of the waveform of the gravitational radiation emitted in the fission of a vacuum white hole. At early times, the waveforms agree with close-approximation perturbative calculations but they reveal dramatic time and angular dependence in the nonlinear regime. The results pave the way for a subsequent computation of the radiation emitted after a binary black hole merger. 
Roberto Gomez, Sascha Husa, Luis Lehner and Jeffrey Winicour