Splitting of an Extremal Reissner-Nordstr\"om Throat via Quantum   Tunneling
  The interior near the horizon of an extremal Reissner-Nordstr\"om black hole is taken as an initial state for quantum mechanical tunneling. An instanton is presented that connects this state with a final state describing the presence of several horizons. This is interpreted as a WKB description of fluctuations due to the throat splitting into several components. 
Dieter R. Brill