Destruction of the Cauchy horizon in the Reissner-Nordstrom black hole

The Cauchy horizon instability in the Reissner-Nordstrom solution is investigated numerically using (2+2) formalism. The formalism is based on the metric decomposition along two null coordinates parallel to the black hole horizons. The authors show that a spacelike singularity forms to prevent an observer's reaching the Cauchy horizon and the properties of the singularity are discussed in detail. They found that if the mass of the perturbation is of an order of or greater than the mass of the initial Reissner-Nordstrom black hole, the position of the singularity tends to those in the Schwarzschild solution. They also present a highly reliable numerical scheme based on the (2+2) formalism and discuss the properties of the initial value equations which in (2+2) formalism are reduced to linear equations.