Stability of self-dual black holes
  We study the stability properties of the Cauchy horizon for two different
self-dual black hole solutions obtained in a model inspired by Loop Quantum
Gravity. The self-dual spacetimes depend on a free dimensionless parameter
called a polymeric parameter P. For the first metric the Cauchy horizon is
stable for supermassive black holes only if this parameter is sufficiently
small. For small black holes, however the stability is easily implemented. The
second metric analyzed is not only self-dual but also "form-invariant" under
the transformation r -> r*^2/r and r* = 2 m P. We find that this symmetry
protects the Cauchy horizon for any value of the polymeric parameter.
