Can Dirac fermions Destroy Yang-Mills Black Hole?
  We study the four-dimensional Einstein-Yang-Mills black hole in the presence of Dirac fermion field. Assuming a spherically symmetric static asymptotically flat black hole spacetime we consider both massless and massive fermion fields. The (4+1)-dimensional Einstein-Yang-Mills system effectively reducing to Einstein-Yang-Mills-Higgs-dilaton model, was also taken into account. One finds that fermion vacuum leads to the destruction of black holes in question. 
Lukasz Nakonieczny, Marek Rogatko
hep-th gr-qc