The Rubakov-Callan Effect and Black Holes
  The Rubakov-Callan effect is reexamined by considering the gravitational effects caused by the heavy monopole mass. Assuming that the Higgs vacuum expectation value is as large as (or larger than) the Planck mass, we show that the calculational scheme of Rubakov and Callan may be extended in the presence of curved background field. It is argued that the density of the fermion condensate around a magnetically charged black hole is modified in an intricate way. 
T. Kubota