Cerenkov Emission by Neutral Particles in Gravitoelectro-magnetic Fields
  It is shown that under the post-Newtonian approximation the Einstein equations can be reduced to the standard Maxwell-type field equations in a medium; in such a context the Cerenkov emission by a neutralparticle gives large energy loss while the particle moves at faster than the phase speed of waves in the medium. 
X.Q.Li and S.Q.Liu