Using traversable wormholes as theoretical background, we revisit a deep qu
estion of general relativity: Does a uniformly accelerated charged particle
radiate? We particularize to the recently proposed gravitational Cerenkov
radiation, that happens when the spatial part of the Ricci tensor is negati
ve. If R-(3+1)(i)i < 0, the matter threading the gravitational field violat
es the weak energy condition. In this case, the effective refractive index
for light is larger than 1, i.e. particles propagate faster than photons in
that medium. This leads to a violation of the equivalence principle.