Superluminal censorship

@inproceedings{Visser1998SuperluminalC,
  title={Superluminal censorship},
  author={M. Visser and B. Bassett and S. Liberati},
  year={1998}
}
We argue that ``effective'' superluminal travel, potentially caused by the tipping over of light cones in Einstein gravity, is always associated with violations of the null energy condition (NEC). This is most easily seen by working perturbatively around Minkowski spacetime, where we use linearized Einstein gravity to show that the NEC forces the light cones to contract (narrow). Given the NEC, the Shapiro time delay in any weak gravitational field is always a delay relative to the Minkowski… Expand