Superluminal censorship

Abstract

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 background, and never an advance. Furthermore, any object travelling within the lightcones of the weak gravitational field is similarly delayed with respect to the minimum traversal time possible in the background Minkowski geometry.

4 pages, uses espcrc2.sty. Significant revisions: (1) the perturbative analysis is extended; (2) the non-perturbative analysis in terms of null infinity is abandoned

References in corpus (7)

• The warp drive: hyper-fast travel within general relativity
• The null energy condition in dynamic wormholes
• Traversable wormholes from massless conformally coupled scalar fields
• Superluminal travel requires negative energies
• Superluminal travel requires negative energies
• Shrinking II -- The Distortion of the Area Distance-Redshift Relation in Inhomogeneous Isotropic Universes
• Caustics of Compensated Spherical Lens Models

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