Abstract
A class of spacetimes (comprising the Alcubierre bubble, Krasnikov tube, and a certain type of wormhole) is considered that admits “superluminal travel” in a strictly defined sense. Such spacetimes (they are called “shortcuts” in this paper) were suspected to be impossible because calculations based on “quantum inequalities” suggest that their existence would involve Planck-scale energy densities and hence unphysically large values of the “total amount of negative energy” I argue that the spacetimes of this type may not be unphysical at all. By explicit examples I prove that (1) the relevant quantum inequality does not (always) imply large energy densities, (2) large densities may not lead to large values of and (3) large being physically meaningless in some relevant situations does not necessarily exclude shortcuts.
- Received 3 January 2003
DOI:https://doi.org/10.1103/PhysRevD.67.104013
©2003 American Physical Society