Superluminal Travel Requires Negative Energies
Abstract
I investigate the relationship between fasterthanlight travel and weakenergycondition violation, i.e., negative energy densities. In a general spacetime it is difficult to define fasterthanlight travel, and I give an example of a metric which appears to allow superluminal travel, but in fact is just flat space. To avoid such difficulties, I propose a definition of superluminal travel which requires that the path to be traveled reach a destination surface at an earlier time than any neighboring path. With this definition (and assuming the generic condition) I prove that superluminal travel requires weakenergycondition violation.
 Publication:

Physical Review Letters
 Pub Date:
 October 1998
 DOI:
 10.1103/PhysRevLett.81.3567
 arXiv:
 arXiv:grqc/9805003
 Bibcode:
 1998PhRvL..81.3567O
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 5 pages, RevTeX, 2 figures with epsf. This paper now contains all the material of grqc/6805003 and grqc/9806091 since these became a single article in Phys. Rev. Lett