Ghost condensation has been recently proposed as a mechanism inducing the spontaneous breaking of Lorentz symmetry. Corrections to the Newton potential generated by a static source have been computed: they yield a limit M≲10 MeV on the symmetry breaking scale, and - if the limit is saturated - they are maximal at a distance L∼1000 km from the source. However, these corrections propagate at a tiny velocity, vs∼10-12 m/s, many orders of magnitude smaller than the velocity of any plausible source. We compute the gravitational potential taking the motion of the source into account: the standard Newton law is recovered in this case, with negligible corrections for any distance from the source up to astrophysical scales. Still, the vacuum of the theory is unstable, and requiring stability over the lifetime of the Universe imposes a limit on M which is not too far from the one given above. In the absence of a direct coupling of the ghost to matter, signatures of this model will have to be searched in the form of exotic astrophysical events.
|Original language||English (US)|
|Number of pages||8|
|Journal||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|State||Published - Jul 22 2004|
Bibliographical noteFunding Information:
It is a pleasure to thank Andy Albrecht, Paolo Creminelli, Nemanja Kaloper, Manoj Kaplinghat, Markus Luty, David Mattingly, Shinji Mukohyama, Keith Olive, Erich Poppitz, and Arkady Vainshtein for very fruitful discussions. The work of L.S. was supported in part by the NSF Grant PHY-0332258.