Superluminal Kinematics in the Milne Universe: Causality in the Cosmic Time Order |
| |
Authors: | Roman Tomaschitz |
| |
Institution: | (1) Department of Physics, Hiroshima University, 1-3-1 Kagami-yama, Higashi-, Hiroshima 739-8526, Japan |
| |
Abstract: | The causality of superluminal signal transfer in the galaxy background is scrutinized. The cosmic time of the comoving galaxy
frame determines a distinguished time order for events connected by superluminal signals. Every observer can relate his rest
frame to the galaxy frame, and compare so the time order of events in his proper time to the cosmic time order. In this way
all observers arrive at identical conclusions on the causality of events connected by superluminal signals. The energy of
tachyons (superluminal particles) is defined in the comoving galaxy frame analogous to the energy of subluminal particles.
It is positive in the galaxy frame and bounded from below in the rest frames of geodesically moving observers, so that particle-tachyon
interactions can be based on energy-momentum conservation. We study tachyons in a Robertson-Walker cosmology with linear expansion
factor and open, negatively curved 3-space (Milne universe). This cosmology admits globally geodesic rest frames for uniformly
moving observers, synchronized by Lorentz boosts. In this context we show that no signals can be sent into the past of observers.
If an observer emits a tachyonic signal, then the response of a second observer can never reach him prior to the emission,
i.e., no predetermination can occur. The proof is based on the positivity of tachyonic energy.
This revised version was published online in July 2006 with corrections to the Cover Date. |
| |
Keywords: | tachyons superluminal signals cosmic time causality Robertson-Walker cosmology hyperbolic space |
本文献已被 SpringerLink 等数据库收录! |
|