On the time delay between ultra-relativistic particles
Abstract
The time delay between the receptions of ultra-relativistic particles emitted simultaneously is a useful observable for both fundamental physics and cosmology. The expression of the delay when the particles travel through an arbitrary spacetime has been derived recently by Fanizza et al., using a particular coordinate system and self-consistent assumptions. The present article shows that this formula enjoys a simple physical interpretation: the relative velocity between two ultra-relativistic particles is constant. This result reveals an interesting kinematical property of general relativity, namely that the tidal forces experienced by ultra-relativistic particles in the direction of their motion are much smaller than those experienced orthogonally to their motion.
Cite
@article{arxiv.1604.03543,
title = {On the time delay between ultra-relativistic particles},
author = {Pierre Fleury},
journal= {arXiv preprint arXiv:1604.03543},
year = {2016}
}
Comments
5 pages, 1 figure, v2 matches published version