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arXiv · 1604.03543

On the time delay between ultra-relativistic particles

Pierre Fleury
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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.

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Pierre Fleury. 2016-07-16. On the time delay between ultra-relativistic particles. https://doi.org/10.1016/j.physletb.2016.07.010

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