Special relativity and superluminal motions: A discussion of some recent experiments

Citation
E. Recami et al., Special relativity and superluminal motions: A discussion of some recent experiments, INT J MOD P, 15(18), 2000, pp. 2793-2812
Citations number
107
Categorie Soggetti
Physics
Journal title
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
ISSN journal
0217751X → ACNP
Volume
15
Issue
18
Year of publication
2000
Pages
2793 - 2812
Database
ISI
SICI code
0217-751X(20000720)15:18<2793:SRASMA>2.0.ZU;2-O
Abstract
Some experiments, performed at Berkeley, Cologne, Florence, Vienna, Orsay a nd Rennes led to the claim that something seems to travel with a group velo city larger than the speed c of light in vacuum. Various other experimental results seem to point in the same direction: For instance, localized wavel et-type solutions of Maxwell equations have been found, both theoretically and experimentally, that travel with Superluminal speed. Even muonic and el ectronic neutrinos - it has been proposed - might be "tachyons," since thei r square mass appears to be negative. With regard to the first-mentioned ex periments, it was very recently claimed by Guenter Nimtz that those results with evanescent waves or "tunneling photons" - implying Superluminal signa l and impulse transmission - violate Einstein causality. In this note, on t he contrary, we want to stress that all such results do not place relativis tic causality in jeopardy, even if they refer to actual tachyonic motions: In fact, special relativity can cope even with Superluminal objects and wav es. For instance, it is possible (at least in microphysics) to solve also t he known causal paradoxes, devised for "faster than light" motion, even if this is not widely recognized. Here we show, in detail and rigorously, how to solve the oldest causal paradox, originally proposed by Tolman, which is the kernel of many further tachyon paradoxes. The key to the solution is a careful application of tachyon mechanics, as it unambiguously follows from special relativity.