Superluminal propagation

J. P. Vigier, Superluminal propagation of the quantum potential in the causal interpretation of quantum mechanics, Lett. Nuovo Cimento 24(8) (Ser. 2), 258-264 (1979). 

The results of this analysis show that anomalous dispersion of light in a cesium cell is a consequence of superluminal motion of electrons and superluminal propagation of electromagnetic waves. The Feynman diagram, presented in Fig. 8, is used in the analysis, to explain the phenomena that are taking place in cesium atomic cell and that cause superluminal effects [30]. 

Still another type of evanescent wave has been considered by the Florence group [20]. They worked with microwaves traveling in free space between two horn antennas. The waves were observed to travel at subluminal speed if the antennas faced each other.1 On the contrary, a superluminal propagation occurs... 

The original aim of the Florence group was just to repeat the experiment by T. K. Ishii and G. C. Giakos, who claimed in 1991 to have observed, by a similar device, superluminal propagation in free space. Such an experiment was basically flawed by the confusion made by the authors between phase and group velocity. 

We want also to stress that (as shown by Chiao and co-workers [32]) there is still another situation in which one expects e.m. wavepacket propagation in a medium at speed higher than c. This occurs for off-resonance pulses through a medium with inverted atomic populations. Experiments aimed at detecting superluminal propagation in such a kind of medium are presently being performed at Berkeley [4]. 

In addition to the long-range interaction at infinite speed, there are proposals for the existence of superluminal phenomena that should manifest themselves in propagation at a finite speed, but being larger than c. There now seems to be observational evidence for such phenomena, as well as indications thereof in the theoretical analysis, but further investigation is needed. 

The longstanding idea of superluminal motion has become subject to renewed interest, due to a number of recent discoveries and observations, as described in a survey by Recami [27]. Thus the squared mass of muon-neutrinos is found to be negative. There are further observations that can be interpreted as superluminal expansions inside quasars, in some galaxies and in galactic objects. Also, so called X-shaped waves have been observed [69] to propagate at a... 

The central assumption underlying the standard approach to tachyon theory is that the usual Lorentz transformation also applies to the superluminal case. One therefore simply takes the Lorentz factor [1 — (v/c)2)]1/2 and substitutes v > c into it [27,74]. This leads directly to an imaginary rest mass and propagation time for tachyons, with many difficulties of interpretation [74]. 

The presented analysis is based on the SLRT concepts [5], and the results show that Vg > c for discussed example and for many others in the visible spectrum of light. This provides theoretical verification of the observed superluminal light propagation in WKD experiment [30]. 

The final results of the analysis show that an electron can travel and electromagnetic waves can propagate in curved spacetime between cesium atoms, which is faster than the speed of light in vacuum, which has been observed in the WKD superluminal experiment [6,7,30]. 

V. Superluminal Optical Propagation in Media with Anomalous Dispersion... 

The interest in superluminal processes has been revived, due to some new experimental results (mainly based on electromagnetic wave propagation) that provided incontrovertible evidence for motions occurring at faster-than-light... 

V. SUPERLUMINAL OPTICAL PROPAGATION IN MEDIA WITH ANOMALOUS DISPERSION... 

X waves constitute the most striking example of superluminal effects, because they propagate in free space over large distances. We want to stress that the existence of superluminal X-shaped waves was predicted by ER. This is, in our opinion, one of the most impressive among the (verified) ER predictions, and was just put forward as early as 1982 in a fundamental paper by Barut et al. [50]. The point is that, on the basis of ER, an (extended) tachyon is just expected... 

M.S. Bigelow, Superluminal and slow Hght propagation in a room-temperature solid. Science 301 (2003) 200. 

---