If one can build a transmitter and a receiver to transmit and detect wave packets travelling with sub c group velocity why can't one do the same for wave packets with group velocity much greater than c and achieve communication which is much faster than c? Harry
On Fri, May 3, 2019, 11:51 PM Axil Axil <[email protected] wrote: > > > It should be noted that while Einstein's theory of special relativity > prevents (real) mass, energy, or information from traveling faster than the > speed of light c (Lorentz et al. 1952, Brillouin and Sommerfeld 1960, Born > and Wolf 1999, Landau and Lifschitz 1997), there is nothing preventing > "apparent" motion faster than c (or, in fact, with negative speeds, > implying arrival at a destination before leaving the origin). For example, > the phase velocity and group velocity of a wave may exceed the speed of > light, but in such cases, no energy or information actually travels faster > than c. Experiments showing group velocities greater than c include that of > Wang et al. (2000), who produced a laser pulse in atomic cesium gas with a > group velocity of -310c. In each case, the observed superluminal > propagation is not at odds with causality, and is instead a consequence of > classical interference between its constituent frequency components in a > region of anomalous dispersion (Wang et al. 2000). > > Keith Fredericks has an opinion that strange radiation is a tachyon. This > SR quasiparticle might be tachyonic is that it is most likely based on the > polariton. The polariton does generate superluminal light in the form of > x-waves. > > https://www.nature.com/articles/lsa2017119 > > Superluminal X-waves in a polariton quantum fluid > > This article shows that a polariton can naturally produce superluminal > light (X-waves) when excited with a pulsed laser. > > This unexpected behavior of light may explain how Strange radiation (SR) > can be considered a tachyon, a superluminal particle. > >
