Diskuse:Grupová rychlost

Grupová rychlost vs rychlost světla

Píše se zde: Přenosem energie se mohou šířit signály, takže grupová rychlost nemůže být větší než rychlost světla ve vakuu (na rozdíl od fázové rychlosti).

A pár citací z anglické Wikipedie:

Since the 1980s, various experiments have verified that it is possible for the group velocity of laser light pulses sent through specially prepared materials to significantly exceed the speed of light in vacuum. However, superluminal communication is not possible in this case, since the signal velocity remains less than the speed of light.

It is possible for the group velocity of light to exceed c and in an experiment in 2000 laser beams traveled for extremely short distances through caesium atoms with a group velocity of 300 times c. It is not, however, possible to use this technique to transfer information faster than c since the velocity of information transfer depends on the front velocity, which is always less than c. Mykhal 15. 6. 2009, 19:51 (UTC)