Velocity of Phase Wave in Vacuum - Contradicting Relativity?

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SUMMARY

The discussion centers on the concept of phase wave velocity in a vacuum, which is stated to exceed the speed of light, contradicting the principles of relativity. It emphasizes that while phase velocity can exceed light speed, it is unobservable and does not allow for information transmission. The group velocity of wave packets, which is relevant for information transfer, remains constrained by the speed of light, aligning with De Broglie's hypothesis and Dirac's advancements in wave theory. Ultimately, the phase velocity's implications are deemed negligible in practical terms.

PREREQUISITES
  • Understanding of wave mechanics and wave packets
  • Familiarity with the principles of relativity
  • Knowledge of De Broglie's hypothesis and Dirac's wave theory
  • Concept of group velocity versus phase velocity
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  • Research the implications of phase velocity in quantum mechanics
  • Study the differences between group velocity and phase velocity in wave theory
  • Explore the historical context of De Broglie's hypothesis and its evolution
  • Investigate the limitations of information transmission in wave mechanics
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Physicists, students of quantum mechanics, and anyone interested in the implications of wave theory and relativity.

kmajhi
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Velocity of phase wave in vacuum is grater than light velocty. This contradict the princles of relativity,so how this can be possible.
 
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You cannot transmit information with a wave of a single frequency. In order to transmit information, you need to turn the wave on and off somehow. This introduces additional frequencies and you get a wave packet. Your information then propagates with the group velocity of this wave packet and not with the phase velocities of its wave components.

For matter waves, the group velocity is equal to the particle velocity which can't exceed c.
 
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kmajhi said:
Velocity of phase wave in vacuum is grater than light velocty. This contradict the princles of relativity,so how this can be possible.

That's from De-Broglies hypothesis which was simply a historical way-station to the full theory developed by Dirac in late 1926 and those old ideas were consigned to the dustbin of history - forget about them except in a historical context.

That said phase velocity is unobservable so that it propagates FTL is of zero concern.

Thanks
Bill
 

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