Do Matter Waves Travel Faster Than Light?

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Discussion Overview

The discussion revolves around the question of whether matter waves, as described in wave-particle duality, can travel faster than the speed of light. Participants explore theoretical implications, relativistic considerations, and specific scenarios related to particle behavior in various contexts.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant asserts that matter waves, such as those associated with electrons, do not travel faster than the speed of light (c) and can never reach c.
  • Another participant mentions that while particles can exceed the speed of light in a medium (e.g., Cherenkov radiation), this speed is still less than c.
  • A claim is made that even in cases where particles appear to exceed c, special relativity is not violated because such particles cannot carry information.
  • It is proposed that the phase speed of matter waves can appear to exceed c, depending on the material speed, with an explanation rooted in the theory of Special Relativity.
  • A reference to a paper discussing relativistic de Broglie wave packets is provided, suggesting further reading on the topic.
  • A participant introduces the concept from Quantum Field Theory (QFT) that there exists a nonzero probability for a particle to propagate faster than light, while still being compatible with relativity.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of matter waves and their relationship to the speed of light, indicating that multiple competing perspectives remain without consensus.

Contextual Notes

Some statements rely on specific interpretations of quantum mechanics and relativity, and the discussion includes references to theoretical frameworks that may not be universally accepted or understood.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, special relativity, or particle physics, particularly in relation to wave-particle duality and the implications of speed limits in physics.

shaan_aragorn
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Why do matter waves (as in wave-particle duality) travel faster than light? How is it possible?
 
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shaan_aragorn said:
Why do matter waves (as in wave-particle duality) travel faster than light? How is it possible?

Welcome to PhysicsForums!

"Matter waves" (such as electrons, which have a relativistic mass) do not travel faster than c (the speed of light in a vacuum). In fact they can never equal c either.

There are rare/special occasions (Cherenkov radiation) in which such a particle can exceed the speed of light in a particular medium, but it is still less than c. In particle accelerators, electrons are regularly accelerated to over 99% of c, but never all the way up to c.
 
Another interesting thing to understand that even in such circumstances special theory is not violated since they cannot carry any information
 
shaan_aragorn said:
Why do matter waves (as in wave-particle duality) travel faster than light? How is it possible?

It is only the phase speed which appears to move faster than c. This apparent
speed depends on the actual material speed v like, phase speed = c2/v.

This means for instance that the phase speed becomes infinite as the
material speed becomes zero! This may sound all weird but the explanation
is actually simple and beautiful. It's the theory of Special Relativity at work.

I wrote an illustrated explanation which you can read here:

http://www.chip-architect.com/physics/deBroglie.pdf

You'll find it as well as you google for: relativistic de broglie wave packet



Regards, Hans
 
Last edited:
Nice paper!

That's a very interesting and informative paper - thanks!
Ed
 
In QFT, there is a nonzero probability for a particle to propagate faster than light (or, as they say, "outside the light cone"). Read the causality section 2.4 in Peskin and Schroeder for how this is nevertheless compatible with relativity.

Carl
 

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