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Quantum Fluctuations of Negative Energy

  1. Dec 20, 2008 #1
    It is my understanding that quantum fluctuations arise from implications of the Uncertainty Principle. Specifically:

    http://upload.wikimedia.org/math/b/d/1/bd1bb25a5159f9c74803afca6ad65935.png

    And that this means that conservation of energy can appear to be violated for a set time "T."

    My question is, if we can have a positive change in energy, can we get a negative change?

    And if not, why not?
     
  2. jcsd
  3. Dec 22, 2008 #2
    Anyone?
     
  4. Dec 22, 2008 #3
    Yes, it can be negative as well. For example, a particle can bounce from a barrier even if its evergy is higher then the barrier.
     
  5. Dec 22, 2008 #4
    So negative energy is quite plausible?
     
  6. Dec 22, 2008 #5
    Yes, sure.
    Check the Casimir effect for example
    The vacuum between the casimir plates has less density then a normal vacuum!
     
  7. Dec 22, 2008 #6
    Ah, is this what happens in the casimir effect? Negative energy quantum fluctuations?
     
  8. Dec 23, 2008 #7

    Mentz114

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    Gold Member

    The Casimir effect is supposed to occur because some modes of the EM vacuum are 'short-circuited' by the conducting plates, thereby reducing the vacuum energy density between them.

    If negative and positive energy fluctuations were cancelled out to the same degree, there would be no energy difference between the plates and outside the plates (?), no Casimir effect.
     
  9. Dec 23, 2008 #8

    LURCH

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    Science Advisor

    Also being discussed here.
     
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