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Virtual particles

  1. Nov 10, 2004 #1
    I've got a few questions about virtual particles here. If in a vacuum, the virtual particle come in a particle, anti-particle pair. What are these particles usually??? Also, is it possible that these virtual particles exert a gravitational force on an object during its short existence?? And finally, can virtual particles be used to account for the dark matter in our universe???
  2. jcsd
  3. Nov 10, 2004 #2
    It is a result of combining special relativity with quantum mechanics that all particles have an identical one with certain properties (that are negative of the original) called anti-particles. The electron's antiparticle is the positron, photon's antiparticle is another photon and so on.

    In the presence of a field (there is a field everywhere) there is a probability that particle- anti-particle pairs will come into existence. These particles help to transmit "the force" of the field. These particles also will have gravitational effects, but their existence is so momentary that no discernible effects of them can ever be measured. That's why they are called virtual particles.

    They cannot account for dark matter, since their existence cannot be verified, but other effects of their existence can be verified. That's why we know they do exist.
  4. Nov 10, 2004 #3
    Is negative energy created when a virtual particle pair is created? I ask this because I remember an experiment where two plates separated in a vaccum are pushed together by the "negative" energy between them due to the differential in virtual particles. Is this negative energy there because it counteracts the postive energy of the virtual particles?
  5. Nov 11, 2004 #4
    But won't the gravitational effects virtual particles in a vacuum be apparent since we're not just talking about the gravitational effect of one virtual particle alone. If there are a hell lot of virtual particles popping in and out at the same time, won't there be a noticeable gravitational effect?

    And also, if the existence of virtual particles are verified, can they be used to account for dark matter???
  6. Apr 20, 2005 #5
    Is there anywhere I can find out about the 'density' of virtual particle creation?
  7. Apr 20, 2005 #6
    https://www.physicsforums.com/journal.php?s=&action=view&journalid=13790&perpage=10&page=2 [Broken]

    Scroll down to the 'what are virtual particles' entry

    Last edited by a moderator: May 2, 2017
  8. Apr 27, 2005 #7
    Ah! so as light travels through the 'vacuum' of space it will be impinge upon these virtual particals and loose energy to them. Any two photons will loose almost exactly the same amount of energy over large distances. This will appear as red shift. As the photons wavelengths grow the volume of space they occupy will grow and so they will loose energy at an increases rate - giving the impression of
    1) the expansion of space
    2) the acceleration of the expansion of space
    3) given that shorter wavelengths are less affected, brighter than expected gamma ray bursts!
    4) I'm not sure how the virtual particle recombination is affected but it could lead to a constant backgound radiation.

    Now wheres my calculator...
  9. Apr 27, 2005 #8
    What is written here really is not the best of impressions of what virtual particles really are and how they arise in QFT. Besides, the fact that virtual particles can be a candidate for dark matter is indeed proposed by some scientists and denied by others. Rather then repeating myself ad nauseum, i refer to my journal for info on both virtual particles and the articles on virtual particles and their 'connection' to dark matter and dark energy

  10. Apr 27, 2005 #9
    Sure, just look for the non-commutation of the number operator with the Hamiltonian in non-free field theories. Besides, just attempt to calculate the energydensity that arises when the vaccuum is distrubed...I refer to Zee's book QFT in a Nutshell for an introductory (yet very complete) summary

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