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No coupling of Photons with eletric fields

  1. Dec 2, 2008 #1
    I heard in the school a long time ago, that photons do not have a coupling with an electric field. Can someone explain it detailed? Does someone have good online literature?
    Thanks in advance!
  2. jcsd
  3. Dec 2, 2008 #2


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    I don't have time right now to explain it in detail but here's the basics...

    Classically an electromagnetic field does not interact with itself.
    But in Quantum Electrodynamics there is very weak higher-order
    photon-photon scattering due to virtual electron loops. This
    is called Delbruck scattering, and has been experimentally observed
    via scattering of gamma rays off nuclei, iirc. I vaguely remember
    that certain ultra-high-power lasers can also demonstrate the effect

    I don't know online references off the top of my head, but
    Delbruck scattering is discussed in Greiner's textbook on
    quantum electrodynamics.
    Last edited: Dec 3, 2008
  4. Dec 3, 2008 #3
    Thank you for the
    I read in several Publications that Delbruck-effect is the scattering of high-energy photons (MeV to GeV gamma rays) on a Coulomb-Field of a Nucleus.
    My question is:
    Why is it needed that the Photonenergies are this high?
    Which magnitude is required for the Coulomb-Field?
    Is it possible that an electrostatic field of a charged object (same scale) has the same effect?

    It is hard to find some good literature online.
  5. Dec 3, 2008 #4


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    A full answer to this requires working through the detailed math to
    see what the quantum correction terms look like. Some people
    explain it heuristically by noting that quantum corrections to
    the usual Coulomb potential get stronger at small distances.
    With higher energies you can probe smaller distances and
    thus have more hope of seeing weak effects because of th
    stronger EM field.

    But I take such explanations with a grain of salt.

    I suspect that if you tried to create such a huge electrostatic
    field it would tend to decay via electron-positron pair creation.
    (This sort of thing happens in heavy ion collisions.)

    I know. A visit to the nearest University physics library is
    probably needed.
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