Given that my previous question, namely "What is the number density of virtual photons around a unit charge?" has no precise answer, here is a more precise wording:

What is the virtual photon spectral density due to the electric field of a unit charge at rest (or, better, its difference with respect to the no-field case)?

Or: How many virtual photons per volume and per energy are found around a unit charge, at a distance r?

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    $\begingroup$ Dear George, "spectral density" surely sounds fancy but it doesn't fix the problem of your question. One simply can't "count" virtual photons in this sense exactly because they're virtual and not "real". You won't ever find any unique answer to such questions. $\endgroup$ Feb 27, 2011 at 16:51
  • $\begingroup$ Here is an excellent descrption of virtual particles -in particular, why we should NOT think of them as particles at all. $\endgroup$
    – FrankH
    Oct 13, 2011 at 13:09

1 Answer 1


It is wrong to think of virtual photons as of some surrounding of the electron. It is interaction and is interaction-dependent thing, if you like.

EDIT: If you calculate a field of some charge at some distance $\vec{r}$, it has the only physical meaning - as an external filed in the equations of motion of another charge placed at this point.

  • $\begingroup$ I understand what you're saying, but I've also heard particles having a "dressing" of virtual particles around them contributing to their self-energy. And the running of the fine structure constant is explained (as I understand it from Griffiths) as the polarization of virtual pairs. It sounds like there is an SED of virtual e+e- pairs. So, why can't we ask about the SED of virtual photons. $\endgroup$
    – Paul
    Jul 20, 2022 at 6:26

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