I have been researching quantum electrodynamics recently and I have found out that when electrons repel each other, they constantly exchange photons with each other. When two protons repel, do they also exchange photons? If not, what do they exchange (if at all anything)?

  • $\begingroup$ If one considers proton in QED framework (i.e. does not take into account its internal structure), the answer is yes: two protons repel by virtual photon exchange. $\endgroup$ Nov 22, 2021 at 10:12
  • $\begingroup$ @ArtemAlexandrov What if we do take into account its internal structure? $\endgroup$
    – MathGeek
    Nov 22, 2021 at 10:14
  • $\begingroup$ The full picture becomes more complicated: one should consider possible QCD processes, but in general the answer is still yes. In QED, the proton is represented by fermion field and its interaction with photon field is exactly the same as for electron/positron/etc. $\endgroup$ Nov 22, 2021 at 10:15
  • $\begingroup$ @ArtemAlexandrov Thank you. $\endgroup$
    – MathGeek
    Nov 22, 2021 at 10:19
  • 1
    $\begingroup$ Bear in mind that these are virtual photons, not real ones. FWIW, Wikipedia has a cute anim of the residual nuclear force binding a proton & neutron via the exchange of virtual pions. (Essentially the same process acts between a pair of protons or a pair of neutrons, although of course the proton pair are also exchanging virtual photons). $\endgroup$
    – PM 2Ring
    Nov 22, 2021 at 10:32

1 Answer 1


This is the lowest Feynman diagram showing the exchange of virtual photons in electron electron scattering |ee

Depending on the problem one would be studying with proton-proton elastic scattering, a similar diagram with "p" instead of "e" would be used for the electromagnetic interaction.

Considering that the protons are composed of charged quarks, for high enough energies of the proton scattering strong interactions will become important, even the quark structure..


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