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As we know that photon is its own antiparticle so how can we confidently say this is true? Is there any theory that describes it?

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    $\begingroup$ That is a necessary feature of, for instance, QED which is the physical theory that can lay claim to the most precisely tested agreement between theory and experiment in all of science. That's pretty much as good as 'proof' gets. This isn't mathematics. $\endgroup$ Commented Aug 28, 2017 at 17:31
  • $\begingroup$ @dmckee so there is explanation of light or not?? $\endgroup$ Commented Aug 28, 2017 at 17:35
  • $\begingroup$ Yes. Quantum ElectroDymanics (QED) is the theory of light in terms of photons. $\endgroup$ Commented Aug 28, 2017 at 17:38

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This is part of the standard model. But experimentally, two photons may collide to form an electron-positron pair.

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    $\begingroup$ A single photon can spontaneously convert to an electron-positron pair under certain conditions, so this proves nothing about the anti-particle of the photon. $\endgroup$ Commented Aug 28, 2017 at 16:29
  • $\begingroup$ @StephenG not on its own, while conserving energy and momentum. But the point of two photons colliding to form an electron position pair is that photon number is clearly not a conserved quantity, unlike lepton numbers (with a bit of flooding over vector bosons in weak interactions) $\endgroup$
    – PhillS
    Commented Aug 28, 2017 at 16:41
  • $\begingroup$ @dr-xorile You're missing the point. The production of a pair of antiparticles by a photon or multiple photons does not imply anything about a photon being it's own anti-particle (or otherwise). $\endgroup$ Commented Aug 28, 2017 at 16:48
  • $\begingroup$ @StephenG so it is not confirmed that photon has it's antiparticle Right? $\endgroup$ Commented Aug 28, 2017 at 17:13
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    $\begingroup$ I would say we had no evidence at this time that the photon's antiparticle is not a photon. $\endgroup$ Commented Aug 28, 2017 at 17:24
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Due to the photon being electrically neutral, it can be said to be its own antiparticle, given that an antiparticle has the opposite charge as the original particle.

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    $\begingroup$ Neutrinos are electrically neutral, but there is a clear distinction between neutrinos and anti-neutrinos $\endgroup$
    – PhillS
    Commented Aug 28, 2017 at 16:38
  • $\begingroup$ @PhillS is there any relation between photon and neutrinos.? $\endgroup$ Commented Aug 28, 2017 at 17:14
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    $\begingroup$ NaturalNonThinker, your post attempts to draw a straight line between neutrality and a particle being it's own antiparticle. Any clear counter example calls that in to question. Mind you, I would have used the neutron or the neutral kaon as an example because the Fermi or Majorana character of the neutrino is still a matter of inquiry and if they are Majoranic (as predicted by the standard model) they would not represent a good example. @PhillS $\endgroup$ Commented Aug 28, 2017 at 17:29
  • $\begingroup$ So what is the good example @dmckee $\endgroup$ Commented Aug 28, 2017 at 17:38
  • $\begingroup$ The neutron or the neutral kaon. Just like I said. $\endgroup$ Commented Aug 28, 2017 at 17:39

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