- #1
maline
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QED predicts photon-photon scattering, via a fourth-order Feynman diagram with four external photon legs connected to an electron loop. It seems to me that the same diagram should also predict a process where a single incoming photon decays spontaneously into three photons. This is not forbidden by energy-momentum conservation, as long as the final energies add up to the original one and the momenta are all parallel.
Is this correct? If so, has this decay rate been calculated? Or at least, what is its order of magnitude? If the decay does not occur, why not?
I wonder whether this attenuation could be measurable, perhaps in the CMBR? By Lorentz invariance, or just dimensional analysis, the rate of decay (events per second per photon) should be linear in the starting frequency. Perhaps this signature could distinguish the pure photon decay from other sources of attenuation such as intergalactic dust, or processes involving more than one photon.
Is this correct? If so, has this decay rate been calculated? Or at least, what is its order of magnitude? If the decay does not occur, why not?
I wonder whether this attenuation could be measurable, perhaps in the CMBR? By Lorentz invariance, or just dimensional analysis, the rate of decay (events per second per photon) should be linear in the starting frequency. Perhaps this signature could distinguish the pure photon decay from other sources of attenuation such as intergalactic dust, or processes involving more than one photon.