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Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation

Brett Altschul
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Abstract

If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10^(-32) e level if all photons have the same charge and 10^(-46) e if different photons can carry different charges.

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Brett Altschul. 2007-06-29. Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation. https://doi.org/10.1103/physrevlett.98.261801

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