Do photons travel faster than gravitons?

Abstract

The vacuum polarization in an external gravitational field due to one loop electron-positron pair and one loop millicharged fermion-antifermion pair is studied. Considering the propagation of electromagnetic (EM) radiation and gravitational waves (GWs) in an expanding universe, it is shown that by taking into account QED effects in curved spacetime, the propagation velocity of photons is superluminal and can exceed that of gravitons. We apply these results to the case of the GW170817 event detected by LIGO. If the EM radiation and GWs are emitted either simultaneously or with a time difference from the same source, it is shown that the EM radiation while propagating with superluminal velocity, would be detected either in advance or in delay with respect to GW depending on the ratio of millicharged fermion relative charge to mass $\epsilon /m_{\epsilon }$.

Version to be published in JCAP. With respect to the previous version (v2), in this version (v3) the text has been sectioned and typos have been corrected. As required by the referee, a comparison of our results with the current limits on the millicharged fermions has been done

References in corpus (8)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence
• GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2
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• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
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• Superluminality, Black Holes and Effective Field Theory
• Fermi observations of the LIGO event GW170104