Superluminal Gravitational Waves


The quantum gravity effects of vacuum polarization of gravitons propagating in a curved spacetime cause the quantum vacuum to act as a dispersive medium with a refractive index. Due to this dispersive medium gravitons acquire superluminal velocities. The dispersive medium is produced by higher derivative curvature contributions to the effective gravitational action. It is shown that in a Friedmann-Lema\^{i}tre-Robertson-Walker spacetime in the early universe near the Planck time tPL≳10βˆ’43 sect_{\rm PL}\gtrsim 10^{-43}\,{\rm sec}, the speed of gravitational waves cg≫cg0=c0c_g\gg c_{g0}=c_0, where cg0c_{g0} and c0c_0 are the speeds of gravitational waves and light today. The large speed of gravitational waves stretches their wavelengths to super-horizon sizes, allowing them to be observed in B-polarization experiments.Comment: 5 pages, no figure

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