2009/05/31 by Timothy J. Hollowood, Timothy J Hollowood, Graham M. Shore +3 · 3 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Black Holes and Theoretical Physics #Black hole (networking) #Causality (physics) #Formalism (music) #Friedmann–Lemaître–Robertson–Walker metric #Gravitation #Polarization (electrochemistry) #Quantum Electrodynamics and Casimir Effect #Refractive index #Spacetime #hep-th
paper · pdf · doi:10.1088/1126-6708/2009/08/089
published as JHEP 0908:089,2009 · 62 pages, 14 figures, some signs corrected in formulae and graphs
openalex publication_date 2009/08/25 · arxiv created 2011/11/10 · arxiv updated 2011/11/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
This work considers the way that quantum loop effects modify the propagation of light in curved space. The calculation of the refractive index for scalar QED is reviewed and then extended for the first time to QED with spinor particles in the loop. It is shown how, in both cases, the low frequency phase velocity can be greater than c, as found originally by Drummond and Hathrell, but causality is respected in the sense that retarded Green functions vanish outside the lightcone. A "phenomenology" of the refractive index is then presented for black holes, FRW universes and gravitational waves. In some cases, some of the polarization states propagate with a refractive index having a negative imaginary part indicating a potential breakdown of the optical theorem in curved space and possible instabilities.