Light-cone fluctuations in flat spacetimes with nontrivial topology - art.no. 084023

The quantum light-cone fluctuations in hat spacetimes with compactified spa tial dimensions or with boundaries are examined. The discussion is based up on a model in which the source of the underlying metric fluctuations is tak en to be quantized Linear perturbations of the gravitational field. General expressions are derived, in the transverse trace-free gauge, for the summa tion of graviton polarization tensors, and for vacuum graviton two-point fu nctions. Because of the fluctuating light cone, the flight time of photons between a source and a detector may be either longer or shorter than the li ght propagation time in the background classical spacetime. We calculate th e mean deviations from the classical propagation time of photons due to the changes in the topology of the flat spacetime. These deviations are in gen eral larger in the directions in which topology changes occur and are typic ally of the order of the Planck time, but they can get larger as the travel distance increases. [S0556-2821(99)10118-8].