Quantum-Gravitational Diffusion and Stochastic Fluctuations in the Velocity of Light |
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Authors: | John Ellis N E Mavromatos D V Nanopoulos |
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Institution: | (1) Theory Divison, CERN, CH-1211 Geneva 23, Switzerland;(2) Department of Physics, Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, UK;(3) Department of Physics, Texas A & M University, College Station, TX 77843-4242, USA;(4) Astroparticle Physics Group, Houston Advanced Research Center (HARC), Mitchell Campus, Woodlands, TX 77381, USA;(5) Division of Natural Sciences, Academy of Athens, Chair of Theoretical Physics, 28 Panepistimiou Avenue, Athens, 10679, Greece |
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Abstract: | We argue that quantum-gravitational fluctuations in the space-time background give the vacuum non-trivial optical properties that include diffusion and consequent uncertainties in the arrival times of photons, causing stochastic fluctuations in the velocity of light in vacuo. Our proposal is motivated within a Liouville string formulation of quantum gravity that also suggests a frequency-dependent refractive index of the particle vacuum. We construct an explicit realization by treating photon propagation through quantum excitations of D-brane fluctuations in the space-time foam. These are described by higher-genus string effects, that lead to stochastic fluctuations in couplings, and hence in the velocity of light. We discuss the possibilities of constraining or measuring photon diffusion in vacuo via -ray observations of distant astrophysical sources. |
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Keywords: | Space-time foam |
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