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Causality and Superluminal Light
Graham Shore
Time and Matter, Pages: 45 - 66
Swansea University Author: Graham Shore
Abstract
The causal properties of curved spacetime, which underpin our sense of time in gravitational theories, are defined by the null cones of the spacetime metric. In classical general relativity, it is assumed that these coincide with the light cones determined by the physical propagation of light rays....
| Published in: | Time and Matter |
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| Published: |
Singapore
World Scientific
2006
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| Online Access: |
http://arxiv.org/abs/gr-qc/0302116 |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa17507 |
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| Abstract: |
The causal properties of curved spacetime, which underpin our sense of time in gravitational theories, are defined by the null cones of the spacetime metric. In classical general relativity, it is assumed that these coincide with the light cones determined by the physical propagation of light rays. However, the quantum vacuum acts as a dispersive medium for the propagation of light, since vacuum polarisation in QED induces interactions which effectively violate the strong equivalence principle (SEP). For low frequencies the phenomenon of gravitational birefringence occurs and indeed, for some metrics and polarisations, photons may acquire {\it superluminal} phase velocities. In this article, we review some of the remarkable features of SEP violating superluminal propagation in curved spacetime and discuss recent progress on the issue of dispersion, explaining why it is the high-frequency limit of the phase velocity that determines the characteristics of the effective wave equation and thus the physical causal structure. |
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| College: |
Faculty of Science and Engineering |
| Start Page: |
45 |
| End Page: |
66 |