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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....

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Published in: Time and Matter
Published: Singapore World Scientific 2006
Online Access: http://arxiv.org/abs/gr-qc/0302116
URI: https://cronfa.swan.ac.uk/Record/cronfa17507
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first_indexed 2014-03-22T02:30:07Z
last_indexed 2018-02-09T04:51:11Z
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spelling 2014-03-21T15:20:40.7857302 v2 17507 2014-03-20 Causality and Superluminal Light 28a24f55687c82d6f3ee378ead3cf234 Graham Shore Graham Shore true false 2014-03-20 FGSEN 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. Book chapter Time and Matter 45 66 World Scientific Singapore 1 2 2006 2006-02-01 http://arxiv.org/abs/gr-qc/0302116 COLLEGE NANME Science and Engineering - Faculty COLLEGE CODE FGSEN Swansea University 2014-03-21T15:20:40.7857302 2014-03-20T22:48:48.0860880 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics Graham Shore 1
title Causality and Superluminal Light
spellingShingle Causality and Superluminal Light
Graham Shore
title_short Causality and Superluminal Light
title_full Causality and Superluminal Light
title_fullStr Causality and Superluminal Light
title_full_unstemmed Causality and Superluminal Light
title_sort Causality and Superluminal Light
author_id_str_mv 28a24f55687c82d6f3ee378ead3cf234
author_id_fullname_str_mv 28a24f55687c82d6f3ee378ead3cf234_***_Graham Shore
author Graham Shore
author2 Graham Shore
format Book chapter
container_title Time and Matter
container_start_page 45
publishDate 2006
institution Swansea University
publisher World Scientific
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Physics{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Physics
url http://arxiv.org/abs/gr-qc/0302116
document_store_str 0
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description 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.
published_date 2006-02-01T03:20:13Z
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score 11.013148

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