The velocities of light in modified QED vacua
(1998)cite arxiv:hep-th/9810221Comment: 7 pages Revtex, 5 LaTeX generated figures, file uses axodraw.sty, epic.sty; talk delivered at the workshop ``Superluminal(?) Velocities'', Cologne, July 7-10, 1998, submitted to the Proceedings to appear as a special issue of the Annalen der Physik (v2: typos in the references corrected, minor stylistic changes).DOI: 10.1002/(SICI)1521-3889(199812)7:7/8<700::AID-ANDP700>3.0.CO;2-K
Abstract
QED vacua under the influence of external conditions (background fields,
finite temperature, boundary conditions) can be considered as dispersive media
whose complex behaviour can no longer be described in terms of a single
universal vacuum velocity of light c. Beginning in the early 1950's (J.S.
Toll), quantum field theoretic investigations have led to considerable insight
into the relation between the vacuum structure and the propagation of light.
Recent years have witnessed a significant growth of activity in this field of
research. After a short overview, two characteristic situations are discussed:
the propagation of light in a constant homogeneous magnetic field and in a
Casimir vacuum. The latter appears to be particularly interesting because the
Casimir vacuum has been found to exhibit modes of the propagation of light with
phase and group velocities larger than c in the low frequency domain omega<<m
where m is the electron mass. The impact of this result on the front velocity
of light in a Casimir vacuum is discussed by means of the Kramers-Kronig
relation.
Description
The velocities of light in modified QED vacua