Causality Between Conducting Plates*
نویسنده
چکیده
. A two-loop QED effect, uncovered by Scha.rnhorst, causes the phase and group velocities of an electromagnetic wave with w << m, to slightly exceed c, when the wave is travelling in vacua between, and perpendicular to, two parallel conducting plates. Using causal rather than Feynma.n graphs, we show that the wavefront still travels at exactly c. The two-loop effect thus poses no threat to causality in QED. Submitted to Phys. Lett. B * Work supported by the Department of Energy, contra,ct DE-AC03-76SF00515. -
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