# Can light signals travel faster than c in nontrivial vacua in flat space-time? Relativistic causality II

@article{Fearn2007CanLS, title={Can light signals travel faster than c in nontrivial vacua in flat space-time? Relativistic causality II}, author={Heidi Fearn}, journal={Laser Physics}, year={2007}, volume={17}, pages={695-699} }

In this paper, we show that the Scharnhorst effect (vacuum with boundaries or a Casimir-type vacuum) cannot be used to generate signals showing measurable faster-than-c speeds. Furthermore, we aim to show that the Scharnhorst effect would violate special relativity, by allowing for a variable speed of light in a vacuum, unless one can specify a small invariant length scale. This invariant length scale would be agreed upon by all inertial observers. We hypothesize the approximate scale of the…

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