Can Light Signals Travel Faster than c in Nontrivial Vacuua in Flat space-time? Relativistic Causality II

TL;DR

This paper argues that the Scharnhorst effect cannot produce measurable faster-than-c signals and would violate special relativity unless a universal invariant length scale is defined.

Contribution

It demonstrates that the Scharnhorst effect does not enable faster-than-light communication and discusses the necessity of an invariant length scale to preserve relativistic invariance.

Findings

Scharnhorst effect cannot generate measurable superluminal signals

Faster-than-c signals would violate special relativity

An invariant length scale is necessary for consistency

Abstract

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 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 invariant length.