Faster than light signals and relativistic causality.

摘要

Recently there have been many claims of signals travelling faster the speed of light in a vacuum. This work will show that if the refractive index, or rather, [n(ω) − 1] satisfies the dispersion relations then, it is implied by Titchmarsh's theorem, that, n (ω) → 1 as ω → ∞. Any other limiting value for n(ω) would violate relativistic causality, by which we mean not only cause must precede effect but also that signals cannot travel faster than the speed of light in a vacuum.