[ExI] Faster than light??

scerir scerir at alice.it
Sat Sep 24 16:05:36 UTC 2011

Anders writes:
> I noticed that most popular media prematurely claiming Einstein was wrong don't notice
> that there is an even more plausible conclusion if these findings are real: causality is
> wrong. It could simply be that we live in a relativistic universe where there is
> retrocausation going on, and paradoxes are avoided by the Novikov self-consistency
> principle. In many ways relativity seems to have a more solid conceptual footing
> (physics is invariant under the Poincare group) than causality (there is a strict
> symmetry breaking along the timelike direction); if I were forced to drop one it would
> be causality.

Faster-than-c signals, special relativity, and causality
Stefano Liberati, Sebastiano Sonego, Matt Visser
Abstract: Motivated by the recent attention on superluminal phenomena, we investigate
the compatibility between faster-than-c propagation and the fundamental principles of
relativity and causality. We first argue that special relativity can easily accommodate --
indeed, does not exclude -- faster-than-c signalling at the kinematical level. As far as
causality is concerned, it is impossible to make statements of general validity, without
specifying at least some features of the tachyonic propagation. We thus focus on the
Scharnhorst effect (faster-than-c photon propagation in the Casimir vacuum), which is
perhaps the most plausible candidate for a physically sound realization of these
phenomena. We demonstrate that in this case the faster-than-c aspects are 'benign' and
constrained in such a manner as to not automatically lead to causality violations.

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