Although the existence of tachyons is not ruled out by special relativity, it appears that causal paradoxes will arise if there are tachyons. The usual solutions to these paradoxes employ some form of the reinterpretation principle. In this paper it is argued first that the principle is incoherent, second that even if it is not, some causal paradoxes remain, and third, the most plausible “solution,” which appeals to boundary conditions of the universe, will conflict with special relativity.

In the approximation that every inertial observer experiences a homogeneous, uniform flow of time and sees a space that is Euclidean, the arena of physics is Minkowskian and one speed is the same in all intertial frames. If a given intertial observer finds an infinitesimal source or particle traveling faster than this fundamental speed near a given event, the source must appear in some inertial frame spread over neighboring positions at a given time as a spacelike structure. If this structure (...) persists over a period of proper time, it can be interpreted as a wave group. If it is conserved, it can be interpreted as a line or tube of force. (shrink)

Tachyon paradoxes, including causality paradoxes, have persisted within tachyon theories and left little hope for the existence of observable tachyons. This paper presents a way to solve the causality paradoxes, along with two other paradoxes, by the introduction of an absolute frame of reference in which a tachyon effect may never precede its cause. Relativity for ordinary matter is unaffected by this, even if the tachyons couple to ordinary particles. Violations of the principle of relativity due to the absolute frame (...) would appear only in the case of free tachyons. (shrink)