It is shown that cosmological structures can be used to make tachyonic theories that do not contain logical paradoxes. A general-relativistic Proca equation is then analyzed as an example of a field-theoretic model that can have this type of tachyonic behavior. It is found that only one form of this equation never gives tachyon-type behavior.

• Received 23 May 1974

DOI:https://doi.org/10.1103/PhysRevD.10.2358