Looking for a theory of faster-than-light particles
  Several principal aspects of a theoretical approach to the theory of faster-than-light particles (tachyons) are considered in this note. They concern the resolution of such problems of tachyon theory as the causality violation by tachyons, the stability of the tachyon vacuum, and the stability of ordinary particles against the spontaneous emission of tachyons, i.e. the problems which are generally used as arguments against the possibility of such particles. It is demonstrated that all these arguments contain nontrivial loopholes which undermine their validity. A demand for a consistent tachyon theory is formulated, and several ideas for its construction are suggested. 
V. F. Perepelitsa
physics.gen-ph hep-th