There are two different concepts of tachyons: Quantum fields with imaginary mass and faster-than-light particles. Tachyonic fields still (anti)commute at space

There are two different concepts of tachyons: Quantum fields with imaginary mass and faster-than-light particles. Tachyonic fields still (anti)commute at space-like separation, which preserves causality. Such fields are maximally unstable and do not permit a particle picture. They are used to describe spontaneous symmetry breaking. Tachyonic particles are a concept from special relativity. While one can also attribute an imaginary mass to such particles, this basically encodes a sign convention. These theoretical particles exhibit some perculiar properties (zero-energy particles which travel at infinite velocity and finite momentum, different observers will disagree on emitter and absorber - in fact, during a tachyonic interaction, both endpoints may claim to be emitter or absorber in their respective rest frames depending on their relative motion, ...). According to Recami[1], no causal paradoxa occur. [1] http://dinamico2.unibg.it/recami/erasmo%20docs/SomeRecentSCIENTIFICpapers/ExtendedRelativity/TachyonCausalParadoxesSOLVED.pdf http://dinamico2.unibg.it/recami/erasmo%20docs/SomeRecentSCI...