Question: would a charged tachyon generate an infinite electromagnetic shock wave (e.g., Cerenkov radiation)? It seems to me that it would, but I see no reference to this online. My reasoning is twofold. First, if the tachyon is moving at a fixed speed, then we can take a reference frame where its worldline lies on the x axis, and then it looks like a line of charge with infinite charge density. Clearly, this produces a singular EM field. Of course, the tachyon may accelerate, and then we can only make the x axis tangent to its worldline at any point. But still, it seems that the charge density at that point looks infinite and the EM field should be singular. Also, clearly there must be Cerenkov radiation, which must have a certain power spectrum over different frequencies. In terms of dimensional analysis, I don't see how a frequency can be constructed where the power would start to decay. I guess, if the tachyon was accelerating, then one could combine the acceleration with c and get a frequency, but this seems kind of odd.