The existence of radiation-free states in the transient motion of dislocations was investigated. By analyzing an edge dislocation which jumped, from rest, to a supersonic speed it was seen that the Mach fronts disappeared at 1.414 times the shear-wave velocity. This was because, at this dislocation velocity, the pole singularity in the complex plane was replaced by a removable one. However, radiated stress waves existed which propagated at the shear-wave velocity. Due to radiated longitudinal waves, a force was required in order to sustain such motion.

On “Radiation-Free” States in Transient Motion of Dislocations. X.Markenscoff: Applied Physics Letters, 2001, 78[4], 440-2