Tachyons in the Galilean limit

Understand

The Souriau massless Galilean particle of "colour" $k$ and spin $s$ is shown to be the Galilean limit of the Souriau tachyon of mass $m = ik$ and spin $s$.

• We compare and contrast this result with the recent Galilean limit of the Nambu-Goto string and the Green-Schwarz superstring.