The continuous spin limit of higher spin field equations

摘要

We show that the Wigner equations describing the continuous spinrepresentations can be obtained as a limit of massive higher-spin fieldequations. The limit involves a suitable scaling of the wave function, the massgoing to zero and the spin to infinity with their product being fixed. Theresult allows to transform the Wigner equations to a gauge invariantFronsdal-like form. We also give the generalisation of the Wigner equations tohigher dimensions with fields belonging to arbitrary representations of themassless little group.