Wigner's infinite spin representations and inert matter

Positive energy ray representations of the Poincar\'e group are naturally subdivided into three classes according to their mass and spin content: m>0, m=0 finite helicity and m=0 infinite helicity. For a long time the localization properties of the massless infinite spin class remained unknown before it became clear that such matter does not permit compact spactime localization and its generating covariant fields are localized on semi-infinite spacelike strings. Using a new perturbation theory for higher spin fields we show that infinite spin matter cannot interact with normal matter and we formulate condition under which this also could happen for finite spin s>1 fields. This raises the question of a possible connection between inert matter and dark matter.