### Abstract

We revisit the construction of the Hilbert space of non-relativistic particles moving in three spatial dimensions. This is given by the space of sections of a line bundle that can in general be topologically non-trivial. Such bundles are classified by a set of integers–one for each pair of particles–and arise physically when we describe the interactions of dyons, particles which carry both electric and magnetic charges. The choice of bundle fixes the representation of the Euclidean group carried by the Hilbert space. These representations are shown to recover the ‘pairwise helicity’ formalism recently discussed in the literature.

###### Research Associate in High Energy Theoretical Physics

My research interests include string theory, M-theory and conformal field theory