  The coadjoint representation of the BMS$_3$ group, which governs the
covariant phase space of three-dimensional asymptotically flat gravity, is
investigated. In particular, we classify coadjoint BMS$_3$ orbits and show that
intrinsic angular momentum is free of supertranslation ambiguities. Finally,
the link with induced representations upon geometric quantization is discussed.

High Energy Physics - Theory;General Relativity and Quantum Cosmology