Unitary representations of the infinite-parameter group $\mathrm{Diff}\left(R^3\right)$ are presented which describe particles with spin as well as tightly bound composite particles. These results support the idea that $\mathrm{Diff}\left(R^3\right)$ can serve as a "universal group" for quantum theory.

• Received 27 September 1983

DOI:https://doi.org/10.1103/PhysRevLett.51.2246