Halfintegral spin from quantum gravity
Abstract
For a certain class of threemanifolds, the angular momentum of an asymptotically flat quantum gravitational field can have halfintegral values. In the absence of a full theory of quantum gravity, this result relies on a set of apparently natural assumptions governing the kinematics of such a theory. A key feature is that state vectors are in general invariant only under asymptotically trivial diffeomorphisms that can be continuously deformed to the identity. Angular momentum is associated with diffeomorphisms that look asymptotically like rotations; and the question of whether halfintegral values occur depends on whether the diffeomorphism associated with a 2π rotation is itself deformable to the identity.
 Publication:

General Relativity and Gravitation
 Pub Date:
 July 1982
 DOI:
 10.1007/BF00761452
 Bibcode:
 1982GReGr..14..615F