General relativity with spin and torsion: Foundations and prospects
Abstract
A generalization of Einstein's gravitational theory is discussed in which the spin of matter as well as its mass plays a dynamical role. The spin of matter couples to a nonRiemannian structure in spacetime, Cartan's torsion tensor. The theory which emerges from taking this coupling into account, the U_{4} theory of gravitation, predicts, in addition to the usual infiniterange gravitational interaction medicated by the metric field, a new, very weak, spin contact interaction of gravitational origin. We summarize here all the available theoretical evidence that argues for admitting spin and torsion into a relativistic gravitational theory. Not least among this evidence is the demonstration that the U_{4} theory arises as a local gauge theory for the Poincaré group in spacetime. The deviations of the U_{4} theory from standard general relativity are estimated, and the prospects for further theoretical development are assessed.
 Publication:

Reviews of Modern Physics
 Pub Date:
 July 1976
 DOI:
 10.1103/RevModPhys.48.393
 Bibcode:
 1976RvMP...48..393H