Spin in Special and General Relativity

Abstract

General remarksBroadly speaking, the "role of spin and rotation in General Relativity" covers two topics; the behavior of spinning particles in GR -this "spin" being either classical or quantum mechanical, and the physics associated with (noninertial) rotations. The papers presented to this session cover both these aspects of the subject. To the non-specialist, the most familiar heading in this general area is the Lense-Thirring effect, a precessional effect which is predicted (though so far not observed) to take place close to a rotating body. The papers of Ciufolini and Teyssandier are both devoted to this effect. Also well-known is the (gravitomagnetic) clock effect; as its name implies, this is concerned with time nonintegrability, rather than with precession. Tartaglia and Maleki both address this topic; and we live, moreover, at a time when both the Lense-Thirring and gravitomagnetic clock effects have the enticing possibility of experimental confirmation in the near future.Connections with gravitational waves (also soon to be detected?) are made, though in very different ways by Cooperstock, Slagter, and Suzuki and Maeda. The behavior of spinning particles in various types of gravitational fields is analyzed by Mohseni, Tucker and Wang, by Mukhopadhyay and by Singh and Papini, the latter two contributions being concerned specifically with Dirac particles, while White and Raine -alone in this session -consider a theory with torsion. Bini, Gemelli and Ruffini give a more general account of the description of spinning particles in GR. In a nonquantum context, Wu and Xu include 1

Dirac particles in a gravitational shock wave

“…It is known that in a general semi-Riemannian spacetime we cannot define a conserved spin operator [20]. Nevertheless, in the situation discussed in the present paper, our Dirac particle is in flat (Minkowski) spacetime both before (region F ) and after the passage of the shock wave (region B).…”

“…Classical spinning particles in gravitational wave backgrounds, in the weak-field approximation, were considered in [17,18] and recently in [19], but to our knowledge there has not been an investigation of a Dirac particle in an exact gravitational wave. This may be due in part to the non-existence of a conserved spin operator in curved spacetime [20].…”