Elementary particles in a curved space. IV. Massless particles

If physics is stable with respect to a class of perturbations of the spacetime metric, including that of "small" constant four-dimensional curvature, then it may be shown that (1) left-handed and right-handed neutrinos are distinguished by a superselection rule; (2) magnetic monopoles cannot exist; (3) the conformal symmetry associated with the field equations for massless particles with spin 0, , and 1 is spontaneously broken---except in the case of neutrinos with fixed chirality.