IL NUOV() (~IMI,'.NTO VOL. 55 B, N. 1 11 Gcnnaio 1980 Weyl-Dirac Theory with Torsion ('). D. GREGORASH and G. PAPINI Department of Physics and Astronomy, University of Regina Regina, Saskatchewan, Canada $4S 0A2 (ricevuto il 21 Agosto 1979) Summary. -- Dirac's unified theory of gravitation and electromagnetism is extended to include torsion. The conformal invariance of the resultant theory seems to imply charge quantization for source fields. The electro- magnetic-field equations in vacuum bear a strong resemblance to those of the Ginzburg-Landau formulation of superconductivity. In the general theory, which involves a cosmological constant, the conformal invariance is spontaneously broken if the ratio of the scalar curvature and the cosmological constant is negative. 1. - Introduction. The formulation of a viable unified theory of interaction has long been a major goal in theoretical physics. In spite of recent successes with the non- gravitational interactions (1,~), gravitation has so far been largely neglected. Although gravity is extremely weak, its neglect represents a serious deficiency in any theory. We have known for a long time, even in the classical approxima- tion, that any theory based on a fiat space-time is intrinsically incomplete. (*) Work supported in part by the Natural Sciences and Engineering Research Council of Canada. (1) S. WEINBERG: Phys. Rev..Lett., 19, 1264 (1967); A. SALAM:in Elementary Particle Theory, edited by N. SVAttTHOLM (New York, N.Y., 1969). (3) An interesting, but rather complicated, unification of the three nongravitational interactions is reported by I. BARS, N. B. HALPERN and M. YOSHIMURA: Phys. Rev. D, 7, 1233 (1973). 37