Fermions and gravity

In order to establish a satisfactory framework of a gravitational theory for fermions, the gauging of the Poincare (inhomogeneous Lorentz) group seems necessary. A corresponding formalism is presented; in particular, the two general field equations (3.15), (3.16) of the Poincare gauge field theory (PG) are derived. We discuss the general form of the gauge field lagrangian yielding quasi-linear 2nd-order field equations. In addition to the usual weak Einstein gravity (''gravitons''), we find a strong Yang-Mills type gravity (''rotons''). A particular model Lagangian quadratic in torsion and curvature is exhibited, and a spherical-symmetric vacuum solution carrying torsion and curvature is discussed