Abstract

Within the context of gravity formulated as a gauge theory of the Lorentz group, we derive the field equations for a gravitational action consisting of a generic analytic function of the curvature scalar, in the presence of general matter fields. In the vacuum case we obtain universal equations in agreement with Ferraris et al . We also show explicit non-trivial examples of universal behaviour in the presence of matter fields, which in the general case produces a non-zero torsion field, leading to an Einstein–Cartan geometry and universal Einstein–Cartan field equations.