Cauchy constraints and particle content of fourth-order gravity in n dimensions

The full class of purely metrical gravitational theories in n 3 dimensions which follows from a Lagrangian composed of linear and quadratic curvature terms is analyzed. The type of the field equations in a suitable gauge is discussed. The principal symbol and the particle content of the linearized field equations are investigated. The space+time decomposition and the ADM formalism are used to derive the constraints and evolution equations for the variational derivative tensor.