Exact gravitational shock wave solution of higher order theories

We fmd an enact pp-gravitational wave solution of the fourth-order gravity field equations. Outside the (delta-like) source this is not a vacuum solution of general relativity. It represents the contribution of the massive, m=(-beta)(-1/2), spin-two field associated while the Ricci-squared term in the gravitational Lagrangian. The fourth-order terms tend to make the singularity of the curvature milder at the point where the particle is located. We generalize this analysis to D dimensions, extended sources, and higher than fourth-order theories. We also briefly discuss the scattering of fields by these kinds of plane gravitational waves.