Exact self-consistent gravitational shock wave in semiclassical gravity

We find a self-consistent pp-gravitational shock wave solution to the semiclassical Einstein equations resulting from the 1/N approach to the effective action. We model the renormalized matter stress-energy momentum tensor by N massless scalar fields in the Minkowski vacuum pins a classical particle. We show that quantum effects generate a milder singularity at the position of the particle than the classical solution, but the singularity does not disappear. At large distances from the particle, the quantum correction decreases slowly, as 1/rho(2) (rho being the distance to the particle in the shock wave plane). We argue that this large distance correction is a necessary consequence of quantum gravity.