On the semiclassical Einstein-Langevin equation
  We introduce a semiclassical Einstein-Langevin equation as a consistent dynamical equation for a first order perturbative correction to semiclassical gravity. This equation includes the lowest order quantum stress-energy fluctuations of matter fields as a source of classical stochastic fluctuations of the gravitational field. The Einstein-Langevin equation is explicitly solved around one of the simplest solutions of semiclassical gravity: Minkowski spacetime with a conformal scalar field in its vacuum state. We compute the two-point correlation function of the linearized Einstein tensor. This calculation illustrates the possibility of obtaining some ``non-perturbative'' behavior for the induced gravitational fluctuations that cannot be obtained in perturbative quantum gravity. 
Rosario Martin and Enric Verdaguer