Semiclassical corrections to the metric of multiple cosmic strings - Addendum

In the framework of semiclassical approach to quantum gravity we calculate the first order in h corrections to the metric around N parallel static, st raight-line cosmic strings due to the back-reaction effects of massless qua ntized fields propagating in the multi-conical spacetime. The Einstein fiel d equations which as a source in the right-hand side involve the vacuum ave rage of the energy-momentum tensor of massless scalar, electromagnetic and spinor fields are solved perturbatively. We show that the semiclassical met ric is no longer locally Bat, there is a 'Newtonian-like' potential which r esults in an attractive, or repulsive, gravitational force near multiple co smic strings.