Running coupling constants, Newtonian potential, and nonlocalities in the effective action.

We consider a quantum scalar field on an arbitrary gravitational background. We obtain the effective in-in equations for the gravitational fields using a covariant and nonlocal approximation for the effective action proposed by Vilkovisky and collaborators. From these equations, we compute the quantum corrections to the Newtonian potential. We find logarithmic corrections which we identify as the running of the gravitational constants. This running coincides with the renormalization group prediction only for minimal and conformal coupling.