GEODESICS, GRAVITONS, AND THE GAUGE-FIXING PROBLEM

When graviton loops are taken into account, the background metric obta ined as a solution to the one-loop corrected Einstein equations turns out to be gauge-fixing dependent. Therefore it is of no physical relev ance. Instead we consider a physical observable, namely, the trajector y of a test particle in the presence of gravitons. We derive a quantum corrected geodesic equation that includes backreaction effects and is explicitly independent of any gauge-fixing parameter. [30556-2821(97) 02024-9].