Curved spacetime one-loop gravity in a physical gauge

We study the hamiltonian formulation of perturbative quantum gravity. For a Friedmann-Robertson-Walker background, the gravitational constraints can be solved, and the physical degrees of freedom can be isolated explicitly. The resulting action is bounded from below in the euclidean regime. In the context of wormhole physics this implies that there is no phase of the sum over spheres. We use the zeta-function regularization technique to calculate the so-called scaling behavior of the one-loop partition function about the S4 saddle point. We find an answer that differs by an integer from the value obtained from the covariant approach using the 'conformal rotation' prescription of Gibbons, Hawking, and Perry. These results indicate that the 'conformal rotation' prescription does not yield the correct partition function for curved backgrounds. (orig.)