Stabilizing the gravitational action and Coleman's solution to the cosmological constant problem

We use the fifth-time action formalism introduced by Halpern and Greensite to stabilize the unbounded euclidean 4D gravity in two simple minisuperspace models. In particular, we show that, at the semiclassical level (h {combining short solidus overlay}→0), we still have as a leading saddle point the S⁴ solution and the Coleman peak at zero cosmological constant, for a fixed De Witt supermetric. At the quantum (one-loop) level the scalar gravitational modes give a positive semidefinite hessian contribution to the 5D partition function, thus removing the Polchinski phase ambiguity.