Wave function of the inflationary universe

If one is interested in cosmological models with inflation occurring at or near the Planck energy then the effects of quantum gravity have to be taken into account. We may still hope to use an approximation with the Einstein action as a starting point but the semiclassical approach breaks down, forcing us to use the superspace construction for the wave function of the Universe. Using a recently proposed formulation of the ground state of the Universe, we obtain a unique quantum cosmology for a given inflationary model. Besides recovering the semiclassical inflationary picture, the wave function has other consequences, such as the following: (1) The wave function is suppressed for small values of the scale factor and can therefore be interpreted as corresponding to the nucleation of a bubble universe. (2) The parameters of the wave function become uncorrelated at small values of the scale factor which means that the concept of time breaks down. (3) The wave function at later times possesses structure on scales smaller than the Planck scale which leads to a spacetime-foam picture of the Universe. We may therefore view the existence of the Universe itself as a consequence of inflation.