@article{Hartle1983WaveFO,
title={Wave Function of the Universe},
author={J. Hartle and S. Hawking},
journal={Physical Review D},
year={1983},
volume={28},
pages={2960-2975}
}

The quantum state of a spatially closed universe can be described by a wave function which is a functional on the geometries of compact three-manifolds and on the values of the matter fields on these manifolds. The wave function obeys the Wheeler-DeWitt second-order functional differential equation. We put forward a proposal for the wave function of the "ground state" or state of minimum excitation: the ground-state amplitude for a three-geometry is given by a path integral over all compact… Expand