In the new paper, this concept is taken very seriously. “The wave function” is interpreted as nothing else than the Hawking-Hartle wave function of the Universe. You know, the Hawking-Hartle wave function is something like a wave functional of quantum gravity that solves the Wheeler-deWitt equation (a sophisticated definition of the quantum equation

    H.psi = 0

that is appropriate in general relativity but whose exact meaning requires a working quantum theory gravity, i.e. it requires string theory). The Hawking-Hartle wave function is a functional of the fields of quantum gravity on S^3, if you allow me to deal with the “most realistic” example, and this functional may be calculated as the path integral of quantum gravity defined in the ball B^4 inside this S^3, with the right boundary conditions at the sphere S^3. The Hawking-Hartle state is then the functional of these boundary conditions.

— Lubos Motl

2012.08.06 Monday ACHK