Abstract
We show why the universe started in an unstable de Sitter state. The quantum origin of our universe implies one must take a “top down” approach to the problem of initial conditions in cosmology, in which the histories that contribute to the path integral depend on the observable being measured. Using the no boundary proposal to specify the class of histories, we study the quantum cosmological origin of an inflationary universe in theories such as trace anomaly driven inflation in which the effective potential has a local maximum. We find that an expanding universe is most likely to emerge in an unstable de Sitter state, by semiclassical tunneling via a Hawking-Moss instanton. Since the top down view is forced upon us by the quantum nature of the universe, we argue that the approach developed here should still apply when the framework of quantum cosmology will be based on M theory.
- Received 27 August 2002
DOI:https://doi.org/10.1103/PhysRevD.66.123509
©2002 American Physical Society
Collections
This article appears in the following collection:
The Work of Stephen Hawking in Physical Review
To mark the passing of Stephen Hawking, we gathered together his 55 papers in Physical Review D and Physical Review Letters. They probe the edges of space and time, from "Black holes and thermodynamics” to "Wave function of the Universe."