### Abstract

The tunneling wave function of the Universe is calculated exactly for a de Sitter minisuperspace model with a massless conformally coupled scalar field, both by solving the Wheeler-DeWitt equation and by evaluating the Lorentzian path integral. The same wave function is found in both approaches. The backreaction of quantum field fluctuations on the scale factor amounts to a constant renormalization of the vacuum energy density. This is in contrast to the recent suggestion of Feldbrugge et al. that the backreaction should diverge when the scale factor gets small, a→0. Similar results are found for a massive scalar field in the limit of a large mass. We also verified that the tunneling wave function can be expressed as a transition amplitude from a universe of vanishing size with the scalar field in the state of Euclidean vacuum, as was suggested in our earlier work.

Original language | English |
---|---|

Article number | 066010 |

Journal | Physical Review D |

Volume | 99 |

Issue number | 6 |

DOIs | |

Publication status | Published - 2019 Mar 15 |

Externally published | Yes |

### ASJC Scopus subject areas

- Physics and Astronomy (miscellaneous)

## Fingerprint Dive into the research topics of 'Tunneling wave function of the universe. II. the backreaction problem'. Together they form a unique fingerprint.

## Cite this

*Physical Review D*,

*99*(6), [066010]. https://doi.org/10.1103/PhysRevD.99.066010