Schulz, Benjamin (2019): Quantum gravity and space-time foam. Dissertation, LMU München: Faculty of Physics |

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Licence: Creative Commons: Attribution-NonCommercial 4.0 (CC-BY-NC) Schulz_Benjamin.pdf 974kB |

**DOI**: 10.5282/edoc.25592

### Abstract

This thesis argues that Hawking's model on space-time foam predicts, after several modifications, a cosmological constant of the observed order. Inconsistencies of Hawking's model that were pointed out by Christensen and Duff are removed. A mechanism is given that can be used to remove the Ostrogradski instability of the effective matter action. The modified space-time foam model of Hawking describes a space-time filled with a gas of microscopic black- and wormholes. It is noted that particles which fly through such a space-time are governed by different equations of motion than in vacuum, since they scatter with the Hawking radiation of the microscopic black-holes and they are additionally under a collective influence of the gravitational field on long time scales. Under the assumption that Hawking radiation restores any information that was removed by the black-holes, one can derive the Schrödinger equation at low energies if one puts a classical particle into the space-time foam. The space-time foam model implies topology changes of the space-time during the expansion of the universe. It is argued that ordinary quantum field theory on Lorentzian space-times is incompatible with such changes since they give rise to singularities. It is proposed that if a stochastic model with non-differentiable paths underlies quantum mechanics at small scales (the usual path integral formulation is restricted to differentiable paths) then this could be used near the singularities during a topology change of the space-time.

Item Type: | Theses (Dissertation, LMU Munich) |
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Keywords: | quantum gravity, Euclidean quantum gravity, cosmological constant, topology change in quantum gravity |

Subjects: | 500 Natural sciences and mathematics 500 Natural sciences and mathematics > 530 Physics |

Faculties: | Faculty of Physics |

Language: | English |

Date of oral examination: | 15. October 2019 |

1. Referee: | Lüst, Dieter |

MD5 Checksum of the PDF-file: | db0014dfcd7cd1f855ccfb66b27332ce |

Signature of the printed copy: | 0001/UMC 28270 |

ID Code: | 25592 |

Deposited On: | 18. Oct 2021 14:10 |

Last Modified: | 18. Oct 2021 14:10 |