# Victor FRANKEN

**PhD Student**

**Research group:** String Theory

**Thesis: "**Holography, entanglement, and quantum cosmology**"**

**Advisor: ****Hervé Partouche**

**Research**

*Quantum gravity, de Sitter holography, Holographic entanglement, Wavefunction of the universe*

This thesis's general motivation is to make progress toward understanding the first moments of our universe. The quantum effects are certainly crucial for this early phase of time, therefore we probably will have to resort to quantum gravity. String theory is a very successful attempt to unify gravity with gauge theories at the quantum level. However, there is a hot debate concerning the possibility of formulating a consistent string theory in cosmological models (in particular in de Sitter space). For some time, the duality between gravity in anti-de Sitter space and conformal field theory (AdS/CFT) has become a great source of progress in the nonperturbative description of string theory in AdS space. It is an example of the holographic correspondence between quantum gravity in a given spacetime and a field theory living on its boundary. Yet, very little is known about the existence of a holographic dictionary for cosmological backgrounds.

Two of the principal goals of my thesis are to study holographic conjectures for de Sitter space and to better understand the particular causal structure of de Sitter space, which resembles that of black holes. In particular, we use recent realizations concerning the strong relation between quantum entanglement and the geometry of spacetime. This link could offer a window into the nature of the candidate dual theory to de Sitter space. Another approach is that of quantum mechanics applied to the metric of the universe itself. To do so, we define a "wavefunction of the universe", which depends on the metric, by analogy to the wavefunction of a particle depending on its position.

**Publication**

Franken V, Partouche H, Rondeau F, Toumbas N.

Bridging the static patches: de Sitter holography and entanglement.

Journal of High Energy Physics. 2023(8):74.

DOI: 10.1007/JHEP08(2023)074.

Address |
CPHT, Ecole Polytechnique, 91128 Palaiseau cedex, France |

Phone number |
33 (0) 1 69 33 42 82 |

Contact |
firstname.lastname@polytechnique.edu |

Office |
"Aile zéro", office 00.1028 |