# The simplicial Lorentzian path integral and spin foams

### APA

Dittrich, B. (2023). The simplicial Lorentzian path integral and spin foams. Perimeter Institute. https://pirsa.org/23100068

### MLA

Dittrich, Bianca. The simplicial Lorentzian path integral and spin foams. Perimeter Institute, Oct. 27, 2023, https://pirsa.org/23100068

### BibTex

@misc{ pirsa_PIRSA:23100068, doi = {10.48660/23100068}, url = {https://pirsa.org/23100068}, author = {Dittrich, Bianca}, keywords = {Quantum Gravity}, language = {en}, title = {The simplicial Lorentzian path integral and spin foams}, publisher = {Perimeter Institute}, year = {2023}, month = {oct}, note = {PIRSA:23100068 see, \url{https://pirsa.org}} }

Perimeter Institute for Theoretical Physics

Talk Type

**Subject**

Abstract

I will discuss two versions of the simplicial Lorentizian path integral, namely the (Lorentzian) quantum Regge and the spin foam version. I will do so in the simple context of de Sitter cosmology. This simple example will reveal the important role of light cone irregular configurations in the simplicial path integral — I will show that these can either lead to an exponentially enhanced or an exponentially suppressed amplitude.
I will then highlight an important difference between the spin foams and quantum Regge path integral, which affects the probability for the creation of the (de Sitter) universe.