The simplicial Lorentzian path integral and spin foams

          @misc{ scivideos_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 for Theoretical Physics},
            year = {2023},
            month = {oct},
            note = {PIRSA:23100068 see, \url{https://scivideos.org/pirsa/23100068}}
          }
          

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.