The Remarkable Roundness of the Quantum Universe

          @misc{ pirsa_PIRSA:20070007,
            doi = {10.48660/20070007},
            url = {https://pirsa.org/20070007},
            author = {Loll, Renate},
            keywords = {Cosmology, Particle Physics, Quantum Foundations, Quantum Gravity, Quantum Information},
            language = {en},
            title = {The Remarkable Roundness of the Quantum Universe},
            publisher = {Perimeter Institute},
            year = {2020},
            month = {jul},
            note = {PIRSA:20070007 see, \url{https://pirsa.org}}
          }
          

Abstract

It has taken several decades of exploring statistical models of quantum gravity (aka nonperturbative gravitational path integrals) to understand how diffeomorphism-invariance, unitarity and the presence of a causal structure can be simultaneously accounted for in a lattice gravity framework. Causal Dynamical Triangulations (CDT) incorporates all of these features and provides a toolbox for extracting quantitative results from a first-principles quantum formulation, with very few free parameters. Recently, we have introduced the "quantum Ricci curvature", an observable that --somewhat remarkably-- remains meaningful in a maximally nonclassical, Planckian regime. Measuring this curvature in fully-fledged 4D quantum gravity, we have discovered exciting evidence that the quantum universe dynamically generated in CDT is compatible with a constantly curved de Sitter space.