Quantum cosmological instabilities - with and without boundaries

          @misc{ scivideos_PIRSA:17060100,
            doi = {10.48660/17060100},
            url = {https://pirsa.org/17060100},
            author = {Lehners, Jean-Luc},
            keywords = {Cosmology},
            language = {en},
            title = {Quantum cosmological instabilities - with and without boundaries},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2017},
            month = {jun},
            note = {PIRSA:17060100 see, \url{https://scivideos.org/pirsa/17060100}}
          }
          

Abstract

The big bang singularity might be avoided by replacing it with a theory of initial conditions, or by considering a bounce from an earlier contracting phase. I will describe how both proposals can run into difficulties with instabilities when the spacetime must be treated semi-classically (i.e. when bounces occur due to a quantum tunneling transition rather than as classically non-singular solutions). The absence of such instabilities places new restrictions on the available theories, implying a selection criterion whose consequences remain to be explored.