Quantum Energy Conditions and Bouncing Cosmologies

          @misc{ pirsa_PIRSA:24070089,
            doi = {10.48660/24070089},
            url = {https://pirsa.org/24070089},
            author = {Hull, Brayden},
            keywords = {},
            language = {en},
            title = {Quantum Energy Conditions and Bouncing Cosmologies},
            publisher = {Perimeter Institute},
            year = {2024},
            month = {jul},
            note = {PIRSA:24070089 see, \url{https://pirsa.org}}
          }
          

Abstract

Classical energy conditions are used to provide restrictions on the matter fields present in the stress-energy tensor to avoid possible unphysical spacetimes. These classical energy conditions are imperative to the singularity theorems of Hawking and Penrose. However, we know that spacetime breaks down near said singularities and a quantum theory of gravity is needed. One insight into this area is semi-classical gravity where the spacetime is kept “classical” and the stress-energy tensor is quantized. In this regime one may ask what reasonable restrictions should be imposed on the quantum expectation of the stress-energy tensor? One such possibility is the smeared null energy conditions (SNEC). We will review motivation for the SNEC and explore its consequences in cosmological spacetimes that would otherwise violate the classical null energy condition, such as bouncing cosmologies.