PIRSA:17060099

Unitary Cosmological Bounces

de Rham, C. (2017). Unitary Cosmological Bounces. Perimeter Institute. https://pirsa.org/17060099

de Rham, Claudia. Unitary Cosmological Bounces. Perimeter Institute, Jun. 27, 2017, https://pirsa.org/17060099 

          @misc{ pirsa_PIRSA:17060099,
            doi = {10.48660/17060099},
            url = {https://pirsa.org/17060099},
            author = {de Rham, Claudia},
            keywords = {Cosmology},
            language = {en},
            title = {Unitary Cosmological Bounces},
            publisher = {Perimeter Institute},
            year = {2017},
            month = {jun},
            note = {PIRSA:17060099 see, \url{https://pirsa.org}}
          }

Claudia de Rham Imperial College London

DOI 10.48660/17060099
Collection
Talk Type Conference
Subject

Abstract

A non-singular cosmological bounce in the Einstein frame can only take place if the Null Energy Condition (NEC) is violated. I will explore the constraints imposed by demanding tree level unitarity on a cosmological background in single scalar field theories before focusing on the explicit constraints that arise in P(X) theories. In that context, perturbative unitarity makes it impossible for the NEC violation to occur within the region of validity of the effective field theory but I will show explicitly how unitarity may be restored by involving irrelevant operators that arise at a higher scale.