PIRSA:23030102

On past geodesic (in)completeness, spacetime (in)extendibility, and singularities in inflationary cosmology

Quintin, J. (2023). On past geodesic (in)completeness, spacetime (in)extendibility, and singularities in inflationary cosmology. Perimeter Institute. https://pirsa.org/23030102

Quintin, Jerome. On past geodesic (in)completeness, spacetime (in)extendibility, and singularities in inflationary cosmology. Perimeter Institute, Mar. 06, 2023, https://pirsa.org/23030102 

          @misc{ pirsa_PIRSA:23030102,
            doi = {10.48660/23030102},
            url = {https://pirsa.org/23030102},
            author = {Quintin, Jerome},
            keywords = {Cosmology},
            language = {en},
            title = {On past geodesic (in)completeness, spacetime (in)extendibility, and singularities in inflationary cosmology},
            publisher = {Perimeter Institute},
            year = {2023},
            month = {mar},
            note = {PIRSA:23030102 see, \url{https://pirsa.org}}
          }

Jerome Quintin

University of Waterloo

Talk number
PIRSA:23030102
Collection
Talk Type
Subject
Abstract

Inflationary cosmology is notoriously past geodesically incomplete in many situations. However, it is generally unknown whether the geodesic incompleteness implies the existence of an initial spacetime curvature singularity or whether the spacetime may be extended beyond its null past boundary. In homogeneous and isotropic cosmology with flat spatial sections, we classify which past inflationary histories have a scalar curvature singularity and which might be extendible/non-singular. We derive rigorous extendibility criteria of various regularity classes for quasi-de Sitter spacetimes that evolve from infinite proper time in the past. Beyond homogeneity and isotropy, we show that continuous extensions respecting the Einstein field equations with a perfect fluid must have the equation of state of a de Sitter universe asymptotically. An interpretation of our results is that past-eternal inflationary scenarios are most likely physically singular, except in very special situations.

Zoom link:  https://pitp.zoom.us/j/98334550627?pwd=UnR3eUxZRFZpeEZoOGEwNkJuc0M0UT09