Cosmological singularities in Bakry-Émery spacetimes

Gregory J. Galloway, Eric Woolgar

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

We consider spacetimes consisting of a manifold with Lorentzian metric and a weight function or scalar field. These spacetimes admit a Bakry-Émery-Ricci tensor which is a natural generalization of the Ricci tensor. We impose an energy condition on the Bakry-Émery-Ricci tensor and obtain singularity theorems of a cosmological type, both for zero and for positive cosmological constant. That is, we find conditions under which every timelike geodesic is incomplete. These conditions are given by "open" inequalities, so we examine the borderline (equality) cases and show that certain singularities are avoided in these cases only if the geometry is rigid; i.e., if it splits as a Lorentzian product or, for a positive cosmological constant, a warped product, and the weight function is constant along the time direction. Then the product case is future timelike geodesically complete while, in the warped product case, worldlines of certain conformally static observers are complete. Our results answer a question posed by J Case. We then apply our results to the cosmology of scalar-tensor gravitation theories. We focus on the Brans-Dicke family of theories in 4 spacetime dimensions, where we obtain "Jordan frame" singularity theorems for big bang singularities.

Original languageEnglish (US)
Pages (from-to)359-369
Number of pages11
JournalJournal of Geometry and Physics
Volume86
DOIs
StatePublished - Dec 1 2014

    Fingerprint

Keywords

  • Bakry-Émery
  • Brans-Dicke theory
  • Cosmological singularity
  • Lorentzian
  • Scalar-tensor theory
  • Singularity theorem

ASJC Scopus subject areas

  • Mathematical Physics
  • Physics and Astronomy(all)
  • Geometry and Topology

Cite this