No open or flat bouncing cosmologies in Einstein gravity

@article{Parikh2015NoOO,
  title={No open or flat bouncing cosmologies in Einstein gravity},
  author={Maulik Parikh},
  journal={Journal of High Energy Physics},
  year={2015},
  volume={2015},
  pages={1-11}
}
  • M. Parikh
  • Published 19 January 2015
  • Physics
  • Journal of High Energy Physics
A bstractWe show that, to first approximation, strings cannot propagate in bouncing open or flat Friedmann-Robertson-Walker universes. Specifically, the Virasoro constraint translates to the Ricci convergence condition in spacetime at leading order in the alpha-prime expansion. Thus one must go beyond minimally-coupled classical Einstein gravity in order to find bounce solutions that could be consistent with string theory. We map out some remaining possibilities for finding string-compatible… 

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