No Open or Flat Bouncing Cosmologies in Einstein Gravity
arXiv:1501.04606
Abstract
We show that bouncing open or flat Friedmann-Robertson-Walker cosmologies are inconsistent with worldsheet string theory to first approximation. Specifically, the Virasoro constraint translates to the null energy condition in spacetime at leading order in the alpha-prime expansion. Thus one must go beyond minimally-coupled Einstein gravity in order to find bounce solutions.
11 pages, LaTeX, discussion expanded and references added