Abstract
We 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 cosmological bounces.
Highlights
A∗ is the scale factor at the bounce and c is a strictly positive constant; the case of interest is n > 1
One must go beyond minimally-coupled classical Einstein gravity in order to find bounce solutions that could be consistent with string theory
Even though ρ + p can be zero at the bounce, ρ + p must be strictly negative for arbitrarily small, nonzero t in order for a bounce solution to exist
Summary
A∗ is the scale factor at the bounce and c is a strictly positive constant; the case of interest is n > 1. One must go beyond minimally-coupled classical Einstein gravity in order to find bounce solutions that could be consistent with string theory.
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