The primordial curvature perturbation in the ekpyrotic Universe
Abstract
In the ekpyrotic scenario the Universe is initially collapsing, the energy density coming from a scalar field with a negative exponential potential. On the basis of a calculation ignoring the gravitational back-reaction the authors of the scenario claim that during collapse the vacuum fluctuation creates a perturbation in the comoving curvature, which has a flat spectrum in accordance with observation. In this note the back-reaction is included, and it is found that the spectrum during collapse is strongly scale-dependent with negligible magnitude. The spectrum is continuous across the bounce if the spacetime is smooth, making it unlikely that the ekpyrotic scenario can be compatible with observation.
Cite
@article{arxiv.hep-ph/0106153,
title = {The primordial curvature perturbation in the ekpyrotic Universe},
author = {David H. Lyth},
journal= {arXiv preprint arXiv:hep-ph/0106153},
year = {2009}
}
Comments
6 pages. The Guth-Pi-Olson formalism of the original ekpyrotic paper translated, results from a forthcoming paper reported