General conditions for scale-invariant perturbations in an expanding universe
Cosmology and Nongalactic Astrophysics
2015-05-28 v1
Abstract
We investigate the general properties of expanding cosmological models which generate scale-invariant curvature perturbations in the presence of a variable speed of sound. We show that in an expanding universe, generation of a super-Hubble, nearly scale-invariant spectrum of perturbations over a range of wavelengths consistent with observation requires at least one of three conditions: (1) accelerating expansion, (2) a speed of sound faster than the speed of light, or (3) super-Planckian energy density.
Keywords
Cite
@article{arxiv.1107.1241,
title = {General conditions for scale-invariant perturbations in an expanding universe},
author = {Ghazal Geshnizjani and William H. Kinney and Azadeh Moradinezhad Dizgah},
journal= {arXiv preprint arXiv:1107.1241},
year = {2015}
}
Comments
4 pages, RevTeX