Université de GenèveDépartement de Physique ThéoriqueCAP Genève

General conditions for scale-invariant perturbations in an expanding universe

6. July 2011
Cite as: 
G. Geshnizjani, W. H. Kinney, A. Moradinezhad Dizgah, JCAP 1111 (2011) 049
Members involved: 
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.


Département de Physique Théorique
Université de Genève
24, quai Ernest Ansermet
1211 Genève 4
Directions & contact