Causality and Sound Speed for General Scalar Field Models, including w < -1, tachyonic, phantom, k-essence and curvature corrections
| dc.creator | de la Macorra, Axel | |
| dc.creator | Vucetich, Hector | |
| dc.date | 2002-12-12 | |
| dc.date | 2004-09-08 | |
| dc.date.accessioned | 2026-07-25T18:52:35Z | |
| dc.description | The result from the SN1a projects suggest that the dark energy can be represented by a fluid with w<-1. However, it is commonly argued that a fluid with |w|>1 contradicts causality. Here, we will show that a fluid with |w|>1 does not contradict causality if $w$ is not constant. Scalar field are the most promising candidates for describing the dark energy and they do not have a constant equation of state parameter w. Scalar potentials may lead to regions where w is larger or smaller than one and even regions where the group velocity $d p/dρ$ diverges. We study the evolution of scalar field perturbations and we show that the "sound speed" is always smaller than the speed of light independently of the value of w=p/ρor d p/dρ. In general, it is neither the phase velocity nor the group velocity that gives the "sound speed". In the analysis we include the special cases of $|w|>1$, tachyonic, phantom, k-essence scalar fields and curvature corrections. Our results show that scalar fields do not contradict causality as long as there is dispersion. | |
| dc.description | LaTeX 12 pages, 3 figures. Accepted in JCAP. We included explicit discussion on k-essence, tachyonic and curvature corrections models. We corrected small typos | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0212302 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0212302 | |
| dc.identifier.uri | https://dspace.dare.co.zw/handle/123456789/59286 | |
| dc.subject | Astrophysics | |
| dc.title | Causality and Sound Speed for General Scalar Field Models, including w < -1, tachyonic, phantom, k-essence and curvature corrections | |
| dc.type | text |