The Effective Theory of Quintessence: the w<-1 Side Unveiled
Abstract
We study generic single-field dark energy models, by a parametrization of the most general theory of their perturbations around a given background, including higher derivative terms. In appropriate limits this approach reproduces standard quintessence, k-essence and ghost condensation. We find no general pathology associated to an equation of state w_Q < -1 or in crossing the phantom divide w_Q = -1. Stability requires that the w_Q < -1 side of dark energy behaves, on cosmological scales, as a k-essence fluid with a virtually zero speed of sound. This implies that one should set the speed of sound to zero when comparing with data models with w_Q < -1 or crossing the phantom divide. We summarize the theoretical and stability constraints on the quintessential plane (1+w_Q) vs. speed of sound squared.
Keywords
Cite
@article{arxiv.0811.0827,
title = {The Effective Theory of Quintessence: the w<-1 Side Unveiled},
author = {Paolo Creminelli and Guido D'Amico and Jorge Noreña and Filippo Vernizzi},
journal= {arXiv preprint arXiv:0811.0827},
year = {2009}
}
Comments
35 pages, 5 figures, v3: minor modifications, JCAP published version