TY - JOUR

T1 - The effective theory of quintessence

T2 - The w<-1 side unveiled

AU - Creminelli, Paolo

AU - D'Amico, Guido

AU - Norẽa, Jorge

AU - Vernizzi, Filippo

N1 - Funding Information:
The study was supported by the grant of AZV CR - Health Research Council , Ministry of Health of Czech Republic n. 17-30101A .

PY - 2009

Y1 - 2009

N2 - 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.

AB - 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.

KW - Cosmological perturbation theory

KW - Dark energy theory

UR - http://www.scopus.com/inward/record.url?scp=65649144744&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2009/02/018

DO - 10.1088/1475-7516/2009/02/018

M3 - Article

AN - SCOPUS:65649144744

SN - 1475-7516

VL - 2009

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

IS - 2

M1 - 018

ER -