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. © 2009 IOP Publishing Ltd and SISSA.

The effective theory of quintessence: The w<-1 side unveiled / Creminelli, Paolo; D'Amico, Guido; Norẽa, Jorge; Vernizzi, Filippo. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - 2009:2(2009), pp. 018-018. [10.1088/1475-7516/2009/02/018]

The effective theory of quintessence: The w<-1 side unveiled

D'Amico, Guido;
2009

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. © 2009 IOP Publishing Ltd and SISSA.
The effective theory of quintessence: The w<-1 side unveiled / Creminelli, Paolo; D'Amico, Guido; Norẽa, Jorge; Vernizzi, Filippo. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - 2009:2(2009), pp. 018-018. [10.1088/1475-7516/2009/02/018]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2856393
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