Year: 2009
Type: article
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.
Institutions: The Abdus Salam International Centre for Theoretical Physics (ICTP), Scuola Internazionale Superiore di Studi Avanzati, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Institut de Physique Théorique
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2094446423