Résumé / Abstract Seminaire_GReCO
SÉMINAIRE DU GRECO

"The Effective Theory of Quintessence: the w less than -1 Side Unveiled"

P. Creminelli

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 wQ < -1 or in crossing the phantom divide wQ = -1. Stability requires that the wQ < -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 wQ < -1 or crossing the phantom divide. We summarize the theoretical and stability constraints on the quintessential plane (1+wQ) vs. speed of sound squared.

jeudi 11 décembre 2008 - 11:00
Salle des séminaires Évry Schatzman,
Institut d'Astrophysique de Paris

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