The effective theory of quintessence: the w < -1 side unveiled
- Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34014 Trieste (Italy)
- SISSA/ISAS, via Beirut 2-4, 34014 Trieste (Italy)
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{sub Q} < -1 or in crossing the phantom divide w{sub Q} = -1. Stability requires that the w{sub 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{sub Q} < -1 or crossing the phantom divide. We summarize the theoretical and stability constraints on the quintessential plane (1+w{sub Q}) vs. speed of sound squared.
- OSTI ID:
- 22156903
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2009, Issue 02; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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