PIRSA:09070027

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

Creminelli, P. (2009). The effective theory of quintessence: the w<-1 side unveiled. Perimeter Institute. https://pirsa.org/09070027

Creminelli, Paolo. The effective theory of quintessence: the w<-1 side unveiled. Perimeter Institute, Jul. 17, 2009, https://pirsa.org/09070027 

          @misc{ pirsa_PIRSA:09070027,
            doi = {10.48660/09070027},
            url = {https://pirsa.org/09070027},
            author = {Creminelli, Paolo},
            keywords = {Quantum Fields and Strings, Particle Physics, Cosmology},
            language = {en},
            title = {The effective theory of quintessence: the w\<-1 side unveiled},
            publisher = {Perimeter Institute},
            year = {2009},
            month = {jul},
            note = {PIRSA:09070027 see, \url{https://pirsa.org}}
          }

Paolo Creminelli The Abdus Salam International Centre for Theoretical Physics (ICTP)

Talk numberPIRSA:09070027
DOI10.48660/09070027
Collection
Talk Type Conference
Subject

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