Can the dark energy equation - of - state parameter w be less than -1?

By S. Carroll, M. Hoffman, M. Trodden. 2003

1,070 citations recorded by the source corpus.

Models of dark energy are conveniently characterized by the equation-of-state parameter $w=p/\ensuremath{\rho},$ where $\ensuremath{\rho}$ is the energy density and p is the pressure. Imposing the dominant energy condition, which guarantees stability of the theory, implies that $wg~\ensuremath{-}1.$ Nevertheless, it is conceivable that a well-defined model could (perhaps temporarily) have $wl\ensuremath{-}1 ,$ and indeed such models have been proposed. We study the stability of dynamical models exhibiting $wl\ensuremath{-}1$ by virtue of a negative kinetic term. Although naively unstable, we explore the possibility that these models might be phenomenologically viable if thought of as effective field theories valid only up to a certain momentum cutoff. Under our most optimistic assumptions, we argue that the instability time scale can be greater than the age of the universe, but only if the cutoff is at or below ${10}^{\ensuremath{-}3}\mathrm{eV}.$ We conclude that it is difficult, although not necessarily impossible, to construct viable models of dark energy with $wl\ensuremath{-}1;$ observers should keep an open mind, but the burden is on theorists to demonstrate that any proposed new models are not ruled out by rapid vacuum decay.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/602c1ec4e2fa4d9eae61b610fd1928b461f31530

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Citations in the corpus

Crossing the w = - 1 barrier in the D3-brane dark energy model (2005, methodology): “The model is close to the model considered by [24] which is also considered in the DE context.”
The Effective Field Theory of nonsingular cosmology (2016, background): “Usually the violation of NEC may lead to the ghost instability [21, 22].”
WMAP constraints on low redshift evolution of dark energy (2004, background): “…2003; Gibbons 2003a; Jassal 2004; Kim, Kim & 2003; Sen 2003; Aguirregabiria & Lazkoz 2004; Gorini et al. 2004), phantom fields (Caldwell 2002; Carroll et al. 2003; Dabrowski et al. 2003; Frampton 2003; Gibbons 2003b; Gonzalez-Diaz 2003b; Hao E-mail: hkj@mri.ernet.in (HKJ);…”
D‐branes in Standard Model building, gravity and cosmology (2003, background): “Such matter, coined phantom matter [236]-[238] appears naturally here.”
Approaches to understanding cosmic acceleration (2009, background): “Such a question has been studied in some detail by several authors [86, 87].”