Crossing the phantom divide: Dark energy internal degrees of freedom

By Wayne Hu. 2004

253 citations recorded by the source corpus.

Dark energy constraints have forced viable alternatives that differ substantially from a cosmological constant {lambda} to have an equation of state w that evolves across the phantom divide set by {lambda}. Naively, crossing this divide makes the dark energy gravitationally unstable, a problem that is typically finessed by unphysically ignoring the perturbations. While this procedure does not affect constraints near the favored cosmological constant model it can artificially enhance the confidence with which alternative models are rejected. Similar to the general problem of stability for w<0, the solution lies in the internal degrees of freedom in the dark energy sector. We explicitly show how to construct a two scalar field model that crosses the phantom divide and mimics the single field behavior on either side to substantially better than 1% in all observables. It is representative of models where the internal degrees of freedom keep the dark energy smooth out to the horizon scale independently of the equation of state.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7b3a1bc0a9c320024ee21ceda6a5df5b4632eff7

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Citations in the corpus

A kinematical approach to dark energy studies (2006, background): “…‘phantom’ dark energy models, violate the dominant energy condition (Carroll et al. 2003; Onemli & Woodard 2004) and present serious problems relating to the treatment of dark energy perturbations (Hu 2005; Vikman 2005; Caldwell & Doran 2005; Zhao et al. 2005) when w(z) crosses the boundary w = −1.”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, methodology): “However, there is a simple model (called the quintom model Feng et al. 2005; Hu 2005) consisting of two fluids of the same type as in the previous Sect.”
Cosmological Parameters from Observations of Galaxy Clusters (2011, background): “Generically, descriptions of dark energy as a fluid with w 6= −1 should include the effects of spatial variations in dark energy density (e.g. Hu 2005).”