Multiple kinetic k-essence, phantom barrier crossing and stability
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Date
2015-12-15
Authors
Sur, Sourav
Das, Saurya
Journal Title
Journal ISSN
Volume Title
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Abstract
We investigate models of dark energy with purely kinetic multiple k-
essence sources that allow for the crossing of the phantom divide line, without violating
the conditions of stability. It is known that with more than one kinetic k-field one
can possibly construct dark energy models whose equation of state parameter wX
crosses −1 (the phantom barrier) at recent red-shifts, as indicated by the Supernova Ia
and other observational probes. However, such models may suffer from cosmological
instabilities, as the effective speed of propagation cX of the dark energy density
perturbations may become imaginary while the wX = −1 barrier is crossed. Working
out the expression for cX we show that multiple kinetic k-essence fields do indeed lead
to a wX = −1 crossing dark energy model, satisfying the stability criterion c2
X ≥ 0 as
well as the condition cX ≤ 1 (in natural units), which implies that the dark energy
is not super-luminal. As a specific example, we construct a phantom barrier crossing
model involving three k-fields for which cX is a constant, lying between 0 and 1. The
model fits well with the latest Supernova Ia Union data, and the best fit shows that
wX crosses −1 at red-shift z ∼ 0.2, whereas the dark energy density nearly tracks the
matter density at higher red-shifts.
Description
Sherpa Romeo green journal. “This is an author-created, un-copyedited version of an article accepted for publication/published in Journal of Cosmology and Astroparticle Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it.”
Keywords
Dark energy , Kinetic k-essence , Phantom barrier , Stability , Dark energy theory , Supernova type Ia , Cosmological perturbation theory
Citation
Sur, S., & Das, S. (2009). Multiple kinetic k-essence, phantom barrier crossing and stability. Journal of Cosmology and Astroparticle Physics, 2009(01), 007. https://doi.org/10.1088/1475-7516/2009/01/007