2008/06/30 by Sourav Sur, Saurya Das
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #astro-ph #gr-qc #hep-th
paper · pdf · doi:10.1088/1475-7516/2009/01/007
published as JCAP 0901:007,2009 · 26 pages, 3 figures
openalex publication_date 2009/01/07 · arxiv created 2009/02/09 · arxiv updated 2010/04/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
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 w X 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 c X of the dark energy density perturbations may become imaginary while the w X = −1 barrier is crossed. Working out the expression for c X we show that multiple kinetic k-essence fields do indeed lead to a w X = −1 crossing dark energy model, satisfying the stability criterion c X 2 ⩾ 0 as well as the condition c X ⩽ 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 c X 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 w X crosses -1 at red-shift z ∼ 0.2, whereas the dark energy density nearly tracks the matter density at higher red-shifts.