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Slow-roll k-essence | | Takeshi Chiba
; Sourish Dutta
; Robert J. Scherrer
; | | Date: |
3 Jun 2009 | | Abstract: | We derive slow-roll conditions for thawing k-essence with a separable
Lagrangian $p(X,phi)=F(X)V(phi)$. We examine the evolution of the equation of
state parameter, $w$, as a function of the scale factor $a$, for the case where
$w$ is close to -1. We find two distinct cases, corresponding to $X approx 0$
and $F_X approx 0$, respectively. For the case where $Xapprox0$ the evolution
of $phi$ and hence $w$ is described by only two parameters, and $w(a)$ is
model-independent and coincides with similar behavior seen in thawing
quintessence models. This result also extends to non-separable Lagrangians
where $Xapprox0$. For the case $F_X approx 0$, an expression is derived for
$w(a)$, but this expression depends on the potential $V(phi)$, so there is no
model-independent limiting behavior. For the $X approx 0$ case, we derive
observational constraints on the two parameters of the model, $w_0$ (the
present-day value of $w$), and the $K$, which parametrizes the curvature of the
potential. We find that the observations sharply constrain $w_0$ to be close to
-1, but provide very poor constraints on $K$. | | Source: | arXiv, 0906.0628 | | Services: | Forum | Review | PDF | Favorites | |
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