Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A new generic evolution for $k$-essence dark energy with $w \approx -1$   We reexamine $k$-essence dark energy models with a scalar field $\phi$ and a
factorized Lagrangian, $\mathcal L = V(\phi)F(X)$, with $X = \frac{1}{2}
\nabla_\mu \phi \nabla^\mu \phi.$ A value of the equation of state parameter,
$w$, near $-1$ requires either $X \approx 0$ or $dF/dX \approx 0$. Previous
work showed that thawing models with $X \approx 0$ evolve along a set of unique
trajectories for $w(a)$, while those with $dF/dX \approx 0$ can result in a
variety of different forms for $w(a)$. We show that if $dV/d\phi$ is small and
$(1/V)(dV/d\phi)$ is roughly constant, then the latter models also converge
toward a single unique set of behaviors for $w(a)$, different from those with
$X \approx 0$. We derive the functional form for $w(a)$ in this case, determine
the conditions on $V(\phi)$ for which it applies, and present observational
constraints on this new class of models. We note that $k$-essence models with
$dF/dX \approx 0$ correspond to a dark energy sound speed $c_s^2 \approx 0$.

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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: quant-ph
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The categories of this paper are: math-ph