Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Restrictions on purely kinetic k-essence   We restrict purely kinetic k-essence. Assuming the equation of state is a
power law of the kinetic energy: $w=w_0X^{\alpha}$, to obtain accelerated
phases, we must have $\alpha>0$ as one of necessary conditions, constrained
from the conditions for stability and causality, and the k-essence must behave
like phantom. We also study the evolutions of the equation of state and the
speed of sound with numerical simulation.

15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph