Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tracking quintessence and k-essence in a general cosmological background   We derive conditions for stable tracker solutions for both quintessence and
k-essence in a general cosmological background, H^2 \propto f(\rho). We find
that tracker solutions are possible only when \eta = d ln f /d ln \rho is
constant, aside from a few special cases, which are enumerated. Expressions for
the quintessence or k-essence equation of state are derived as a function of
\eta and the equation of state of the dominant background component.

29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph