Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observational constraints on the time-dependence of dark energy   One of the most important questions nowadays in physics concerns the nature
of the so-called dark energy. It is also a consensus among cosmologists that
such a question will not be answered on the basis only of observational data.
However, it is possible to diminish the range of possibilities for this dark
component by comparing different dark energy scenarios and finding which models
can be ruled out by current observations. In this paper, by asssuming three
distinct parametrizations for the low-redshift evolution of the dark energy
equation of state (EOS), we consider the possibility of discriminating between
evolving dark energy and $\Lambda$CDM models from a joint analysis involving
the most recent radio sources gravitational lensing sample, namely, the Cosmic
All Sky Survey (CLASS) statistical data and the recently published \emph{gold}
SNe Ia sample. It is shown that this particular combination of observational
data restricts considerably the dark energy parameter space, which enables
possible distinctions between time-dependent and constant EOS's.

8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th