Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Alternatives to Quintessence Model Building   We discuss the issue of toy model building for the dark energy component of
the universe. Specifically, we consider two generic toy models recently
proposed as alternatives to quintessence models, known as Cardassian expansion
and the Chaplygin gas. We show that the former is enteriely equivalent to a
class of quintessence models. We determine the observational constraints on the
latter, coming from recent supernovae results and from the shape of the matter
power spectrum. As expected, these restrict the model to a behaviour that
closely matches that of a standard cosmological constant $\Lambda$.

19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs