Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Generalized Chaplygin gas with $\alpha = 0$ and the $\Lambda CDM$
  cosmological model   The generalized Chaplygin gas model is characterized by the equation of state
$p = - \frac{A}{\rho^\alpha}$. It is generally stated that the case $\alpha =
0$ is equivalent to a model with cosmological constant and dust ($\Lambda
CDM$). In this work we show that, if this is true for the background equations,
this is not true for the perturbation equations. Hence, the mass spectrum
predicted for both models may differ.

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The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph