Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Linear Gas Dynamics in the Expanding Universe: Why the Jeans Scale does
  not Matter   We investigate the relationship between the dark matter and baryons in the
linear regime. This relation is quantified by the so-called ``filtering
scale''. We show that a simple gaussian ansatz which uses the filtering scale
provides a good approximation to the exact solution.

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
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs