Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Wave equation and dispersion relations for a compressible rotating fluid   A fundamental non-classical fourth-order partial differential equation to
describe small amplitude linear oscillations in a rotating compressible fluid,
is obtained. The dispersion relations for such a fluid, and the different
regions of the group and phase velocity are analyzed.

21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat