Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Conserved quantities in the perturbed Friedmann world model   The evolutions of linear structures in a spatially homogeneous and isotropic
world model are characterized by some conserved quantities: the amplitude of
gravitational wave is conserved in the super-horizon scale, the perturbed
three-space curvature in the comoving gauge is conserved in the
super-sound-horizon scale, and the angular momentum of rotational perturbation
is generally conserved.

31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics