Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Irrotational-fluid cosmologies in fourth-order gravity
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph