Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: On Shear-free perturbations of f(R) gravity
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th