Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Singularity phenomena in viable f(R) gravity   The curvature singularity in viable f(R) gravity models is examined when the
background density is dense. This singularity could be eliminated by adding the
$R^{2}$ term in the Lagrangian. Some of cosmological consequences, in
particular the source for the scalar mode of gravitational waves, are
discussed.

32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math