Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: The Parameterized Post-Friedmann Framework for Theories of Modified
  Gravity: Concepts, Formalism and Examples
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph