Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlocal theories of gravity: the flat space propagator   It was recently found that there are classes of nonlocal gravity theories
that are free of ghosts and singularities in their Newtonian limit [PRL, 108
(2012), 031101]. In these proceedings, a detailed and pedagogical derivation of
a main result, the flat space propagator for an arbitrary covariant metric
theory of gravitation, is presented. The result is applied to analyse f(R)
models, Gauss-Bonnet theory, Weyl-squared gravity and the potentially
asymptotically free nonlocal theories.

8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
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The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat