Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Conformal frames and the validity of Birkhoff's theorem   Birkhoff's theorem is one of the most important statements of Einstein's
general relativity, which generally can not be extended to modified theories of
gravity. Here we study the validity of the theorem in scalar-tensor theories
using a perturbative approach, and compare the results in the so-called
Einstein and Jordan frames. The implications of the results question the
physical equivalence between both frames, at least in perturbations.

22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
2
The categories of this paper are: math