Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the equivalence of Jordan and Einstein frames in scale-invariant
  gravity   In this note we consider the issue of the classical equivalence of
scale-invariant gravity in the Einstein and in the Jordan frames. We first
consider the simplest example $f(R)=R^{2}$ and show explicitly that the
equivalence breaks down when dealing with Ricci-flat solutions. We discuss the
link with the fact that flat solutions in quadratic gravity have zero energy.
We also consider the case of scale-invariant tensor-scalar gravity and general
$f(R)$ theories. We argue that all scale-invariant gravity models have Ricci
flat solutions in the Jordan frame that cannot be mapped into the Einstein
frame. In particular, the Minkowski metric exists only in the Jordan frame. In
this sense, the two frames are not equivalent.

14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol