Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Microscopic and Macroscopic Behaviors of Palatini Modified Gravity
  Theories   We show that, within modified gravity, the non-linear nature of the field
equations implies that the usual naive averaging procedure (replacing the
microscopic energy-momentum by its cosmological average) is invalid. We discuss
then how the averaging should be performed correctly and show that, as a
consequence, at classical level the physical masses and geodesics of particles,
cosmology and astrophysics in Palatini modified gravity theories are all
indistinguishable from the results of general relativity plus a cosmological
constant. Palatini gravity is however a different theory from general
relativity and predicts different internal structures of particles from the
latter. On the other hand, and in contrast to classical particles, the
electromagnetic field permeates in the space, hence a different averaging
procedure should be applied here. We show that in general Palatini gravity
theories would then affect the propagation of photons, thus changing the
behaviour of a Universe dominated by radiation. Finally, Palatini theories also
predict alterations to particle physics laws. For example, it can lead to
sensitive corrections to the hydrogen energy levels, the measurements of which
could be used to place very strong constraints on the properties of viable
Palatini gravity theories

15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th