Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Big-bang nucleosynthesis and cosmic microwave background constraints on
  non-minimally coupled theories of gravity   In this paper we show that the baryon-to-photon ratio $\eta$ is in general
not conserved before decoupling in non-minimally coupled theories of gravity.
We use big-bang nucleosynthesis and cosmic microwave background limits on the
baryon-to-photon ratio $\eta$ to derive new constraints on modified gravity
theories with a universal non-minimal coupling between matter and curvature,
showing that they rule out a specific class of models previously considered in
the literature as a substitute for the dark matter. We also compare these new
constraints with the ones obtained from the COBE-FIRAS limits on CMB spectral
distortions, highlighting the complementarity between them.

2
The categories of this paper are: math
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess