Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anisotropic neutron stars in $R^2$ gravity   We consider static neutron stars within the framework of $R^2$ gravity. The
neutron fluid is described by three different types of realistic equations of
state (soft, moderately stiff, and stiff). Using the observational data on the
neutron star mass-radius relation, it is demonstrated that the characteristics
of the objects supported by the isotropic fluid agree with the observations
only if one uses the soft equation of state. We show that the inclusion of the
fluid anisotropy enables one also to employ more stiff equations of state to
model configurations that will satisfy the observational constraints
sufficiently. Also, using the standard thin accretion disk model, we
demonstrate potentially observable differences, which allow us to distinguish
the neutron stars constructed within the modified gravity framework from those
described in Einstein's general relativity.

26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph