Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Slowly Rotating Anisotropic Neutron Stars in General Relativity and
  Scalar-Tensor Theory   Some models (such as the Skyrme model, a low-energy effective field theory
for QCD) suggest that the high-density matter prevailing in neutron star
interiors may be significantly anisotropic. Anisotropy is known to affect the
bulk properties of nonrotating neutron stars in General Relativity. In this
paper we study the effects of anisotropy on slowly rotating stars in General
Relativity. We also consider one of the most popular extensions of Einstein's
theory, namely scalar-tensor theories allowing for spontaneous scalarization (a
phase transition similar to spontaneous magnetization in ferromagnetic
materials). Anisotropy affects the moment of inertia of neutron stars (a
quantity that could potentially be measured in binary pulsar systems) in both
theories. We find that the effects of scalarization increase (decrease) when
the tangential pressure is bigger (smaller) than the radial pressure, and we
present a simple criterion to determine the onset of scalarization by
linearizing the scalar-field equation. Our calculations suggest that binary
pulsar observations may constrain the degree of anisotropy or even, more
optimistically, provide evidence for anisotropy in neutron star cores.

37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga