Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutron stars with hyperon cores: stellar radii and EOS near nuclear
  density   The existence of 2 Msun pulsars puts very strong constraints on the equation
of state (EOS) of neutron stars (NSs) with hyperon cores, which can be
satisfied only by special models of hadronic matter. The radius-mass relation
for these models is sufficiently specific that it could be subjected to an
observational test with future X-ray observatories. We want to study the impact
of the presence of hyperon cores on the radius-mass relation for NS. We aim to
find out how, and for which particular stellar mass range, a specific relation
R(M), where M is the gravitational mass, and R is the circumferential radius,
is associated with the presence of a hyperon core.
  We consider a set of 14 theoretical EOS of dense matter, based on the
relativistic mean-field (RMF) approximation, allowing for the presence of
hyperons in NSs. We seek correlations between R(M) and the stiffness of the EOS
below the hyperon threshold needed to pass the 2 Msun test. For NS masses
1.0<M/Msun<1.6, we get R>13km, because of a very stiff pre-hyperon segment of
the EOS. At nuclear density, the pressure is significantly higher than a robust
upper bound obtained recently using chiral effective field theory.
  If massive NSs do have a sizable hyperon core, then according to current
models the radii for M=1.0-1.6 Msun are necessarily >13km. If, on the contrary,
a NS with a radius R<12 km is observed in this mass domain, then sizable
hyperon cores in NSs, as we model them now, are ruled out. Future X-ray
missions with <5% precision for a simultaneous M and R measurement will have
the potential to solve the problem with observations of NSs. Irrespective of
this observational test, present EOS allowing for hyperons that fulfill
condition M_max>2 Msun yield a pressure at nuclear density that is too high
relative to up-to-date microscopic calculations of this quantity.

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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: gr-qc
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The categories of this paper are: q-alg
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg