N. Chamel, A. F. Fantina, J. M. Pearson, S. Goriely
The recently measured mass of pulsar PSR J1614$-$2230 has revived the question of the composition of matter at the high densities prevailing inside compact stars. The impact on the maximum possible neutron-star mass of an "exotic" core consisting of non-nucleonic matter is studied by starting with a set of purely nucleonic equations of state (EoS) that have been developed to permit a unified treatment of all parts of neutron stars; the different members of this set have very similar properties at nuclear and subnuclear densities but quite different degrees of high-density symmetry stiffness. It is found that even if there is a significant softening of the EoS associated with the actual transition to an exotic phase there can still be a stiffening at higher densities closer to the center of the star that is sufficient to increase the maximum possible mass. In particular, by invoking such a phase transition it becomes possible to support PSR J1614$-$2230 with a nucleonic EoS that is soft enough to be compatible with the $\pi^-/\pi^+$ production ratio measured in heavy-ion collisions.
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http://arxiv.org/abs/1205.0983
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